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electronics.stackexchange.com

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6451

|components|

<p>It's not exactly what you are looking for, but potentiometers' resistive elements often get a bit oxidised as they get older.</p> <p>Generally, potentiometers are designed to be <em>self-wiping</em>, meaning that cycling the pot back and forth will often break through the oxide layer and restore some of the functionality.<br> Alternatively, any electronics <a href="http://www.google.com/search?q=contact+cleaner" rel="nofollow">contact cleaner</a> may be very effective. Just squirt a bit down the sides into the pitch-bend controller, and work it back and forth repeatedly.</p> <p>As a last ditch attempt, if the above does not work, the wiper may have relaxed a bit, and therefore may not be making good contact with the resistive element in the pot (see the <a href="http://en.wikipedia.org/wiki/Potentiometer" rel="nofollow">wikipedia article</a> for info on how the internals fit together). It may be possible to disassemble the pitch-bend assembly and manually bend the wiper to help it make better contact.</p> <p>I realize it may not be information on how to obtain replacement parts, but many companies are a nightmare to deal with regarding obtaining any information about the internals of their products, let-alone parts. It may be worth the time to try and fix the issue yourself before simply trying to replace the defective assembly en-masse.</p>

<p>Any idea where I can get parts for Roland synthesizers?</p> <p>I have a Roland Fantom (FA-76, the original without sequencers and what not) and its pitch bender seems to be a bit worn out, or possibly dusty. (As I pitch up/down, sometimes the pitching skips around a bit, especially near center.) I'd like to get a replacement for the pitch bender, but can't figure out where to order parts. E-mails to Roland never get replied.</p> <p>Any thoughts?</p>

Pitch Bender for Roland Fantom FA-76

2010-11-09T03:12:40.157

6452

|pcb|capacitor|

<p>Flexing can occur in the manufacturing process for long PCBs. Cracked caps can not all be found in manufacturing tests and could fail in the field. </p>

<p><a href="http://www.kemet.com/kemet/web/homepage/kechome.nsf/weben/500731829C9D2F51852572EC006DFE40/%24file/F3281_X7R_FlexCap.pdf" rel="nofollow">These capacitors from Kemet</a> have flexible termination.</p> <p>The datasheet says it caters for applications where the board flexes and normal ceramic caps can fail. However, I fail to see a situation where PCB's flex? If PCB's had the potential to flex, wouldn't you just get a tougher enclosure?</p>

What situation would you use flexible termination ceramic capacitors?

2010-11-09T03:18:24.253

6454

|pcb|manufacturing|gerber|

<p>E-testing is primarily used to detect bad plated holes, as this is the most common failure as it's more process-sensitive. Bear in mind that a flying-probe e-test rarely checks for shorts as it requires a huge amount more checks (therefore test time) than a continuity test - each node to each other possible node. Probably easier on a bed-of-nails tester which has connectivity to all nodes at the same time. I've certainy had a few supposedly e-tested boards with shorts. </p>

<p>I always see the option for E-testing when sending PCB's off to a fab house. I gather it is an electrical test to test all the connections. But how do they do it? They don't have my schematic! Only gerbers? And surely it is done by machine?</p>

How does E-Test at a PCB Fab work?

2010-11-09T03:30:00.153

6468

|i2c|gyro|

<p>This is my first time that I am writing something to forum (in 15 year using the internet). I have just been reading/consuming until now. Even if this thread seems to be old I will use it for my debut. So: I had the same SDA problem with the ITG-3200 in the same configuration. The power-up sequence seems to be really important, but the datasheet says implicitly:just connect VDD+Vlogic. So I did and it does not work. I traced this using the eval-board and found one suspicious resistor R1 in the schematic. 10k before Vlogic? Somebody seems not to trust it's own chip. Tests showed me why. If you connect VDD+Vlogic @ 3.3V SDA sticks to 2/3 VDD. Adding the 10k resistor solved this problem. There are several explanation possible, but I do not have the time to trace it any further.</p> <p>I hope that this helps some more people Rene</p>

<p>I'm developing a gyro+accelerometer data logging device using the Invensense ITG3200 gyro device and I'm having a real struggle getting it to talk to me. I have tried 5 of them and none of them are responding to I2C commands. Has anyone had experience using these and had to overcome hurdles to make them work?</p> <p>I have two other sensors on the same I2C bus and they are behaving as expected, so my I2C comms is working fine. The sole bus master is a PIC microcontroller. I have wired the chip up exactly as shown in the specs, and use a common 3.3V supply for Vdd and Vlogic. Pullup resistors are 4k7, but have tried reducing them to 1k5 with no effect.</p> <p>The gyro chip is a bit odd electrically too - it is behaving as if it has a pullup on the SDA line to a voltage at 2/3 the supply voltage, but that ceases to supply current when the SDA voltage drops below about 0.6V. That behaviour kind of makes sense but is not documented in the spec sheet.</p> <p>I am wondering if I have managed to damage all 5 chips in exactly the same way, but that seems unlikely. One of them I purchased on a breakout board and it behaves exactly the same as the others: 2 of those are reflow soldered onto a PCB, the other 2 I glued upside down and hand soldered fine wires to the pads (getting desperate there!).</p> <p>It would be good to hear from anyone who has used this chip successfully - seems like a great device but I am getting a tad frustrated ;)</p> <p>I did send a query to Invensense but haven't heard anything back from them.</p> <p>Thanks for any clues.</p>

Any tips on using the Invensense ITG-3200 gyro?

2010-11-09T11:16:53.060

6475

|potentiometer|

<p>Can "potentiometer with switch" be the name ? You need just wire the switch to A and W. So it will guarantee a very good zero (when turned counter clock wise all way until click).</p>

<p>Is there a special name for a potentiometer whose A-W or B-W resistance can drop to zero? I have a 1k +/-10% pot and I can only vary A-W or B-W resistance from 118 ohms to 1.2k. Note A, B refer to the outer pins and W the wiper pin.</p>

Potentiometer that goes to zero

2010-11-09T13:18:50.243

6484

|protection|dc-motor|

<p>I have bad experience of similar attempt. The cause is that contemporary switching supplies are too smart for dynamic inductive load with regenerative an other switching spikes. The only workaround is to use raw power supply (transformer, bridge, zero active components).</p> <p>What you will possibly see if you try direct connection:</p> <ul> <li>Motor will accelerate OK on low torgue</li> <li>Motor will trip supply when acceleration is high on start from zero velocity</li> <li>Motor will accelerate OK with high acceleration but will trip supply protection when decelerated</li> <li>Motor will never burn, but supply very likely will</li> <li>Nothing will will break and will work ok, but you will trip mains 20A breaker once in a while.</li> <li>Trying to put ferrite chokes on positive wire will make no difference, supply will keep tripping</li> <li>Overall currents will never be near 50% of rated by supply, but peak values will keep protection tripping even if the motion is smooth</li> <li>The protection diode (overvoltage 50V surge diode in parallel to 48V supply) can help for 90% of motions, but supply will be ever tripping unpredictably over long run</li> <li>etc.</li> </ul> <p>So answer is probably the thing we did not try, but which can help:</p> <ul> <li>Calculate the energy budget for motions and double it and put super large capacitor at the output. With surge diode with voltage rating 1-2V greater than nominal voltage and a bit lower than overvoltage protection of supply.</li> </ul> <p>Other aspects involved:</p> <ul> <li>The breakdown of high power semiconductors is caused not by voltage, but by speed of voltage increase (about 5000V/microsecond typically). Rule of thumb "Everything is thyristor"</li> <li>The TVS is a must. They survive at 49..50V 400W loads with no sweat.</li> <li>The regenerative energy absorbtion (large capacitor and/or power resistor with few diodes) is a must if voltage is over 100V. Can be skipped for low voltage setup unless you need 24/7 run in hard conditions.</li> <li>Custom FET switching is cause of trouble, simply because you cause mechanical shock with infinite torgue on start, unless you use PWM with clever S-curve acceleration.</li> <li>Safety is also not last aspect if you deal with near horsepower motion.</li> </ul>

<p>I need to find a safe and reliable way to power a DC hobby motor off mains supply. The motor is large (i.e. 500W) 14.4V. Therefore, the current requirements are large i.e. 35A for a 14.4V supply.</p> <p>I can't find such a power supply to purchase and my budget is small. Therefore, I thought I could use an ATX power supply from a computer. They typically have a high current 12V line that can deliver the required current, 42A in this case.</p> <p>I will be using a power MOSFET to regulate the power going to the motor by switching it on and off using pulse width modulation PWM. There should be some huge inductive spikes created. I need a way to protect the power supply from these. </p> <p>I was thinking of using several layers of protection just to be safe as long as they are compatible with each other. There location in the order that I mention them is arranged starting closest to the motor and moving towards the supply. The first line of defense is a freewheeling diode put in parallel with the motor forward biased from 0 to the positive supply direction. In addition, perhaps an RC snubber also in parallel. Then a 12V standoff TVS also in parallel in case the other two fail. However, this will short the power supply if it is triggered. If the supply doesn't have over current protection it will kill the supply. I need some sort of fast acting fuse or polyswtich to at as a current limiter in series with the supply. I've noticed that a the polyswitches are very slow. like 9 seconds to "disconnect" the line and I don't want to use a fuse that I have to replace when this happens. Is there a good solution to this problem, or is this all too much? That is, should I just leave the TVS and polyswitch out of the design?</p>

How do I safely drive a 500W inductive load with a computer power supply and suppress voltage spikes from switching?

2010-11-09T16:09:40.383

6488

|pcb-fabrication|

<p>Study on thermal crosslinking reaction of <strong>o-naphthoquinone diazides</strong> and application to electrodeposition positive photoresist.</p> <p>Authors: Kenji Miyagawa, Keisuke Naruse, Shinsuke Ohnishi, Koji Yamaguchi, Kenji Seko, Nobushige Numa and Naozumi Iwasawa</p>

<p>Anybody has reference of the what chemicals photoresist for PCB patterning are made of? I would like something as specific as possible. No brand names please. Peer reviewed papers would be awesome.</p>

Photoresist for PCB patterning

2010-11-09T16:55:35.147

6489

|power|solar-cell|

<p>First: the solar panel has a V/I curve which is shaped like this:</p> <p><img src="https://i.stack.imgur.com/CIbb5.gif" alt="A random picture about PV panels"></p> <p>As you can see, for low currents the voltage varies slightly, and for low voltages the current is almost constant. So you will have the maximum current when the panel is short-circuited, and the maximum voltage when the panel is open-circuited. But, since the power is V*I, you have to find the point in which their product is maximum.</p> <p>As you can see in the second picture, the power has a peak at abour the 80% of the open circuit voltage, and some Max Power Point Tracking (MPPT) systems will just bias the panel at that voltage. But smarter ones, will use tricks like measuring the slope of the power curve, which is zero when the MPP is reached.</p> <p><img src="https://i.stack.imgur.com/AiJXI.jpg" alt="Another random picture about PV panels"></p> <p>The picture shows also another interesting fact: changing the light, the curve scales vertically, which means that the current will be proportional to light, but the voltage will remain about the same (with rough approximation).</p> <p>Increasing the temperature, instead, will lower the open circuit voltage, shifting the curve leftwards and thus reducing the total amount of power that it's possible to obtain. That's why it's important to keep the panel cool.</p> <p>So, to find the maximum power point, you can do this way: </p> <ol> <li><p>First, fix the light level to a stable (and possibly known) value;</p></li> <li><p>Then, connect the panel to a voltage source capable of sinking current and measuring both voltage and current accurately;</p></li> <li><p>Starting from 0 V, increase the voltage at which you bias the panel until you reach the open circuit voltage Voc, while measuring the current for each point.</p></li> </ol> <p>To find the MPP, you have several ways:</p> <ul> <li><p>measuring the open circuit voltage Voc or the short circuit current Isc. The MPP is usually an almost constant fraction of these parameters. This is the roughest method, because it's not accurate and will need adjustments when the light changes.</p></li> <li><p><strong>derivative</strong>: when the panel is biased to a point, introduce a small change in the voltage of the panel, and measure the change in the current. Depending on this ratio (dI/dV) it's possible to adjust again until reaching the MPP. There are several different implementations of this technique, which is the most common.</p></li> <li><p>other solutions may use an external light meter, and derive from it the right biasing voltage for the panel.</p></li> </ul>

<p>What is the best way to measure the maximum power generated by a solar panel? </p>

How to measure the maximum power of a solar panel

2010-11-09T17:59:43.563

6492

|connector|ffc|

<p>I'm using <a href="https://easyeda.com/amirgonnen/ztl_01" rel="nofollow noreferrer">this</a>.<br> You can order it cheaply from China (I used <a href="https://jlcpcb.com" rel="nofollow noreferrer">JLCPCB</a>).<br> Reflowing the <a href="https://www.buydisplay.com/default/50-pin-0-5mm-pitch-top-contact-zif-connector-fpc-connector" rel="nofollow noreferrer">connector</a> requires some practice, though...</p> <p><a href="https://i.stack.imgur.com/iFapL.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/iFapL.jpg" alt="enter image description here"></a></p>

<p>What is the best way to break out a Flat Flexible Cable (FFC)? Specifically I've got a sensor which uses the 0.5mm pitch FFC that I would like to break out onto a breadboard. As you might already know these cables are extremely small and thin and soldering wires directly to them is almost impossible. </p> <p>Note I DO NOT have access to the inside of the sensor so solder/connecting to the board directly is not an option.</p>

Breakout for FFC cables?

2010-11-09T18:33:56.633

6499

|microcontroller|comparator|common-mode|

<p>In terms of actual behavior, one may imagine each input of a comparator has having up to five operational regions, which I'll call "way too high", "slightly too high", "good", "slightly too low", and "way too low". If either input is "way too high" or "way too low" there's no guarantee as to what the comparator will do (it may attempt to source or sink a larger-than-specified amount of current to/from the inputs, or arbitrarily report either input as being higher than the other, etc.) If both inputs are "slightly too high" or both are "slightly too low", the comparator may arbitrarily report either input as being higher than the other. The comparator will work correctly in the seven other cases where both inputs either are "good" or only "slightly" out of range.</p> <p>Unfortunately, many comparator data sheets fail to make a distinction between "slightly out of range" and "way out of range", even though in practice some (if not most) designs would behave as though they are no worse than "slightly out of range" for all values within their Absolute Maximum Ratings.</p>

<p>The comparators on my MCU, a dsPIC33FJ128GP802, give the common-mode input range as AVdd-1.15V. AVdd is 3.3V, so does this mean the comparators can't compare voltages in the range of 2.15V to 3.3V?</p>

Common mode input voltage range and comparators on an MCU

2010-11-09T20:50:56.620

6500

|frequency|sound|bjt|

<p>I have experienced this with a bjt before as well .A piezo crystal is a very high impedance part. You'll want some other lower impedance load in parallel with the piezo. Maybe start with a 47K? Then work up and down from there for the required volume.</p>

<p>I have a 4 KHz piezo buzzer and a microcontroller (arduino) that outputs that 4 KHz from one of it's pins. All is fine if I connect the buzzer to the output with one pin and to the ground with another. Also all works as expected if I try to control it with MOSFET: +5V to the drain, buzzer between source and ground, and the output pin to the gate.</p> <p>However if I replace MOSFET with BJT, something goes wrong and the buzzer emits just a very-very-very quiet sound. Here's what I have:</p> <ul> <li>Buzzer between +5 V and the collector</li> <li>Output pin connected to the base through 2K2 resistor</li> <li>Emitter connected to the ground</li> </ul> <p>I have tried few other configurations with BJT, but result is the same. I use BC337 as a transistor (AFAIK it is analogue of 2N2222).</p> <p>Could anybody clarify why this happens?</p> <p><strong>UPD</strong>:</p> <p>I've measured voltage levels. I have 2.51 V between the microcontroller output and the ground. I get 5 V / 2 because it generates square waves, isn't it? Then I have 2.1 V around the base resistor. And, surprisingly I've got 5 V around the buzzer! Shouldn't I get 2.5 V?</p> <p>Also I noticed that once I measure voltage across the buzzer the sound become a bit louder. So I've tried to add a resistor in parallel to it. Aaaand… now it works!</p> <p><img src="https://i.stack.imgur.com/nl1Ld.png" alt="alt text"></p> <p>The question left open: why it doesn't work as expected if I remove <em>R2</em>?</p>

Connecting piezo buzzer with BJT

2010-11-09T21:16:14.467

6503

|stepper-motor|

<p>From <a href="http://www.allegromicro.com/en/Products/Part_Numbers/Archive/index.asp" rel="nofollow">http://www.allegromicro.com/en/Products/Part_Numbers/Archive/index.asp</a>:</p> <blockquote> <p>5804: BiMOS II Unipolar Stepper-Motor Translator/Driver</p> <p><a href="http://www.allegromicro.com/en/Products/Part_Numbers/Archive/5804.pdf" rel="nofollow">http://www.allegromicro.com/en/Products/Part_Numbers/Archive/5804.pdf</a></p> <p>discontinued October 2004; replaced by A3967 and A3977</p> </blockquote>

<p>I know this is like my other question on the SAA1027 but i can't find the UCN5804 anywhere. Are they obsolete now? </p>

What has happened to the UCN5804?

2010-11-09T21:29:02.047

6510

|resistors|potentiometer|switch-mode-power-supply|digital-logic|

<p>Bear in mind you will only be able to adjust output voltage over a limited range, maybe +/-25% before stability or other issues like popping output caps cause problems</p>

<p>Is it possible to use a digital potentiometer with an SMPS, to adjust the voltage? I'm looking at one with a 2 MHz -3dB bandwidth. What does this mean for a 300 kHz switcher?</p>

Using a digital potentiometer with a SMPS?

2010-11-10T00:28:59.173

6514

|batteries|solar-cell|charger|

<p>If they are just bare cells, you probably don't have much chance in salvaging all of them. In my experience of building panels (only a few), I usually end up using 10-20% more panels than actually end up in the panel.</p> <p>As far as actually building the panel, just solder all of the tabs together in some order (whatever size/shape you are going for), and then mount them between sheets of acrylic. Use some spacers so that the acrylic sheets don't put pressure on the cells. You can also use some sort of silicone adhesive to hold the cells down to one of the sheets.</p> <p>As far as charging a battery, you probably want a boost converter to get the panel voltage to a battery charging voltage. Past that, it should just be a normal lead-acid charge circuit, there are several of these floating around the internet as schematics or off-the-shelf solutions.</p> <p>Depending on your cells, you may not have enough power to really charge a big battery in any sort of reasonable timeframe, so that's something you may want to consider.</p>

<p>I found 12 solar panels, but they are very thin and fragile. They put out approximately .5V under an incandescent bulb. What would be the best way to turn these 12 panels into a 12V car battery charger? I am looking at bumping up the voltage to ~13V, possibly by using a Maxim converter. Has anyone else done this? Thanks!</p> <p>Kyle</p> <p><strong>EDIT:</strong> Schematics would be very helpful. And tips on how to mount very fragile solar panels.</p>

How can I build a solar powered car charger?

2010-11-10T03:38:50.400

6520

|usb|connector|cable-assemblies|mechanical-assembly|

<p>No need to buy a connector, pick up another male USB cable then:</p> <ul> <li>Cut the head off the broken one.</li> <li>Cut the tail off the replacement (leaving some excess wire underneath the connector).</li> <li>Strip about 1/2" both sides of insulation (including the 4 wires).</li> <li>(Optional) Add heatshrink to one side of the wire (but don't heat).</li> <li><a href="http://www.youtube.com/watch?v=BLfXXRfRIzY" rel="nofollow">Solder them together</a>.</li> <li>Wrap each wire in electrical tape or position and heat the heatshrink.</li> <li>Wrap the whole join in electrical tape to reinforce.</li> </ul>

<p>This one should be obvious, but I'd rather ask here then get some unexpected surprises.</p> <p>One of my friends fried a proprietary USB cable which has male USB A connector at one end and TRS connector at the other end. As far as we can see, only the USB A connector seems to be damaged (one of the pins melted). I'm thinking of removing damaged connector and replacing it with something like <a href="http://mikroprinc.com/proizvodi.aspx?sub=pp&amp;pg=F3550&amp;pid=15702" rel="nofollow">this</a>. How would I assemble that connector? </p> <p><strong>EDIT</strong>: Results for future users with same problem: Step one was to cut off burnt connector in such way that there is a bit of cable remaining connected to it. Then I removed metal shield from old connector and found relation between pins on connector and colors of internal cables. In retrospective, I think it would have been better to remove shield and to see which pin is connected to which ring before cutting off the connector. Maybe some crazy product uses internal wires of same color?</p> <p>After that I removed piece of insulation from the healthy part of the cable, placed heatshrink and removed pieces of insulation from individual wires. To me it looked like the black part of the connector was there to facilitate cold welding, but it turned out that I had to solder wires to white plastic part. After that I placed black part on the white part. I was surprised with big metal part as it turned out that the protruding metal part should go next to the black plastic part. To me opposite it looked logical, but plastic parts would go in in only one orientation. In the end, small metal part is just placed on the exposed area of big metal part and small metal jaws are tightened. After that I moved heatshrink so that it covers the jaws and applied heat.</p>

How to assemble male USB A connector?

2010-11-10T11:26:34.053

6529

|batteries|battery-charging|lm317|

<p>Quoting Russell from the PIClist: "AA cells of over 2000 or so mAh from reputable manufacturers recommend NO trickle charge or low AND extremely short duration trickle charge." Low capacity cells (e.g, 800 mAh AA) are OK with trickle charge.</p> <p>You are definitely into high-capacity cells with 1000 mAh AAAs. Check the manufacturer's datasheet before charging them with the indefinite-trickle method. However reputable manufacturers place a catalyst that will handle small amounts of excess trickle charging and will be able to handle a few extra hours of C/40 or less charge rate after charged.</p> <p>The most dependable smart chargers(in relation to ensuring full charge) must use overcharge heating to detect overheating. It is almost unavoidable.</p>

<p>I was told that i could make a simple battery charger from a LM317 and a resistor to charge some Ni-MH Batteries. Can someone just expand on this a little such as how it works as I don't really understand it. Some more information is that there are 12 AAA batteries that hold a charge of 1000mAh and 1.2v per cell. </p>

Building a Battery Charger with an LM317

2010-11-10T15:00:20.767

6534

|voltage-regulator|ldo|

<p>At such a low current level I would be inclined to pre-regulate down with say a 12v zener and stick a cheap-as-chips LDO on there</p>

<p>Any ideas on how to get 3.3V from 5V - 35V at a low 10mA current level? 3.3V need not be precise. It can be 3.5V or 3V, it is powering a small microcontroller. </p> <p>I'm looking for a small and cost effective solution. That pretty much rules out through hole stuff.</p>

3.3V @ 10mA from 5V - 35V

2010-11-10T16:18:21.123

6541

|physics|

<p>A simple explanation, not what 'really' goes on but good enough for introduction:</p> <p>Covalent bonds exist between atoms, basically 2 atoms 'share' an electron. In a pure semi-conductor crystal used for electronics, for example, silicon, all atoms are bound to 4 neighboring atoms via covalent bonds. This should make sense given that silicon has 4 valence electrons and therefore 'wants' to bind with 4 additional electrons to fill its valence orbital.</p> <p>When you dope a semiconductor you blast out some of the silicon atoms and replace them with atoms that have either 3 or 5 valence electrons. This means that you will either have 1 extra electron or be missing an election to fill the doped atom's valence orbital. The bonds in the crystalline structure are very strong and the dopant percentage of the structure is low so the crystalline structure in maintained despite these impurities imparting a "desire to change" the structure. </p> <p>The presence of the free electron or electron hole is what changes the nature of the material to be a donor (n-type) or acceptor (p-type).</p>

<p>In the intrinsic semi-conductors,the electrons are bonded by covalent bonds to the nearby electron,when we do doping the electrons make bond with the atom we doped,so the covalent bonds between the semi-conductor electron is broken?How are they still connected to each other?</p>

Bonding in intrinsic semi-conductors

2010-11-10T18:21:42.080

6543

|microcontroller|pic|programming|

<p>The firmware and host software for <a href="http://www.embedinc.com/products" rel="nofollow">our PIC programmers</a> is available via <a href="http://www.embedinc.com/picprg/sw.htm" rel="nofollow">free download</a>. The <a href="http://www.embedinc.com/picprg/picprg_prot.txt.htm" rel="nofollow">interface spec</a> is also publicly available.</p>

<p>I started a project with my students to build a full open source PIC IDE in windows. My first try was to port <a href="http://piklab.sourceforge.net/" rel="nofollow">Piklab</a> to windows but it is dependent on Qt and KDE. We decide then to use <a href="http://www.eclipse.org/cdt/" rel="nofollow">Eclipse CDT</a> as IDE, SDCC as compiler and GPUtils as linker and assembler. We managed to make the compiler-chain plugin so we can build the whole project in eclipse and generate the binary.</p> <p>The problem now is how to use eclipse to program the PIC (we are targeting specifically on ICD2 because it is what we have available on our lab). Does anyone knows an open-source programmer that can run on command line on windows?</p> <p>Thanks</p>

Open source pic programmer in windows

2010-11-10T18:57:10.963

6545

|microcontroller|i2c|

<p>Apart from the other answers, which are more about the electrical/logical interface, how about the I2C-processor interafce?</p> <p>A PIC runs 1 instruction every 4 clock cycles, so at 32 kHz you get 8 KIPS. I am not sure how many clock cycles I2C needs to get a byte over the bus, but 10 is a good order-of-manitude guess. At 400 kHz that would mean 40 kbyte/s, so you could get 5 bytes stuffed down your throat for every instruction your poor PIC executes! So <em>without serious clock strectching</em> you won't stand a chance.</p> <p>You say "runs a 32kHz". You you mean that, or do you just want to use a 32 kHz crystal? If the latter, you can run some PICs (but not this one) at a higher CPU clock frequency by (temporarily) switching to the internal 8 MHz oscillator.</p>

<p>I am going to use a 400 kHz I2C bus, but I want to talk to a slave MCU, a PIC16F690 (<a href="http://ww1.microchip.com/downloads/en/DeviceDoc/41262C.pdf" rel="nofollow">datasheet</a>), running at 32 kHz. Is it possible to do this? I think so, because the master does the clocking, but are there any unforeseen problems that might occur? (e.g. MCU can't load data into RAM quick enough.)</p>

Is it possible to use 400 kHz I2C buses with a 32 kHz slave?

2010-11-10T19:19:09.717

6551

|avr|pcb|ethernet|rfid|pcb-design|

<p>I'd be really surprised if this operates, at least with any reliability. You desperately need a power plane and a ground plane with components like these. </p> <p>For instance the ENC28J60SS is a current mode driver, those traces from it to the pulse transformer to the jack are going to be carrying high currents switching at high speeds with no reasonable supply or ground path for them. I'd also be concerned with the crystal as its tuning capacitors have a very long high inductance path to ground. I would guess that this design will emit a ton of EMI, possibly enough to interfere with any nearby electronics.</p> <p>The layout for the switcher is also huge, i would expect you to have serious amounts of noise and supply ringing throughout this design coming from the switcher and the ethernet components.</p> <p>You also mentioned POE but there is no POE controller on this board. If your planning to just plug into a POE switch there is a negotiation procedure to request power (in various levels). The only way you could power this off the ethernet port as is would be to find a mid run injector that just dumped voltage on the unused pairs in 10/100 Base-T. If you plugged this into a gigabit switch that could cause major problems. Those pairs also aren't center tapped as they should be for POE. Dumping pins 7/8 directly to ground could cause major problems for both this device and the switch.</p> <p>There is a lot i could go into but 90% of it is a result of not having power/ground planes, clear that up first.</p> <p>Also the mid point of R5 and R6 should not be connected to the center tap of the pulse transformer and the jack side of the Output transformer should have a small, high voltage cap to chassis ground at its center tap</p>

<p>I'm designing an Open Hardware door-lock-controller for our hackerspace, to these basic requirements:</p> <ul> <li>Be made exclusively from available and inexpensive parts.</li> <li>Read external Wiegand keyboard</li> <li>Read external Wiegand RFID reader</li> <li>Control various door-locks and other actuators.</li> <li>Read 125 kHz EM4100 RFID directly with an onboard reader.</li> <li>Passive POE powered, to make cabling easier.</li> <li>Run off unregulated 15-30V DC (cheap and easy high-capacity UPS via SLA)</li> <li>Provide a regulated 12V DC out @ 300 mA to 1.5A peak for external gear.</li> <li>Talk Ethernet to the server.</li> <li>Keep a local list of allowable keys, so only power is needed to let us in.</li> <li>Control external 230V gear using two relays.</li> </ul> <p>This is the second spin of the PCB with a few changes to fix the problems I've found, the biggest change I've made is to throw away the LDO that regulated the 3.3V rail, in exchange for a simple MC34063 based switcher.</p> <p>I'm pretty sure it's going to work, but I'd like some comments to check if I've overlooked something.</p> <p>Compromises I've had to make in the design are:</p> <ul> <li>The primary (35V) capacitor is stacked on top of the Ethernet transformer to save space.</li> <li>The Ethernet transformer is huge, but I have a bunch of them and they were cheap, so I'm going to use them, even if they are huge.</li> </ul> <h1>Main questions</h1> <ul> <li>Is there a cheaper and better way to implement the two power supplies (I need around 200mA@3.3V and 300mA@12V with peaks to 1.5A) ?</li> <li>Does the MC34063 switcher circuit/layout look sane?</li> <li>I have no idea how inefficient the MC34063 is so I've tried to heat sink it as well as possible using the copper I have available, any hints for improvements?</li> </ul> <p><a href="http://www.hackaarhus.dk/forum/download/file.php?id=33" rel="nofollow noreferrer">Schematic in pdf</a></p> <p><a href="http://www.hackaarhus.dk/forum/download/file.php?id=32" rel="nofollow noreferrer">Click to embiggen PCB image</a> <img src="https://i.stack.imgur.com/LSTpR.png" alt="alt text"></p>

(Why) does this design suck?

2010-11-10T20:46:59.500

6552

|soldering|

<p>You found out that the copper plane takes <em>a lot</em> of heat away, so that the temperature at the via will hardly be high enough to melt the solder. When the vias are connected to the plane they will be through thermal reliefs, which isolate most of it from the plane, leaving only a few bridges to make the connection.<br> I would use a Dremel Moto-Tool with an engraving tool bit </p> <p><img src="https://i.stack.imgur.com/eFlr7.jpg" alt="enter image description here"></p> <p>to cut away part of the copper around the via to emulate these thermal reliefs. This may require some patience, but I guess just trying to solder was taxing your patience as well. :-) </p> <p>What also might work is to separate the bridging operation from the plane soldering. The bridge will require rather much solder before it connects to both ground plane and via. First solder a tinned wire on the ground plane, so that it runs over the via, or maybe even insert it into the via. You'll see that soldering it then to the via is a piece of cake. (The ground plane will remove enough heat from the wire that this side won't come loose again.)</p>

<p>I have boards that through a mistake of my own have a bunch of vias that <strong>should</strong> connect to the ground plane, but are actually isolated. See all of the holes that are isolated:</p> <p><img src="https://i.stack.imgur.com/oldZK.jpg" alt="alt text"></p> <p>So, I need to bridge all of them to the ground plane. Since there is no solder mask I figured I could just use solder to bridge the connections. Here is what my solution looks like:</p> <p><img src="https://i.stack.imgur.com/7iV0c.jpg" alt="alt text"></p> <p>Not so pretty. I am wondering if there are any suggestion of what I can do to short these in a better manner. I will have it fixed in my next board revision, but it is a few weeks before I will have the boards and need to solder a few of these up now.</p> <p>ADDITION: The biggest problem I was having was the ground plane heated up very slow and It didn't seem to want to stick to both the pad and the ground plane at the same time.</p>

How do I neatly bridge to a ground plane?

2010-11-10T21:24:57.113

6561

|debugging|8051|

<p>I have been using Mon51 with the Cypress FX2 for going on 10 years with very good success. In addition we use the RTXtiny task switcher and code banking. I have found the monitor to be generally solid and with enough functionality for our needs.</p> <p>To use it we had to "von neumanize" our memory; logically AND PSEN# with RD#, which hasn't been a problem.</p> <p>We also use the hardware bootloader from serial eeprom which also works tremendously well in my opinion.</p>

<p>I'm working with an 8051 (Cypress FX2LP) that doesn't have jtag/bdm capability. Typically, developers on this project have been using ad-hoc serial printfs for debugging. I'm looking into options for serial debug monitors such as Keil's Mon51, Isd51 or IAR's generic ROM-monitor.</p> <p>I'll need to modify/configure this debug monitor to write to code RAM (to set software breakpoints). I'd guess that most 8051 debug monitors offer the ability for such modifications in order to support Harvard architecture or bank switching.</p> <p>The Keil tools come with Mon51 and Isd51. The Isd51 is very small and comes as source that can optionally be embedded in the application. C:/Keil/C51/ISD51/Examples/Generic_8052 works as-is on the Cypress eval board. This can all be done with the free Keil eval (subject to the eval size limitations).</p> <p>This pdf <a href="ftp://www-s.ti.com/pub/data_acquisition/MSC_CD-ROM/Application_Notes/sbaa078_MSC1210_Debugging_Strategies.pdf" rel="nofollow">'MSC1210 Debugging Strategies'</a> from TI, explains some strategies for serial debugging on an 8051.</p> <p>If this Cypress part had jtag/bdm - it would be a no-brainer - I'd use that. </p> <p>Does anybody have recommendations for serial debuggers for 8051 or similar processors?</p> <p>Have you had to modify it to write to Harvard code RAM or flash etc?</p>

8051 serial debug monitors

2010-11-11T02:58:37.590

6563

|peltier|

<p>Peltiers are almost always a disappointment. You will find that the fantastic headline figures they quote are always for when there is no temperature gradient across the device. </p> <p>In reality that's rarely what you want (particularly if when you're trying to get something cold, rather than merely stop it getting hot). The device itself acts as a thermal short-circuit, busily conducting heat back from the hot site to the cool side.</p> <p>I'm not saying they're useless, but ultimately your question is unlikely to be 'how much can I under-drive this device' and much more likely to be 'how much can I squeeze out of this (and the poor PSU) by running it at 120%'.</p>

<p>Say I've got a peltier block that is rated at 15.2V and 6A, providing 90W of cooling power to one side. </p> <p>Will I be able to operate it at 5V, and will it draw 2A, providing 30W of cooling power?</p> <p>EDIT: sorry, error above. :P brain was not working. 5V and 2A would indeed be 10W instead of 30W above.</p>

Are peltier devices linear?

2010-11-11T05:16:28.920

6565

|prototyping|oscilloscope|probe|

<ol> <li><p>Get a header of 0.1" pins.</p></li> <li><p>Attach this to your prototype board with hot glue or double-sided tape, securely enough that you can attach test probes without it pulling off. Or glue on a suitable piece of protoboard and solder the header to that.</p></li> <li><p>Get some small gauge enameled magnet wire and connect each node you are interested in to the header.</p></li> <li><p>Get a paper label of appropriate size and label all of the debug connections.</p></li> </ol> <p>Obviously, this is no good for RF or precision analog or very high-speed digital circuits. For those things a very short ground path is needed.</p> <p>I have lately switched to Digikey part S5493-ND (picture follows). This mates with the <a href="http://www.seeedstudio.com/depot/open-workbench-logic-sniffer-p-612.html" rel="nofollow noreferrer">Open Workbench LA</a>. Or I can plug a normal pin header in for oscilloscope connections or whatever.</p> <p><img src="https://i.stack.imgur.com/Bd7Bz.jpg" alt="enter image description here"></p>

<p>I still haven't found a really good solution for grabbing tiny surface mount stuff.</p> <ol> <li><a href="http://en.wikipedia.org/wiki/Crocodile_clip" rel="noreferrer">Alligator clips</a> are definitely way too big.</li> <li><p>Mini-grabbers like this with the spring-loaded hook are an ok solution for bigger stuff, but no good for little surface mount components. I can solder on little bits of wire and then mini-grab those, but it's tedious and time-consuming. And in my experience they tend to be broken more often than not:<br> <img src="https://i.stack.imgur.com/u1sjA.jpg" alt="minigrabbers"></p></li> <li><p>I got some Tektronix KlipChips and some HP 5090-4356 clips on eBay.<br> <img src="https://i.stack.imgur.com/YjmDy.jpg" alt="Tektronix KlipChips and HP 5090-4356"><br> The Tektronix clips are hard to open, because the plastic head tips to the side and jams instead of sliding down when you try to squeeze it. The HPs don't have that problem. The Tek pincers are made of wire, so they splay out sideways instead of grabbing well (and get permanently bent, making them jam on each other and not close completely, so connections to thin wires are intermittent).<br> <img src="https://i.stack.imgur.com/VKH8N.jpg" alt="Wire tips jammed together"> </p></li> </ol> <p>The HP pincers are made of thin strips of metal, so they are more rigid in that direction. The wire pincers depend on the bendiness of the wire to overlap each other side-by-side (which doesn't work very well) while the HP pincers fold inside each other, with one a little shorter than the other. This seems to work better, but they get bent outward, and the tubes are plastic, so they get bent outwards by any angular stress and no longer close well.<br> <img src="https://i.stack.imgur.com/WllQz.jpg" alt="Tip splayed open"><br> The orientation of the pincers on the HP relative to your fingers is more natural. </p> <p>These work on SOICs or bigger, but after they've become worn they don't stay on as well. They don't work for surface mount resistors (they just pop off if disturbed even a little) or smaller-pitch ICs.</p> <p>And I've broken the retractable hook tip for oscilloscope probes by attaching it to a circuit and then letting go, and the weight of the bulky probe and wire put too much stress on the plastic tip and bend it. </p> <p>Ideally I'd like something that can grip one side of a surface mount resistor, or a pin on a smaller pitch IC, not fall off, not produce any stress on anything, and not break easily. Any advice, ideas, tips, tricks, ingenious alternatives, cheap Chinese knock-offs of better clips?</p> <p>(Previously asked on <a href="http://forums.xkcd.com/viewtopic.php?f=18&amp;t=20673" rel="noreferrer">xkcd forums</a> and <a href="http://forums.adafruit.com/viewtopic.php?f=8&amp;t=5659" rel="noreferrer">adafruit forums</a>.)</p>

What do you use to probe small circuits quickly?

2010-11-11T06:07:55.677

6574

|charge|

<p>this isn't what charge pumps are really designed for, they aren't variable input regulators but supply multipliers/dividers/inverters. They're not really designed to be fed an unregulated voltage.</p> <p>Just use a <a href="http://www.linear.com/pc/productDetail.jsp?navId=H0,C1,C1042,P88521" rel="nofollow">buck converter</a> or a <a href="http://www.linear.com/pc/productDetail.jsp?navId=H0,C1,C1040,P86928" rel="nofollow">linear regulator</a>, examples linked.</p>

<p>Related to my <a href="https://electronics.stackexchange.com/questions/6534/3-3v-10ma-from-5v-35v">last question</a>, I decided to go with a step-down charge pump to convert 5V to 35V down to 3.3V at 10mA, due to the smaller required component size. However, I can't find a single charge pump IC rated to go up to 35V. Does anyone have any suggestions? If there are no ICs to do this, woudl there be any way of dropping 35V down to 18V with minimal loss and a small surface area?</p> <p>I'd also be open to using a buck regulator, but it seems like a waste for only 10mA.</p>

High input voltage charge pump

2010-11-11T13:40:23.460

6584

|remote|button|repair|

<p>I saw on another page to hammer out cuts of copper wire flat then glue them to the the button backs. </p>

<p>On almost every remote controller the buttons stop reacting after a while, and you end up squeezing the remote out of his life while trying to switch the channel...</p> <p>I found some <a href="http://www.wikihow.com/Repair-a-Remote-Control" rel="noreferrer">link</a> where it explains how to "refresh" the contact-making surface on the backside of the buttons, but that kit is not something I can find around. Could you suggest what would be a good replacement?</p>

Fix remote controller button contacts

2010-11-11T18:09:41.140

6588

|components|prototyping|development|

<p>Go to a vendor that might sell it, then check their cross reference. For example for a National analog part I would go to TI, Linear and Analog Devices. Also their FAE or the distributor's FAE.</p>

<p>I was looking for an equivalent MOSFET and haven't had any success.</p> <p>I'd like to know if are there any websites or software which gives a list of alternative equivalent components?</p> <hr> <p><strong>Edit:</strong></p> <p>The purpose of this question is not only for MOSFET's, but for any type of component. </p> <p>I want to learn how to find equivalents (or similar) components without having the need to ask about specific components here.</p>

How does one find an equivalent component?

2010-11-11T18:48:18.000

6591

|led|ac|dimming|

<p>There are far less complicated ways to achieve what you want to do at a reasonable cost. There was a recent article on Planet Christmas about pixel lights where each individual LED is controllable. The WS2812 light string mentioned above is one example. I recently came across two 5 meter WS2811 ribbon strings at a local second hand store. They operate on 12V DC. I bought a controller on eBay for $12 that works with WS2811 and WS282B. It has 160 built in sequences on a remote control plus it has the option for four DIY programs. It also works with voice control by connecting to Alexa or your smart phone using something called the FairyNest app. It's pretty amazing for something with so many options. I tested it with the canned applications and was very happy with just those. It will control up to 900 pixels and has two separate outputs. You can search &quot;WiFi Music LED Controller For WS2812B WS2811 Addressable RGB Pixel Lights&quot; for similar controllers.</p>

<p>I'm planning on building some dimmable lighting controller for Christmas lights, but with LEDs being all the rage nowadays, I was thinking that instead of using TRIACs and dimming at 60/120 Hz, I would rectify the AC to DC and use MOSFETs to reduce the strobing that is more evident in LEDs. This might allow the controller to be smaller and/or cheaper.</p> <p>This would depend on how the LED strings are actually wired up. I don't currently have any to look at, and I could imagine a few different ways they might be connected, such as diodes that only conduct for half the cycle, which would axe the DC idea if true.</p>

How are LED Christmas lights wired?

2010-11-11T19:19:59.607

6593

|arduino|usb|serial|spi|interface|

<p>With proper hardware, Windows can handle serial communication up to 921600bps (115200 x2, x4, x8). There are PCI communication cards that support this baudrate, but more popular are USB&lt;>RS232 convertors. If I remember well, all FTDI based convertors can handle it. The bigger problem is AVR side, where you will not be able to do anything else while data is received. RX should be the only interrupt allowed on AVR side. You will also probably have to clock your AVR as high as you can (16 or 20MHz depending on the model, 14.746 Mhz if you want to have <a href="http://www.wormfood.net/avrbaudcalc.php?postbitrate=921600&amp;clock_speed_table=on&amp;postclock=20" rel="nofollow">921600 exactly</a>). Then you will send from PC the whole communication packet, AVR does the job after receiving it, and sends acknowledge byte that it is ready for next packet. When PC gets acknowledge then it can send another packet. And so on... Simple timers on PC side are (because of multitasking in windows) very bad at handling 10ms like resolution and they are not accurate at all (except multimedia timers when handled properly), so using simple acknowledge byte already described is a much better option.</p>

<p>I need to send 800 bytes of data from a computer to an arduino board every 20ms (approximately). I began with the serial library which works nicely but it is too slow even at its highest rate (115200 baud) for interfacing with a computer.</p> <p>What other interfaces are available that can send at a faster rate? Can I use usb or spi? I can't seem to find libraries for these. I need something with about a 320 kBaud rate.</p> <p><strong>edit</strong></p> <p>Are there any shields that might be able to do this? Bluetooth or wifi?</p>

Computer to Arduino Interface Options

2010-11-11T19:30:54.377

6594

|potentiometer|

<p>Nick has it pretty much dead on. Whenever modeling a Sensor, motor etc you will find that you end up with a very broad range that often makes it difficult to fine tune things. Adding to what Nick said there is also the difference between static and dynamic friction the means you will have different frictions and oppoing forces depending on how the arm i moving or if it is stopped. The best solution is to design it for the worst problem X 2 then your covered.</p>

<p>I've got a Chinese pot datasheet, and the rotational torque is listed as "20~200gf.cm".</p> <p><a href="http://www.bourns.com/data/global/pdfs/PDB182-GTRB.pdf" rel="nofollow">This Bourns datasheet</a> lists </p> <blockquote> <p>Rotational Torque ............. 10 to 150 gf-cm</p> </blockquote> <p>Why such a wide range? Is this a tolerance issue, or is it something like the difference between slip and stick friction?</p>

Meaning of potentiometer torque measurements

2010-11-11T20:03:46.277

6607

|arduino|netduino|

<p>The problem is that the Netduino uses the USB port for communicating the debugging information required so you can live debug through visual studio.</p> <p>It is possible to switch the Netduino and use an FTDI serial cable to do the programming/debugging which will leave the USB port free for communications. There is a thread about this <a href="http://forums.netduino.com/index.php?/topic/178-serial-communication-between-the-computer-and-the-netduino/" rel="nofollow">on the Netduino forums</a>.</p> <p>There are also discussions <a href="http://forums.netduino.com/index.php?/topic/449-serial-comms-via-usb-in-the-cards/" rel="nofollow">here</a> and <a href="http://forums.netduino.com/index.php?/topic/481-serialread-via-usb-yu-know-like-on-the-good-ol-arduino/page__p__3549__hl__serial__fromsearch__1#entry3549" rel="nofollow">here</a> that confirm they are working on the problem.</p>

<p>A <a href="http://forums.netduino.com/index.php?/topic/366-netduino-serial-port-code-review/" rel="nofollow">serial port demo</a> shows how to use GPIOs to communicate through a second USB connection.</p> <p>But as a Arduino developer I'm used to use the same USB for both programming and runtime communication.</p> <p>Can I do the same with Netduino?</p>

Can I use the Netduino USB as a serial port?

2010-11-12T01:59:11.143

6614

|sensor|

<p>One solution I see in use a lot is having rubber hoses stretched across the road surface. They are sealed at one end, and have a pressure sensor at the other end. By having one at the end of an intersection (counting the outflow) and having one as far back as plausible (counting the inflow) you can get a count of how many axles are waiting at that intersection. It could also be done with IR beams, similar to the entryway chimes at some stores.</p>

<p>My idea is to implement <code>Automatic and Dynamic Traffic Control System</code>.</p> <p>I want to get the Vehicles density that were stopped along in all the roads in a particular junction. I want to get the binary information. For ex: If I get 1111s that means it has the highest traffic. If I get 0001s that means it has very less traffic. </p> <p>Something like this. I am Ok if I get the information in any other format. I can redesign my implementation.</p> <p>Based on the information I will change the timings for each road to clear.</p> <p>I have implemented the logic using a simple flash software. But I need to implement this on board for the demo purpose. The sensor should cost low. Or any other circuit from which I can get information is also very helpful. </p>

Is there any Low cost sensor or sensory circuit which can figure out the Traffic density in a Junction?

2010-11-12T05:11:37.330

6621

|sensor|adc|

<p>The <a href="http://en.wikipedia.org/wiki/Piezoresistive_effect">piezoresistive effect</a> just means the resistance of the sensor changes with pressure. With their circuit, the -5 V supply will be inverted and amplified with the gain varying with the sensor resistance. The output voltage will vary from 0 to 5 V.</p> <p>Instead of using a -5 V supply, you could just connect the bottom of the sensor to ground, and connect the positive input of the op-amp to a 2.5 V bias voltage. Then the voltage at the output would vary from 2.5 to 5 V.</p> <p>Depending on what you're using it for, you could just <a href="http://www.doctronics.co.uk/voltage.htm">connect it as a voltage divider</a>, and then follow that by an inverting amplifier with an adjustable gain and DC bias so that you can get 0 to 5 V for whatever pressure range you want.</p>

<p>I recently purchased piezoresistive <a href="http://www.tekscan.com/flexible-force-sensors" rel="nofollow noreferrer">Flexiforce pressure sensors</a> but I´m having some problems connecting it to an A/D converter.</p> <p>On their website <a href="http://www.tekscan.com/flexiforce-sample-circuit" rel="nofollow noreferrer">they show an example of an excitation circuit</a> but it is using negative voltage which is something I don´t have access to. I need to make a circuit that does pretty much the same thing but with only positive voltage.</p> <p>This is the circuit they recomend:</p> <p><img src="https://i.stack.imgur.com/KQH0O.jpg" alt="alt text"></p>

Flexiforce pressure sensor with positive voltage

2010-11-12T13:10:04.950

6625

|layout|stripboard|

<p>For simple projects on Veroboard, they're exactly equivalent electrically. However, there are other things you need to consider.</p> <p>However, I think that a better question is to ask whether they're equivalent to you. </p> <p>There's been some research (I can't remember where at the moment - Can anybody help?) that there's an inverse correlation between the number of wires coming from a single node and the readability of a schematic. For some circuits it makes sense, but for others it makes more sense to treat one wire as a bus and have the others coming off of it at different points instead of one crowded location on the schematic.</p> <p>On a more physical sense, consider the ease of reworking the above wires. If you wanted to remove or replace a component, would it be easier to work on a joint which branches in three directions or just connects to a single wire?</p> <p>They're electrically equivalent, but there are differences in their perceived meaning in a schematic and their physical construction.</p>

<p>I'm currently trying to lay out my first from scratch project on veroboard. While I get connecting things in series and parallel I'm trying to work out if a + shaped connection and a pair of + shapes would be equivalent. </p> <p><img src="https://i.stack.imgur.com/O3bfV.png" alt="T shaped connections"></p> <p>Would they?</p>

Layouts - would a joint at 1 point, or 2 be the same?

2010-11-12T13:48:11.863

6629

|led|power|light|

<p>Those little T1-3/4 LEDs aren't very good for illumination. The high power ones are more efficient. Check out DIY forums on www.candlepowerforums.com for really good resources on LED lighting and flashlights. </p>

<p>I'm thinking about making a simple LED flashlight. </p> <p>After doing some research, I think I'm going to use some 5 mm 12 Cd white LEDs with 3.6 V drop which can pass 20 mA. I'm not yet sure how much LEDs I'd need, but for now, I'm thinking about 5 or 10.</p> <p>For power supply, I was thinking about single 6LR61 battery or 4 serially connected LR6 batteries or maybe even two serially connected 6LR61 batteries (but I'd like to avoid that as 6LR61 are pretty expensive here). </p> <p>The 6LR61 batteries popular here according to data sheet have capacity 550 mAh while LR6 have capacity of 2600 mAh. Minimal voltage for 6LR61 is 4.8 V and 0.8 V for LR6. Since LR6 batteries have considerably higher capacity, I'm most likely going to use them, unless you provide a reason why to go with 9V battery. Also, if I serially connect batteries, would pack's capacity increase?</p> <p>As for circuit itself, I was thinking something like battery pack with a switch serially connected to it. I'd the use parallel connection to connect a number of branches consisting of a resistor and LED to the switch on one end and battery pack on the other end.</p> <p><img src="https://i.stack.imgur.com/6MBVz.png" alt="circuit sketch"></p> <p>However I'm concerned about energy usage. I'll have lots of resistors and each one will consume some energy. If I go for 9 V option or even 18 V option, I'd reduce amount of energy wasted by resistors, since I could connect several LEDs serially with a single resistor.</p> <p>Another point which bothers me is what type of resistors to choose. I'd like to use up as much of the batteries as possible and have device work as long as possible. I've been experimenting with results form <a href="http://ledcalc.com/" rel="nofollow noreferrer">http://ledcalc.com/</a>, but I'm still not certain what to choose.</p> <p><strong>EDIT 1</strong><br> Another idea: Would a 555 timer plus a transistor as a switch be a good choice for making device PWM controlled?</p>

Need comments and ideas for LED flashlight project

2010-11-12T15:07:32.197

6631

|analog|dc-motor|555|

<p>You can use an inverter chip connected to your 555 timer output. That way you will get two signals, your normal 555 timer output and an inverted version. It sounds like you can use these two signals for your H-bridge.</p> <p>555 timer output connected to H-bridge input A and inverter input, inverter output connected to H-bridge input B.</p>

<p>I am trying to design an analog direction driver circuit for an H-bridge configuration on a small DC motor. I have a pretty tight space constraint, and a simple requirement for my design, hence why I am trying to avoid microcontrollers. What I want to happen is for the motor to travel in one direction for 2.5 seconds, then to switch directions and travel for another 2.5 seconds. That's it for right now. In my design so far I have a 555 timer driving the timing side of things, and it is giving the desired output (HI for 2.5, OFF for 2.5 seconds). I also have the motor driver circuit built and functioning such that:</p> <p>Input A = LO, Input B = HI - Output=Clockwise</p> <p>Input A = HI, Input B = LO - Output=Counter-Clockwise</p> <p>If In A = In B, Output = Stopped</p> <p>My question is: How can I use the output of the 555 timer to drive the inputs of the H-bridge in the manner mentioned above? I am missing the link between the two sides of the circuit, and was wondering what suggestions you might have.</p>

555 timer as Dual Direction H-bridge driver

2010-11-12T15:37:23.833

6644

|schematics|checklist|dxdesigner|

<p>A list I use for Multisim:</p> <ul> <li>Do all tantalum caps on rails have at least ~20% overhead? No 25V caps on 24V lines?</li> <li>Are there bypass caps on the power rails of <em>every</em> chip? Even the ones that don't look like chips, like regulators?</li> <li>Are there filters on <em>every</em> transistor gate/base? Even the ones in processors?</li> <li>Are there filters on A/D converter pins?</li> <li>Are there pullups or pulldowns on <em>every</em> pin where it could matter? Look especially for diodes driving processor inputs or transistor gates, or hanging off an input to the board. Also, outputs of comparators.</li> <li>Is there impedance on every pin feeding directly into a processor from off-board? A transistor? <em>Something</em> to eat noise and keep it from frying your chip?</li> <li>Do you have test points on all rails and signals of interest? Including at least one debug pin off any processor?</li> <li>Is there an LED to indicate power to the board? A second LED, processor controlled, for blink codes?</li> <li>Is there <em>too much</em> cap on any power rail? Switching regulators have a limit on how much cap they can pull up.</li> <li>Are all op-amps negative feedback, and all comparators positive feedback? (Obviously there are exceptions to this, I just find it a useful basic rule to check in my applications.)</li> <li>Are all op-amp and comparator power rails connected in the correct polarity?</li> <li>Are there any capacitors or zeners directly on the output of an op amp? Should be impedance between.</li> <li>Are all unused op-amps and comparators tied down properly? Tie op-amp outputs to the negative input, and tie the positive input to common. Tie to common all pins on an unused comparator.</li> <li>Do all optocouplers have resistors and caps in parallel with their diodes, for noise immunity?</li> <li>Make sure all user accessible power rails are short-circuit protected.</li> </ul>

<p>I'm looking for a good schematic capture checklist to use when reviewing schematics. This is for the usual issues such as check that you don't have similar but different nets (e.g. GND and GROUND) that are separate and style/readability issues (e.g. no 4-way ties). Either your list or a link to an external one would help.</p> <p>For what it's worth, I'm using DX Designer, so if you have specific checks you run, let me know about that too.</p>

Good schematic checklist

2010-11-12T17:59:36.880

6647

|capacitor|ceramic|ldo|

<p>ceramic should work as long as you meet the requirements in the datasheet: 0.1ohm &lt; esr &lt; 5ohm and srf > 1mhz. </p> <p>Its probably easier to find those properties in a tantalum cap, especially back in 2002 when that datasheet was released.</p> <p>EDIT: Some more info about LDO stability and why the ESR has to fall in a particular range.</p> <p>A generic LDO works by comparing the output voltage to an internal voltage reference with an error amplifier and driving a PNP transistor to correct for this error. </p> <p>The problem comes in when you look at the phase shift and loop gain of this feedback path. The error amplifier and the load being driven both contribute poles to the frequency response of the feedback loop. These poles act as a low pass filter resulting in loop gain decreasing as frequency increases. As we know a pole also introduces a negative phase shift. If this phase shift is allowed to reach -180deg the feedback loop becomes unstable and the LDO will oscillate. </p> <p>What this means is that every time the error amp tries to compensate for an error the result of its correction is 180deg out of phase, or inverted, consequently the error amp is basically thrown for a loop and begins making the opposite correction that it should be making, resulting in wild instability.</p> <p>To avoid this situation we need to prevent the phase shift in the feedback loop from ever getting to -180deg, actually we only need to keep it from reaching -180deg within the region that the LDO can generate gain > 1 as the damped response of the system past this point will prevent oscillation. This frequency is defined by the unity-gain point of PNP pass transistor.</p> <p>The way we prevent this phase shift is by using a capacitor with a ESR in a certain region. The capacitance will shift the pole created by the load but more importantly the ESR will contribute a higher frequency zero. Basically you've added a high pass filter to the feedback loop. The phase shift introduced by the ESR will work to counteract the phase shift introduced at lower frequencies by the poles from the error amp and the load. </p> <p>The reason that the ESR has to be in a particular range is that if its too low, the zero contributed to the frequency response will be located very high in frequency, above the unity-gain point of the pass transistor. As a result its not effective in making sure the phase shift of the feedback loop doesn't reach -180deg before the unity-gain frequency.</p> <p>If the ESR is too high, the zero will be very low in frequency. There is another pole in the frequency response created by the parasitics of the pass transistor, if the zero from the capacitor ESR is too low in frequency, this pole will be reached while we still have gain > 1, this will cancel out the effect of the ESR zero and we will likely reach -180deg phase shift before we reach unity gain.</p> <p>All that said, these problems are indicative of older LDO designs. Many/Most/All new designs include additional internal compensation in the feedback loop which uncouples LDO stability from the ESR specification of the output capacitors.</p>

<p>I have a negative LDO (-5V from -5.5V to -10V) which requires a tantalum or aluminum capacitor. I'm wondering why it can't use a ceramic capacitor? Is there any specific reason for this?</p> <p>Regulator is a TC59 (<a href="http://ww1.microchip.com/downloads/en/DeviceDoc/21438b.pdf">datasheet</a>).</p> <p>(Correction: the regulator I originally gave was stable with ceramics, this one is not.)</p>

Tantalum capacitors vs. ceramic capacitors

2010-11-12T18:33:52.693

6651

|soldering|surface-mount|surface-mount|

<p>Perhaps attaching a small flat piece of aluminum to a conventional solder iron tip would work. Solder will not "wet" or flow onto aluminum. But the aluminum would get as hot as the tip. </p> <p>First get solder onto each pad, using an iron or solder paste. Position the chip on top. Press the flat edge of the hot aluminum against all the chip leads along one side of the chip at once. The heat will reflow the solder already there.</p> <p>I haven't tried this yet.</p>

<p>I have a MSOP10 package with an exposed pad. How do I solder this, if at all possible, with just my temperature controlled iron?</p>

How to solder MSOP-EP package with just an iron?

2010-11-12T19:29:26.830

6653

|components|switch-mode-power-supply|ratings|

<p>The answer is "all of the above".</p> <p>For saturation of the chokes, you need to worry about the peaks. If the choke saturates before your transistor turns off, your peaks will be much higher than you expected! Which has effect on things like EMF spray and inductive kicks, but also on the RMS currents, and thus heating. Not to mention making your entire system non-linear and difficult to control.</p> <p>Heating for most components, including FETs, is about RMS current. Power loss is proportional to the square of the RMS current. One exception is if you're talking about a junction drop (say across a diode, BJT, or IGBT). Thermally, those components can be roughly modeled as a fixed voltage source in series with a resistance. The power loss in the resistance is proportional to the square of the RMS current, like any other component. But the loss in the fixed voltage source is proportional to the average current. So average current <em>can</em> matter for heating.</p> <p>Now, RMS current is a function of peak current. What function depends on the shape of the wave; you can get the same average current and wildly different RMS currents. A 1 mS 1000A pulse has the same average current as a continuous 1A DC, but over 30x higher RMS. So by reducing your peaks and otherwise maintaining the same general wave shape, you should also reduce the RMS current.</p> <p>So if you know the RMS current through the FET, and the RDS of the FET, you can find the losses in the FET. Knowing your ambient temperature, the max junction temperature of the FET, and the thermal resistance between the junction and ambient (accounting for any heat sink attached), you should be able to determine whether a given FET will survive the currents.</p>

<p>I am designing a SEPIC supply around an LT3757. The MOSFET will have ~6.5A pulses with a strange ramping pattern (see image), but the RMS current is only 3.38A and the average current is 2.60A. Assuming 50% over-rating, which rating should I be looking for in a suitable FET? Also, does this apply for resistors, inductors and capacitors, or are there other specifications to look out for?</p> <p><img src="https://i.stack.imgur.com/lX1wt.png" alt="alt text"></p>

Should I select components based on peak current, RMS current, or average current?

2010-11-12T19:48:50.703

6657

|inductor|sepic|

<p>In support of what Marc &amp; Jose said, the inductor dot indicates where the wire starts to be rolled on the core. Because that dot point is below the rest of the windings, it is shielded by them. In a SEPIC or other switch mode designs, the SW node is basically your noise source, and you want to make sure you wire the shielded dot point to your noisy SW node.</p> <p>SOURCE: <a href="https://ez.analog.com/power/f/q-a/117901/lt8362-coupled-inductor/370556" rel="nofollow noreferrer">Larsen at ADI Engineer Zone</a></p> <p><strong>Emissions Example #1</strong>: The URL in Jose's post is now a dead link, but while searching the Wurth website, I found that the middle section of <a href="https://www.we-online.com/web/en/electronic_components/news_pbs/blog_pbcm/blog_detail-worldofelectronics_109450.php" rel="nofollow noreferrer">this blog entry</a> emphasizes the importance of putting the inductor dots toward the switch node. It provides E-field &amp; H-field emissions graphs.</p> <p><strong>Emissions Example #2</strong>: <a href="https://www.analog.com/en/analog-dialogue/articles/does-the-assembly-orientation-of-an-smps-inductor-affect-emissions.html" rel="nofollow noreferrer">AnalogDialogue</a> shows several emissions graphs from both inductor orientations, and explains that the polarization indicator is a line (not a dot) on some Coilcraft inductors. The article goes on to explain what to do when no polarization indicator is present.</p>

<p>I have a SEPIC supply with coupled inductors. The inductors have phase dots. What do these "phase dots" mean? Is it important to have the phase dot in the same place?</p>

What do phase dots on an inductor mean?

2010-11-12T20:55:26.203

6664

|capacitor|

<p>Some capacitors exhibit capacitance which varies with voltage. As a physical analogy, a "perfect" capacitor will behave as a cylinder filled with liquid (adding a particular volume of liquid will increase the pressure, always at the same rate) while some caps behave more like a point-up code (the amount of liquid required for each unit increase in pressure decreases as the cap fills up). Note that beyond the fact that one may have to use a higher-rated cap to get the capacitance one wants at the actual working voltage, there's another consequence of this behavior for intermittently-powered devices in battery-operated systems: whereas a normal cap will take 9/16 as much energy to charge to 3 volts as to charge to 4 volts, a cap with whose capacitance decreases with voltage will require more energy for the lower-voltage part of the charge. If a cap will be charged to 4 volts and needs to supply a certain amount of energy before the voltage drops to 3 volts, the latter cap will effectively waste more energy each time it's switched on.</p> <p>What would be ideal would be if someone could construct a cap which had the opposite sort of behavior--something electrically equivalent to a cap wired in series with a battery (so that capacitance would be maximized at voltages near the battery voltage). There would be no net current flow into or out of the battery, but shifting the maximum-capacitance voltage would allow intermittently-powered devices to work more efficiently. I wonder if using different metals for the anode and cathode of a cap would have such an effect?</p>

<p>I'm looking at some capacitors, namely ceramic, 10µF 50V caps. <a href="http://uk.farnell.com/jsp/search/browse.jsp?N=500006+1000225&amp;Ntk=gensearch_001&amp;Ntt=10u+50V&amp;Ntx=mode+matchallpartial" rel="nofollow">Here are the search results</a> on Farnell UK.</p> <p>Most are in big packages, 2220 or some form of stacked capacitor. But then there are the occasional X7R and X5R caps in 1206 and 1210 packages, like this one: <a href="http://uk.farnell.com/murata/grm31cr61h106ka12l/capacitor-1206-10uf-50v/dp/1845762" rel="nofollow">GRM31CR61H106KA12L</a>. It seems too good to be true, it's half the size of others and very low cost. It's not available yet, otherwise I would have bought some and tested them.</p> <p>Any opinions? Has anyone tried these?</p>

Large-value ceramic caps in small packages?

2010-11-12T23:19:18.847

6668

|comparator|

<p>In this context, it means that the comparator can be triggered by comparison of the inverting input against both of the two non-inverting inputs. My impression (though I'm not 100% certain on this) is that the inverting input needs to exceed <em>both</em> of the non-inverting inputs to switch the output. The input hooked to the soft-start pin is dominant at start up, but during normal operation, the 800 mV reference is dominant. This means that at start-up, the inductor current cycles more slowly than during normal operation.</p> <p>Here's the description from the datasheet of the what the comparator does during normal operation:</p> <blockquote> <p>The inductor current increases until either the current exceeds the peak current comparator threshold or the voltage on the VFB pin exceeds 800mV, at which time the high side power switch is turned off, and the low side power switch (N-channel MOSFET) turns on. The inductor current ramps down until the reverse current comparator trips, signaling that the current is close to zero. If the voltage on the VFB pin is still less than the 800mV reference, the high side power switch is turned on again and another cycle commences.</p> </blockquote>

<p>On page 7 of the <a href="http://cds.linear.com/docs/en/datasheet/3631fe.pdf" rel="nofollow">LTC3631 datasheet</a>, the diagram shows a comparator with two noninverting inputs. What does such a comparator do?</p>

Comparator with two noninverting inputs?

2010-11-13T00:54:53.197

6669

|datasheet|fault|

<p>Some devices can be very sensitive to stray conduction paths. For example, an ultra-low-quiescent regulator might have a multi-meg input impedance on its feedback pin. If a combination of board contamination and humidity allowed even 0.1 microamp to leak from the feedback pin to ground (equivalent to a 10M or so parallel resistance) that could cause the output of the regulator to be significantly higher than designed, potentially causing damage to the circuitry being supplied.</p> <p>I'm not quite sure how such a thing would be a problem here, though, since it would take 100uA of stray current on an input to cause erroneous operation. Further, while dust contamination could cause overheating of a metal-cased or heat-sinked part, I really wouldn't think that would be much of an issue with a plastic-cased DIP.</p> <p>Could the warning perhaps be boilerplate that appears in many data sheets, and is more applicable in some than others?</p>

<p>I read the following in the datasheet of <a href="http://www.hestore.hu/files/uln2803.pdf" rel="nofollow" title="ULN2803">ULN2803</a></p> <blockquote> <p>Utmost care is necessary in the design of the output line, COMMON and GND line since IC may be destroyed due to short−circuit between outputs, <strong>air contamination fault</strong>, or fault by improper grounding.</p> </blockquote> <p>I understand what short-circuit is, but what does "air contamination fault" mean?</p>

What is air contamination fault?

2010-11-13T01:07:26.853

6674

|books|

<p>According to <a href="http://www.eevblog.com/forum/chat/the-art-of-electronics-3rd-edition-finished-writing-and-copy-editing/msg286789/#msg286789" rel="nofollow">this newspost</a>, the writing phase is completed and the book is now in typesetting, scheduled for a mid-2014 release. </p> <p><strong>Update</strong> The book is scheduled to be released in <a href="http://www.cambridge.org/us/academic/subjects/physics/electronics-physicists/art-electronics-3rd-edition" rel="nofollow">April 2015</a>.</p>

<p>Will the 3rd edition be published ?</p>

When will the 3rd edition of "Art of Electronics" by Horowitz and Hill finally be published?

2010-11-13T03:18:41.080

6676

|led|components|spi|74hc595|pov|

<p>I hadn't looked at the 74HC4094, having always used the 74HC595, but the 74HC4094 looks like it has a couple of interesting differences:</p> <ol> <li><p>The load signal is level-sensitive, rather than edge sensitive, allowing the device to be used in a "transparent" mode, where bits from the input are immediately shown on the output.</p></li> <li><p>It has a cascading output which triggers on the same clock edge as the input, as well as a cascading output which is delayed by half a clock. Use of this latter output will greatly improve sample and hold margins when feeding the output of the device into another one; the former may be useful in some situations when feeding a device which is known to receive the clock before the data.</p></li> <li><p>The 74HC4094 does not have the asynchronous clear function of the 74HC595. There have been times I would have used the 74HC595's asynchronous clear if the load signal was level-sensitive (so that asserting clear and load simultaneously would clear the outputs), and times I would have used a synchronous clear (wire the cascade output to synchronous clear and synchronous load signals, and reduce communications requirement to two wires), but I don't think the signal will be missed on the 74HC4094.</p></li> </ol>

<p>I want to drive lots of LEDs in a spinning persistence-of-vision (POV) device. I need one output pin per LED, because matrix techniques don't work right in spinning POV devices. A serial-input, parallel-output (SIPO) chip is the best way to independently control lots of output pins using only a few pins on my microcontroller, right? Which SIPO chip should I choose?</p> <ul> <li>74HC4094 used in <a href="http://reprap.org/wiki/Doboz" rel="nofollow noreferrer">Doboz</a></li> <li>74HC595 used in <a href="http://code.google.com/p/bicycleledpov/" rel="nofollow noreferrer">bicycleledpov</a> aka <a href="https://electronics.stackexchange.com/search?q=spokepov">spokepov</a></li> <li>TPIC6595 used in ... (a POV device I can't find the link to right now)</li> <li>... or perhaps something I'm overlooking?</li> </ul> <p>Does one SIPO chip clearly have more capabilities or easier to use than another, or are they all more-or-less equivalent functionality? They all can be connected in the "<a href="http://en.wikipedia.org/wiki/Serial_Peripheral_Interface_Bus#Daisy_chain_SPI_configuration" rel="nofollow noreferrer">daisy-chain SPI</a>" configuration, right? If I only have room for one kind of SIPO chip in my box of <a href="https://electronics.stackexchange.com/questions/966/which-electronics-components-should-i-always-have-on-hand">"electronics components I always have on hand"</a>, which one should it be?</p>

Which SIPO chip is better, 74HC4094 or 74HC595 or something else?

2010-11-13T06:23:02.763

6681

|digital-logic|cmos|ttl|

<p>I'm playing around with TI's <a href="http://focus.ti.com/docs/prod/folders/print/tlc5925.html" rel="nofollow">TLC5925</a>, which is functionally very similar to what you're asking for. It is designed for driving LED's at a constant current, and the logic is 3.3/5V CMOS. The output is tolerant of up to 17V, although I don't know how well it would drive the outputs to logic levels. Not sure if this is suitable - just taking a wild guess at your intended application.</p>

<p>I've been looking for a 3.3V compatible shift register (SIPO) with latched open-drain outputs. I've settled on a 74xx596 (not a '595!), but of all the 74xx CMOS series I've been looking at omit this one. Any idea on why? and if it's possible to get CMOS variants of these, because of the open-drain outputs?</p> <p>Correction: I was getting confused between 595 and 596. 595 has tri-state outputs, 596 has open collector outputs.</p>

CMOS (or CMOS compatible) shift register with latched open-drain outputs

2010-11-13T11:22:20.080

6684

|antenna|

<p>Agree with the answers above. Just wanted to add that the zero-ohm type is not so uncommon these days. This could be a very popular PIFA antenna. You will not measure exactly zero ohm with PIFAs, loops or folded dipoles, the DC resistance would be a couple of ohms.</p>

<p>What should be the DC resistance of an external Wi-Fi antenna (when measured between center and shield of the SMA connector)?</p> <p>In case of: </p> <ol> <li>DIY "Pringles" antenna </li> <li>Consumer grade antenna, connected to external USB WiFi adapter</li> </ol> <p>I believe there should be no difference between #1 and #2, right?</p>

What is DC resistance of the Wi-Fi antenna?

2010-11-13T12:24:48.733

6687

|soldering|soldering|buying|

<p>You might be better off buying a second-hand STSS power unit (they often come up on Ebay) with the later MX-500 handpiece and cartridges. That's what I did. It works out a lot cheaper and you get a better system.</p>

<p>I am looking to upgrade my iron for SMT components and recon it's probably worth skipping the middle ground and getting myself a Metcal (as almost everyone I have asked has mentioned that they are close to as good as they get).</p> <p>I was looking on Farnell and <a href="http://uk.farnell.com/oki-metcal/mfr-1110/soldering-station-cartridge-style/dp/1629771" rel="nofollow">found one</a> at a reasonable price but it seems it has no temperature control. Is this something I need or would this iron still be an excellent investment?</p>

Metcal but no temperature control?

2010-11-13T13:24:52.507

6698

|wire|speakers|colour-coding|

<p>I've replaced connectors on a <em>lot</em> of different headphones over the years. What I have found is that there is <em>no</em> standard for wire colors. They are all different.</p> <p>Consumer headphones, professional headphones, intercom headsets: they are all different.</p> <p>The <em>proper</em> way to check to see which wire does what function is to measure it. </p> <p>Put the headphones on and do a continuity check between each of the wires. Listen for the "tick" that comes out as you touch each wire.</p> <p>Common to left hot: tick comes from left speaker. Common to right hot: tick comes from right speaker. Left hot to right hot: tick comes from both speakers.</p> <p>If you are using a multimeter on the low-ohms range, you will see that the left-hot to right-hot resistance is about double that from the common wire to either the left or right speakers.</p> <p>Bottom line: don't rely on wire colors. Test it and ensure that you get it right the first time.</p>

<p>How do I tell which wire is which if I have a copper wire, red and green coded wire? Is the unshielded copper wire ground?</p>

Headphone wire color coding

2010-11-13T19:54:43.967

6705

|failure|

<p>If you were using really old IDE cables without the bump to position it properly, it's possible you were off by a row/column of pins. I did this once in a highschool computers class and it definitely burned something on the drive, smoke and all.</p>

<p>I found an old 15 GB HDD lying around in a pile of spare computer parts. I decided to see if it would still work because it could be an emergency backup. So I plugged it into my ATX PSU only to find one of the chips on the board had several holes in it glowing red hot and it was smoking. A catastrophic failure! But why? What could cause the IC to fail so badly? The IC glowed for about 30 seconds before the supply tripped off. I have no idea on the circumstances of this failure - I did not do extensive tests, and I didn't examine the drive beforehand.</p> <p>It was something like this, <a href="http://www.youtube.com/watch?v=ni_PA0as47g" rel="nofollow">http://www.youtube.com/watch?v=ni_PA0as47g</a>, but a different IC, and a different drive.</p>

What causes an IC to glow RED hot?

2010-11-13T22:28:27.460

6706

|microcontroller|memory|flash|ram|documentation|

<p>Some basic information about different types of memory. Nice place to get started:</p> <p><a href="http://computer.howstuffworks.com/computer-memory.htm" rel="nofollow">http://computer.howstuffworks.com/computer-memory.htm</a></p> <p>Once you have an idea of the different types of memory out there, each one's purpose etc., then you can go into the detailed architecture.</p> <p>Basic information about Microcontrollers, also to get you started: <a href="http://www.howstuffworks.com/microcontroller.htm" rel="nofollow">http://www.howstuffworks.com/microcontroller.htm</a></p>

<p>I'm learning about the different kinds and functionalities of electronic memories (i.e. RAM, flash, etc) but I'm a little confused because all the sources show something different and I don't know which of them is correct.</p> <p>What manuals or documents are accurate?</p> <p>Documentation about micro-controllers would be good too. The purpose of this is only learning. I'm not looking for documentation about a specific device.</p>

Where can I find good documentation about memories?

2010-11-13T22:36:03.670

6712

|components|damage|

<p>The most common form of electrical damage to things is overheating caused by total power dissipation. In many cases, one can safely get by either limiting voltage to a very low level and not worrying about current, or limiting current to a very low level and not worrying about voltage. There are some exceptions, though:</p> <ol> <li>It is possible for excessive voltage to cause a sudden current flow, or for excessive current to cause a sudden voltage drop, and these currents or voltage drops may be sufficiently localized that damage can occur with very small total power dissipation. In some cases, particularly with overvoltage, it may possible for localized capacitance to hold enough energy to damage the device even if current is externally limited. <li>As others have noted, excessive voltage or current applied to a pin of a device which is powered may cause the device to enter a mode (such as latch-up) that converts a lot of supply power into heat. Even if the power into the over-voltage or over-current pin is limited, the supply may feed enough power to totally destroy the device. <li>Overvoltage and overcurrent conditions may accelerate physical or chemical changes in a device sufficiently to cause it to fail prematurely or go out of spec; an electrolytic capacitor which is charged beyond its rated voltage, for example, may have its dielectric gradually get thicker as a result, reducing its capacitance. Note that such effects can cause damage even if power dissipation is slight and cooling is sufficient to prevent overheating. </ol>

<p>With higher voltages (more than about 5V), microcontrollers may be damaged. Is this because the voltage actually physically damages them, or because it allows excessive current to flow? - and thus increases power dissipation beyond safe limits. How does this apply for other devices?</p>

Is it current (and power dissipation) which damages things, not voltage?

2010-11-14T00:15:06.363

6713

|how-does-it-work|

<p>Just had some fun trying to scope the signals, something really funky is going on there.</p> <p>"Here is a good web page" &lt;- that page? wrong! not what is happening there at all, there is only one input signal, not sin and cos</p> <p>"The key is using unevenly patterned conductors in proximity of two capacitors." &lt;-- wrong again</p> <p>If you ever find a webpage where someone has actually built a copy of one of these then i'll believe what they are saying.</p> <p>Anyway this is what i measured, cant find any of that info from google</p> <p>The vertical strips that are grouped by 8, these are connected to digital outputs of the chip on blob, they are driven by PWM signals - approximating sinewave. 8phases, sinewave period 1800us(YMMV), pulse period ~5.6us. Each phase shifted by 1800us/8 = 225us</p> <p>The receive plate gets the summa summarum that comes through stator by capacitive coupling. Now the receive signal is bunch of garbage mostly, but the signal peaks that correspond with output pulse rising edges do form a sinusoid. Phase of that sinusoid depends on position of the stator. Im guessing rx measurements must be timed with output pulses, and then there is some funky signal proccessing to get the phase shift, im not 100% sure on how to do the rx side of this.</p> <p>As stator pattern and pattern of tx plates repeats every 5mm that means the final value is summa of coarse and fine measurements. Coarse measurement is the count of 5mm repetitions, counted and remembered just like regular encoder values, you can mess this count up is you move the scanning head on the caliper too fast, caliper loses its 0 point. Fine measurement is the phase shift measurement of the output sinusoid. These are summed and displayed on the LCD.</p> <p>Here is an illustration: <img src="https://i.stack.imgur.com/mbTYc.jpg" alt="enter image description here"></p> <p>Why is this even important?</p> <p>a) If anyone has managed to copy it to a diy project, then atleast i cant find it on google. Im sure someone has done it just doesnt seem like they published their project. Meaning that for such a common item the how-to information is simply not out there.</p> <p>b) Ability to make dirt cheap diy linear encoders counts for a lot, for example you know how prone to failiure all the diy 3D printers are? Thats because they are open loop control systems, little jam or slippage and control system doesnt know where the robot is anymore. Now for an industrial robot you buy a linear encoder, one for each axis. Heidenhein and 100 other companies will gladly sell you one for ~1k€. Basement hobbyists unfortunately dont kave that kind of budgets. But they would gladly buy(or make, manufacturing is simple enough) capacitive linear encoder like ones used in digital calipers. If the how to information was out there somewhere.</p>

<p>How do these electronic calipers work?:</p> <p><img src="https://i.stack.imgur.com/AtTpr.gif" alt="Caliper"></p> <p>I know they work by measuring the capacitance of the running track, somehow. But how do they use capacitance to measure distances - is it a linear relationship of capacitance to distance, or is there something else going on? These are really accurate - specification of ±0.02mm from 0-100mm, and the resolution is down to 0.01mm. I'm also surprised at how these can meet the specifications at the very low price point - I picked up mine for £8 and tried it against a few common objects I knew the dimensions of, and it checks out.</p>

How does an electronic caliper work?

2010-11-14T00:22:00.557

6714

|power-supply|atx|

<p>Allow me to quote <a href="http://en.wikipedia.org/wiki/Power_supply_unit_%28computer%29" rel="nofollow">Wikipedia: Power supply unit (computer)</a>:</p> <blockquote> <p>In computer power supplies that have more than one +12V power rail...</p> <ul> <li>Multiple 12V power supply rails are separately current limited as a safety feature; they are not generated separately.</li> <li>... the IEC 60950 standard, which requires that no more than 240 volt-amps be present between any two accessible points. Thus, each {12 V} wire must be current-limited to no more than 20 A; ... Unlike a fuse or circuit breaker, these limits reset as soon as the overload is removed.</li> <li>Because of the above standards, almost all high-power supplies claim to implement separate rails, however this claim is often false; many omit the necessary current-limit circuitry,{5} both for cost reasons and because it is an irritation to customers.{1} (The lack is sometimes advertised as a feature under names like "rail fusion" or "current sharing".)</li> </ul> <p>...</p> </blockquote> <p>So it's apparently for exactly the same reason that electricians claim that different outlets in your house are on "different circuits", even when they are all electrically connected to each other. Each circuit is allegedly current-limited with a fuse or circuit breaker. And yet it is an irritation to customers when a circuit breaker blows because I have too much stuff plugged into it, when that same stuff works just fine if they are plugged into outlets in different rooms, or if someone replaces that fuse with a penny :-/.</p>

<p>This is in danger of becoming a computer question, but I've always wondered why do computer power supplies have so many 12V "rails". I have a 800W dead supply with four 12V 16A "rails", but internally, they are all connected to the same transformer, use the same diodes and the same capacitors - in fact, they are all electrically connected to each other. So why call them separate rails (given they are in fact the same rail), is it just marketing or is there some proper reason?</p>

What's all this "rails" nonsense on a computer power supply?

2010-11-14T00:27:05.657

6728

|gyro|

<p>Can't you order one from Element 14(Formerly Farnell) in Australia? Ive found the first part in their <a href="http://au.element14.com/stmicroelectronics/ly330alh/gyroscope-mems-10lga/dp/1838548?Ntt=LY330" rel="nofollow">system</a>. </p>

<p>I was going to use the LY330 or the LY530 from ST Microelectronics and they should do the job very well. However, due to the stupid US Export Restrictions, Digikey won't sell any to me (I live in Australia).</p> <p>Are there any recommended gyroscopes that I can buy (Z-axis) that are easily sourced (no export restrictions from digikey), offer ranges of at least 300 deg/sec (don't care if it is digital or analogue), and are highly accurate?</p> <p>Thanks.</p>

Looking for a ~300 degree/sec gyro

2010-11-14T06:09:40.923

6731

|light|dimming|

<p>Looking at your illustration, it seems that the mains wires are the two left wires, and the lamp would connect to the two right wires. You mentioned that the dimmer is in an enclosure. I would strongly recommend ensuring that there is absolutely no way that a determined toddler could get a screwdriver, paperclip, ham sandwich, etc... into the enclosure. Also ensure that the wires are protected with some sort of strain relief, so that when the dog trips on the cord, the wires won't come out.</p> <hr> <h2>EDIT:</h2> <p>I looked at your drawing again. It seems that there are two possibilities: </p> <p><em><strong>First Possibility</em></strong> </p> <p>You are seeing 4 wires because they are 2 from the cord, and 2 from the socket. This one's easy. Connect the two wires from the plug to the left two wire positions on the dimmer. Connect the other two wires to the right two wire positions on the dimmer.</p> <p><em><strong>Second Possibility</em></strong></p> <p>Your lamp socket is wired for a three-way lamp. Usually these have 3 wires, though. One would be the neutral, one would be low, and one would be medium. With power applied to both low and medium, you get high power. You would need to check this with an ohmmeter. With a 3-way bulb installed, measure resistances across all of the wires. You should come up with something like this:</p> <pre><code>Pair Measurement 1-2 360 1-3 240 1-4 0 2-3 600 2-4 360 3-4 240 </code></pre> <p>Note that these numbers are approximate, and depend on the wattage of your bulb. This table is built on the assumption of a 40-60-100 Watt bulb. In this case, 1 and 4 are Neutral and Ground, and can be tied together. 2 is low power, and 3 is medium power. Using an external dimmer, these should also tie together for the hot side. Check across the neutral/ground and the hot side. If it reads short, there's a problem!</p> <h1><em><strong>CAUTION</em></strong></h1> <p>If you can't figure out exactly what each wire is for, get help! Magic smoke stinks, and so do house fires. (Been there. Not cool.)</p> <p>As tronixstuff mentioned before, though, mains can kill. I've been "tagged" a few times (lucky -- I'm still here to write about it) and you need to exercise the utmost caution. </p>

<p>I have a light dimmer i want to connect to a a floor lamp. I have tried to look for some diagrams but haven't been able to find some.</p> <p>There is a diagram on the dimmer but I don't understand it.</p> <p>I have made an illustration to show how the small diagram looks (it's the diagram in the middle, the lamp and the 4 wires and the power plug are my additions.</p> <p><a href="http://000fff.org/uploads/LightDimmer.pdf" rel="nofollow">http://000fff.org/uploads/LightDimmer.pdf</a></p> <p>Can anyone tell me how to connect this. I have 1 wire from the lamp to the dimmer with a blue and a brown wire and 1 wire from the dimmer to the power with a blue and a brown wire.</p>

How to connect a light dimmer for my lamp

2010-11-14T09:33:41.937

6740

|led|reliability|failure|

<p>MTBF is assurance that reasonable derating guidelines are met. Nothing more. An MTBF of 250k hours does not mean any single piece of equipment will last 30 years. It's possible to get that sort of MTBF on equipment that uses electrolytic capacitors, which almost certainly will dry out in much less time than that.</p> <p>Drive the LED with the minimum amount of current that provides a useful amount of 'signal' (i.e. is viewable under whatever conditions you deem inportant.) The LED manufacturer should have datasheet information about operating current / temperature rise / ambient temperature, so you can judge how 'hard' you're driving it and make your own decision about reliability.</p>

<p>I am trying to develop a very high reliability product, with a MTBF exceeding 100,000 hours, hopefully in the 250,000 hours range. Yep, I know - stupidly high reliability, at least 10 years. </p> <p>Most LED's I've seen have a reliability rating of only 20,000 hours. What happens after this? Do they reduce in output too much? Are they usable as power indicators past this point?</p>

How do LEDs fail?

2010-11-14T22:20:57.927

6745

|eeprom|pricing|

<p>It seems clear to me. The FC component has a higher clock frequency, but it also has a lower maximum operating temperature. The LC extends this maximum operating temperature, but at the cost of some of the clock frequency. </p> <p>That gives you the choice of either high temperature, or high clock frequency. </p>

<p>24AA1025: operates from 1.7V - 5.5V, 400kHz, $2.37</p> <p>24FC1025: operates from 2.5V - 5.5V, 1 MHz, $2.37</p> <p>24LC1025: operates from 2.5V - 5.5V, 400kHz, $2.37</p> <p><a href="http://www.microchip.com/ParamChartSearch/chart.aspx?branchID=70012&amp;mid=&amp;lang=en" rel="nofollow">See here</a>.</p> <p>24AA1025 is unique, because of the lower operating range. What I don't understand is why Microchip produce both 24FC1025 and 24LC1025 at the same price with different maximum clock frequencies. Why not just make one? Am I missing something?</p>

What's the difference between 24AA1025, 24FC1025 and 24LC1025

2010-11-14T23:38:42.477

6748

|analog|operational-amplifier|

<p>Sine_Max_slew = 2*pi*f* <strong>Vpeak</strong></p> <p>so "V peak" which should not to be confused with V peak-to-peak (Vpp).</p> <p>However, the equation can be reduced further though when using Vpp because Vp = Vpp/2 which means:</p> <pre><code>Sine_slew = 2*pi*f*Vpp / 2 </code></pre> <p>and the 2's cancel, which leaves:</p> <pre><code>Sine_Max_slew = pi*f*Vpp </code></pre> <p>There's also a linear slew (triangle waveform) and sine waveform max slew amplitude relationship occurring under equal frequency. To understand this relationship, a reduced amplitude sine waveform will fit inside a triangle waveform of higher amplitude but same frequency when the sine waveforms max slew equals the linear slew rate. At that point, the sine waves amplitude is:</p> <pre><code>Sine(Vpp) = 2/pi * Triangle(Vpp) </code></pre> <p>There's also a relationship for equal slew rates between linear and sine when amplitudes are the same but frequency is different:</p> <pre><code>Sine(Hz) = 2/pi * Triangle(Hz) </code></pre> <p>Just a little noteworthy background on the whole slew subject...</p>

<p><a href="http://microchip.com/ParamChartSearch/chart.aspx?branchID=11015&amp;mid=11&amp;lang=en&amp;pageId=79" rel="nofollow">Many, many choices</a>. And this is just Microchip's offerings.</p> <p>I'm going to be amplifying by a maximum of 5x using an op-amp. So I choose an op-amp with a GBWP of 50 kHz * 5 = 250 kHz. That still leaves many op-amps. What slew rate should I be looking for? (with low distortion on the output.) And are there any other parameters to look out for, like input noise and offset?</p> <p>EDIT: It seems I need to clarify. I'm only looking for a single channel op-amp for amplifying a mono signal with reasonable levels of distortion. I'm not looking for high quality prosumer gear audio.</p>

Regarding slew rates, what would be the minimum for amplifying audio using an op-amp?

2010-11-14T23:57:13.630

6760

|power|isolation|

<p>We can't rely on either of the supply conductors being safe for several reasons.</p> <ol> <li>In some countries you can't rely on which conductor is live and which is neutral either because the sockets are unpolarised, because the installers don't pay much attention to polarity or because use of extensions/adapters that may not correctly maintain polarity is common.</li> <li>Wires can break, if the neutral wire breaks and there is load on the system then the neutral wire will come up to mains volts.</li> <li>Even in normal operation with correct polarity there can be voltage on the neutral due to volt drop. While the voltage is low the impedance is also very low, so it can be a fire risk.</li> </ol> <p>As a result of this modern appliance standards generally treat both the live and neutral conductors as potentially hazardous. This leaves appliance vendors with two main options for protecting the uses.</p> <ol> <li>Insulate and touchproof all electrical parts, that works ok for simple devices but it's not really practical for things like computers with a bunch of user-accessible ports.</li> <li>Put an isolation barrier in the power supply so that the low voltage part is safe to touch.</li> </ol>

<p>In all the computer power supplies and other power supplies I've taken apart, I've noticed they are fully isolated from the mains. Galvanic isolation through transformers, and often optical isolation for feedback. There is usually a very visible gap in the traces between the primary and secondary sides, at least 8mm across. Why is it important that these supplies be isolated?</p>

Why is it important for mains power supplies to be isolated?

2010-11-15T11:06:28.767

6765

|generator|

<p>Once upon a time you might have been able to get a weak voltage from soggy newspapers. The ink that was used had small amounts of various metals that would be conductors. The paper itself was bleached and certain amount would not get rinsed out.</p> <p>Today the ink is soy based, it does not contain any metal. The paper has little if any chemicals left in it from processing. You could add metal as electrodes and add a electrolyte like acetic acid (citrus juice), but if you do that you don't need the newspaper.</p> <p>There has been some attempts to use cellulose (paper) with carbon nano tubes suspended in ink for manufacturing batteries, but this is much more the wet newspapers. </p>

<p>For a project we're thinking of generating electricity out of wet newspapers. Is that possible? How much current would it generate?</p>

Generating electricity with wet newspapers?

2010-11-15T13:24:51.190

6767

|pcb-fabrication|cad|pcb-design|

<p>Laptop electronics could be reused but you might have trouble finding/using the connectors. For one, they're TINY - full of flex cables and iddy biddy surface mount contacts that you certainly won't be able to hand-solder. Also, some of the connectors are proprietary so you'll be reduced to scavenging them from old boards - have an SMD rework station handy. Or, they might just be plain hard to find. If it's a connector dedicated for use in a computer you might not be able to find it in quantities fewer than 1000, or the places you'll find them don't sell in the US or really anywhere other than China/Hong Kong/Taiwan. As far as they're concerned there's no reason to sell them abroad - everything's manufactured in that area so why ship? </p> <p>But as far as designing the PCB I doubt you'll have too many problems. You'll have to generate CAD drawings of the interior to determine where to put mounting holes, place connectors, etc. You'll have to watch out and make sure you use the right parts - I'd imagine laptops have low-profile <em>everything</em> so don't assume you can use standard height components. You'll have to keep an eye on how you're dissipating heat - the cases are probably designed for one and only one solution for removing heat so if you can't fit the same heat pipe they use on your board you might be out of luck.</p>

<p>I have taken an interest in a current effort to create a (mini- or micro-) ATX <a href="http://natami.net/" rel="nofollow">motherboard with a custom CPU</a>.</p> <p>But ideally, I would want this system in a laptop instead. I got this idea, how hard would it be to rip out a motherboard from a laptop, such as the EeePC or Thinkpad, and replace it with a custom board?</p> <p>Could parts of the laptop electronics be reused, such as the power supply etc? Or are laptop motherboard form factors etc changed too often for this to be useful as a semi-reliable source of laptops to be remade? (The goal being a laptop Natami built to order, or in small runs.)</p>

Recad laptop motherboard PCB?

2010-11-15T13:40:47.650

6773

|pcb|checklist|

<p>This is my list for boards I lay out in Ultiboard.</p> <ul> <li>Are there any antennas? Edit -> Copper Delete -> Open Trace Ends</li> <li>Are there any unused vias? Design -> Remove Unused Vias</li> <li>Are there any design rule errors you can't explain?</li> <li>Are there any connectivity errors at all?</li> <li>Does it <em>look</em> wrong? Look at the board for obvious stupidity like parts that have been eaten or moved.</li> <li>Are there bypass caps <em>directly</em> on the power rails of EVERY chip? Even the ones that don't look like ICs, like regulators?</li> <li>Are there filters directly on EVERY transistor gate/base? Even the ones in processors? Half an inch is probably too far away.</li> <li>Are there filters directly on A/D converter pins?</li> <li>Are the traces wide enough? Especially power traces? Make the traces as large as reasonable, unless you have specific reason not to.</li> <li>Use power planes where possible, especially under processors</li> <li>Are the thermal reliefs as you intended? High-current components get no thermal relief, but also no solder mask! Otherwise it will be very difficult to solder. Make sure there's plenty of exposed copper on both sides of the board for those components. Everything else gets standard thermal reliefs, 10 mil or so is probably fine spoke width.</li> <li>Are all test points labeled?</li> <li>Is the board name (or part number) printed on the silkscreen? Correct revision?</li> <li>Is there sufficient distributed cap on the power rails? One big cap in the corner isn't as good as four smaller caps spread around the board.</li> <li>Are all isolation barriers wide enough?</li> <li>Are all high voltage clearances in place? Look particularly for traces under heat sinks tied to high voltage through a transistor tab. Also look for clearances to any mounting holes.</li> <li>Check <em>all</em> the layers. Sometimes I've left the solder mask layer turned off, only to find that there was some odd shape on it that I'd placed by accident.</li> <li>Are all footprints and pinouts correct? Collector-emitter reversal has happened to me on more than one occasion.</li> <li>Is the silkscreen correct, showing reference designators, not values? Check the actual exported gerber.</li> <li>Are all user terminals marked with function, + -, other relevant information?</li> <li>Are all op-amp power rails connected? Ultiboard likes to randomly eat them.</li> <li><em>Don't trust the auto-router</em>. It's tempting, but ultimately not worth the effort. Only use it if there's a question if something is at all routable.</li> </ul>

<p>I don't do my own CAD work. I have a mental checklist of what to look for when the PCB is placed, critical routed and routed. But is there a good checklist you have or can point me to? I'm not looking for schematic items, that is covered <a href="https://electronics.stackexchange.com/questions/6644/good-schematic-checklist">here</a>.</p>

Good checklist for PCB design to be used by the EE (not by the PCB designer)

2010-11-15T16:30:59.897

6778

|switch-mode-power-supply|dc-dc-converter|

<p>I just tried injecting some DC voltage into a 5 V wall-wart power supply (100-240 VAC, switch mode), suitable for powering a small computer like a Raspberry Pi.</p> <p>The supply did nothing until the input reached 30.2 VDC and then it switched on and operated normally, only drawing 20 mA (it is rated at 2 amps output). Once it was on, the input voltage could drop back but once it got below 25 VDC the output started dropping below 5 V, and the input current increased up to 60 mA before it switched off due to too low an input voltage.</p> <p>However even at 30 VDC input, the device would shut off (and switch back on a second later) if you tried to draw anything more than a few mA through it, even though it's rated to deliver 2 A. I was surprised it worked at all as low as 30 V, but clearly it needs a higher voltage to deliver any sort of useful current.</p> <p>Since my bench power supply only goes up to 30 V, next I tried a 96 V battery pack, and I had much more success with this. This time the device drew closer to 50 mA with minimal load, and it increased to 80 mA (at 96 V) when successfully delivering 5 VDC @ 1 A.</p> <p>As a bonus this device also appears to be isolated, as there was less than 1 V potential between GND and either terminal on the 96 V battery bank.</p> <p>So for me, it looks like I don't have to find an expensive power supply that can convert 96 VDC to 5 VDC to run an RPi for monitoring my battery bank, I can just use an ordinary wall wart to do the job.</p>

<p>I have this crazy idea of using a computer SMPS with active PFC boost to take high voltage DC battery banks (144V+) and drop it down to 3.3V, 5V and 12V.</p> <p>Here's my thinking: the power supply internally rectifies the AC to DC, and the PFC boost should then boost the 144V to an acceptable 350V-400V for the power supply. The 144V input is okay for it because it falls in the 100VAC range, and most are rated down to 85VAC if not lower. </p> <p>I'm not looking for a guaranteed solution - it's a one-off problem I'm trying to solve, but I think it could be a cheap and viable solution.</p>

Would this work? Using a computer SMPS as a DC-DC converter

2010-11-15T20:06:06.470

6781

|stepper-motor|

<p>The maximum rate you can move a stepper motor is based on the shaft torque and coil current. Attempting to move too fast against too high a torque will cause the motor to become desynchronized with the step impulses and move unpredictably/uncontrollably.</p> <p>Here's a generalized graph:</p> <p><img src="https://i.stack.imgur.com/2XTRn.jpg" alt="Stepper motor graph"></p> <p>The whole curve shifts up and down with current.</p> <p>Most drivers' speed will be orders of magnitude faster than any motor, the few exceptions are things with a bunch of protection/intelligence (of which the Darlington driver you linked has neither)</p>

<p><br> I am controlling two stepper motors in from a Genie Microcontroller and driving them by a ULN2803A. I want to know what is the shortest time i can change the phase. Is it dependent on the ULN2803A?<br> Thanks in Advance,<br> Dean</p>

Controlling Stepper Motors

2010-11-15T20:50:18.587

6782

|pcb|batteries|connector|12v|

<p><em>"The nice thing about standards is that you have so many to choose from."</em> -- Andrew S. Tanenbaum.</p> <p>There are a variety of standard <a href="http://en.wikipedia.org/wiki/DC_connector" rel="nofollow">12 VDC power connectors</a>. Perhaps the most common are:</p> <ul> <li>Anderson Powerpole (formerly Sermos)</li> <li>Deans Ultra</li> <li>Gold Bullet Connectors</li> <li>Tamiya connectors</li> </ul> <p>Many battery packs have a wire soldered directly to the battery with one of these connectors on the other end of the wire.</p> <p>There seem to be quite a few people on the internet comparing these connectors. ( <a href="http://rc.runryder.com/helicopter/t659659p1/" rel="nofollow">a</a> <a href="http://www.radioracecar.com/pitlane/article.aspx?a=4286" rel="nofollow">b</a> <a href="http://hobbyunicorn.com.au/categories/Plugs/" rel="nofollow">c</a> <a href="http://www.rcuniverse.com/forum/m_3910474/printable.htm" rel="nofollow">d</a> <a href="http://www.helifreak.com/archive/index.php/t-21729.html" rel="nofollow">e</a> <a href="http://www.tamiyaclub.com/forum/lofiversion/index.php?t2747.html" rel="nofollow">f</a> <a href="http://www.helifreak.com/showthread.php?t=56967" rel="nofollow">g</a> )</p> <p>There are PCB mount connectors that fit PowerPole connectors (<a href="http://www.connex-electronics.com/?url=/html/products/anderson/anderson_main_select.html" rel="nofollow">h</a>). I've also seen PCB-mount high-current spade connectors.</p>

<p>I'm looking for a right-angle PCB board mate for the standard 12V hobby battery connectors.</p> <p>Where can I find these connectors?</p>

What are the standard connectors used on 12V hobby batteries?

2010-11-15T21:18:46.980

6788

|operational-amplifier|

<p>The TL081 has a FET input stage, whereas many older opamps have a BJT input stage. This makes a great difference for the input bias current. While the input bias current for the LM741 may look low at typically 80nA, for the TL081 this is 5pA! (Analog's <a href="http://www.analog.com/static/imported-files/data_sheets/AD549.pdf" rel="nofollow">AD549</a> does even 2 orders of magnitude better with 60fA, that's about 1 electron every 3\$\mu\$s).<br> The higher the input impedance of the opamp the easier the inputs will work as antennas an pick up from the ever present electric fields in the air, and cause a voltage at the output. With the LM741 for instance this will be hardly a problem.</p>

<p>In Electronics class today we were using a TL081 op-amp. When I disconnected the inverting and noninverting inputs, the op-amp's output (driving an LED) started switching on and off rapidly. What causes these weird oscillations?</p>

Why does my op-amp swing randomly when the inputs are disconnected?

2010-11-15T23:07:28.497

6789

|surface-mount|

<p>One last reason that I haven't seen here (And it's likely the most relevant one): </p> <p>SMD components are too small.</p> <p>I mean literally. When you're dealing with high voltage, you have to worry about <a href="http://en.wikipedia.org/wiki/Creepage#Design">flashover/board creepage</a> distances, which means that the connections for high voltage have to be separated by a certain amount (There are standards for this, which are required to get UL or similar ratings).</p> <p>With 240V AC, the distance is (off the top of my head) ~.25", which is far larger then even 1206 parts.<br> This is also the explanation behind the slots cut into the PCB, which you often see under optocouplers/input filter caps. Basically, to pass testing, the separation on the component's leads is not great enough, so they have to actually mill slots the board. This increases the overall path-length between component pins on the PCB.</p> <p>Lastly, most of the power devices are through hole because through hole packages can dissipate more power than SMT parts. It's much easier and cheaper to mount a TO-220 package to a cheap extruded aluminium heatsink then have a board with very thick copper fabbed that can dissipate the same amount of power from a TO-263 device.</p>

<p>Why are power supplies almost always made using through hole components? Every computer PSU I've taken apart uses through hole components, though occasionally (not in all cases) surface mount components are found on the bottom. Don't these have to be hand assembled? (before reflow or wave soldering) If so, why are they still doing this, even though labour costs are low in China, it still must cost less for a machine to pick and place SMT stuff... or am I missing something?</p>

Why are power supplies almost always made using through hole components?

2010-11-15T23:11:46.997

6790

|led|

<p>You can do this with a bi-color LED that has the two LEDs back-to-back if you connect one LED terminal to an intermediate voltage eg 2.5V on a 5V design and connect the other side to the MCU via a suitable resistor (I used 560R). </p> <p>Then a low output gives one colour, high gives the other and tri-state leaves the LED off. Pulse width modulation will allow you to control brightness (switching output between active and tri-state) or mix the colours (switching output low to high).</p> <p>You can adjust the intermediate voltage to compensate for different LED forward voltages too. </p> <p>I used an LM2904 op-amp to provide the intermediate voltage - it works with supply voltage down to 5V. There are plenty of other devices that can operate at lower voltages and still sink and source enough current to drive the LEDs.</p>

<p>Is it possible to control a bicolor LED with just one pin of a microcontroller?</p> <p>Instinct says NO, because you can have one end grounded and the other going to the micro's pin, allowing you to turn it on or off but not change its color.</p> <p>But maybe someone has a better idea?</p>

Control a bicolor LED with just one pin

2010-11-15T23:17:57.863

6805

|batteries|operational-amplifier|

<p>Will is correct, but on the other hand if this project isn't audio or simply doesn't require positive and negative voltages then you just need to use an op-amp that can operate with unbalanced supplies such as (pulls random op-amp out of digikey) LT1494IN8. You just connect -ve to ground and +ve to your rail and you're good. You are of course limited to your voltage range for output (0-12V or whatever your battery is) so if you are using audio you'd need to do what Will says, but if you just want to amplify something you can use this.</p> <p>I'm sure this is a typical question BTW. When I was in school they never let on that single-supply op-amps existed. We always used +/-15V and I always figured that was the only way to use op-amps. But positive and negative supplies are so uncommon in the real world that it pays to learn about these things.</p>

<p>I'd like to use a simple non-inverting amp circuit in a small project I am working on. The project is battery powered, so naturally the only voltage I have access to is 3.3v. My question is: how should I get the voltage for the -ve rail? Of course I can add a DC-DC converter but I'm sure this is already a solved problem so I figured I'd ask first.</p> <p>Thanks!</p>

using an op amp in a battery powered circuit

2010-11-16T08:05:00.490

6811

|transformer|resonant-converter|compact-fluorescent-lamp|

<p>Transformers can have any number of coils. Usually only one of them is used to put power into the core, and is called the primary, while the others take power out and are called secondaries. </p> <p>You can have as many secondaries as you need. One thing you can do with two secondaries is to make isolated supply sections. Another purpose is not so much to pull power out, but feedback signals, which can be used to drive an oscillator.</p> <p>Of course I went and said 'usually' only one of them is used to put power in. There are cases where two coils can be used to put power in. So called Push-Pull amplifier sections do this, as do some DC to AC inverters.</p>

<p>I found a device which has a ferrite core and 3 coils on it. It looks like some type of transformer. What would be its use? I found it in a compact fluorescent lamp.</p>

What is the use of transformers with 3 pairs of wires?

2010-11-16T11:44:08.277

6815

|amplifier|

<p>If you really need to mux the inputs, how about something like this?</p> <p><img src="https://i.stack.imgur.com/Z5G0C.jpg" alt="mux and buffer"></p> <p>Since your DAC output is already DC biased, if the bias it uses is provided on another pin, you could eliminate the cap and resistor for the DAC output, and use that pin as the bias for the other input. Otherwise use one of these:</p> <p><img src="https://i.stack.imgur.com/yIERi.png" alt="DC bias source"></p> <p>Depending on what your inputs and outputs are connected to, you might need grounded resistors on the other side of the coupling caps, RF bypass caps to ground, etc.</p>

<p>At the moment I'm using an amplifier based around a NPN transistor and some resistors. Its configuration is as an emitter follower. Pin 25 supplies internal audio from a DAC on the chip.</p> <p><a href="http://super-osd.googlecode.com/hg/hardware/V3%20Lite/OSD.png" rel="nofollow">See this schematic, on the righthand side</a>.</p> <p>This handles DC offset (offsetting the AC signal into a DC signal), overvoltage input protection, switching between internal/external audio, and output. It is a bit distorted, but it works well. </p> <p>Ideally, I'd like to integrate this on to one or two IC's with the minimum space usage. It'd be nice if cost was lower, but this is not critical. (Currently component cost is around $2.50 total for all components in the audio amp, in low quantities.) Also, it would be ideal if the IC did not require a dual rail power supply.</p>

Smallest audio amplifier?

2010-11-16T13:25:56.340

6817

|pcb|header|

<p>Global Connector Technology (GCT) offers a range of small and inexpensive vertical SMT headers, either <a href="http://www.gct.co/pcb-board-to-board/header-socket-products.aspx?Pitch=2.00mm&amp;MountType=Surface%20mount&amp;Gender=Header&amp;Orientation=Straight&amp;" rel="nofollow">in 2.00mm (.079")</a> or <a href="http://www.gct.co/pcb-board-to-board/header-socket-products.aspx?Pitch=1.27mm&amp;Gender=Header&amp;MountType=Surface%20mount&amp;Orientation=Straight&amp;" rel="nofollow">1.27mm (.050")</a>.</p> <p>They should be stocked by Newark (and Farnell/Element 14) in 2-10 positions, click the distribution links from the GCT pages (look for the green tick) to navigate to the exact range. If you can't find what you seek MOQ's are circa 1,000+ to deal direct/vis distribution.</p> <p>Actually 1.27mm (.050") connectors are superseding 2.00mm (.079") in volume sales, not by much, but they shade it. Anyway, it's horses for courses so pick whichever ones you like.</p> <p>GCT also product economical 1.00mm (.039") straight SMT headers which are freely available from Newark/Farnell in 2-10 positions.</p>

<p>Currently, I'm using standard headers with a pitch of 2.54mm (0.1"). These are quite big on my boards. Are there any surface mount standard headers, say in 0.05"?</p>

Standard small header size

2010-11-16T14:23:13.227

6830

|rs232|

<p>A craft interface is a command line interface for directly configuring a network device - typically an ip router or switch. The connection is often over an rs232 or similar serial port on the physical device itself but can also be via telnet, ssh or various other methods.<br> Typically these interfaces are complex and hard to use for those not familiar with them. Each is specific to the manufacturer, device type and often the particular device. They can have hundreds of complex commands and multiple contextual modes with many inconsistencies in the way different commands and modes work. For this reason the word "craft" is often thought to come from the idea that when you're faced with the cli prompt you "Can't Remember A F...n Thing."</p>

<p>In what way is a Craft Port different from a conventional RS-232 Port? It seems to be similar. Are there any interface or other important differences? Does craft port imply a higher level protocol on top of RS-232 as well?</p>

In what way is a Craft Port different from a conventional RS-232 Port

2010-11-16T15:50:06.773

6835

|arduino|

<p>There is an Arduino compatible device called a Ruggeduino designed by Rugged Circuits that can sustain +24 volts and higher.</p> <p><a href="http://ruggedcircuits.com/html/ruggeduino.html" rel="nofollow">http://ruggedcircuits.com/html/ruggeduino.html</a></p>

<p>I would like to use a Arduino as "simulator" in a training class. It would connect to an industrial controller that has 24 VDC inputs and outputs. The Arduino program would simulate the IO from a production line (sensor inputs and motor controls for example)</p> <p>Is there a shield which can interface with 24 VDC IO? I know I could use separate relays, but I want to see if there is a better solution. </p> <p>I could use 12 VDC instead of 24, but nothing lower. </p> <p>I am considering the Arduino as cost is factor. So I want to keep the component count and price as low as I can.</p>

24 VDC control using Arduino

2010-11-16T16:39:21.917

6839

|radio|decibel|

<p>What is not explicitly stated so far in the answers is that while a power level should be stated with a reference unit - dBm or dBw or similar, a difference in power levels must not have a unit "I tuned the coil and brought the output up 4 dB"</p> <p>This is because when you subtract logarithms, what you are actually doing is dividing (the exponential values), and in division the units cancel leaving just a ratio.</p> <p>So while seeing dB by itself may indicate someone is being sloppy, in well-written engineering documents you will often see a mix of referenced units such as dBm to state absolute powers, and unreferenced ratios in dB to state relative differences.</p>

<p>When working with radios, I've seen the term "dBm". What does this mean?</p> <p>The <a href="http://en.wikipedia.org/wiki/DBm">wikipedia page</a> gives a table showing the equivalent power in Watts. Is the dBm output just the power level of a transmitter?</p> <p>How does this differ from signal strength measured in dB?</p>

What does dBm mean?

2010-11-16T17:20:05.377

6848

|microcontroller|avr|

<p>The AVR32A architecture is a 3 stage pipeline and it doesn't look like that model supports branch prediction so any branches in your code will stall the pipeline. Also not all instructions are single cycle.</p> <p>Generally speaking never choose a processor based on its MIPS rating. In almost all real world scenarios you'll never get close to its theoretical peak MIPS rating.</p>

<p>I'm considering using an AT32UC3B in my project (the Super OSD Pro version.) However, something about the datasheet has me worried.</p> <p>Page 31</p> <ul> <li>0 Wait State Access at up to 30 MHz in Worst Case Conditions</li> <li>1 Wait State Access at up to 60 MHz in Worst Case Conditions</li> </ul> <p>What is a "worst case condition"? The output stage for my OSD needs to be able run at 60 MIPS (the processor's maximum operating frequency), and I presume a "wait state" means it has to wait to load data from the memory... which would limit me to &lt;60 MIPS. </p> <p>I suppose, worst case, I could load the code into RAM and execute it from there (I presume this is possible with AVR32s?), but it still has me confused.</p>

What does "Wait State" access mean on a MCU's datasheet and how does it affect me?

2010-11-16T20:05:01.693

6857

|video|hd|

<p>Ok, until today I believed it was impossible to carry a HD signal over a composite cable, however that is not entirely true. I have a 1920 x 1080i HDMI signal, which is converted to HD-SDI signal to carry over a long distance (50m) to a monitor. At the monitor end I used a HD-SDI to Component converter to drive the component input of the monitor in HD. </p> <p>Unfortunately the Monitor developed a fault and it was replaced (By a non -technical person) with a Monitor that only had a composite input (and HDMI). Using the same HD-SDI to component converter I just connected the Y signal to the composite input (In theory shouldn't work, and the picture should be black &amp; white if it did work). However I got full colour and full resolution - The Monitor reports 1920 x 1080 @ 50hz (I am in the UK hence 50Hz). I understand composite video perfectly, and this hsould not work for 1000 reasons - but it does. The composite cable is only 16" long. </p> <p>There is no down or cross conversion - so bemused at how it works.</p>

<p>Does anyone know if there exists an electrical/electronic standard for high definition video on a single wire, like composite TV which integrates luma, chroma and sync? I'm still interested in this long distance high bandwidth project, and maybe transmitting analog HD is the answer. 720p would be good, 1080p would be fantastic. And a way to convert between component and composite would need to be figured out by me, but I figure a very fast DSP or even FPGA ought to be the solution.</p>

High definition video on a composite cable

2010-11-16T23:43:15.933

6858

|transistors|

<p>As found at <a href="http://en.wikipedia.org/wiki/List_of_Intel_microprocessors" rel="nofollow">Wiki</a> there are </p> <p><strong>"Number of Transistors 29,000 at 3 µm"</strong> on an x86, </p> <p><strong>"Number of transistors 3.1 million"</strong> on a 32-bit processor original pentium, and </p> <p>in a 64 bit xeon processor <strong>"781 million transistors"</strong></p>

<p>For my product's blurb, it would be really great if I could find out how many transistors average MCU's have, as a comparison to something bigger, like a computer, or even a low-end x86 processor. The blurb is about the virtual challenges part of it which offloads rendering of 3D games to the Real World™ (augmented reality), so I'm comparing GPUs to Super OSD. It sounds a bit obtuse but it's fun and I think it's a cool metaphor. </p> <p>I'm thinking of asking the manufacturers, but I suspect I'll just get "that's proprietary information" back. Some chips, especially those from Analog Devices and ONsemi, have "chip complexity" or "number of transistors" in the datasheet, but others don't. I'm wondering why they don't include this information, because you could hardly build another chip just by knowing the number of fets, and if you were really dedicated (and paid a lot), you could probably count them yourself with a microscope or an image of the die, or at the very least estimate them by knowing the die area and average feature size.</p> <p>I'm interested in the AT32UC3B0512, dsPIC33FJ128GP802, dsPIC33FJ256GP506A, PIC24F64GA002 and PIC16F689, as well as some non-MCU's, like LMH1980, LM1881 and 24AA1025 (EEPROM.) But even if someone can hint towards a general number of transistors in their respective classes (AT32, dsPIC33F, PIC24F, PIC16F) it would be great!</p>

How many transistors on an IC?

2010-11-16T23:58:15.733

6860

|microcontroller|memory|

<p>Highly unlikely. On-chip memory on MCUs doesn't fail. RAM tests are only needed for external RAM. Far more likely it is a code problem putting something in RAM where it shouldn't - bad pointer etc.</p>

<p>One of my older prototypes for Super OSD always had one little bug. A single pixel in the video, about midway in the frame would always be off. It did not really affect anything as most pixels normally stayed in the off mode, but it was noticeable during test patterns. I could never narrow down what the cause was.</p> <p>Thinking about it now, could it have been a failed bit in the memory array? Is this at all common with MCU's with SRAM? The prototype was not abused: a fixed +3.38V (within the rated 3.0V - 3.6V), room temperature operation, minimal load on the outputs. It was a dsPIC33FJ128GP802.</p> <p>I'm designing a new prototype now and I think it's the same chip as I used last time, so I will see if the problem occurs again. Does anyone know if it is prudent to run a "memory test" on a chip? </p>

Can MCU memory be subject to bit errors and failures?

2010-11-17T00:36:36.213

6862

|capacitor|power-supply|

<p>The main things that you need to look at when selecting capacitors for a power supply is the voltage rating of the capacitor, if it needs to be polarized, and the equivalent series resistance.</p> <p>The datasheet of the IC that you are using will specify what value of capacitor you need and many times will specify the actual type of capacitor required.</p> <p>Electrolytic Caps are polarized which doesn't work well for AC signal, but is the cheapest way to get a high value capacitance, which is why they are used a lot in power supplies.</p> <p>So, in short, yes, any cap should work OK as long as you are in the allowable voltage range.</p>

<p>I've noticed that certain types of capacitors seem to be used more commonly in certain applications. I've got a few over-sized 1uf PET caps that are a little too large for the application I originally got them for, and I should have enough spares to build <a href="https://web.archive.org/web/20070127051114/http://www.tkk.fi/Misc/Electronics/circuits/lm317.html" rel="nofollow noreferrer">this</a> power supply design:</p> <p><img src="https://i.stack.imgur.com/8Itbl.png" alt="schematic"></p> <p>^{<a href="/plugins/schematics?image=http%3a%2f%2fi.stack.imgur.com%2f8Itbl.png">simulate this circuit</a> &ndash; Schematic created using <a href="https://www.circuitlab.com/" rel="nofollow">CircuitLab</a>}</p> <p>On the other hand, I've never seen anyone use anything but electrolytic caps in power supplies (and in general nothing but PET and other plastic capacitors for audio use, other than a handful of tantalum capacitors). Would it be OK? I'm feeding it off a switch mode power supply, and I'd like to get as clean an output as possible.</p>

Can I use a PET capacitor in a power supply? What's the difference?

2010-11-17T00:49:03.753

6863

|components|

<p>Companies try their best to keep products around as long as they can. However, every product has cost associated with it in order to just keep it as a separate SKU. Usually an end of life product either has a replacement that can replace the old component with no changes needed by you. If they haven't done this then they probably have very few orders for that item and are just selling off all remaining stock.</p> <p>10,000 units probably isn't enough for a company to go back on their decision. There is always a chance for negotiation, but financially they have already decided they are better off selling other components.</p>

<p>I'm just wondering about this. Luckily I'm not faced with the problem myself.</p> <p>If I design a product around a specific MCU and have that produced in a niche market, selling maybe a few hundred every year (maximum), would that MCU going NRND (not recommended for new designs) affect me badly? I can imagine I'd have to start a redesign around another chip... how long would I have to do this? Why does a chip go NRND anyway? Is it due to insufficient demand? What if I were a bigger company and just had an order for 10,000 units - would the manufacturer reconsider their decision?</p> <p>Does anyone have any experience with this? I'm worrying about this, because I'd like the same design to work for as long as possible.</p>

Does NRND spell the end for a niche product?

2010-11-17T00:51:30.210

6870

|embedded|reset|arm9|debugging|

<p>Looking at the datasheet:</p> <blockquote> <p>14.3.4.5 Watchdog Reset The Watchdog Reset is entered when a watchdog fault occurs. This state lasts 3 Slow Clock cycles.</p> <p>When in Watchdog Reset, assertion of the reset signals depends on the WDRPROC bit in WDT_MR: If WDRPROC is 0, the Processor Reset and the Peripheral Reset are asserted. <strong>The NRST line is also asserted</strong>, depending on the programming of the field ERSTL. However, the resulting low level on NRST does not result in a User Reset state.</p> </blockquote> <p>Could it be that the watchdog is firing and driving the reset line?</p>

<p>I'm working on debugging a boot problem with an Atmel AT91SAM9G20 board. Everything goes great for the first 700 ms or so. It seems that about 700 ms after reset, the processor freezes. What's curious is that the CPU drives the reset line after I release the reset button.</p> <p>Here's a scope shot that shows what's going on. The yellow trace is the reset line. The first dip is the time I'm actually holding down the reset button. The second dip is, I believe, generated by the CPU.</p> <p>The blue trace is serial data coming out of the CPU. The first two bursts come from the initial bootloader. The third burst is U-boot starting. The CPU stops sending out characters when the third blue burst ends.</p> <p>If I'm interpreting the traces correctly, this means that the reset line is low for almost exactly the time that the processor is loading U-boot from NAND flash.</p> <p><img src="https://i.stack.imgur.com/Bw5YK.png" alt="two oscilloscope traces"></p> <p>I have a few questions:</p> <ul> <li>Is this sort of CPU-controlled reset normal?</li> <li>Any suggestions about how to debug this?</li> </ul> <p>A few more details: I should add that I've looked at the power rails, and they look clean. The behavior below is reproducible. I can vary the length of the initial reset dip (in yellow) by a few seconds, and the rest of the behavior happens the same way. If I plug in the JTAG cable, the behavior changes-- sometimes it boots, sometimes it doesn't, but after a few seconds, JTAG takes over, and the processor is halted.</p> <p>Under JTAG, I can boot successfully. Here's what a successful JTAG-controlled boot looks like:</p> <p><img src="https://i.stack.imgur.com/9SJcx.png" alt="another scope screenshot, but with more serial data evident"></p> <p>Note that the timescale is different, and I'm not pushing the reset button-- it's software controlled. The same reset dip occurs. In both cases, the length is around 500 ms.</p> <p><strong>Update (still baffled)</strong></p> <p>Prompted by Mr. Taffey's suggestion below, I have investigated the watchdog timer and the reset controller in more detail. The watchdog timer is in fact disabled by the first bootloader; I'm pretty sure that code is being executed because it occurs before text is sent out the debug serial port, and I can read the text successfully.</p> <p>In reading about the details of the reset controller, I learned that the processor is <em>supposed</em> to grab control of the reset pin and pull it low for a short period. This is to ensure that other hardware on the board listening to the same line receive a long enough reset. Digging through U-boot, I found that the duration of the reset was set to 0x0D using the ERSTL field:</p> <pre><code>at91_sys_write(AT91_RSTC_MR, AT91_RSTC_KEY | (AT91_RSTC_ERSTL &amp; (0x0D &lt;&lt; 8)) | AT91_RSTC_URSTEN); </code></pre> <p>The datasheet explains that the duration is set to 2^(ERSTL + 1) slow clock periods.</p> <p>The reset duration looks around 500 ms long, the slow clock crystal is 32768 Hz, and Google tells me that log(0.500 * 32768) / log(2) = 14, and 0x0D + 1 = 14, so this all makes sense.</p> <p>I think the real problem may be U-boot crashing; the fact that it happens just after this reset is probably irrelevant. What's confusing is why U-boot would crash only when JTAG is <em>not</em> connected.</p> <p><strong>Second update</strong></p> <p>I still don't know what's going awry or why JTAG makes it behave differently, but I think I have figured out a workaround (sort of). It looks like the U-boot crash is being caused in some way by the NAND flash on the board. By chance, the next revision of the board, which just arrived recently, uses a microSD card rather than NAND flash for bulk nonvolatile storage (well, there's NAND flash inside the microSD card, but you see the point).</p> <p>My "solution" is just to start using the next revision of the board. U-boot also crashes on that, but for known reasons-- it is configured to look for a NAND flash, which it cannot find. Hence, it dies a fiery death.</p> <p>So, problem "solved." (Expect another question shortly along the lines of "How do I make AT91Bootstrap load U-boot from a serial flash?" or "How do I make U-boot work with a microSD card?" or "Why am I doing this?")</p> <p>I guess the green check mark goes to Joby for noticing that the reset line can be driven by the micro, even though it turned out to be irrelevant in the long run. Thanks for the help, all of you. I appreciate it.</p> <p><strong>Third update (about a week later)</strong></p> <p>I've been mostly working on other stuff recently, but I did figure out what the problem was eventually. My last mystery I summarized above as:</p> <blockquote> <p>What's confusing is why U-boot would crash only when JTAG is not connected.</p> </blockquote> <p>In fact, it turns out that I was mistaking U-boot failing to send characters out the debug serial port for U-boot crashing. I still don't understand the details, but I've discovered that it's not JTAG that makes U-boot work-- it's a common ground between my circuit and the USB host of my PC, which JTAG was providing, because it runs through the USB port. In fact, U-boot was working fine the entire time, but whenever JTAG was disconnected, the RS-232-to-USB level shifter I had breadboarded would stop working, the serial port would fail, and I would assume U-boot was dead. In reality, I discovered that I could, for example, still type ping commands and see the ICMP packets produced, even though my characters weren't echoed on the terminal.</p> <p>I don't understand exactly what was going wrong, but I don't really care-- I can easily find another way to read the serial port, and in the short term, I can just make the connection to USB ground with a wire.</p> <p>Thanks for the help, all.</p>

(Updated) Strange reset behavior with ARM9 processor

2010-11-17T02:30:17.783

6884

|button|debounce|

<p>One approach to debouncing which hasn't yet been mentioned is to use a double-throw switch with one throw tied to VDD and the other to ground. Feed that into a pin which (either via software or hardware) will be weakly pulled to its present state. Such an approach will provide the advantages of a double-throw switch, but will only require one I/O pin rather than two.</p>

<p>I recently read an <a href="http://www.ganssle.com/debouncing.htm">article</a> about button debouncing and was wondering if I should keep this in mind when working with, for example, an Arduino (ATMega mC)? I assume it is an issue, especially when working with interrupts.</p> <p>So is it better to detect bounce in code, or should this be taken care of with hardware? Please elaborate.</p>

Debouncing buttons

2010-11-17T14:32:16.237

6889

|microcontroller|serial|ttl|

<p>You don't say in so many words, but the "idle high" suggests you mean a UART. UARTs a <strong>point-to-point</strong> connected to line-transceivers, like the ubiquitous but dated MAX232 (there are far better solutions nowadays). The line between microcontroller and transceiver will also be short; if there's distance to be bridged it will be between transceivers.<br> The controller's output is a push-pull. </p> <p><img src="https://i.stack.imgur.com/xzL94.gif" alt="enter image description here"> </p> <p>The P-MOSFET will provide the high level, the N-MOSFET the low level. One of them must be active or the line level would float and be undefined (or defined by a load in the transceiver). Both are able to source/sink some current and will pull the line to the rails, so the signal shape will almost be ideal.<br> Which would be different if it were really TTL, as in your question (the microcontroller is HCMOS). TTL outputs are highly asymmetrical: they can only supply little current, typically 0.4mA. Sinking current is OK, at 8mA. The low source current may be a problem if the line has a high capacitance and is high speed. The low drive current means that the capacitance will only charge relatively slowly, and rising edges will be slow, which at high speed may cause serious signal distortion. TTL is never used for this. </p> <p>Your question could also refer to a <strong>multidrop line</strong>, where several devices can talk. In that case you can't use the push-pull output: if one device would drive the line high while another drives it low we would have a short-circuit. Multidrop lines almost always use pull-up resistors to keep the line idle high. Then only a low level requires driving the line, and instead of the push-pull output we'll have an open-drain, with just the N-MOSFET. The line is now also driven asymmetrically: the pull-up resistor can only deliver little current, while the pull-down FET can drive the line fast to ground. High speed multidrop lines therefore put a limit to the pull-up resistors. An example is I2C.</p>

<p>I've been trying to find a good description of the TTL serial "standard" without much luck. I understand that serial transmit (TX) and receive (RX) lines idle high (at VCC) and that they drop to ground when a bit is transmitted. As such, they're inverted from the norm, where a "1" is high and "0" is low. </p> <p>What I don't understand is who's responsible for holding the line high and how a zero is transmitted. Does the sender drive the line to high and low? Or does the receiver hold the line high with the sender pulling the line low (open collector)?</p>

How does TTL serial work?

2010-11-17T14:55:52.247

6891

|usb|uart|ftdi|

<blockquote> <p>a small USB to RS232 (or TTL serial) converter... [smaller than a] SSOP28 or QFN32.</p> </blockquote> <p>You want something smaller than a 5mm x 5mm QFN32 <a href="https://www.sparkfun.com/products/8551" rel="nofollow">FTDI FT232RQ</a> ? What are you doing that you are so short on space?</p> <p>Some options:</p> <ul> <li><p>Upgrade one of the processors you're already using to a processor that supports USB. I agree with Kortuk that this is probably the smallest-total-area approach, even if you have to use a slightly larger processor.</p></li> <li><p>don't bother doing USB on-board -- use some simpler protocol (perhaps "RS232 at TTL levels") that wires more-or-less directly to the processor already on your board. Then use some cable with built-in translation from USB at one end to your chosen protocol at the other end, perhaps something like the <a href="https://www.sparkfun.com/products/9718" rel="nofollow">Sparkfun FTDI Cable</a> but with a smaller connector.</p></li> <li><p>Use some other dedicated chip in a smaller form factor, such as the <a href="https://www.sparkfun.com/products/11736" rel="nofollow">FT231XQ</a> in a 4mm x 4mm QFN-20 package or <a href="http://www.ftdichip.com/Products/ICs.htm" rel="nofollow">several other chips</a> in a 3mm x 3mm DFN package.</p></li> <li><p>Osamu Tamura <a href="http://www.recursion.jp/avrcdc/cdc-232.html" rel="nofollow">CDC-232</a> shows that it is possible to program a 8-pin processor to translate between USB on one side and RS232 on the other side.</p></li> </ul> <p>There seem to be <a href="http://en.wikibooks.org/wiki/Embedded_Systems/Atmel_AVR#USB_Interface" rel="nofollow">many projects</a> that connect such an 8-pin ATTiny45 or a ATTiny85 chip to USB:</p> <ul> <li><a href="http://www.fourwalledcubicle.com/LUFA.php" rel="nofollow">LUFA (Lightweight USB Framework for AVRs</a>, formerly known as MyUSB)</li> <li><a href="http://dicks.home.xs4all.nl/avr/usbtiny/" rel="nofollow">USBtiny</a></li> <li><a href="http://www.obdev.at/products/vusb/index.html" rel="nofollow">V-USB</a> and its list of <a href="http://www.obdev.at/products/vusb/prjall.html" rel="nofollow">V-USB projects</a>, including a <a href="http://codeandlife.com/2012/03/03/diy-usb-password-generator/" rel="nofollow">DIY USB password generator</a></li> </ul> <p>The ATtiny45 and ATtiny85 used in those projects are available in several different packages, including 8DIP (for easy prototyping) and a 4.0 mm x 4.0 mm QFN/MLF -- is that small enough for you?</p>

<p>I am looking for a small USB to RS232 (or TTL serial) converter. FTDI was the first stop, but the smallest IC they have is in SSOP28 or QFN32. I'm looking to go even smaller. I don't need high speed - max probably 38400 baud, and USB Low Speed or Full Speed class. I can see how the pins are used up: some for data (TX, RX, CTS, RTS), USB pins (D+, D-, 5V), voltage regulator, crystal, etc. </p> <p>I'm not sure what product category I should be looking for, other than FTDI's website, which I already checked. I suppose I could also use a USB micro (I already have two micros on the board), but this adds size and complexity to an already complex product. Does anyone know of any possible chips? (preferably also low component count, this is not critical but would be nice.)</p>

Small "FTDI"-like chip

2010-11-17T17:27:50.837

6899

|arduino|robotics|linux|software|mobile|

<p>As far as the Kinect goes, check out the <a href="http://www.joystiq.com/2010/12/10/primesense-releases-open-source-drivers-middleware-for-kinect/" rel="nofollow">PrimeSense devkit</a> (the makers of the Kinect)</p> <p>The manufacturer released the Kinect's (and DevKit) Windows and Unix drivers here: <a href="http://www.openni.org/" rel="nofollow">http://www.openni.org/</a></p>

<p>I'd like to build a bot that when placed in an area would have the ability to find the perimeter of the area and map the obstacles present. Later it should be able to navigate to different parts of the area on demand (e.g. navigate to the NW corner or continually monitor the entire area or return to a specific point in the area). What hardware/software would be necessary to make this happen? I've considered using IR to detect the obstacles &amp; wall but it seems like the resolution may be a bit low for these purposes (could IR recognize an area is just large enough for the bot to fit into?). What prior work is available on these subjects, what sensors might I consider to get started?</p>

Strategies for mapping an area perimeter with a mobile robot

2010-11-17T21:43:04.487

6909

|motor|batteries|solar-cell|waterproof|

<p>The problem with this question in my opinion is that it is too broad. If you want good answers, you should separate it in several questions. </p> <p>I'd start by first getting the fountain part done. Find appropriate fountain body and see what volume of water you'd need for it. This will probably give you a starting point for pump selection.</p> <p>I can't recommend you a good pump, because I have no experience in that field, but <a href="http://www.backwoodshome.com/articles2/yago91.html">this</a> article seems like an interesting starting point. Basically, you'll need a low voltage DC pump. </p> <p>While selecting a pump, you should be checking put what types of solar power sources are available in your area. After you research that, it would be a good time to post a question here about driving a specific pump with specific solar power source. </p> <p>Next comes the assembly part. How difficult it is going to be will depend on previous steps. You could probably find a prefabricated pump controller which will most likely going to be just plug and play or you could be building your own. This is where it gets really complicated. If you are going to be making your own, you will need to make a circuit will require soldering skills and equipment. You will also need a circuit board which you can make yourself or get one from a factory (if you can find one which will take small orders in your area) or use some type of prototyping board. If you are going to be making it yourself, you'll probably need to ask several questions for that step alone, since making a controller will require some experience.</p> <p>After that, if something goes wrong, comes the debugging part. If the design is good, most likely the only problem would be bad solder joint. A good multimeter will come in handy there.</p> <p>I do know that this answer isn't very specific, but your question as I said is very very very broad so I'm posting this more to give you idea for size of your project, because what you are asking here is pretty much equivalent of asking "How do I make simple text editor with absolutely no programming experience?" on StackOverflow.</p> <p>You mentioned voltage details in your comment. A good question when asking for that would be something like "I have a pump which needs XX volts and YYY milliamps. I have ZZZ, XXX, YYY solar panels available. How do I make a circuit which could drive the pump using one of them?" or something like that. </p>

<p>I am planning of building a solar water fountain which would serve as a bird bath in my backyard this summer.</p> <p>My requirements are simple: The fountain should be powered by solar energy, a small output motor (or whatever) connected to this solar source which pumps out the water. I just need a small working model in a economic price.</p> <p>I have no experience in building basic electronics model, please guide me on how this can be accomplished, where I can get solar panels and how do I configure it with a motor etc. I am from India and would like to purchase raw materials available in India rather than getting it shipped from elsewhere. Any help is greatly appreciated.</p> <p>Thanks, Raj</p>

Solar powered water fountain

2010-11-18T09:20:49.573

6915

|microcontroller|pic|

<p>I just looked at the code I wrote a while ago to set up timer 2 for a periodic interrupt of 1 ms for a PIC24F (essentially same timer hardware as dsPIC33F), and it looks like so:</p> <pre><code>#define CPU_CLK_RATE 32000000L #define PERIPH_CLOCK_RATE (CPU_CLK_RATE/2L) #define TIMER_2_RATE 1000L #define TIMER_2_PRE 64L // clock rate is (32000000/2)/64 = 250 KHz #define TIMER_2_MATCH (PERIPH_CLOCK_RATE/(TIMER_2_RATE * TIMER_2_PRE)) T2CON = 0; // set control register to defaults T2CONbits.TSIDL = 1; // discontinue when idle T2CONbits.TCKPS1 = 1; // prescaler of 64 T2CONbits.TCKPS0 = 0; // prescaler of 64 T2CONbits.T32 = 0; // 16 bit timer T2CONbits.TCS = 0; // FOSC/2 (32Mhz/2) TMR2 = 0-TIMER_2_MATCH*19; // 20 millisecond delay before starting PR2 = TIMER_2_MATCH; SetPriorityIntT2(TIMER2_INTERRUPT_PRIORITY); // set to very high priority EnableIntT2; // enable interrupts T2CONbits.TON = 1 </code></pre> <p>Very similar to yours, except I pre-initialized TMR2 so there would be a delay before the first interrupt. Don't know if that would help in your case or not, but you might try it.</p>

<p>I'm trying to get the Timer2 period match interrupt on my dsPIC33FJ128GP802 working. I want it to interrupt after ~480 cycles. I'm using MPLAB C30.</p> <p>I have, to initialize the timer and interrupt:</p> <pre><code>// Initialize Timer2, which is used for output timing. T2CONbits.TON = 1; T2CONbits.TSIDL = 0; T2CONbits.TCKPS = 0; T2CONbits.TCS = 0; T2CONbits.T32 = 0; // Initialize Timer2 interrupt with a slightly // higher priority. IPC1bits.T2IP = 5; IFS0bits.T2IF = 0; IEC0bits.T2IE = 0; </code></pre> <p>(the timer interrupt is initially disabled)</p> <p>I have already got pin change interrupts working with a priority of 4. I want the Timer2 interrupt to have a higher priority.</p> <p>And to set up the interrupt I have this:</p> <pre><code>T2CONbits.TON = 1; TMR2 = 0; timer2_osd = 480 + vid_hoffset; PR2 = timer2_osd; IEC0bits.T2IE = 1; </code></pre> <p>I also have an ISR,</p> <pre><code>void _MY_ISR _T2Interrupt() { IFS0bits.T2IF = 0; return; } </code></pre> <p>However I find the processor just resets and will not run with this enabled. It will work with a busy loop checking the timer, but that wastes cycles.</p> <p>Can anyone see where I've gone wrong?</p>

Timer2 period match interrupt on dsPIC33F not working

2010-11-18T17:58:42.830

6918

|sensor|current-measurement|4-20ma|

<p>Have a look in to the HART protocol - it allows multi-drop communications over existing 4-20mA lines</p>

<p>How can I design a system that would allow me to put multiple receivers on a single 4-20mA current loop? Assume that I have design control over only one of the receivers.</p> <p>Sensor:</p> <ul> <li>Loop powered (2-wire)</li> <li>Supply voltage: 12-28VDC</li> <li>Max Load: 250 Ohms @ 12VDC (500 Ohms @ 24VDC)</li> </ul> <p>Current Receiver Design:</p> <ul> <li>250 Ohm resistor to ground</li> <li>Loop power supply ground is connected to ADC ground</li> </ul>

Multiple receivers in a 4-20mA current loop?

2010-11-18T19:40:46.253

6919

|relay|switches|

<p>6A @ 125V (assume DC for simplicity) is 750 Watts. 3A @ 250V = 750 Watts That sis why they have same rating. Its expressed this way because this switch is designed for switching mains current. In USA thats 115V and in UK/Asia its 230-250V So the manufacturer is trying to help you select this switch based on your current draw. The same applies to wiring in the USA and elsewhere. In the USA you need a thicker cable to carry more current at a lower voltage than in Europe (for example) - all to supply the same power.</p> <p>But we generally do not rate these items by power - so the conversion to V/A is printed to make your life easier.</p>

<p>I have a switch which reads 6A 125VAC / 3A 250VAC. </p> <p>I can't figure out why this would be the case. The only reason I can think of the rating is the wires and contacts are only rated to take so much current and so much power dissipation. A higher voltage should not lead to more power dissipation. So why do switches and relays have lower current ratings at higher voltages?</p>

Why do switches and relays have lower current ratings at higher voltages?

2010-11-18T19:41:46.417

6934

|voltage-regulator|msp430|

<p>Another option is to put the regulators in series. A rangefinder and MSP430 are both going to be very low-power, but when you're regulating from 9.6V, 12V, or more, it's usually cheaper to put one heavy-duty regulator at your highest voltage, and then run your lower voltage regulators off of that. </p> <p>Usually, you can get away with heatsinking just the pre-regulator in this situation, instead of heatsinking two independent regulators. You'll just have to make sure that you have sufficient capacitance that you don't get any oscillation from their interaction.</p>

<p>I have this rangefinder <a href="http://www.hobbyengineering.com/H2951.html" rel="nofollow">http://www.hobbyengineering.com/H2951.html</a> and my MCU is running on 3.3v (MSP430G2231), will this thing work poorly if I feed it 3.3v instead of 5v? I really don't want to have TWO voltage regulators on this board. If not what else can I do to get it the voltage it needs? The power source is a 9.6v battery pack with a LD33V - 3.3V regulator.</p> <p>Spec sheet: <a href="http://www.parallax.com/dl/docs/prod/acc/PingDocs.pdf" rel="nofollow">http://www.parallax.com/dl/docs/prod/acc/PingDocs.pdf</a></p>

What will happen if I feed this rangefinder 3.3v?

2010-11-18T22:52:52.487

6936

|heatsink|packages|

<p><a href="http://www.google.com/url?sa=t&amp;source=web&amp;cd=1&amp;ved=0CBcQFjAA&amp;url=http%3A%2F%2Fwww.linear.com%2Fdesigntools%2Fpackaging%2FLinear_Technology_Thermal_Resistance_Table.pdf&amp;ei=5LnlTPaZDsP58Ab1t-ChCQ&amp;usg=AFQjCNGZJwO3JZqS9RJQdtfy6Ze3ieLbIA" rel="noreferrer">Linear publishes this information</a></p> <p>\$\theta_{JA}\$:</p> <p>TO-3: 35°C/W</p> <p>TO-92: 160°C/W</p> <p>TO-220: 50°C/W </p> <p>So the TO-3 wins in \$\theta_{JA}\$, which implies that it would be able to transfer the most heat to a heatsink as well. Never seen a TO-92 attached to a heatsink, i would thing it would require a lot of support to try to do so.</p> <p>In terms of physical attachment, the TO-220 and TO-3 are about the same, just a different type of heatsink is needed. TO-3 would take up more space in most applications.</p> <p>Several other companies publish similar charts but a quick google-fu didn't turn one up for national, send em an e-mail, I'm sure they have the data somewhere.</p>

<p>I'm buying a LM317 and it comes in 3 different packages. Which is the best for attaching a heat sink? The options are:</p> <ul> <li>TO-3</li> <li>TO-220</li> <li>TO-92 </li> </ul>

Best package for heat sinking?

2010-11-18T23:23:59.907

6940

|components|

<p>As an amateur radio operator, removing components from old pcbs is one of my favorite ways of building up my junk box. Always good to have some stuff on hand. Here's some hints:</p> <p><a href="http://www.overclock.net/faqs/33671-info-perfectly-preserving-removing-electronic-components.html" rel="nofollow">Using hot air gun.</a></p> <p><a href="http://www.instructables.com/id/Recycle-old-PCB-components/" rel="nofollow">An Instructable.</a></p> <p><a href="http://www.qsl.net/iz7ath/web/02_brew/14_howto/04_rec/index.htm" rel="nofollow">Another "hot air" system.</a></p> <p>Try not to burn the house down or breath too much solder smoke.</p>

<p>Has many of you acquired used parts (motors, expensive IC chips, sensors, actuators, etc.) from the dumpsters, recycling, or trash and used them for your projects? <strong>How did you feel benefited from such choices, on top of saving the environment, despite the challenges of finding the true specifications?</strong></p> <p>Thanks in advance for the feedback!</p>

Electronics Freeganism

2010-11-19T00:34:49.580

6946

|arduino|voltage-regulator|

<p>The L7805C has a dropout voltage of 2v typical.</p> <p>So with 5.43 volts input you can expect an output of 3.43 volts typical.</p> <p>(Although dropout is not really spec'd when the output is below regulation voltage.) <img src="https://i.stack.imgur.com/cTy8G.png" alt="alt text"></p>

<p>I made a power supply using two 47uf electrolytic (aluminum, I believe) caps and a L7805CV 5v power regulator. I also added a 100ohm resistor and an led to vout. I'm using a battery pack of 4 NiMH AA batteries. The pack reads 5.43 on the multimeter with no load. When I hook up a motor to vout and ground, I get 3.85v instead of the expected 5v. </p> <p>I'm wired up like so:</p> <ul> <li>battery positive -> vin</li> <li>battery negative -> ground</li> <li>vout -> 100ohm resistor -> led -> ground</li> <li>vin -> 47uf cap -> gnd</li> <li>vout -> 47uf cap -> gnd</li> </ul> <p>Here's a pic: http://sphotos.ak.fbcdn.net/hphotos-ak-snc4/hs1169.snc4/154180_170665839624424_100000430264071_471279_1472098_n.jpg"></p> <p>Any ideas?</p>

Why is my power supply putting out 3.85v instead of 5v?

2010-11-19T04:42:12.703

6952

|crystal|

<p>Smaller crystals of the same rated frequency may operate differently, series/parallel or fundamental/overtone.</p>

<p>Is there any point in using a big crystal over a smaller one? Apart from the tolerance spec, how come crystal manufacturers have all these different models of crystals from really tiny ones to big ones? I don't think I know the advantage to using a big crystal. </p> <p><img src="https://i.stack.imgur.com/FtC75.png" alt="enter image description here"></p>

Difference between crystals?

2010-11-19T08:51:01.017

6956

|pcb|eaglecad|

<p>If you're willing to live with octagonal soldermasks on your vias, then try the following:</p> <ol> <li>Define the SMD ground pad, and disable the stop mask.</li> <li>Place pads where you want your vias. Make the pads have the same characteristics as the vias you want. We will delete these pads later.</li> <li>Show the soldermask layer (tStop)</li> <li>Draw a polygon on the tStop layer in strips. This is to prevent your polygons from enclosing any area, and so that it's easier to draw. If you want a 3x3 grid of vias, then you would need four polygons.</li> <li>Delete pads used as a template. The package is now done.</li> <li>Place package in layout</li> <li>Place vias</li> <li>Use the "NAME" function to change the via net to the same net as the pad - probably "GND"</li> <li>Route vias / add pour <img src="https://i.stack.imgur.com/NhCBJ.png" alt="My package in progress. You can see the dummy guide pins (green) and the STOP mask fill polygon"></li> </ol> <p>After this, you will have the vias on the correct net, and your soldermask will come out as you wanted. The drawbacks that I see are:</p> <ul> <li>The vias must be manually placed in the final board</li> <li>Each via must be renamed to the target net (I couldn't get the GROUP function to work).</li> <li>The soldermask is an octagon instead of a circle</li> <li>There isn't an automatic way to draw the STOP mask for the package</li> <li>Each via gives an overlap error in DRC (can be ignored).</li> <li>No easy way for a STOP mask on the bottom side without drawing it manually</li> </ul> <p>I was able to get this to work using Eagle 5.1 in about 15-20 minutes, so not too bad.</p> <p><img src="https://i.stack.imgur.com/OfbhK.png" alt="A simple layout showing the finished STOP mask"></p>

<p>How do I define a tented via-in-pad in a parts library in Eagle PCB? (<a href="http://screamingcircuits.typepad.com/.a/6a00d8341c008a53ef0120a6ca866f970b-800wi" rel="noreferrer">Example of result here</a>:)</p> <p>Once I define the large pad underneath the QFN, I seem to be able to turn the soldermask on and off. However, once I turn the soldermask off, it seems impossible to just define little circular areas of soldermask (soldermask layer in Eagle is just tStop).</p>

How do I define a tented via-in-pad in Eagle?

2010-11-19T12:27:24.220

6958

|capacitor|audio|

<p>Considering the specific application (1V p-p, 1V "offset" - I'm assuming offset in this case means the output is 1V above the ground reference), there's no reason to worry about any audible distortion or microphonics; these only come into play with high voltage swings and is, allegedly, part of the "mojo" in Trainwreck guitar amps, which have a ceramic in parallel with a poly cap coupling the first two gain stages with about 300VDC at the plate and a signal that can exceed 200V p-p passing through the cap. At line levels, your MLCC should be sonically transparent.</p> <p>In most line-level coupling applications, anything over 1uF is usually overkill; if your application is anything close to typical, 10uF will pass frequencies down into the decihertz range.</p> <p>I too am curious about the 20KHz rolloff in your simulation. Perhaps there's some decoupling between the signal and one of the rails that you haven't accounted for, like the output impedance of the amplifier itself? A 1 ohm resistance at the output would give a corner frequency of about 16KHz with a 10uF capacitor...which really isn't a bad thing, since most humans' hearing is also attenuated above 16KHz. If you really needed to pass everything from subsonic to ultrasonic, you probably want something closer to 4.7uF for the coupling capacitor and a higher impedance input for the next amplifier.</p>

<p>What kind of capacitors should I use to couple audio? I'm dealing with line level 1Vp-p audio, with a 1V dc offset (typ.) I want to convert this into 1Vp-p AC, at up to 20 kHz. My first version used ceramic 10u 10V caps - a simulation showed attenuation by about 15% at 20 kHz.</p> <p><strong>Update:</strong> I eventually went for 10u 6.3V. I did not need Hi-Fi quality and the fact that 10u 6.3V caps were available in 0603 packages was useful for me.</p>

Audio AC coupling capacitors

2010-11-19T13:42:45.487