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4679 | |power|ac|zero-crossing| | <p>I've had success with the following processing chain:</p>
<ol>
<li>Resistor divider network (using MOhm value resistors) and optocoupler to couple and isolate the signal from the source</li>
<li>An op-amp comparator to rail the signal from the optocoupler to a known voltage range</li>
<li>An extremely tight, multi-stage bandpass filter using opamps (might also need some gain in here to account for filter loss)</li>
<li>An opamp phase shifter circuit to adjust for any phase offset introduced in the filtering (+/-360 degrees is a good amount of tolerance to design for, the desired phase shift can be calibrated with a pot and an oscilloscope)</li>
<li>One more comparator to get the signal to a clean digital output for a microcontroller</li>
</ol>
| <p>I need to detect zero crossing for a soft starter. A long while ago, I have done it using a 1 Mega ohm resistor directly connected to micro controller at one side and live power at another side. I was successful but is it advisable ? what other way I can do it cheaply and reliably ?</p>
| detecting zero cross in ac? | 2010-10-01T04:54:42.150 |
4696 | |design|parallel| | <p>You bring up the point of a PIC. The PIC's pins will either source or sink the current necessary to drive the output pin to 5V or 0V.</p>
<p>Let's say you have an LED's anode connected to a PIC output pin. The cathode is then connected to ground through your current limiting resistor. If you tell the PIC to output a 0, then we have 0V across the LED, so no current will flow through it.</p>
<p>Now, let's say you switch the output to a 1. Now there's 5V across the LED and resistor; the output begins to <em>source</em> current. The "1" connects the output pin to the VDD rail of the PIC, so that's where the current is coming from.</p>
<p>So now there's this burst of current where there was no current before. The PIC is demanding more power. Unfortunately, the power supply is "far away", and it takes some time for the PIC's demands to propagate across the board, and more time for the regulator to respond, and more time for the regulator's response to propagate back to the PIC's VDD pin. During this time, there could be a catastrophic droop in the power supply at the VDD pin of the PIC.</p>
<p>To compensate for this, we use <em>bypass capacitors</em>. Think of them as little puddles of charge. When the output pin switches, the PIC will demand more current, and the capacitor will be able to provide some of it until the regulator can react. This is why bypass caps must be placed as close as possible to the VDD/GND pins...they need to be able to react as fast as possible when the current gets switched on.</p>
| <p>I am very new to electronics so please go easy on me.</p>
<p>Whilst I have read a couple of electronics fundementals books so far, one of the things that confuses me the most about electronics is how voltage and current is managed based on the fact that current affects the whole circuit.</p>
<p>Here is a very simple explanation of a situation that would confuse me.</p>
<p>Say I had an LED which had a 330R resistor on a 5V DC supply and I decided to connect 4 more in parallel. According to the laws of electronics, this should increase the current going into each LED (as according to my calculations, each LED now has a resistance of 66R - raising the current to <em>pop</em> levels).</p>
<p>What would be the best way to solve this?</p>
<p>A more complex example would be where I had a PIC driven circuit for detecting voltage and checking for a specific combination of keys (an electronic keypad). I then decide to add in a power LED, in parallel, to determine if the circuit is even on. I assume this would affect the voltage and current delivered in my original circuit and potentially break things, would it not?</p>
<p>If so, again, what would be the best way to solve this?</p>
<p><strong>I think, to sum it up, I am confused as to how circuits of any complexity are managed when adding a component can completely upset the balance of voltage and current.</strong></p>
| Managing circuits beyond a basic level | 2010-10-01T12:55:32.560 |
4708 | |microcontroller|pic|communication|can| | <p>There have been great answers. I do not know what micro you use, but here are links to some info from microchip.</p>
<p><a href="http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=1824&appnote=en020237">J1939 library</a></p>
<p><a href="http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=1824&appnote=en012120">DeviceNet™ Group 2 Slave Firmware for PIC18 with CAN</a> </p>
<p><a href="http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=1824&appnote=en020605">CANopen</a></p>
<p>They each have code and a basic datasheet letting you know what you need to implement them.</p>
| <p>I am planning on using CAN bus in an industrial automation application, however I'm having a hard time deciding how to implement the network layer. Does anyone here have any recommendations for a higher layer protocol to use over CAN that provides guidelines for how to assign message IDs and how to format data packets? Should I develop my own proprietary network layer or implement an existing standard like CANopen?</p>
| Selecting a network layer over CAN bus | 2010-10-01T14:49:05.420 |
4712 | |layout|impedance|trace|high-frequency| | <p>You don't need to make the traces the same length unless your circuit requires it. For example DDR memories require it within a certain amount and differential traces require it.</p>
<p>The standard for simulation is <a href="http://www.mentor.com/products/pcb-system-design/circuit-simulation/hyperlynx-signal-integrity/%22HyperLynx%22" rel="nofollow">HyperLynx</a> (by Mentor). LineSim does it pre-layout; BoardSim does it post-layout.</p>
| <p>I do low-speed circuit design for microcontrollers and such (usually at less than 20 MHz), and now I'm getting started on some more high-speed circuits. What I want to know is:</p>
<ul>
<li><p><strong>What considerations need to be made for traces in high-speed circuits?</strong></p></li>
<li><p>Do I have to impedance-match each line between two high speed devices?</p></li>
<li><p>Do all the traces need to be the same length?</p></li>
<li><p>Is there a good reference for these rules?</p></li>
<li><p>Can this be done using open-source circuit design tools (<a href="http://en.wikipedia.org/wiki/GEDA" rel="noreferrer">gEDA</a> and company)?</p></li>
</ul>
| When laying out circuit board traces, what impedances do I need to consider? | 2010-10-01T15:10:08.453 |
4730 | |microcontroller|audio|dac| | <p>I have come up with my own solution to this.</p>
<p>As I'm not worried about distortion I simply use a passive adder circuit which adds 3V to a ±2V signal. This can be switched using conventional, ground referenced circuits. Then, when I want to output it, I pass it through a capacitor + emitter follower amplifier.</p>
<p><img src="https://i.stack.imgur.com/kA3Xb.png" alt="The biasing adds some DC to the AC, muxes it appropriately (not shown), then amplifies it and converts it back to AC"></p>
| <p>I am developing an OSD project which also manipulates audio signals. </p>
<p>The aim is to add a 'mux' system, which allows a microcontroller to select between the input audio and an internally generated audio signal as the output. This allows it to add a voice to the signal or transmit data in the right audio channel.</p>
<p>Does anyone have any solutions for this? I would like to avoid something like a 4066 which takes up valuable space. Also, since line level is alternating current, it needs to somehow work well with this.</p>
| Line level audio and muxing | 2010-10-01T19:41:13.173 |
4742 | |audio|transistors|relay| | <p>A completely different approach could be to feed your audio signal into the PWM input of a servo. You could then use one of the audio channels to do some fairly sophisticated motion.</p>
| <p>I need a circuit that fires a relay when it detects audio pulses from one channel of an mp3 player. I'm going to record audio pulses in sync with the music to control a motor for mouth movement.</p>
<p>Its been 20 years since I've done this kind of stuff, so I need some help with this design.<br>
This is what I'm thinking so far:</p>
<p><a href="http://www.excellerate.com/images/acr.jpg" rel="nofollow noreferrer">audio controlled relay circuit http://www.excellerate.com/images/acr.jpg</a></p>
<p>The idea is to convert the AC audio to a DC level with D1 , use C1 to smooth it out. Set R1 so the transistor is just below switching on.</p>
<p>Does this look like it will work? If so, what would be a reasonable value for C1? Does it have to be electrolytic, or can it be ceramic?</p>
<p>Clarification - I'm mostly interested in knowing:
- will my design work?
- suggestions for improvement?</p>
| audio controlled relay circuit | 2010-10-02T02:34:27.330 |
4749 | |pic|mosfet| | <p>You may also use a TPS2041B device from TI. This is a high side switch with low on resitance and overcurrent protection.</p>
| <p>I'm working on a low power application. With a PIC24F (3.3V) I want to control the power to an SD card, turning it on and off. Typical current draw is 50mA, but can go as high as 200mA. I already have a 3.3V supply. </p>
<p>I was thinking of something using a 2N7000 MOSFET. What gate-source voltage would saturate these? Is it possible to do this on the high side or will it have to be on the low side?</p>
| Controlling power to an SD card | 2010-10-02T10:38:25.983 |
4752 | |operational-amplifier|simulation|multisim| | <p>Multisim does have ideal opamps, they can be found in the master database under Analog>Analog_Virtual_OPAMP_3T_VIRTUAL, but as Kortuk said, you should strongly consider using an opamp that forces you to include a power supply.</p>
<p>If you have a particular opamp that you know you will be using in a lab, you should see if you can find it in the multisim database. Multisim has very good models for how the opamps will actually act even more then just how you are powering them.</p>
<p>As for your question about Vin and Vout, in Multisim you can go to Simulate>Instruments and select what ever instrument you want to place. So you could put a function generator in for Vin and a Oscope for Vout.</p>
| <p>I'm attempting to draw the following two circuits up in NI Multisim 10, to attempt simulation and confirm my calculations.</p>
<p>However, I'm not sure how to represent the Vin and Vout sources. Also, multisim only seems to have amplifiers with power supplies, but all theory I read seems to draw the amplifiers without. Does that matter for a eventual simulation?</p>
<p>Also, ff there's any better software for the purpose than Multisim, then please tell.</p>
<p>Thanks.</p>
<p><img src="https://i.stack.imgur.com/WDWcg.png" alt="Circuits"></p>
| Drawing a comparator op-amp in Multisim | 2010-10-02T11:54:00.293 |
4755 | |flash| | <p>There is a lot of trade-off to it.</p>
<p>Wikipedia also:</p>
<blockquote>
<p>Despite the additional transistors,
the reduction in ground wires and bit
lines allows a denser layout and
greater storage capacity per chip. In
addition, NAND flash is typically
permitted to contain a certain number
of faults (NOR flash, as is used for a
BIOS ROM, is expected to be
fault-free). Manufacturers try to
maximize the amount of usable storage
by shrinking the size of the
transistor below the size where they
can be made reliably, to the size
where further reductions would
increase the number of faults faster
than it would increase the total
storage available.</p>
</blockquote>
<p>So, NOR flash can address easier, but is not even close to as dense.</p>
<p>If you take at a look at a <a href="http://maltiel-consulting.com/NAND_vs_NOR_Flash_Memory_Technology_Overview_Read_Write_Erase_speed_for_SLC_MLC_semiconductor_consulting_expert.pdf">pretty decent comparison PDF.</a></p>
<p>NOR has lower standyby power, is easy for code execution and has a high read speed.</p>
<p>NAND has much lower active power(writing bits is faster and lower cost), higher write speed(by a lot), much higher capacity, much much lower cost per bit and is very easy for file storage use. due to it's lower read speed when using it for code execution you really need to ghost it to ram.</p>
<p>To quote a small section with a great table above it...</p>
<blockquote>
<p><a href="http://maltiel-consulting.com/NAND_vs_NOR_Flash_Memory_Technology_Overview_Read_Write_Erase_speed_for_SLC_MLC_semiconductor_consulting_expert.pdf">The characteristics of NAND Flash are:
high density, medium read speed, high
write speed, high erase speed, and an
indirect or I/O like access. The
characteristics of NOR Flash are lower
density, high read speed, slow write
speed, slow erase speed, and a random
access interface.</a></p>
</blockquote>
| <p>What are the differences and where would you use each?</p>
| What are the differences between NAND and NOR flash? | 2010-10-02T12:42:17.263 |
4764 | |capacitor| | <p>I've used a super-cap to power an external real-time clock before. The super-cap works quite well and it will power a DS1306 for almost two weeks.<p>I've never tried implementing a super-cap backed up real-time clock implemented using a PIC24. The problem is how will you isolate the super-cap from the rest of your circuit when you lose primary power? If you just connect the super-cap between your primary power and ground when you lose power the super-cap will be trying to supply power to the whole circuit and it will drain it very quickly.</p>
| <p>I want to use a 0.1F 5.5V supercap to keep time with a PIC24FJ64GA004 device. Does anyone have any idea on how to implement this? </p>
<p>I was thinking of using the supercap on the +3.3V supply line and monitoring the battery input. When the main supply drops below say 5V I would put the micro into ultra low power sleep mode (~400-500nA with RTCC.) </p>
<p>Does anyone know how long a 0.1F cap lasts with <1µA current draw? It'll be charged up to 3.3V and 2.0V is the terminal voltage, though it would probably work down even lower.</p>
| Using a super-cap with a PIC24F to keep time in case of supply failure | 2010-10-02T18:03:35.537 |
4765 | |arduino|remote| | <p>I did a project like this a while back:</p>
<p><a href="http://hackaday.com/2009/10/03/garage-door-packet-sniffer/" rel="nofollow">http://hackaday.com/2009/10/03/garage-door-packet-sniffer/</a></p>
<p>Apart from the protocol being based on rolling code or some encryption scheme like Keeloq, some of the cheaper rf modules have bad response time, you have to have some data on the line for a couple of ms before your receiver starts putting out the correct stream.</p>
| <p>I've bought that famous Receiver/Transmitter RWS-375 and TWS 375. I want to clone the remote control of my garage door.<br>
So I connected the RWS-375 in my Arduino, and build a program to receive the sinal that the remote control send.</p>
<p>However every time I press the button the program writes differente sequence of characters. I mean, I never get the same sequence of characters from the remote control. </p>
<p>I've already tried changing the bits per seconds rate, but I think the correct is 9600, right?<br>
Also is there anything else I should verify in that I'm missing?</p>
<p>Note that I've already check that they operate at the same frequency...</p>
<p>Thanks guys</p>
| Cloning a 433Mhz Transmitter using RWS-375 Receiver | 2010-10-02T19:13:04.740 |
4766 | |remote|infrared|wifi| | <p>Your simplest solution would be a <a href="https://www.ebay.com/sch/i.html?_nkw=mce%20ir%20receiver" rel="nofollow noreferrer">Microsoft Media Center IR blaster</a> many types are available, note that some require you to connect external transmitter diodes, something with wifi running linux (eg a Raspberry Pi) and <a href="http://www.lirc.org/" rel="nofollow noreferrer">lirc</a>. Lirc has a sensible API and a huge library of ir codes.</p>
<p>The traditional solution to this was the logitech harmony, but they recently shuttered their APIs.</p>
| <p>I don't have any experience with electronics really but I do have experience in programming. I'm interested in writing a program to control my stereo, TV etc. To achieve this I'll need a piece of hardware which is WiFi capable and can generate a range of infrared signals to control my TV, stereo and other infrared capable devices. Given my lack of experience with microcontrollers etc, I'd probably find it easier if I could minimize the amount of work the hardware had to do and focussed it on converting data it receives via WiFi into infrared. What components would I require and are there any relatively inexpensive out-of-the-box solutions which will have the majority of what I need without requiring too much additional soldering? Also, at a high level, what way should the operation of such a device be architected?</p>
| Components for a WiFi enabled IR controller | 2010-10-02T19:23:49.133 |
4772 | |sensor|motion| | <p>A PIR sensor usually contains two sensors (sometimes more), which look at different parts of the room through a multifaceted lens. The sensors readings are fed into a difference amplifier. If a person is stationary in the room each of the sensors will have a particular reading. If the person moves the lens will project the radiation differently onto the sensors, so that the difference amplifier's output will change. A differentiator will detect changes in the sensors' readings and switch the output. </p>
<p>In the past I've used Panasonic's <a href="http://www3.panasonic.biz/ac/e/control/sensor/human/napion/index.jsp" rel="nofollow noreferrer">NaPiOn</a> PIR sensor, which has a quad-type sensor, which, combined with the multifaceted lens divides the room in 64 detection zones. </p>
<p><img src="https://i.stack.imgur.com/rZCtN.png" alt="enter image description here"></p>
<p>Even small movements will cause a difference in the quad sensor, which will activate the output signal.</p>
| <p>How does a motion detector work?</p>
| What's the circuit for a PIR sensor? | 2010-10-03T00:35:38.737 |
4780 | |microcontroller|infrared|iphone| | <p>This might be possible with a small FPGA, and a digital rate multiplier circuit (measures the period of the input pulses from the audio jack, and (re)output the pulses at, say, 4X the frequency). For IR input, a 4X frequency divider working the other way might also be interesting to try. Might be possible to implement this in software as well on a reasonably fast microcontroller.</p>
| <p>I have an idea for a project but need some help on achieving what I want to do. I want to create a device which will insert into the audio jack of my iPhone which will emit IR signals to control my TV. Most IR devices use signals in the 35-45K range and the audio out has a max frequency of around 20K. So, since I cant directly tell the IR LED what frequency to emit, I'm thinking this device will need to have a microcontroller in the middle.</p>
<p>So what I'm thinking of doing is, having my iPhone app send a signal via the headphone jack to the device, have the device interpret it and then generate the appropriate IR signal to control the TV. </p>
<p>Any suggestions on how I might achieve this at a high level?<br>
Any suggestions for kits which might allow me to easily prototype this kind of thing?<br>
Any alternatives to my suggested solution which might work better?</p>
| How to use an audio output to generate IR frequencies | 2010-10-03T14:03:01.043 |
4788 | |crystal| | <p>I like to mention some additional - rather important - features:</p>
<ul>
<li><p>The quartz can be operated in <strong>series</strong> as well as <strong>parallel</strong> resonant operation (however, both resonant frequencies are pretty close to each other);</p></li>
<li><p>In some applications (in particular for transistor-based oscillators like the Pierce type) the quartz is used NOT as a resonant circuit but as a high-quality <strong>inductor</strong>. </p></li>
</ul>
| <p>Could you explain how a quartz crystal works, maybe with a simple schematics with the essential things ? I know it acts like a kind of stabilizer for an oscillator, but nothing more than that.</p>
| How does a quartz crystal work? | 2010-10-03T22:03:03.123 |
4799 | |sensor|tutorial| | <p><a href="http://rads.stackoverflow.com/amzn/click/1441918388" rel="nofollow">Handbook of Modern Sensors [3rd Edition] by Jacob Fraden</a><br>
ISBN: 1441918388</p>
<p>This reference book covers a number of different types of sensors and the circuits that can be used to read them.</p>
| <p>I'm looking for tutorials/explained examples on circuit design in general, but specifically on using various sensors.</p>
| Where can I find good tutorials on sensor circuit design? | 2010-10-04T08:24:11.173 |
4803 | |power|components|potentiometer| | <p>That particular pot is similar to those used in old-time hand-held transistor radios. My recollection is that thost are good for perhaps 200 mW at most.</p>
<p>You can often estimate how much power any particular potentiometer can handle based on the physical size and the material that the resistive track is made from. Although experience helps you arrive at an estimate, you can also simply look at a catalog of pots and compare what is in the catalog to what you have. Digikey or Mouser have great on-line catalogs, for example. </p>
<p>Resistive track material is important. You can usually tell if the track is wire-wound by simply rotating the shaft and feeling for the telltale lumps that occur as the wiper moves over the track. If the rotation is smooth, the track is most likely either carbon or carbon film. </p>
| <p>I salvaged a 1kΩ potentiometer from a broken circuit. Is there any way to determine how much power can it take without destroying it?</p>
<p><strong>EDIT</strong> Picture of the potentiometer:</p>
<p><img src="https://i.stack.imgur.com/bjUUt.jpg" alt="potentiometer"></p>
<p>The distance between left-most and right-most connector is about 2cm.</p>
| Is there any way to determine power rating of a potentiometer? | 2010-10-04T09:29:02.300 |
4807 | |kits|android| | <p>I would suggest having a look at a chinese MID. They can be had for 100$ online, but if you have the chance to buy one in china you can get one for around half that price in a copy market. While offering a lower product quality you can get started for a lower price than any development board.
One of the tablets I bought gives me a Wondermedia armv5 compatible processor with 256mb ram and 2gb flash memory which is a way better deal than the friendly arm compatible kit I used at work.</p>
| <p>Is there any kit or board on which I can test out customized android os?</p>
| Is there any kit for android development? | 2010-10-04T11:17:33.600 |
4808 | |resistors|adc|parallel| | <p>Suppose we label the first switch <code>num=1</code>, the last switch <code>num=16</code>, then:</p>
<p>$$R_{hi} = \frac{1M\Omega \times num \times 10k\Omega}{1M\Omega + num \times 10k\Omega}$$
$$R_{lo} = (17 - num) \times 10k\Omega$$
$$V_{out} = \frac{5V \times R_lo}{R_{hi} + R_{lo}}$$</p>
| <p>I've been researching pullup and pulldown resistors after seeing them used in many digital circuits and while I understand what their purpose is, I haven't found any resource on how to determine the resistance values to use in such circuits and how these values affect the circuit's behaviour.</p>
<p>One of the examples I have is...</p>
<p><img src="https://i.stack.imgur.com/DIC0I.jpg" alt="ADC Keypad Circuit"></p>
<p>...which is an A/D converter circuit for a keypad input. I have implemented this and it actually works very well but I can't quite pinpoint why a 1Mohm resistor was picked as the pullup and what exactly happens to it when one of the buttons are pressed - does it affect the voltage of the ADC input in such a small amount that it doesn't register or is it overridden somehow or...?</p>
<p>I know this is probably a very basic question but I can't seem to apply the thoery I have learned to this one.</p>
| Using Pullup and Pulldown Resistors | 2010-10-04T11:38:19.307 |
4814 | |arduino|audio|atmega|sound| | <p><strong>Using Atmel chips in the Arduino IDE</strong></p>
<p>For the ATtiny45 and ATtiny85 you can use <a href="http://hlt.media.mit.edu/wiki/pmwiki.php?n=Main.ArduinoATtiny4585" rel="nofollow">this library</a> that you put in the same directory as your sketches (make a "hardware" directory, then unzip this in there).</p>
<p>I found lots of things just work, but not everything. These chips are pretty tiny. You only get 4 input/outputs (or 5 if you have a high voltage programming device), and you have to be careful which ones can produce the type of output needed by tone (probably only 2 of the pins). These guys are in the $1.25 to $2.25 range.</p>
<p>You can also use ATtiny2313's, but I've not tried using the Arduino IDE with them. I switched to using AVR style GCC, as its not much harder and if something breaks I know its my fault. The 2313 has a ton more pins (not as many as the ATmega), hardware serial support, etc. It is in the $1.50 to $2.50 range.</p>
<p>The ATmega328p is more in the $3.00 to $4.50 range (and currently is often out of stock).</p>
<p>You can think of the Arduino IDE as consisting of 3 main parts:</p>
<ul>
<li>a nice, reduced programming language for AVR style chips (mostly by providing you with simple to use functions like tone)</li>
<li>a nice, easy to use upload mechanism for ATmega and larger ATtiny chips (the bootloader)</li>
<li>a nice GUI interface that makes it easy to use the right part when you need it</li>
</ul>
<p>When you work with the ATtinyX5 chips, the bootloader doesn't work, but you can use an Arduino to program the ATtiny's very easily. The library I linked to makes the first and third parts of the IDE available to you.</p>
<p>If you want something cheaper, but mostly the same as the ATmega328p, I would go with the ATtiny2313. If you want something smaller, then the 8-pin ATtiny85 is nice, but it is not too much cheaper and lacks a lot of the nice features of the ATtiny2313 and the ATmega328p.</p>
<p>I haven't tried the other Atmel AVR product lines, but they definitely have others. Luminet (mentioned in another answer) uses the ATtinyX4 line and has a modified IDE to work with them. They appear to be in the $1.80 to $3.00 range.</p>
| <p>I'm using an Atmega328 chip with the arduino bootloader in a very small circuit. The sketch simply plays a tune using the tone() function to play a melody through a piezo speaker on a single pin.</p>
<p>Clearly using this chip is overkill, but the programming environment is so simple for arduino, and easy for me to use.
Can I use a Attiny with the arduino bootloader or something similar? What would be the right way to miniaturise this project, so I don't feel like I'm wasting components. If it's a case of using a different chip/environment entirely, where do I start?</p>
<p>(for clarity, I am not using an arduino in the circuit, just the Atmega328 chip)</p>
| My Atmega328 seems to be overkill, what should I use instead? | 2010-10-04T13:26:00.233 |
4816 | |capacitor| | <p>You mean like this? </p>
<p><img src="https://i.stack.imgur.com/G0mYv.gif" alt="alt text"> </p>
<p>The peak output voltage would just be the peak input voltage. If it changes fast enough, the output will track it almost exactly, and then decay to smaller values:</p>
<p><img src="https://i.stack.imgur.com/e6owD.png" alt="alt text"></p>
<p>Oh wait. That doesn't take into account a repeating waveform, like this:</p>
<p><img src="https://i.stack.imgur.com/l4llM.gif" alt="alt text"></p>
<p>After the wave has decayed, when you switch the input again, the output will jump to a lower voltage than the input:</p>
<p><img src="https://i.stack.imgur.com/99K1Y.png" alt="alt text"></p>
<p>So I think the worst case would be square waves of low frequency, so that they decay completely to zero before switching, and the peak-to-peak output voltage would then be 2× the input peak-to-peak voltage.</p>
| <p>How do I calculate the peak output voltage of a capacitor differentiator?</p>
| How do I calculate the peak output voltage of a capacitor differentiator? | 2010-10-04T13:42:18.310 |
4828 | |wire|breadboard| | <p>I have always used a dab of solder on stranded wire when needing to use it in a breadboard. It has always worked perfectly for me. Just be careful to make sure that you do not have any excess solder at the end as the wire tends to get stuck in the breadboard if there is anything sticking out that can get caught on it.</p>
<p>I know you asked for local, but here are a few links to items similar to what I have used before:</p>
<p><a href="http://www.mouser.com/ProductDetail/Twin-Industries/TW-E012-000/?qs=sGAEpiMZZMvJBlHRSOGUxOhvehuk8u4qJwTh7IUsHNU%3d" rel="nofollow">http://www.mouser.com/ProductDetail/Twin-Industries/TW-E012-000/?qs=sGAEpiMZZMvJBlHRSOGUxOhvehuk8u4qJwTh7IUsHNU%3d</a></p>
<p><a href="http://www.mouser.com/ProductDetail/SchmartBoard/920-0067-01/?qs=sGAEpiMZZMvJBlHRSOGUxIxWMAp5GnPY3nX1cMlAHE0%3d" rel="nofollow">http://www.mouser.com/ProductDetail/SchmartBoard/920-0067-01/?qs=sGAEpiMZZMvJBlHRSOGUxIxWMAp5GnPY3nX1cMlAHE0%3d</a></p>
<p>You can also use these: <a href="http://www.mouser.com/ProductDetail/3M/2340-6111TG/?qs=R%252bzptqw7cJImGeX9bGiQLA%3d%3d" rel="nofollow">http://www.mouser.com/ProductDetail/3M/2340-6111TG/?qs=R%252bzptqw7cJImGeX9bGiQLA%3d%3d</a>
<br /> They break away into any number you want and are the same spacing as common bread boards.</p>
| <p>I decided to start working with hobby electronics, but I'm having a problem finding a local source of solid wires. As far as I know solid wires are often recommended for use with protoboards because inner wires of stranded wire can get jammed inside protoboards wire holding mechanism.</p>
<p>I'm looking for tips on how to modify stranded wires to work with protoboards.</p>
<p>The obvious solution which comes to my mind is to use solder on the exposed part of the wire and make it solid.</p>
<p>Any other ideas?</p>
| How to modify stranded wire for use in protoboards? | 2010-10-04T15:56:48.757 |
4839 | |soldering| | <p>I don't have any problems hand-soldering connectors like that. I use a Metcal soldering station with a mini-hoof cartridge. I tack the connector down at two opposite corners, making sure it is positioned properly using a stereo microscope, apply plenty of jelly flux, and drag-solder each row.</p>
| <p>I recently purchased this item to use with an arduino:</p>
<p><a href="http://www.sparkfun.com/commerce/product_info.php?products_id=9105" rel="nofollow">http://www.sparkfun.com/commerce/product_info.php?products_id=9105</a></p>
<p>My problem is that I realized after the fact that this wasn't attached to the breakout board. Are these connections too small to be soldered by hand? What is the smallest distance between connections that can realistically be soldered by hand?</p>
| Soldering tiny connectors | 2010-10-04T18:44:39.630 |
4842 | |pic|video| | <p>I had the same problem with varying DC offset based on light level. I got around this by making the PIC code track the level and so the reference for the comparator would always be within the signal deflection range. It works well but now have another problem. I am trying to detect the vertical sync so I know when to switch a video multiplexer and stop any flicker or rolling. I can detect the vertical sync but cannot currently discriminate between even and odd fields. I am still getting a flicker as the two camera feeds and not genlocked. Does anyone know at what point I should switch the multiplexer, do I do it at the start of the odd field only? Or could the problem be due to the camera seeing different light levels and as they change the DC blocking cap need to charge/discharge to a different level? </p>
<p>Thanks,
Jose</p>
| <p>I have a PAL or NTSC video signal and I want to extract the CSYNC information. Preferably, I would like to avoid using an LM1881, because I am short on space and I'm optimising for cost. Also, the LM1881 is limited to an operating range of 0°C to +70°C and I want a full industrial range of -40°C to +85°C.</p>
<p>So I set up a little divider network like this:</p>
<pre><code>3.3V --------------+
|
/
\ 4.7k
/
4.7u 1k |
Inp --| |--/\/\/\-+--- to PIC comparator
|
/
\ 4.7k
/
1k |
---
-
</code></pre>
<p>This produces a signal with ranging from 1.27V to 1.5V, but the signal moves up and down when the brightness in the scene changes! I think this is happening because the DC offset is changing. </p>
<p>Any idea on how to eliminate this offset? I guess I could add some other components, but I'd rather not - I'm trying to keep this as simple as possible.</p>
| Best way to do sync separation without an LM1881 or equivalent | 2010-10-04T19:11:45.227 |
4851 | |infrared| | <p>This is definitely not <a href="http://nenya1.net/electronics/rc5/index.php" rel="nofollow noreferrer">RC-5</a>, which you can easily tell from the preamble in the first and second screenshots. RC-5 is <strong>Manchester modulated</strong> (aka Biphase modulation), which is characterized by its mid-bit edge: </p>
<p><img src="https://i.stack.imgur.com/T0PwK.png" alt="Manchester code"></p>
<p>so you always have a pattern of equally-spaced clock edges (either rising or falling) with data edges (present or not) halfway between two clock edges. Neither the preamble nor the following pulses match this criterion.<br>
The last screenshot indicates that it uses pulse-pause modulation: a pulse with a fixed width followed by a variable pause. A long pause could be a <code>1</code> and a short one a <code>0</code> or vice versa.<br>
This modulation method has the disadvantage that messages aren't the same duration; their duration depends on the number of <code>1</code>-bits in it. An advantage is that decoding is a bit easier than Manchester.</p>
| <p>I'd like to decode some IR signals from a TV remote control. I scavenged a 3 pin IR receiver from some old junk and hooked it up.</p>
<p>From what I've read about RC-5, I was expecting to see a start bit indicating the bit time, which I could synchronize to. But, I'm seeing lots of transitions per bit time.</p>
<p>Is this a sign that I'm mixing 38kHz and 56kHz devices? Or am I expecting the wrong thing?</p>
<p><img src="https://i.stack.imgur.com/Arpa7.jpg" alt="scope screenshot"><br>
<img src="https://i.stack.imgur.com/Nm74H.jpg" alt="scope screenshot"></p>
<p>Edit:</p>
<p>I was concerned that the weirdness I was seeing was the IR receiver being odd. So, I wired up a plain old 2 pin IR LED receiver to compare (bottom trace). With the LED, I see the 32kHz carrier wave and the modulated signal, the "smart" receiver filters out the carrier perfectly leaving just the pulse widths.</p>
<p>Ladyada tutorial explained it all.</p>
<p><img src="https://i.stack.imgur.com/DNw0G.jpg" alt="scope screenshot"></p>
| Confused by IR pulses | 2010-10-04T20:32:26.840 |
4857 | |rfid| | <p>Doing some more Googling on this topic (armed with some hints provided by Kellenjb, tronixstuff and avra), I have turned up an example of the kind of reader I'm interested in:
<a href="http://www.iautomate.com/products/Home-Automation-RFID-Reader.html" rel="nofollow">Home Automation RFID Reader</a></p>
<p>I will be trying to find a tear-down of this or a similar unit that describes the components it uses. I'll try to keep this answer updated with what I learn.</p>
| <p>What are some good RFID readers to look at for a keyless residential entry system? Are there any on the market that can read a key fob or similar RFID token from a range of 3 feet or more? This would be a DIY project for a new home, so price is less of an issue than reliability and ease of integration.</p>
| RFID reader for a keyless residential entry system? | 2010-10-05T01:07:31.183 |
4865 | |capacitor|sound| | <p>Does ladyada recommend the 2N2907? I did not see a label on the schematic.</p>
<p>Since the transistor is being used as a switch a better choice would be a 2N3906
which has much lower Vbe(sat) and Vce(sat) specifications.</p>
| <p>im a beginner at electronics.
im trying make an drawdio circuit with the instructions in the link below:
<a href="http://www.ladyada.net/make/drawdio/drawdio2schem.png" rel="nofollow">http://www.ladyada.net/make/drawdio/drawdio2schem.png</a>
i have following components on the circuit.</p>
<ul>
<li>NE555N 555 timer</li>
<li>PN2907 transistor</li>
<li>100uF 25V capacitor <strong>(instead of 6.3v one on the ladyada's page)</strong></li>
<li>680pF ceramic capacitor </li>
<li>0.1uF non-ceramic capacitor <strong>( instead of ceramic one on ladyada's page)</strong></li>
<li>1/4W 5% 10 MEGAohm resistor</li>
<li>1/4W 5% 10 ohm resistor</li>
<li>1/4W 5% 300K resistor</li>
<li>Small 8ohm speaker 0.5w</li>
</ul>
<p>do you think any of those changes i made might be causing low sound problem??
please help :/</p>
| Drawdio the sound is very very low :S? | 2010-10-05T09:17:55.197 |
4866 | |software|simulation| | <p>Check out <a href="http://sysvis.io/svse" rel="nofollow">SystemVision</a>. It's completely online, free, and has a ton of models and designs for you to use for learning.</p>
| <p>Is there software out there that will take a schematic as input and simulate its functioning?</p>
<p>I don't have a lot of cash for components and tools, so this would be a cheap and easy way for me to learn more about electronics.</p>
| Can you simulate a schematic? | 2010-10-05T10:14:15.057 |
4874 | |rfid| | <p>I don't think you need long range (at least not how I categorize long range, like 15-30ft like a highway toll sensor).</p>
<p>At the Boston Marathon this year all the runners got a very small plastic cased passive RFID tag which was designed to be tied into their shoe laces. </p>
<p>At the 11 check points there was a large thin mat across the race track which detected the tag as they ran over it. I don't know the nature of the mat but i imagine it had multiple antennas so the detection distance was maybe 1 foot.</p>
<p>I've also seen some races where the RFID tag was in the bib but i believe there were still using mats for the antennas, the range would just need to be a few feet longer.</p>
<p>In terms of the final results accuracy, long distance races hardly ever end in a "photo finish" situation. If they were to end in that manner I image the judges would have a photo back up of the finish.</p>
| <p>I am considering building an RFID reader system that can monitor runners times in a foot race. I have read that there are three different types of RFID systems. LF, HF, and UHF. Which one would be best for this application? Has anyone had success building an antenna that can read RFID tags from a distance of a meter or more?</p>
<p>EDIT: Active or Passive? My current thought is to use passive technology. I want to be able to get the tags for as cheap as possible and I don't want there to be a chance of the internal batteries failing. </p>
| Best RFID Technology for long range detection? | 2010-10-05T12:52:29.323 |
4881 | |power-supply| | <p>The most simple solution is to use a differential amplifier stage across your high side resistor to measure the current, and measure that value with your microcontroller. You could much more easily add a second stage, probably, to your power supply to make a current limit. </p>
<p>If you already have a regulating transistor in place, you can probably make a little comperator that compares your set current (a reference voltage) against the measured voltage (representing your current). If you include that in the feedback loop of your power supply, it should regulate rather easily.</p>
<p>I wouldn't do low-side sensing because that makes your ground not fixed (i.e. if you draw 2A, the ground potential shifts when the current drops). Also, if the ground terminal is shorted with a low-side resistor in place, the power supply has not current limit set. This could unbalance your load.</p>
<p>I would also stay with an analog regulation; analog electronics are much easier to set up (it's a few resistors and opamps, maybe a few caps required) instead of a proccesor + some kind of PI regulator.</p>
| <p>I would like to build DIY linear bench power supply, with adjustable, regulated output voltage and current limiting functions. The voltage and current regulation will be implemented using analog feedback loops. The functionality of the device requires sensing of the output current in order to: </p>
<ol>
<li>Use it in feedback loop to limit current </li>
<li>Measure output current </li>
</ol>
<p>Since whole this is to be controlled by microcontroller (voltage and current limit setting, measurement) it means that I need to generate voltage with respect to ground proportional to the current (or not?).</p>
<p>One of the possible solution is to implement high side current sensing using resistor (it is preferable solution due to protection against accidental shorts compering to low side sensing). Examples of the high (and low) sensing circuits can be found in nice <a href="http://www.microchip.com/wwwAppNotes/AppNotes.aspx?appnote=en551198" rel="nofollow noreferrer">app note</a> from microchip. </p>
<p>I am hesitating to use any of the provided solution as that would mean placing two opamps in cascade (opamp for control + current sensing) which may be an issue for circuit stability. Do you have other ideas how high side current sensing could be implemented and be suitable for both analog control and measurement (does not have to be the same circuit)?</p>
| High side current sensing in DIY bench supply | 2010-10-05T18:57:21.273 |
4888 | |power-supply|batteries|charging| | <p>I believe it's based on opamps. An opamp is a simple device that when wired together with others can serve as an indicator of how full a battery is. Think of them as different height holes in a vertical tank. You know where the level of the water in the tank is depending on the height of the hole spilling water.</p>
<p>These get wired into a small board such as battery management systems (bms boards) for charging series- parallel batteries in a pack. Otherwise if you just want to recharge a single battery there are simpler lipo charging modules but I assume you're talking series of batteries since you mentioned battery pack. And this is for lipo batteries which are more commonly used in these projects I think.
. </p>
| <p>We have a device that runs off of a AC adapter, or a pack of 8 AA batteries. Since in normal use we use both, it would seem to make sense to have the battery pack recharge while using the AC adapter - instead of throwing the rechargeable batteries into a separate charge each time they're depleted. </p>
<p>What are the basics of designing/modifying the existing battery pack and AC adapter to implement that kind of charging?</p>
<p>A quick observation shows that the battery pack looks to be just the cells in series, with a capacitor (perhaps for protection from voltage spikes, it's powering a motor). </p>
<p>My thoughts are that I'll need to make sure the AC adapter can provide enough current to power the device and charge the batteries. The pack will have to somehow be modified to charge the cells in parallel (right?) while powering the device in series. </p>
<p>Other than those vague ideas, I don't know where to start/how possible this is. So what are the basics I need to know when it comes to building this kind of charger?</p>
<p><em>Slight Update:</em> I know I need a circuit to control the recharge, I'm not just looking for a circuit to build, but the basic purposes of that kind of circuit. How does it monitor the charge (and determine when charging is needed)? What are the basic components involved and their purposes? </p>
| What are the basics of making a rechargeable battery pack? | 2010-10-06T01:34:13.210 |
4890 | |stepper-motor|driver| | <p>Sometimes.</p>
<p>There are actually three stepper motor topologies. "Bipolar", "Unipolar", and "Universal" (the parlance I have always heard, anyways).</p>
<p>Bipolar motors are 4-leaded, and have two field separate field coils.<br>
Unipolar motors are 5 leaded, and effectively have 4 field coils, with one end of each connected together (The "Common" lead) See <a href="http://www.electronics-project-design.com/StepperMotorControl.html" rel="nofollow">Here</a>.<br>
Universal motors have 6 leads, and are effectively a center-tapped bipolar motor.</p>
<p>A 5-leaded unipolar motor <strong>cannot</strong> be driven with a bipolar stepper motor driver. A bipolar driver can only drive a universal or bipolar motor.</p>
| <p>I would like to universal stepper motor driver circuit. Is it possible for one circuit to be able to drive unipolar and bipolar motors with only a firmware change or do they require much different circuits? I know that bipolar motors use 4 wires and unipolar uses 6 so if i use a connector with 6 pins would it be possible?</p>
| Unipolar and Bipolar Stepper motors | 2010-10-06T02:20:37.107 |
4895 | |clock|pll| | <p>Many years ago I used the Signetics NE565 PLL chip to build a 1 MHz frequency standard phase-locked to the BBC 200 kHz long wave transmission.</p>
| <p>I was wondering if anybody was using PLL (Phase Locked Loop) in DIY hobby project? If yes what was the application? Did you made it from discrete components (as opposed from one placed in uController or FPGA) ?</p>
| PLL usage in DIY hobby project | 2010-10-06T08:28:35.457 |
4904 | |pic|memory|sharedbus| | <p>Incidentally, one approach not yet mentioned for use with parallel memories is to have two or more devices given fixed time slots to access data. This approach was used in many 6502-based computers made by both Apple, Commodore, and some other vendors (not, interestingly, Atari). The popular 6502 microprocessor used a two-phase clock, and always performed its memory accesses on the second half of each cycle (the address was available during the first half, but the data would be written during the second half or latched at the end of the second half). The Apple and Commodore machines would thus during the first half of each memory cycle use an address generated by the video circuitry, latching the data at the end of the half; during the second half of each cycle they would use the address generated by the CPU, and let the CPU either write the data or latch it at the end of its half.</p>
<p>This approach required memory that was twice as fast as would have been required without memory interleaving, and required the addition of 3-state drivers on the processor's address outputs (the 6502's address outputs were always driven high or low) but it otherwise worked very smoothly to make the same memory available to both the processor and to external circuitry.</p>
| <p>I'm looking for a small, 32KB or so SRAM device that two MCUs can read or write (at two different times; I don't need simultaneous reading/writing.) It would be good if it used a serial interface as well.</p>
<p>The problem I'm trying to solve is sending data between two devices without the other device having to pause to receive this. I would transfer an audio sample into the buffer, then the other chip, as required, would read the audio out, and do something with it. </p>
<p>I've found serial SRAM's like Microchip's 23A256/23K256, however, they seem to have a single serial interface. Is there any way to have two chips accessing this?</p>
<p>Additionally, the receiving device only has 2KB data memory free (maximum) so it looks like using DMA or some similar transfer mechanism through I2C or other interface will not work.</p>
| SRAM which two chips can read/write | 2010-10-06T13:13:56.433 |
4905 | |fpga|pic|microcontroller| | <p>My inclination would be to use something to buffer the timing between the processor and the display. Having hardware that can show an entire frame of video without processor intervention may be nice, but perhaps overkill. I would suggest that the best compromise between hardware and software complexity would probably be to make something with two or three independent 1024-bit shift registers (two bits per pixel, to allow for black, white, gray, or transparent), and a means of switching between them. Have the PIC load up a shift register, and then have the hardware start shifting that one out while it sets a flag so the PIC can load the next one. With two shift registers, the PIC would have have 64us between the time it is told a shift register is available and the time all the data has to be shifted. With three shift registers, the PIC would have to average one line every 64us, but it could tolerate a delay of up to 64us.</p>
<p>Note that while a 1024-bit FIFO would be just as good as two 1024-bit shift registers, and in a CPLD a FIFO only costs one macrocell per bit, plus some control logic, in most other types of logic two bits of shift register will be cheaper than one bit of FIFO.</p>
<p>An alternative approach would be to connect a CPLD to an SRAM, and make a simple video subsystem with that. Aesthetically, I like the on-the-fly video generation, and if somebody made nice cheap 1024-bit shift-register chips it's the approach I'd favor, but using an external SRAM may be cheaper than using an FPGA with enough resources to make multiple 1024-bit shift registers. For your output resolution it will be necessary to clock out data at 12M pixels/sec, or 3MBytes/sec. It should be possible to arrange things to allow for data to be clocked in at a rate of up to 10mbps without too much difficulty by interleaving memory cycles; the biggest trick would be preventing data corruption if a sync pulse doesn't come at the precise moment expected.</p>
| <p>I am currently working on Super OSD - an on screen display project. <a href="http://code.google.com/p/super-osd">http://code.google.com/p/super-osd</a> has all the details.</p>
<p>At the moment I'm using a dsPIC MCU to do the job. This is a very powerful DSP (40 MIPS @ 80 MHz, three-register single-cycle operations and a MAC unit) and, importantly, it comes in a DIP package (because I'm using a breadboard to prototype it.) I'm really getting every last bit of performance out of it running the OSD - the chip has about 200ns or 10 cycles per pixel on the output stage so the code has to be very optimised in this part (for this reason it will always be written in assembly.)</p>
<p>Now I was considering using an FPGA for this because due to the parallel architecture of such a chip it is possible to have a simple logic program running the OSD. Things like drawing lines and algorithmic code would be handled by an MCU, but the actual output would be done with an FPGA. And some simple things like setting pixels or drawing horizontal and vertical lines I would like to integrate onto the FPGA, to improve speed.</p>
<p>I have some questions:</p>
<ol>
<li>Will it cost significantly more? The cheapest FPGA's I found were ~£5 each and the dsPIC is £3 each. So it will cost more, but by how much?</li>
<li>The dsPIC fits in a SO28 package. I would not like to go bigger than SO28 or TQFP44. Most FPGA's I've seen come in BGA or TQFP>100 packages, which aren't an option at the moment, due to the shear size, and the difficulty of soldering them myself.</li>
<li>How much current is used by an FPGA? The dsPIC solution currently consumes about 55mA +/- 10mA, which is okay at the moment. Would an FPGA consume more or less? Is it variable, or is it pretty much static, like the dsPIC?</li>
<li>I need at least 12KB of graphics memory to store the OSD graphics. Do FPGA's have this kind of memory available on the chip or is this only available with external chips?</li>
</ol>
| Is an FPGA viable for such a project? | 2010-10-06T13:26:03.423 |
4923 | |power|current|oscilloscope| | <p>Use a B&K (or comparable) isolation transformer to'float' the scope.</p>
| <p>I want to measure how much power my PIC is using. At the output of my 3.3V regulator I put a 1 ohm resistor in series with the rest of the circuit. I was going to measure the voltage drop across that resistor to get the current and so on. With the 1 ohm resistor installed the circuit works just fine but when I put the probe of my o'scope across it it my 3.3V goes to zero. It seems as though the scope is creating a short to ground or something. Does anyone know why this happens or how to make it stop?</p>
| Why does Oscilloscope cause short? | 2010-10-06T20:00:38.080 |
4938 | |pcb|software|library|stellaris| | <p><a href="ftp://ftp.cadsoft.de/eagle/userfiles/libraries/luminary-arm.lbr" rel="nofollow">ftp://ftp.cadsoft.de/eagle/userfiles/libraries/luminary-arm.lbr</a></p>
<p>Symbols and footprints for:
LM3S101
LM3S102
LM3S301
LM3S310
LM3S315
LM3S316
LM3S328
LM3S601
LM3S610
LM3S613
LM3S615
LM3S628
LM3S6911
LM3S6918
LM3S6938
LM3S6950
LM3S6952
LM3S6965
LM3S801
LM3S811
LM3S812
LM3S815
LM3S828
LM3S8962</p>
| <p>Someone pointed me at the freeware version of Eagle as a good starter dev tool. So I start playing around and I can't seem to find a part library for the chips I want to use. I found a library (the works) on the eagle site but it doesn't have the right parts and I found a library on the TI/Luminary Mico site (that I think has the right part) but it wont load (it has .src files and I seem to need .lbr) despite the fact it has files tagged specifically as for eagle.</p>
<p>Does anyone know where I can get files that will work? (Or how to make the files I have work?)</p>
| Stellaris 6/8/9000 part libraries for Eagle? | 2010-10-07T05:28:28.323 |
4939 | |power-supply|batteries|ipad| | <p>No. The ability to use the USB interface for data while charging requires some negotiation WRT current capabilities when the USB device is connected to the computer.</p>
<p>Basically, the computer has to tell the iPad that it can source 2A once it is connected. The charger does this by pulling some of the USB data lines high or low. However, this precludes data transfer.</p>
| <p>Ipad doesn't charge while in use and connected to the usb port. It definitely charges when connected to the supplied 10 watt power adapter.</p>
<p>The USB port, as far as I know, supplies 5 watts. Can we modify it by simply adding an extra usb adapter to the cable of ipad to draw the extra 5 watt? something which the older external hard-drives used to do?</p>
| Ipad charging via usb port | 2010-10-07T05:39:41.587 |
4942 | |programming|flash|pcb-assembly| | <p>The most versatile approach, though I don't know if anyone supports this, would be to have a chip programmer read a chip and write it to a file, then run a user-supplied program to update the file with what should be in the chip, program the resulting file into the chip and read it out, and run the user-supplied program to verify it (possibly repeating the program cycle if the verify program wasn't satisfied with the result). When that isn't practical, I would think the best approach is often to simply have a means of feeding the required data into the target circuit so it can program the memory chip using whatever forms of error-correcting and bad-block memory it uses.</p>
| <p>A project has finally reached the point where prototypes are operational and ducks are lining up in rows for the first pre-production lot of boards. It uses a SOC device that boots its ARM core from an external NAND FLASH chip, which normally contains a boot loader, the embedded application, and other data resources. With a minimal boot loader and application in FLASH, it is easy to field upgrade. The prototypes got boot loaders installed with a JTAG cable, but that seems more than a little unwieldy for production lots larger than a dozen or so boards.</p>
<p>If this were a NOR FLASH or OTP PROM I would expect a vendor to be happy to take an Intel HEX or Motorola SRecord file and deliver devices that just work when soldered down. </p>
<p>Given the different nature of NAND FLASH devices, what issues should we be watching for?
What questions should we be asking vendors?
What form of image should we be expecting to be able to supply?</p>
<p>In short, what is the usual practice for pre-programming a NAND FLASH device before assembly?</p>
<p><strong>Edit:</strong></p>
<p>If it were to make a difference, it is an STM (numonyx or micron, why can't the chip companies stop selling each other their product lines mid design cycle?) NAND512xxx 512 Mb SLC family device that wants programming.</p>
| Best practices for production programming of data/NAND flash devices | 2010-10-07T08:28:13.687 |
4951 | |capacitor|discharge| | <p>The answer is already given above but this is the way I think about it:</p>
<p>Assuming a constant current: I=C*dV/dt --> dt=C*dV/I</p>
<p>dv=5V-3V =2V, I=10mA, C=1F --> dt=1F*2V/10mA= 200sec</p>
| <p>Say I have a 1F capacitor that is charged up to 5V. Then say I connect the cap to a circuit that draws 10 mA of current when operating between 3 and 5 V. What equation would I use to calculate the voltage across the capacitor, with respect to time, as it is discharging and powering the circuit?</p>
| How do I calculate how fast a capacitor will discharge? | 2010-10-07T11:51:13.317 |
4954 | |fpga|interface|camera|xilinx| | <p>We simply don't know enough from the question and comments (as yet). Internally a Spartan 3 family chip could probably do the edge detection, but reading the image sensor at that speed is more of an open question - it depends more on the sensor interface and board layout. Then there's the question of what to do with all the data - it's doable to just feed it out again, possibly using wider connections, but the FPGA itself certainly can't store it. </p>
<p>Unfortunately this question is turning into more of a discussion, which this site wasn't designed for. We keep having to dig to find the new comments. To give a verifiably correct answer, we would have to do half the design work - all the way to component selection and algorithm data flow. </p>
| <p>I am thinking to go in for a FPGA starter kit, I browsed the Xilinx website and found that the Spartan 3 series were quite economical - Spartan3AN, Spartan3A and Spartan3E. The Spartan 3AN seems to be a new board.</p>
<p>Can the Spartan FPGA handle processing of a 5MegaPixel camera, interface would be 8bit parallel data in raw rgb, and do some edge detection 15 times a second?</p>
| Can a Spartan-3A / AN / E implement edge detection for a 5MP camera | 2010-10-07T12:16:04.223 |
4956 | |pic|output|port|input| | <p>If you want to simulate an open collector write a zero to the latch register. Then you do the rest with the TRIS register. When a zero goes to the TRIS bit this will turn the bit to an output and the line will be driven low. Then if you write a one to the TRIS bit the line will become an input and the pull up will cause the line to go high unless an external device is driving it low. The line will also be in an input state at that time. You can read the port at any time and it will show the proper bus state because when TRIS bit is 0 the bus will be low and that is what will be read and if TRIS bit is high it will be an input and then what ever is on the bus will be read as well.</p>
<p>Some pins also have the ability to enable a weak pullup on them and you can also enable the pin change interrupt on some of the pins.</p>
<pre><code>//init
_LATA0 = 0;
//drive low
_TRISA0 = 0;
// let pull up bring pin high.
_TRISA0 = 1;
// read bit
in = _RA0;
</code></pre>
| <p>I am working on a project which uses a PIC24FJ64GA002 mcu.
I am working on a bit-banged serial communication function that will use one wire to send data and then switch to receive mode to receive data on the same pin. A separate pin will be used for clocking which will always be controlled by a different board (always an input). I am wondering is there a way to configure the pin for open-collector operation that that it can be used as an input and and output or do I have to change the pin configuration every time i go from reading to writing?</p>
| Configure a PIC pin for Input and Output | 2010-10-07T13:28:28.537 |
4960 | |pic|power|capacitor| | <p>When your devices power gets too low, your PIC will reset itself. If you have a certain state that you want your pic to be in when it comes back on, you could save settings to eeprom just before putting it to sleep. Then, every time your pic starts you can have it check eeprom for your state settings and act accordingly.</p>
| <p>I am working on a project that uses a PIC24F mcu.
The power to my pic is backed by a very large capacitor (1F).
When there is a main power loss, I can sense that immediately via a port pin but the PIC itself stays powered for several minutes via the capacitor as the charge in the cap slowly dissipates. </p>
<p>Once I detect that the main power is cut, I want to perform some actions (several micro seconds only) and then stop the PIC from doing anything else (sleep or hibernate i guess). But as the caps charge slowly dissipates the power to the pic will VERY slowly decrease below 3.3V down to zero. At any point, if the main power is re-applied, the pic should detect it at the Port Pin, and restart normal operation. I am wondering what would be the best way to handle this in software? I know that the PIC has Brownout detection and some kind of Low Voltage Tracking but I don't quite understand how to use them.</p>
| How can I handle a low power condition with PIC? | 2010-10-07T14:51:27.887 |
4967 | |protection|undervoltage| | <p>You can connect a push/pull voltage detector (PMIC supervisor) such as the Microchip <a href="https://ww1.microchip.com/downloads/en/DeviceDoc/20001889F.pdf" rel="nofollow noreferrer">MCP112</a> or <a href="https://ww1.microchip.com/downloads/en/DeviceDoc/20001434K.pdf" rel="nofollow noreferrer">TC54</a> to a logic-level MOSFET, e.g. as described in the <a href="https://ww1.microchip.com/downloads/en/DeviceDoc/20001434K.pdf" rel="nofollow noreferrer">TC54 datasheet</a>:</p>
<p><a href="https://i.stack.imgur.com/FnCaU.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/FnCaU.png" alt="enter image description here" /></a></p>
<p>(page 6)</p>
<p>There are some popular thresholds versions of these parts, e.g. MCP112-300, MCP112-315, TC54VC30. So perhaps the nominal 3.15 V tripping point is sufficient for your application. In case it isn't you can look into getting a customized version or use one with V_trip=3V and voltage divide V_In as described in the <a href="https://ww1.microchip.com/downloads/en/DeviceDoc/20001434K.pdf" rel="nofollow noreferrer">TC54 datasheet</a>:</p>
<p><a href="https://i.stack.imgur.com/0pWIx.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/0pWIx.png" alt="enter image description here" /></a></p>
<p>(page 6)</p>
<p>For example with V_trip=3V and a target threshold of 3.2V you could chose R1=1780 Ohm and R2=26700 Ohm).</p>
<hr />
<p>In comparison with the MAX809, the above voltage detectors are more efficient (e.g. I_DD_typ=1µA and I_DD_max<4µA instead of 17µA and 50µA) and implement hysteresis.</p>
| <p>What is the simplest way to regulate the min DC voltage in a circuit?
Is it possible to do with zener diodes?</p>
<pre><code>Desired performance:
Input > 3.3 VDC Output = Input
Input = 3.3 VDC Output = Input
Input < 3.3 VDC Output = 0.
</code></pre>
| Circuit to protect against undervoltage? | 2010-10-07T17:57:57.510 |
4970 | |microcontroller|batteries|design|attiny|low-power| | <p>All answers already have important points. I will add one from my experience.</p>
<p>When I was developing devices with consumption of less than 10uA, even less than 1uA in deep sleep mode, cleaning of the board made a difference. Once I had 7 out of 10 boards with the expected current consumption. All were the same and all worked OK. After cleaning them in an ultrasonic cleaner, all the boards went to the expected result.</p>
<p>And finally, estimate your expected/targeted consumption checking the datasheets of all your elements. If you handle them ok, you will reach your estimation. This includes all unused pins in microcontroller. Even if you turn off your ADC, make sure the pin configuration while off is the best depending on your external connection. </p>
| <p>I'm hoping to power an ATtiny85V for a nice long time on some small battery, probably a coin cell.</p>
<p>I've looked into the software side, and my code is watchdog timer driven, has unused analog and digital converters turned off, the chip is running at 1MHz etc. Of course being both busy and new at this, I'm not sure exactly how much current it is drawing, but I'm hoping I have basically minimized it.</p>
<p>Every few seconds it wakes up, does its voltage level checks on the ADCs, records it to ram, and goes back to sleep. If it detects a serial line is connected, it spews the data out.</p>
<p>However, now I'm looking at the circuit as a whole and wondering if there are things I should do to make the circuit as a whole more battery friendly?</p>
<blockquote>
<p>What are the basic dos and don'ts when it comes to designing a long lasting (simple) circuit where one component (the microcontroller) has a repetitive but variable current draw?</p>
</blockquote>
<p>For instance:</p>
<ul>
<li>Is an indicator LED a big deal? Is it using up the battery when it is bright? Should I put a giant resistor on it to make it dim, or does that just make the resistor use the battery?</li>
<li>Should I use bypass/decoupling capacitors to even out the current draw from the battery, or will the capacitor just waste the battery's power?</li>
<li>The microcontroller only needs 1.8V, but I don't have any 1.8V batteries. Should I use two 1.x batteries and send it too much voltage? Can I prolong the battery life by "not using as many volts"? How do I do that?</li>
<li>Does it take extra power to check if a pin is HIGH or LOW? Like compared to a no-op or some arithmetic, is there much additional power usage in checking one of the GP I/O pins for its state?</li>
</ul>
<p>I vaguely know how to compute (and more vaguely how to measure) current, voltage, power, but I'm not really sure which of those things equates to battery life. Is the important measurement of battery life in Coulombs?</p>
<p>I have this vague idea that batteries are full of stuff like:</p>
<ul>
<li>charge, as in amp-hours</li>
<li>energy, as in watt-hours</li>
<li>power, as in watts</li>
</ul>
<p>but I am not really clear on what my circuit "eats" when it runs. I've read a fair amount of EE101 and physics textbooks, but I don't really have any lab experience. In other words, I've read a ton about batteries, but I'm not really sure what most of it means in practice.</p>
<p>Do resistors use up battery life? Do capacitors? Do diodes? I suspect they all do, but which of the numbers are the ones that matter? Impedance? Power dissipation? Current? Voltage?</p>
<p>Is there a way to lower voltage without wasting battery? Is there a way to lower voltage while increasing battery life?</p>
| Making a battery last a long time in a microcontroller circuit | 2010-10-07T19:26:15.163 |
4979 | |led|batteries|design|pwm|low-power| | <p>try running the led with a step down transformer instead.. use the side with more coils in series only,with the led..its provides resistance by making many turns in the transformer coil before reaching the led..wont have much heat also unlike a resistor..wastage will be less</p>
| <p><strong>EDIT:</strong> Here is a much brief version, the meandering motivated version is probably subsumed in <a href="https://electronics.stackexchange.com/questions/4970/making-a-battery-last-a-long-time-in-a-microcontroller-circuit">the parent question on general battery life optimizations</a>.</p>
<blockquote>
<p>How can I lower the current into a LED without wasting battery?</p>
</blockquote>
<p>I think using a resistor to lower the current will use up battery life. Is this true? How does it use up the battery if the current is kept small? Is it the power dissipation?</p>
<p>I think using a diode (and smaller resistor) will still use up the battery (LadyAda said something like "any linear device to lower the voltage uses the same amount of power"). Is this true? Is it the same amount?</p>
<p>Can I lower the voltage "for free", that is, without wasting too much power? How can a regulator IC do what a resistor or diode cannot?</p>
| LEDs on a (battery) budget! – How can I lower the current through a LED without using up the battery? | 2010-10-07T23:35:19.883 |
4981 | |fpga|video|display| | <p>How about something simpler?</p>
<p>Perhaps a compact flash card with a bitmap image file or GIF89a on it?
A microcontroller could read the card and drive the display.</p>
| <p>I help maintain an old beaten down LED sign on the side of a highway. </p>
<p>Right it has a program running on Win98 to generate the image that should be on the sign (FLASH animation, temperature, etc), and drive a PCI IO card which in turn drives the sign logic. I'd like to (be able to) replace the control package of the sign with something less painful. </p>
<p>A different sign we're working on has a DVI input to a control board. The control board takes a specific portion of the video and sends it off to the sign. I like this scheme because it makes it easier to change out the computer if it breaks, and allows a lot of freedom in terms of what software/hardware can be used- so long as a PC has a DVI port, it can drive the sign.</p>
<p>Core Question: How can I go from 'video input' to a copy of what is on the screen for consumption by digital logic? </p>
<p>The one thing I've come up with so far is using a <a href="http://focus.ti.com/docs/prod/folders/print/tfp401a.html" rel="nofollow">TFP401A</a>, and feeding that into an FPGA where a lot of accompanying logic would sit. </p>
<p>Does that seem reasonable? Is there a better way? At least one concern is that I don't have any experience with high frequency design- I'm not certain how much care needs to be taken on the traces between DVI connector and receiver, as well as from receiver to FPGA.</p>
<p><strong>EDIT:</strong></p>
<p>Few added details: </p>
<ul>
<li>The sign is low resolution (47x127 image, 24x64 sign)</li>
<li>It displays animation (refresh rate > 10Hz)</li>
<li>I'd prefer something without dependence on software on the PC (suggests taking a video signal of some format)</li>
<li>This is 80% learning experience- while the goal is a practical replacement system, I would like to end with the knowledge of how this can be done.</li>
</ul>
| How to get Video Input | 2010-10-08T00:25:36.423 |
4989 | |computers|telephone| | <p><img src="https://i.stack.imgur.com/ALiZk.png" alt="alt text"></p>
<p>You can get a transformer from an damaged modem, like that:</p>
<p><img src="https://i.stack.imgur.com/wtVo9.jpg" alt="alt text"></p>
<p>Reminder: In my country (Brazil) it is forbidden to record a phone conversation without the consent of another person on the phone.</p>
| <p>I'd like to connect my landline tellephone to my computer's soudcard, and I was about to do this when somebody warned me that the voltages are all wrong and that I will blow my soundcard.</p>
<p>To what voltages must I change the line, and how do I do that?</p>
<p>Also, the telephone line has two wires. How to I split them into input & output for my soundcards's ports?</p>
| Connecting landline to soundcard | 2010-10-08T09:07:24.957 |
4990 | |arduino| | <p>You need to include the SoftwareSerial Library in your updated sketch. In order to do this, go to the Sketch menu and scroll down through "Import Library..." to the SoftwareSerial Library, selecting it to add it. </p>
<p>Alternatively, add <code>#include <SoftwareSerial.h></code> to the top of your sketch, the above does the same thing.</p>
| <p>FOllowing on from <a href="https://electronics.stackexchange.com/questions/4814/my-atmega328-seems-to-be-overkill-what-should-i-use-instead">this question</a>, I'm following the tutorial for <a href="http://hlt.media.mit.edu/wiki/pmwiki.php?n=Main.ArduinoATtiny4585" rel="nofollow noreferrer">programming an ATtiny45 using an arduino</a>.</p>
<p>Using v0021 of the Arduino IDE, with a Duemilanove which i've replaced the 168 chip with a 328, I'm able to upload the ArduinoISP sketch correctly. However, trying to upload the blink sketch to the Attiny results in the following error:</p>
<pre><code>ArduinoISP.cpp: In function 'void setup()':
ArduinoISP.cpp:79: error: 'Serial' was not declared in this scope
ArduinoISP.cpp: In function 'void loop()':
ArduinoISP.cpp:136: error: 'Serial' was not declared in this scope
ArduinoISP.cpp: In function 'uint8_t getch()':
ArduinoISP.cpp:142: error: 'Serial' was not declared in this scope
ArduinoISP.cpp:143: error: 'Serial' was not declared in this scope
ArduinoISP.cpp: In function 'void readbytes(int)':
ArduinoISP.cpp:147: error: 'Serial' was not declared in this scope
ArduinoISP.cpp: In function 'void spi_init()':
ArduinoISP.cpp:164: error: 'SPCR' was not declared in this scope
ArduinoISP.cpp:165: error: 'SPSR' was not declared in this scope
ArduinoISP.cpp:166: error: 'SPDR' was not declared in this scope
ArduinoISP.cpp: In function 'void spi_wait()':
ArduinoISP.cpp:172: error: 'SPSR' was not declared in this scope
ArduinoISP.cpp:172: error: 'SPIF' was not declared in this scope
ArduinoISP.cpp: In function 'uint8_t spi_send(uint8_t)':
ArduinoISP.cpp:177: error: 'SPDR' was not declared in this scope
ArduinoISP.cpp: In function 'void empty_reply()':
ArduinoISP.cpp:194: error: 'Serial' was not declared in this scope
ArduinoISP.cpp:198: error: 'Serial' was not declared in this scope
ArduinoISP.cpp: In function 'void breply(uint8_t)':
ArduinoISP.cpp:204: error: 'Serial' was not declared in this scope
ArduinoISP.cpp:209: error: 'Serial' was not declared in this scope
ArduinoISP.cpp: In function 'void start_pmode()':
ArduinoISP.cpp:263: error: 'SS' was not declared in this scope
ArduinoISP.cpp:265: error: 'SCK' was not declared in this scope
ArduinoISP.cpp:270: error: 'MISO' was not declared in this scope
ArduinoISP.cpp:271: error: 'MOSI' was not declared in this scope
ArduinoISP.cpp: In function 'void end_pmode()':
ArduinoISP.cpp:277: error: 'MISO' was not declared in this scope
ArduinoISP.cpp:278: error: 'MOSI' was not declared in this scope
ArduinoISP.cpp:279: error: 'SCK' was not declared in this scope
ArduinoISP.cpp:280: error: 'SS' was not declared in this scope
ArduinoISP.cpp: In function 'void program_page()':
ArduinoISP.cpp:348: error: 'Serial' was not declared in this scope
ArduinoISP.cpp:356: error: 'Serial' was not declared in this scope
ArduinoISP.cpp:362: error: 'Serial' was not declared in this scope
ArduinoISP.cpp: In function 'char flash_read_page(int)':
ArduinoISP.cpp:375: error: 'Serial' was not declared in this scope
ArduinoISP.cpp: In function 'char eeprom_read_page(int)':
ArduinoISP.cpp:387: error: 'Serial' was not declared in this scope
ArduinoISP.cpp: In function 'void read_page()':
ArduinoISP.cpp:397: error: 'Serial' was not declared in this scope
ArduinoISP.cpp:400: error: 'Serial' was not declared in this scope
ArduinoISP.cpp: In function 'void read_signature()':
ArduinoISP.cpp:409: error: 'Serial' was not declared in this scope
ArduinoISP.cpp:412: error: 'Serial' was not declared in this scope
ArduinoISP.cpp: In function 'int avrisp()':
ArduinoISP.cpp:436: error: 'Serial' was not declared in this scope
ArduinoISP.cpp:497: error: 'Serial' was not declared in this scope
</code></pre>
<p>How can I fix this please? Or does anyone know if it works with a previous version of the IDE?</p>
| Why am I receiving "error 'Serial' was not declared in this scope" when building my Arduino sketch? | 2010-10-08T10:01:12.923 |
4993 | |microcontroller|fpga| | <p><a href="http://www.xmos.com/" rel="nofollow">Xmos</a> I've never used them although have looked in to them. </p>
| <p>Inspired by <a href="https://electronics.stackexchange.com/questions/4905/is-an-fpga-viable-for-such-a-project">question</a> I would like to ask what microcontrollers with CPLD or FPGA-like functions build in are available? The most interesting would be low-cost ones in friendly packages (non-BGA). The CPLD/FPGA portion should be big enough to allow implementing fairly complicated state machine (10+ states), fairly big logic function (10+ inputs), fairly big counters and shift registers (8+ bits) and be able to run at tens of MHz frequencies. Preferable method of design input for programmable logic function should be HDL based (Verilog or VHDL).</p>
<p>So far I have found two examples:<br>
1) FPSLIC from Atmel<br>
2) PSOC3 and PSOC5 from Cypress (those are not available yet, except in samples volume)</p>
| What microcontrollers with programmable logic built in (FPGA/CPLD like) are available on the market? | 2010-10-08T10:20:02.157 |
5009 | |power-supply| | <p>There are two components to powering a computer: The rectification from AC to DC, and the regulation from one DC voltage to another, like 3.3 or 5.5V. </p>
<p>The PICOPSU-160-XT is a tiny form-factor device that regulates 12V DC down to the +3.3, +5.5, -12V, and other voltages required by the <a href="http://www.formfactors.org/developer%5Cspecs%5Catx2_2.pdf" rel="nofollow">ATX Power Supply Specification</a>. It requires a 12V input from a male plug into a "Female, panel mount, 2.5*5.5*10 mm" jack according to Page 4 of the (brief) <a href="http://resources.mini-box.com/online/PWR-PICOPSU-160-XT/PWR-PICOPSU-160-XT-manual.pdf" rel="nofollow">manual</a>. This jack would presumably be attached to your computer case. </p>
<p>The easiest solution would be to buy four AC-to-DC desktop wall warts, like the kind used to charge laptop batteries. However, <a href="http://www.mini-box.com/110w-12v-8-5A-AC-DC-Power-Adapter" rel="nofollow">the biggest one on the store you used</a> only delivered about 8.5A, which is just over half of the 16A maximum (13A continuous) that the PICOPSU supports. You would need to know how much current your computers will be drawing, but this may be OK.</p>
<p>Another alternative would be to purchase a desktop ATX power supply of sufficient amperage (600-1000W), and run ATX power supply cabling into your four computers. Similarly, four small PSUs could be used to the same effect. Visit <a href="http://www.newegg.com/Store/Category.aspx?Category=32&name=Power-Supplies" rel="nofollow">newegg</a> for a good selection of power supplies. We'd have to know more about your setup to determine whether this is a viable solution. - Would bulky, short cables going into your computers be OK? Would they be located within a few feet of each other? Would a (relatively) bulky ATX power supply fit into the case?</p>
| <p>So I have four computers all using these little <a href="http://www.mini-box.com/picoPSU-160-XT" rel="nofollow">pico itx power supplies</a> and was wondering rather than have 4 power bricks attached to these power supplies could I just use an <a href="http://rads.stackoverflow.com/amzn/click/B000NM4DVW" rel="nofollow">Power-Bright-PW900-12-Inverter</a>. </p>
<p>To me it seems like a better and more power efficient solution unless I am missing something. Also if I were to do this what is the best way to slap DC wires from four different power supplies into this thing?</p>
| Pico ITX Power Supply and AC-DC Inverter | 2010-10-08T19:13:48.700 |
5011 | |voltage|buck|ldo|linear-regulator| | <p>This <a href="http://www.ti.com/lit/ds/symlink/lm2574.pdf" rel="nofollow">buck converter</a> is $1.19 in 1000 unit quantities. Input 4-40v, output fixed at 3.3v or three other voltages or adjustable from 1.3 to 37v, @500 ma.</p>
| <p>For my Super OSD project, I need a +3.3V supply at 250mA from a variable input of 5.5V to 20V. Cost is a concern, as is size. Originally, I considered an LM317 in a SOT-223 package, due to the small size. Unfortunately, it's difficult to get a heatsink for SOT-223 packages.</p>
<p>Then I did some calculations; the LM317 would be dissipating up to 4.175W with 20V input and 250mA of load and with a θJA of 140°C/W, the LM317 would cook along nicely at 584°C above ambient. So not practical.</p>
<p>The next solution would be a little buck converter, but I'm looking to get a small design and a cost of <$3. Does anyone know of an ideal chip for the job? Or is it still possible to use a linear regulator? I'd prefer to do so, but getting rid of the wasted heat is really a problem. Power efficiency is not critical for this application, as an electric motor will be drawing 10's of amps, compared to the few hundred mA for this module. </p>
| Best solution to get 3.3V from 5V-20V @ 250mA | 2010-10-08T20:46:07.843 |
5013 | |wire|home-automation|protocol|x-10| | <p>IP would be my choice, it has become 'the one protocol to rule them all'.</p>
<p>This site has some nice videos of a house being automated this way, he even injected an RFID under his skin!</p>
<p><a href="http://www.superhouse.tv/episode" rel="nofollow">http://www.superhouse.tv/episode</a></p>
| <p>I know the X-10 protocol. X-10 is a good choice or is there better?</p>
| What is the best wired protocol choice for home automation? | 2010-10-08T20:57:52.893 |
5031 | |parallel|port| | <p>I switched my LPT to Normal mode (from ECP + EPP) in BIOS and now everything works.</p>
| <p>I would like to use Control Register controlled pins of LPT (1, 14, 16, 17) as inputs. These are said to be normally used as open collector outputs, but have the ability to operate as inputs too. <a href="http://retired.beyondlogic.org/spp/parallel.htm" rel="nofollow noreferrer">This site</a> describes the use of this pins as inputs, but I'm a bit confused and don't really understand what I'm supposed to do.</p>
<p><a href="https://i.stack.imgur.com/dvqve.png" rel="nofollow noreferrer">Here's what the circuit looks so far.</a> This fails for Control Register pins, but <strong>works</strong> for Status Register pins (10, 11, 12, 15). How do I need to change my schematic to make it work for with the other ones?</p>
| How to use Control Register inputs of LPT port? | 2010-10-09T08:37:12.453 |
5034 | |soldering|soldering| | <p>I wanted to avoid spending a lot of money on special equipment, but already had a heat gun and this worked for me. My PCB had 10 holes filled with solder due to a mistake. I heated the area with the heat gun and tapped the pcb onto the table and all the solder came out. It made a mess of the table, so maybe put down some sacrificial surface first!</p>
| <p>I am trying to swap dead capacitors in my motherboard. Removing them was relatively easy, but I can not insert the new ones. The solder melted into the vias and the desoldering wire does not suck it out of the hole.
Is there any safe method to remove the blocking solder from the vias?</p>
| How to remove solder from via? | 2010-10-09T12:23:07.213 |
5040 | |power-supply| | <p>Apologies for reviving such an old post, but it's a question we see a lot. The problem is running that much current at that voltage through such a small DC barrel connector. Mini-Box has recently modified the power supply to include an inline P4 connector which can be removed and paired the 4-pin mini-DIN connector bundled with this 160w brick: <a href="http://www.mini-box.com/12v-16A-AC-DC-Power-Adapter" rel="nofollow">http://www.mini-box.com/12v-16A-AC-DC-Power-Adapter</a></p>
| <p>So I have 4 systems with <a href="http://www.mini-box.com/picoPSU-160-XT" rel="nofollow">mini itx power supplies</a> and am looking to purchase power bricks from the manufacturer. What confuses me is the <a href="http://www.mini-box.com/110w-12v-8-5A-AC-DC-Power-Adapter" rel="nofollow">power bricks are 102 Watts</a> while the PSU can do 160W with a max of 200W. This is probably obvious question but since the power brick can only do 102 watts that means the PSU can only provide 102W, and if this is the case why would the manufacturer bundle the two together?</p>
| Mini ITX PSU and Power Brick Wattages | 2010-10-09T13:55:55.487 |
5043 | |arduino|motor|driver| | <p>It looks like you have chosen to use arduino pin numbers that are very similar to the necessary pin numbers on the L298. Nothing wrong with that, you can use whichever arduino pins are convenient. But it seems like it would be an easy mistake (with the given code) just to wire pin N from the arduino to pin N of the L298 under such circumstances. </p>
<p>With the L298, you want the analog PWM going into pin 6, and your arduino is producing that at pin 5. So you'd want 5 from the arduino going to 6 on the L298, and 6 on the arduino going to 5 on the L298. Arduino pin 7 would still go to L298 pin 7.</p>
<p><em>OR</em></p>
<p>if want to go with the 5-5, 6-6, 7-7 wiring, you could fix it in software, just by changing</p>
<pre><code>int mot1ana=5;
int mot1a=6;
int mot1b=7;
</code></pre>
<p>to</p>
<pre><code>int mot1ana=6;
int mot1a=5;
int mot1b=7;
</code></pre>
| <p>i just made a motor driver circuit on a veroboard to use with my arduino
but the problem is l298 spinning motor only one way.
here is the code
it was supposed to spin motor forth and backwards every 2 seconds right?</p>
<pre><code>int mot1ana=5;
int mot1a=6;
int mot1b=7;
void setup() {
pinMode(mot1ana,OUTPUT);
pinMode(mot1a,OUTPUT);
pinMode(mot1b,OUTPUT);
}
void loop() {
analogWrite(mot1ana,200);
digitalWrite(mot1a,HIGH);
digitalWrite(mot1b,LOW);
delay(2000);
analogWrite(mot1ana,200);
digitalWrite(mot1a,LOW);
digitalWrite(mot1b,HIGH);
delay(2000);
}
</code></pre>
<p><img src="https://i.stack.imgur.com/dSdaS.jpg" alt="http://farm5.static.flickr.com/4124/5065468848_a210d091aa.jpg"></p>
| L298 Motor Driver spinning motor only one way :/ | 2010-10-09T17:05:59.940 |
5064 | |resistors|breadboard| | <p>you can buy a number of resistors at one time as there is a set of standard values for resistors.</p>
<p><a href="https://i.stack.imgur.com/Z9kdX.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/Z9kdX.jpg" alt="Standard resistor values."></a></p>
| <p>I'm starting with electronics and I don't have a lot of resistors.
Every new project I try to do, I have to buy new resistors, but they take a long time to arrive.</p>
<p>What's the solution?
What variable resistors should I buy?</p>
<p>Thanks</p>
| Variable resistor | 2010-10-10T13:41:14.620 |
5069 | |capacitor|transistors| | <p>PUT (Unijunction) is a "strange" thing, like "Gunn diode" (used in radar circuitry) which has a characteristic curve with a "negative" region of working.</p>
<p>Some "PUT" are "programmable" and in fact are composed of 2 transistors (1 NPN and 1 PNP) connected correctly (B to c, b to C), these are also called thyristors.</p>
<p>The resistor connected to electrode E must be greater then the "negative value" of this PUT in the "working" area (use charge line concept to chose correct value.)</p>
<ul>
<li>If too low, the circuit is a "monostable".</li>
<li>If greater than the negative resistance, it is an "unstable" oscillator.</li>
<li>If too much greater, it is a "stable circuit", but non-linear.</li>
</ul>
| <p>I've been making my way through "MAKE: Electronics: Learning Through Discovery", but have gotten stuck on Experiment 11, where I am making an oscillating circuit.</p>
<p>The book calls for a 2.2uF capacitor, but I only have a 1000uF capacitor. I decided it would be fun to try to create a circuit that functions similarly with the parts I have (or at least to understand why doing so would be impossible)</p>
<p>The circuit specified by the book is this:
<img src="https://i.stack.imgur.com/amoQZ.jpg" alt="Figure 2.98" /></p>
<p>R1: 470K Resistor, R2: 15K Resistor, R3: 27K Resistor, C1: 2.2uF electrolytic capacitor, D1: LED, Q1: 2N6027 PUT</p>
<p>The first thing I did was replace R1 with a 6.7K resistor so it wouldn't take so damn long to charge the capacitor. Next I replaced R2 with a 26K resistor and R3 with a 96K resistor so that the PUT would only let charge through when the capacitor was near the peak of its voltage.</p>
<p>I was expecting the LED to turn on once the capacitor charged to ~5v, and turn off once the capacitor discharged to less than ~5v. Instead, the capacitor charges for a few seconds, and the LED remains dimly lit while the capacitor's voltage remains steady at ~2.7v.</p>
<p>With my very limited knowledge of electronics, I am stumped by this behavior. Am I misunderstanding how a capacitor works? Thanks in advance for your expertise!</p>
<p><strong>UPDATE:</strong> I still don't exactly understand the relationship between the resistor values and the LED/capacitor getting "stuck" (where getting stuck means the LED will stay lit and the capacitor voltage will stay constant around 2.5v). After some more testing it appears that:</p>
<ol>
<li>The larger R2 and R3 are (keeping the R2:R3 ratio approximately constant), the more likely it is the LED/cap will get stuck</li>
<li>The smaller R1 is the more likely the LED cap will get stuck.</li>
</ol>
<p>For example, with R2 at 15K, R3 at 21K, and R1 at 66K, the LED/cap will oscillate properly (although slowly). If I change R1 to 46K the LED/cap gets "stuck"</p>
<p>Does anyone know of an explanation for this behavior?</p>
<p><strong>I believe Mark has the right answer (based on some testing) so I've accepted it. If R1 has much less resistance than R2 and R3, the cap charges much faster than it discharges so that it oscillates quickly while it appears to the multimeter that it is "stuck" at one voltage.</strong></p>
<p><strong>However, I would appreciate if Mark (or anyone else) can explain how to come up with that insight about Rg from the <a href="http://www.onsemi.com/pub/Collateral/2N6027-D.PDF" rel="nofollow noreferrer">datasheet</a></strong></p>
<p><a href="https://i.stack.imgur.com/oIr3t.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/oIr3t.jpg" alt="Load Line Concept" /></a></p>
| Capacitor behavior in oscillating circuit | 2010-10-10T17:58:51.517 |
5070 | |motor| | <p>If you are planning to control the motor with a microcontroller (e.g. Arduino) you may need to have a look at using MOSFETs to switch the motor on and off.</p>
<p>A good introductory description, including a video, of motor control can be found <a href="http://www.nerdkits.com/videos/motors_and_microcontrollers_101/" rel="nofollow">here</a>.</p>
| <p>This question is very basic, but I'd like to ask it anyway.</p>
<p>I need to drive a <a href="http://www.velleman.eu/distributor/products/view/?id=375874">small motor</a>. I'm thinking about connecting it directly to 4 AA batteries and using a simple switch. Is there anything else needed?</p>
<p>Also, it its datasheet unit gcm is mentioned. What is it? I thought that torque is measured in N*m or similar units.</p>
| Driving a small motor: What's needed? | 2010-10-10T18:00:18.660 |
5078 | |mobile|touchscreen| | <p><strong>Capacitive:</strong> Generally more expensive, can support "multi-touch", rely on skin contact because the persons electrical field is what causes changes. This means they don't work well, or at all with gloves on. Doesn't rely on touch pressure, so are generally more responsive to finger use/light taps, etc. Requires a fairly complicated controller.</p>
<p><strong>Resistive:</strong> Cheap, only a single touch point can be detected. Rely on pressure to achieve detection (u may have to push hard on them). Any object touching the screen can create a "press" event, so gloves, non-conductive pens, etc work fine. Controller is very simple, just measures a few resistances.</p>
| <p>I have zeroed it down to these two phones <a href="http://www.gsmarena.com/compare.php3?idPhone1=2922&idPhone2=3229" rel="nofollow">Nokia X6 and Nokia C6</a>.</p>
<p>Apart from others, one difference is the presence of capacitive touchscreen in one and resistive in the other.</p>
<p>If I were to decide only on the basis of these touchscreen technologies, which one should I go for?</p>
| What are the pros and cons of resistive and capacitive touchscreen mobile devices? | 2010-10-10T21:55:32.847 |
5080 | |lcd|tv| | <p>Your camera probably has composite output which goes into some modulator box that encodes the signal to some specific TV channel. Intercept this signal before the box, and buy some cheap baby monitoring wireless camera system (actually you just need some home range CBSV to TV via air system). Every TV in the range will receive camera picture via air (including small 7" LCD if it is capable of receiving air TV signal). It can hardly get simpler then this.</p>
| <p>My building recently installed a CCTV camera system. Anyone with cable TV is able to tune into channel XX and watch the CCTV stream live.</p>
<p>I want to get a cheap and small LCD (≤7") and build a dedicated "television" that would be tuned to channel XX. Eventually, the plan is to hook this up to a caller-id circuit and have the "TV" turn on when I get a call from downstairs.</p>
<p>I'm a programmer by trade and don't have much experience with building circuits.
I'd just like a ballpark figure of what I'll need and how difficult it would be to make a primitive TV these days.</p>
| DIY Single-Channel Television | 2010-10-10T22:48:00.987 |
5082 | |capacitor|transistors|kits| | <p>For a general mad inventor type I'd suggest that, after arming yourself with basic tools, you just go on the scrounge for scrap equipment - old printers, TV's, computers, etc. you will turn up all sorts of buttons, lights, sensors, motors, displays, etc. and often the associated hardware to drive them. And for our favourite price too ;)</p>
<p>Have a read of <a href="http://www.timhunkin.com/control/f_engineering_index.htm" rel="nofollow">Tim Hunkin's website</a> for inspiration.</p>
| <p>I'm going to buy some things for back to the electronic world.</p>
<p>Starting with an Resistor Assorted Kit.
Need to buy some kits containing the most common capacitors and transistors... what to buy???</p>
<p>[I want to buy to create a lot of things that there is schematic on the web without having to buy new components]</p>
<hr>
<p><sub><em>Inward merge from duplicate question, now closed; Summary for reference:</em></sub></p>
<p><sub>Electronics for everyday inventor</sub></p>
<p><sub>... capacitors, trimmers, resistors, pots, diodes, transisters, leds and laser diodes, timers (like the 555), inductors, ICs and common microchips, LOTS of sensors (temperature, gasses, radiation, light, sound, motion etc) and sensor like pieces (like selenium chips), and a bunch of other things ... for the chaotic inventor.</sub></p>
| "Starter Kit for electronics" - What to buy? | 2010-10-11T02:36:36.817 |
5094 | |computers|processing| | <p>If this is professional interest, the VITA standards documents are available for $300 or so for a CD of all of them.</p>
<p>Edit to add: what are you looking for? Performance, price, ubiquity, etc?</p>
<p>Edit: some additional thoughts. Will add to these as I think of them.</p>
<ul>
<li><p>COTS Journal, Embedded Computing Design, and similar trade magazines have high level technical articles on these interfaces. Caveat emptor, since the articles are written by vendors.</p></li>
<li><p>For ADC/DAC applications, how much bandwith do you really need? If this is a control/sensing application (LVDT, etc), you may not need more than a few tens of KHz/channel. Which might imply that you don't need a x16 PCIe interface. My experience is that a lot of folks tend to spec as much CPU, RAM, Flash, and IO bandwidth as they can get. Even if they need to move a few dozen bytes every 50 mSec.</p></li>
<li><p>If you're looking at commercial cards or chassis, you should also consider IO card availability. Don't forget the possibility of using PMC/XMC cards on carriers.</p></li>
<li><p>I would stay away from anything that doesn't have a decent ecosystem yet. VME and cPCI are safe. RapidIO? StarFabric? Maybe not there in 5 years.</p></li>
<li><p>I think VPX's costs will kill it. $140 per board connector, x3 for a 3U IO card? Really?</p></li>
</ul>
| <p>Are there some general resources (other than spec sheets of boards) to compare the differences between computing formats like VPX, VME, IBM bladecenter-h, etc?</p>
<p>I am tasked with doing some legwork what form-factor we should be looking at when buying our processing equipment for a high performance semi-rugged system.</p>
<p>I've read specs on size, connectors, bandwidth density, power usage, etc. Is there anything more I am missing? I'm having trouble comparing the overall possible bandwidth to each server in each architecture. Particularly VPX and all of its dot level specifications. </p>
<p>These would run custom software and FPGAs, DACs, ADCs, a linux machine, etc.</p>
| Pros/Cons of different backplane architectures? | 2010-10-11T13:25:52.223 |
5095 | |pcb|conformal-coating|corrosion|humidity|potting| | <p>We are using a technique called low pressure PCB overmolding. A plastic coating is injection molded around the PCB. The injection process forces out air pockets resulting in a very uniform and non-permeable environmental protection.</p>
<p><a href="https://cavist.com/" rel="nofollow noreferrer">https://cavist.com/</a></p>
<p>Typical tooling for such a process is prohibitively expensive for small one-off boards. But you could do it with a 3D printer and a benchtop injection molding machine.</p>
<p><a href="https://www.techkits.com/" rel="nofollow noreferrer">https://www.techkits.com/</a></p>
<p><a href="https://i.stack.imgur.com/3D2zC.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/3D2zC.png" alt="Injection molded PCB" /></a></p>
| <p>Some of my projects need to live outside for long periods. Sometimes, moisture gets into the enclosures. That means that a circuit board might be sitting around in contact with water for hours on end at upwards of 100F.</p>
<p>I've noticed that solder joints can start to corrode, and recently moisture made it under the solder mask on a board and actually ate through one of the traces, breaking the circuit. I know the ideal answer is to make a perfectly sealed enclosure, but I'd like to toughen the boards up a bit as a second level of defense.</p>
<p>Can anyone suggest some tips and tricks for making PCBs more corrosion resistant? Does scrubbing off excess flux help? What about spray acrylic sealant? Special solder?</p>
| What's the best way to protect a board from corrosion in a hot/moist environment? | 2010-10-11T14:32:49.210 |
5096 | |serial|i2c| | <p>I've just run into this problem with multiple I2C devices with a fixed address. Our solution was to use I/O lines on the microcontroller to force the SDA lines high on the devices that we <em>don't</em> want to address, while the I/O line for the device we're targeting is set as input (high impedance). This means that only the targeted device matches it's I2C address and the others ignore any subsequent data.</p>
<p><a href="https://i.stack.imgur.com/z7npQ.png" rel="noreferrer"><img src="https://i.stack.imgur.com/z7npQ.png" alt="Multiple I2C devices with same address"></a></p>
<p>The resistors on the SDA line for the inactive devices end up acting as pull-ups for the bus, so the exact value will depend on how many devices you have and what pull-up you need for your bus. So if you choose 10K resistors, then 3 inactive devices gives a 3K3 pullup.</p>
<p>The schottky diodes ensure that the device can still pull the SDA line low enough when transmitting data back to the host. </p>
| <p>I want to connect multiple I2C slave devices to a micro controller all on the same set of pins but the I2C devices all share the same address. The addresses are fixed in the hardware.</p>
<p>Is there any way to connect multiple devices with the same address?</p>
<p>Perhaps some kind of I2C address translation module with each device with an configurable address so I can assign my own addresses to each one.</p>
| How to resolve I2C address clashes? | 2010-10-11T14:40:26.117 |
5111 | |microcontroller|control-system|pid-controller| | <p>There is a great <a href="https://www.microsoft.com/en-us/p/pid-simulator/9nbcz6qq5djs?activetab=pivot:overviewtab" rel="nofollow noreferrer">PID</a> simulation app that you can use to practice tuning PID loops and see the live feedback. It's made by PIDexplained.com and available on the Microsoft store.</p>
<p>PIDexplained.com also has a great <a href="https://pidexplained.com/pid-controller-explained/" rel="nofollow noreferrer">write-up</a> on the math behind a PID loop.</p>
| <p>I want to learn PID (Proportional–Integral–Derivative) control mainly for temperature.</p>
<p>I would like to learn preferably through an easy project to do.</p>
<p>Could you please recommend something which would take a few weeks to learn?</p>
<p><strong>Edit:</strong> I want to control the temperature of a water tank. The heating is done by a resistor.</p>
| How to learn PID Control? | 2010-10-11T20:08:00.787 |
5113 | |communication|radio|wifi| | <p>Take a look at the 900MHz band XBEE modules. They can get great range. They are relatively easy to operate and you can sleep them when not being used.</p>
| <p>I am looking for suggestions of a low bandwidth (<1 kbps) mesh network which can be implemented between RC model planes. It should be able to communicate over distances of 500m or more, preferably 1km+, and it should gracefully handle the loss of nodes in the network.</p>
<p>It should be legal worldwide to operate; at least Europe and the USA if that is not possible. And, it must be relatively cheap to implement.</p>
<p>This is for an RC plane game I am developing. Real world model aircraft in dogfights. Or racing each other. It will be part of Super OSD.</p>
| A low bandwidth mesh network for RC planes | 2010-10-11T20:45:34.457 |
5116 | |power-supply|capacitor| | <p>I think that just putting a 2.2mF capacitor across the battery terminals will work well enough to smooth voltage. I presume the voltage dips when the ESC draws large current pulses for the motor.</p>
| <p>I need some help in figuring out what size capacitor I need, and if my idea will even work.</p>
<p>I have a <a href="http://www.xheli.com/newsy3chs1mi.html" rel="nofollow">small remotely-controlled helicopter</a>, and a <a href="http://www.chucklohr.com/808/" rel="nofollow">very small camera</a>. I am trying to record video while flying the helicopter around. So far, cutting down the body of the helicopter and taking the PCB out of the camera and mounting it to the helicopter has worked well. However, the usable flight time is reduced from 10 minutes or so to 1 minute. I noticed that the battery on the camera and the battery on the helicopter are the same type and voltage. What I would like to do is power the helicopter and the camera from the same battery to save on weight.</p>
<p>My original plan was to simply cut the camera battery out of the picture and tie the camera directly do the helicopter. However, I thought this would cause problems, as the voltage while charging would likely fry the camera.</p>
<p>Then, I noticed the decorative LED on the front of the helicopter. The voltage (3.7V or so, depending on battery charge) is exactly what is needed to power the camera. The LED is also off while the helicopter is turned off and/or charging. Now, this helicopter alternates the polarity going to the LED twice a second, as it is a bi-color LED. My current plan is to cut out the LED, rectify the voltage with 4 diodes so I have straight DC, and use this to power the camera. (Barring any current issues of course. I plan to measure the current load of the LED vs. the camera before doing this, but I expect they will be similar, given the amount of time the camera can run off of its own battery [1 hour+] of similar capacity to that of the helicopter.)</p>
<p>I am going to experiment with this plan tonight, but I just realized that there is probably a very short time where the LED driver outputs 0V in between its polarity switch. I'm thinking that sticking a capacitor in there will help with the problem, but I have no idea how to calculate what size I need.</p>
<p>Can you tell me what I need to do to calculate the size cap that would likely keep things running smoothly? Again, the voltage output of the LED driver and the voltage requirement of the camera is 3.7V, but I'm guessing will be anywhere from 4.2 to 3.6 during operation. I don't yet know the current requirements, but plan to figure those out tonight.</p>
<p>Thank you for your time.</p>
| Capacitor to provide power to a circuit during a very small interruption | 2010-10-11T20:58:23.880 |
5120 | |power| | <p>Most people are using this kind of unit all the time.
How much electric energy does your house consume per year? Let’s say 20000 kWh. How would you write this in short hand? 20000 kWh/yr.</p>
<p>Makes sense, doesn’t it? Would it be as clear if I wrote: 20000/(355*24) = 2.28 kW? How much electric energy do you pay for with a larger house, 3.1 kW? But energy is measured and priced in kWh, not in kW which is energy per second, i.e. power, not energy.</p>
<p>The unit kWh/h expresses that you use x kWh energy each hour while kW tells what you are using per second.</p>
| <p>Since MW is actually the rate of energy is being used, why would we use MWh/h as in <a href="http://www.fingrid.fi/en" rel="nofollow noreferrer" title="Fingrid">Fingrid</a>'s electricity market <a href="https://www.fingrid.fi/en/electricity-market/electricity-market-information/load-and-generation/" rel="nofollow noreferrer">Load and Generation forecast page</a>?</p>
<p>Wouldn't MWh/h be the same as MW???</p>
| Does it make sense to use MWh/h as unit of measure? | 2010-10-11T23:39:18.660 |
5129 | |buck|switch-mode-power-supply| | <p>Good first stab, just some thoughts:</p>
<p>1) The R1 / R2 feedback voltage divider has some really long traces and paths to ground. Anything you can do to keep the FB traces short will improve regulation stability and the ground used should be tightly coupled to the IC ground. I'd put R1 and R2 directly next to each other and put em where the small signal diode is, moving the diode over to where R1 is now. Ground R2 to the IC ground via (its low current). The LED can go pretty much anywhere and trace length doesn't matter so just move it to fit.</p>
<p>2) The input caps, C1/C2 and the catch diode D2 should be very tightly coupled, their ground references need to be very very close to each other. I'd flip D2 90 degrees and move it over next to C2, ground them all right there, you should use more than 1 via for this ground. What i normally do for this is a little copper pour on the surface that connects to all 3 pads (D2/C1/C2) and extends out enough to plop 3 decently sized vias in it.</p>
<p>3) the output filter cap C4 is in a really odd place It should also be quite tightly coupled to the ground of D2/C1/C2, move L1 over and you can probably put it right next to D2 and included it in the little ground pour I was talking about in 2).</p>
<p>4) With the above re-organization you can move C3 over just above/to the right a touch of the IC which will get rid of the problem you have with the input supply trace having to fit between C3's pads, as drawn right now that will short out, the trace is way too close to the pads.</p>
<p>Keep in mind that your critical path in this circuit, that is the loop where there will be high current AC and DC spike is from the input -> D1 -> C1+ -> C2+ -> ICin -> ICsw -> D2+ -> L1 -> C4+ -> C4- -> through other grounds back to C1- </p>
<p>Your goal is to minimize the loop area and the resistance in that loop, which moving C1,C2,D2,C4 as close as possible to each other and the IC will help with as well as tightly coupling their grounds through a small pour on the surface with multiple vias to the ground plane.</p>
| <p>I'm using an LM2734 buck regulator to get +3.3V at 400mA. The datasheet is unclear on how to lay out the supply, so I tried to follow some common sense, keeping all power traces short where possible. The power supply has to be very small, which is why it uses ceramic caps and the LM2734, which operates at 3 MHz and thus requires a smaller inductor (it's still pretty massive!)</p>
<ul>
<li>L1: 3.3uH 2A inductor</li>
<li>C1: 4.7uF 50V ceramic cap</li>
<li>C2: 4.7uF 50V ceramic cap</li>
<li>C3: 0.01uF 16V ceramic cap</li>
<li>C4: 22uF 10V ceramic cap</li>
<li>D1: RB160M (input protection)</li>
<li>D2: RB160M</li>
<li>D3: (mislabeled D1, the SOT-23) any small signal silicon diode</li>
<li>R1: 10k</li>
<li>R2: 31.6k</li>
<li>R3: 1k</li>
<li>LED1: any small LED</li>
<li>U1: LM2734, SOT-23-6</li>
</ul>
<p>I'm generating the boost voltage from the output.</p>
<p><img src="https://i.stack.imgur.com/VLcuX.png" alt="my PSU"></p>
| Critique my SMPS buck design | 2010-10-12T13:19:57.430 |
5130 | |motor|robotics|dc|filter|dc-motor| | <p>The capacitor that Nick T mentions is the most important -- directly across the 2 motor leads, mounted directly on the motor.</p>
<p>Occasionally that is not enough.</p>
<p>Some people get further improvements by adding one capacitor per motor lead between that motor lead and the metal case of the motor.</p>
<p>A few people go even further, adding ferrite bead "choke" and another capacitor to form a <a href="http://en.wikipedia.org/wiki/pi_filter">"pi filter"</a> -- see
<a href="http://reprap.org/wiki/Nophead%27s_Extruder_Tweaks#Interference_suppressor">"Nophead's inteference suppressor"</a>
and the pages it links to
for the ugly "before" o'scope traces and the pretty "after" o'scope photos.</p>
| <p>I am looking for any information that would help me reduce the power rail noise and EMI of DC brush motors. I am building a robot that is powered by 2 x 250 W 24V DC motors.</p>
<p>Thank you in advance</p>
| Methods of filtering noise caused by DC brush motors | 2010-10-12T13:24:46.530 |
5139 | |pcb|routing| | <p>There is an interesting article from Altium from 2020, about hatched grounplanes for what they are used today: Rigid flex PCBs and flex PCBs.</p>
<p>The reason for cross hatched copper planes in rigid PCB where adhesion problems.</p>
<p>This article will describe the history of cross-hatch planes, how they are made, the reason they were initially used in rigid PCBs, and their ongoing role and benefit today in flex and rigid-flex boards:
<a href="https://resources.altium.com/p/history-and-use-cross-hatched-planes" rel="nofollow noreferrer">https://resources.altium.com/p/history-and-use-cross-hatched-planes</a></p>
| <p>Recently while routing a PCB, I came across the option to fill/pour my ground plane with either solid or hatched copper. I've also noticed that the old Arduino Duemilanove also had a hatched ground plane.</p>
<p>What benefits does a hatched ground plane have over solid ground plane and vice versa?</p>
| Solid ground-plane vs hatched ground-plane | 2010-10-12T18:02:03.820 |
5144 | |soldering| | <p>Because @nick t said that a solution is mildly acidic I used distilled vinegar as a quick test. Seemed to work wonders and so now i am going to try to keep the tip tinned as this was not something I used to do.</p>
| <p>First, I've read though questions <a href="https://electronics.stackexchange.com/q/216/1240">Soldering Iron Maintenance</a> and <a href="https://electronics.stackexchange.com/q/4470/1240">Going through Soldering tips quickly</a> and was unable to solve my problem. I have recently (as in less then a month ago) obtained <a href="http://www.ersa.com/index.php?modul=entry&id=359&entry_id=1890" rel="noreferrer">Multitip 25 ERSA Microsoldering iron</a> with <a href="http://www.ersa.com/index.php?modul=entry&id=403&entry_id=1675" rel="noreferrer">0172BD/10</a> tip.</p>
<p>From the start I had problems wetting the tip. I tried everything but solder just wouldn't flow over the whole tip. I later found information in one of manufacturer's catalogs that I should wrap solder with flux around the tip and then turn on the iron. After few tries, I managed to get a big part of the tip wet (and it was working great), but one small part wouldn't wet.</p>
<p>After some soldering I decided to try to get whole tip wet and obtained <a href="http://www.ersa.com/index.php?modul=entry&id=386&entry_id=2019" rel="noreferrer">0TR01/SB</a> tip refresher. After using it according to the manual, the whole tip was covered in black substance which should be easily removable, but it isn't.</p>
<p>Now about half of the tip is contaminated and about half seems to be working (I managed to clean the working part).</p>
<p>My question is: Is there any other way to clean the tip? Two things from questions I linked I didn't use were dedicated tip cleaning mesh (couldn't find a source of them in my country) and flux outside the wire (because I don't have any at the moment) and how to decide when a tip is dead and needs replacing?</p>
<p>Also, how do the tip refreshers feel (I'm assuming that they are more or less all alike)? I often find them described as paste, while the one I got is solid (but melts when in contact with hot tip).</p>
| How to clean my soldering iron tip or how to determine that it's beyond repair? | 2010-10-12T20:23:09.247 |
5154 | |dc|batteries|voltage-regulator| | <p>I'm surprised the rocker doesn't have a DC inlet already.</p>
<p>You could connect the 9 V supply to a linear 1.5 V regulator, and it would be easy, but you'd be wasting a lot of energy. It would be better to just go to a thrift store and try to find wall warts that are close (more appropriate transformer turns ratio) to the voltage you need. Regulating a 3.3 V or 5 V supply down to 1.5 V would be more efficient. The voltage might not even need regulating, or could be anywhere within a large range and still work, but you'd have to take the products apart and see what they feed into. I ruined a digital camera by accidentally using a higher voltage adapter, but many things don't care. </p>
| <p>I have multiple stationary baby items for my son Oliver that require a serious supply of batteries each month. I would like to hook a few of these stationary items up to wall warts to conserve the constant expense of alkaline purchase/recharging of batteries. I currently have two spare wall warts laying around the house: first at 9V/1A and the second at 12V/1A. I am located 15km from a Mouser warehouse in case the garage will not suffice.</p>
<p>Two items I would like to wire up right now include a baby rocker which requires one D battery and a crib which includes a mobile electronic toy rotation device requiring 3 AA batteries. </p>
<p>I was lucky enough to get these from a baby shower and due to my current job situation, I can't upgrade. I would like to build a circuit for both but will discuss the baby rocker at this point. </p>
<p>This circuit would need to accept either voltage from the wall warts and drop it to 1.5V to run the baby rocker's vibrator. I have been looking at the 780x type linear regulators at this point but am not sure if this is the way to go. I wanted to see what you might recommend. I need advice that will not only eliminate batteries, hopefully save electricity, and also be easy to solder as I do not have the skills and equipment for SMD applications.</p>
<p>Thx in advance for your help! </p>
| Best Circuit Design for a 12VDC Wall-Wart > Ouput Voltage of 1.5V (Replacing Alkaline Batteries) | 2010-10-13T08:08:19.027 |
5157 | |spi|reverse-engineering| | <p>Try zooming waaaaaaaaaaaaay in with a really high resolution o-scope. Maybe you can see the reflection on the trace? The ringing at the load should be worse than the ringing at the source.</p>
| <p>I'm trying to reverse engineer the SPI communications between two chips. But, it's not clear who's master and who's slave.</p>
<p>I've found the chip select. Without lifting any pins or cutting traces is there a way to detect which end is asserting it?</p>
<p>The chips are:
CC1110 (SoC radio) and CY7C63803 (USB MCU). The chip select comes off of the SSEL (slave select) line on the CY7C63803 and into a GPIO pin on the CC1110.</p>
<p>The CY7C63803 is an SOIC, so I could lift a leg, but I don't want to break it.</p>
| Identifying the SPI master | 2010-10-13T12:35:57.500 |
5173 | |antenna|electromagnetism| | <p>For the metal band to act as an antenna, it needs to be the correct length for 2.4 GHz operation and matched to the transmitter with a suitable network. The field from the magnet is irrelevant, but it might have a detuning effect on the antenna because of its size and position, which will need to be checked. It should be insulated from the antenna, of course.</p>
| <p>I have a project for a small remote control in which I'll use a magnet instead of screws/etc. to close the case.</p>
<p>Basically it is a two-piece plastic case in which one of the pieces has a magnet glued to it, and the other has a matching metal band at the corresponding spot. When the two are put together, the magnet holds them closed.</p>
<p>I was thinking if I could also use that same metal band as the antenna for the remote. I'd connect the magnet to the circuit, and since when the case is closed the band is tightly attached to the magnet, it'd be electrically connected to the circuit.</p>
<p>Would the magnetic field in the magnet prevent this from working? If yes, is there a workaround?</p>
| Can a magnet be an antenna? | 2010-10-13T20:58:02.233 |
5174 | |pic|usb|serial|uart| | <p><strong>USB Sniffing</strong>:</p>
<p>Windows:
<a href="http://sourceforge.net/projects/usbsnoop/" rel="nofollow">http://sourceforge.net/projects/usbsnoop/</a></p>
<p>Linux:
<a href="http://www.linux-usb.org/tools.html" rel="nofollow">http://www.linux-usb.org/tools.html</a></p>
<p><strong>Microchip CDC</strong>:</p>
<p>I'm afraid that I know nothing about their official stack, but...</p>
<p>Over at <a href="http://dangerousprototypes.com" rel="nofollow">http://dangerousprototypes.com</a> they've been building a new <a href="http://dangerousprototypes.com/2010/09/02/open-source-pic-usb-demoed/" rel="nofollow">Open Source PIC USB</a> stack.</p>
<p>They're using it in the new <a href="http://dangerousprototypes.com/docs/Bus_Pirate_v4" rel="nofollow">single chip Bus Pirate</a>. The Bus Pirate <a href="http://code.google.com/p/the-bus-pirate/source/browse/#svn/trunk/HonkenUSBStack" rel="nofollow">CDC driver is here</a>.</p>
<p>Or, you can <a href="http://dangerousprototypes.com/forum/index.php?topic=937.0" rel="nofollow">pick up the original alternative stack version here</a>.</p>
| <p>I'm using the Microchip 16-bit 28-pin starter board and the USB communication with the PC keeps breaking.</p>
<p>There are two microprocessors on the board. The application processor communicates to the USB processor via UART. The USB processor is configured as a CDC class USB device and shows up in device manager as a serial port.</p>
<p>The device enumerates ok and the data being transmitted from the PC to the application processor ok. The application processor is responding to the USB processor, but the response never gets to the PC.</p>
<p>I know the UART communications between the two processors is working ok because I'm using a BusBee to monitor the UART. I did not write the code for the USB processor (that came from Microchip). It's worked before, but I can't seem to get it working again.</p>
<p>Is there a tool or anything I can use to debug the USB end points on the PC?</p>
<p>Something like wireshark, but for USB?</p>
<p>Has anyone else used the 16-bit starter kit from Microchip and had similar problems?</p>
| Problems with CDC Device Class | 2010-10-13T21:06:39.983 |
5186 | |components| | <p>After reading the posts above, I decided to experiment with my digital microscope. It's one of those $40 jobs from Celestron that plugs into a USB port. </p>
<p>Here are two photos of the same chip. I cleaned it with alcohol and a Q-tip and dried it prior to shooting the pictures. Other than that, the <em>only</em> thing that is different is the position of the microscope. I did not even change the focus. The first picture<a href="https://i.stack.imgur.com/e6OKZ.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/e6OKZ.jpg" alt="first picture"></a> </p>
<p>is from directly over the chip. The second picture <a href="https://i.stack.imgur.com/panZz.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/panZz.jpg" alt="second"></a> </p>
<p>is at about a 45-degree angle. </p>
<p>Nothing was done to the chip between the two pictures except to change its position relative to the microscope. The microscope has several LEDs around the lens to provide illumination, so even the lighting is constant.</p>
| <p>I find very difficult to read part numbers. I haven't figured out how which kind the ideal amount of light and inclination would help me.</p>
<p>I also wonder why chipmakers don't paint the numbers in white for a better contrast.</p>
| How to read the text printed on top of every IC? | 2010-10-14T01:23:34.027 |
5196 | |fcc|certification| | <p>About five years ago I got a product CE tested for $7500. The testing house provided advice, and they retested until it passed as part of the upfront cost. It passed on the second attempt (barely). Since, I've read <a href="http://rads.stackoverflow.com/amzn/click/0133957241">High-Speed Digital Design: A handbook of black magic</a> several times until I mostly got it and I probably won't have nearly as much trouble in the future. I highly recommend the book.</p>
| <p>I'm aware that nobody actually does this at the hobbyist level, that successful commercial products have been launched without certification, and it's probably something I can't afford if I have to ask. However, I've always wondered about the ballpark cost. About how much does it cost to receive FCC certification?</p>
| Which products should have FCC certification and about how much does that cost? | 2010-10-14T13:39:18.543 |
5199 | |resistors|colour|colour-coding| | <p>You haven't seen different colors until you've seen inside a scope, or at least an old one.</p>
<p><img src="https://i.stack.imgur.com/OxhTp.jpg" alt="HP 54501A"></p>
<p>From a HP 54501A.</p>
<p>You can take a guess at what the colors mean, but without knowing the manufacturers it is difficult, nigh impossible. In this example suspect the green ones are precision (probably ±0.1%), while the pink and blue ones have larger tolerance, due to the relative quantities of them.</p>
| <p>I don't mean the colored bands, but the colors of the bodies themselves. They come in brown, blue, green, etc. Is there a standard?</p>
<p>For instance, <a href="http://www.epanorama.net/documents/markings/resistor_colorcodes.html" rel="noreferrer">epanorama says</a>:</p>
<blockquote>
<p>But there are two resistor body colors which you should know what they need if youre fixing some electronics circuit. Resistor body colors white and blue are used to mark non-flammable resistors and fusible resistors. If you encounter tjis type of resistor in the circuit do not replace it with normal reistor because this would cause fire danger is something goes wring in the circuit.</p>
</blockquote>
<p>Is this always true? Only with certain manufacturers?</p>
| What do the colors of resistor bodies mean? | 2010-10-14T15:31:36.883 |
5213 | |zener|tl431| | <p>Also bear in mind that the TL431 has a maximum sinking current, beyond which the voltage will no longer be regulated (and the device could be damaged). With 3.3V and 115R you'll not be anywhere close to that.</p>
<p>It is also generally recommended to have a small capacitor from the cathode to the anode, for stability reasons. (431s can and do oscillate). The 'safe' range of capacitor depends on the setpoint and is usually specified in the datasheet. I'd recommend something from 1nF to 10nF, and check to make sure the output isn't a sawtooth.</p>
<p>Note that not all manufactures have the stability region curves, but it's been my experience that the curves in the National Instruments LM431 datasheet hold true for other vendors' 431 regulators (TI, ON Semi, Fairchild, etc. etc. and so on)</p>
| <p>I want to get a stable 3V reference from a +3.3V ±5% supply (so it can go as low as 3.135V and as high as 3.465V.)</p>
<p>I know the TL431 is a shunt/zener regulator, so doesn't really have a dropout voltage, but there probably is some point above 3V at which it cannot maintain the 3V output. What I want to know is will a typical TL431 be able to handle this?</p>
<p>My circuit configuration is below:</p>
<pre><code> 115R
+3.3V-+-/\/\/\---+----------+-------+-- 3V out
| | | |
--- 100n / | --- 4.7u
--- 16V \ 634R | --- 10V
| / ___|__| |
--- | | / \ ---
- +--------/___\ -
| |
/ |
\ 3.16k |
/ |
| |
--- ---
- -
</code></pre>
| Does the TL431 have a "dropout voltage" per se? | 2010-10-14T22:18:08.623 |
5218 | |microcontroller|embedded|temperature|home-automation| | <p>After reading a few posts and doing a little testing with a DMM, I believe I have solved my questions concerning how a home thermostat works. First the posts/info that led to the conclusion:</p>
<p><a href="http://www.ritetemp-thermostats.com/60XX/images/6022_installation_guide.pdf" rel="nofollow">RiteTemp Installation Guide (pg 17 - 4 Wire Heat/Cool No Pump)</a></p>
<p><a href="http://www.eevblog.com/forum/index.php?topic=1528.msg20345#msg20345" rel="nofollow">JohnSAZ from EEVBlog</a>:</p>
<blockquote>
<p>Of course your thermostat may be
different but every one that I've ever
looked at worked the same (and your
color codes pretty much indicate an
industry standard setup).</p>
<p>Think of the thermostat as nothing
more than three switches. The "RH" is
your common. If you short "RH" to "G",
your blower fan will turn on. If you
short "RH" to "Y", the air
conditioning compressor will turn on.
If you short "RH" to "W", the heater
system will turn on. This could be a
gas burner solenoid, or relays to
energize resistive electric heaters.
If the unit is a heat pump, it will
turn on the air conditioning
compressor, but it will also energize
a reversing valve that will make the
freon run the other way around
(kinda).</p>
<p>Obviously you need to ensure that the
"G" and "Y" leads are NEVER turned on
at the same time. You also need to
make sure that the eater system can
not be turned on with the blower off.
Also, you need to make sure that when
the compressor turns off, it is not
allowed to turn back on for some time
(10 minutes? don't know the time limit
for sure). Also, higher quality
thermostats keep the blower running
for some time after the compressor (or
heater) has turned off to suck every
last Btu out of the system before
shutting down.</p>
</blockquote>
<p>I grabbed my trusty DMM and confirmed that W, Y, G, and C all measure 30VAC+ when tested against RH (or R) - GND. When the system is running, G drops to 0.05 for both heat and cold (meaning the fan is running). W drops to 0.05 if the heater is running. Y drops to 0.05 if the Cooler is running.</p>
<p>I still need to research the appropriate timing for cooler/heater shutdown etc.</p>
<p>If anyone can think of any additional circuit protection outside of what JohnSAZ noted, please let me know. I am interested in adding a fail safe to the circuit design in case the unit fails. Not sure if relays in off positions during power outage would take care of business or not. Either way, I do plan on providing battery backup to the project just in case (IE. detect power failure, disable all controls).</p>
| <p>I am currently interested in determining how a home thermostat controls a home HVAC unit. I have run into plenty of schematics that can control a HVAC window unit, walk in freezer, water temperature, etc. However, using a circuit like those on a unit as expensive as a HVAC unit is just nuts as far as I am concerned...plus it doesn't take care of all possible operations.</p>
<p>The question I seek an answer for: How do you build a complete home thermostat. A device that protects and is built to ensure no damage is done to the HVAC unit. I am planning on buying a cheap $10-20 thermostat just to tear it apart and study the board in detailin a few weeks if I cannot find any other answers.</p>
<p>My current home HVAC unit uses a 4 Wire Heat/Cool setup which is referenced on page 17 (10 on adobe reader) of this thermostat installation manual: <a href="http://www.ritetemp-thermostats.com/60XX/images/6022_installation_guide.pdf" rel="nofollow">http://www.ritetemp-thermostats.com/60XX/images/6022_installation_guide.pdf</a></p>
<pre><code>Connections are as follows:
W - Heater Control Line
Y - Cooler Compressor
RH - Heater/Cooler Power
G - Fan Control
C - Optional Thermostat Power (which I have)
</code></pre>
<p>What kind of control does this device use? Is it 1-wire? Where is the GND connection? In addition to this wire diagram, the unit also provides C which powers the thermostat itself ensuring no batteries are required. I wish I could tear this unit apart but do not have another thermostat to put in its place until I get paid.</p>
<p>If you can help me/point me in the right direction; I would be much appreciative.</p>
| ISO Example Home HVAC Control Schematics and Circuit Design Info | 2010-10-15T04:43:40.870 |
5221 | |relay|solid-state-relay| | <p>There are a few problems with replacing electromechanical relays with solid state relays.</p>
<p>1) Most SSR's cannot control an AC signal. They are only rated for DC. They will usually conduct all the time with a reverse biased drain-source current, due to the body diode of the MOSFETs.</p>
<p>2) SSR's can be damaged by exceeding the maximum current through the photodiode, which is usually no more than 10-20mA. A relay will take 100's of mA through its coil. So they aren't a drop in replacement.</p>
<p>3) They are faster than electromechanical relays, which can cause problems for some circuits (the circuit may be designed to reset in the time the relay is transitioning between the two states, for example.)</p>
<p>4) They are sensitive to ESD, electromechanical relays are not.</p>
<p>5) And finally, most importantly, they do not click when they change, which makes them kind of boring. I love hearing my scopes' relays click when you change the attenuation. Don't underestimate how awesome this is.</p>
| <p>I've lost touch with electronics. I used to be an electronics hobbyist in my childhood.</p>
<p>I have some old small hobby project circuits, which I want to repair. One of which is a remote-operated garage gate. It has many (8) old electro-mechanical relays which are dead. What should I replace them with? I just read on wikipedia about the new solid-state relays, are they costly? Are they available?</p>
| What to replace a relay with? | 2010-10-15T07:46:09.720 |
5229 | |capacitor| | <p>One big advantage of high-frequency switching regulators is that they allow you to use <a href="http://en.wikipedia.org/wiki/Ceramic_capacitor" rel="nofollow">ceramic capacitors</a> instead of low-<a href="https://en.wikipedia.org/wiki/Equivalent_series_resistance" rel="nofollow">ESR</a> <a href="http://en.wikipedia.org/wiki/Tantalum_capacitor" rel="nofollow">tantalum</a> (because you don't need such large capacitance values as you would in a lower-frequency regulator).</p>
<p>Tantalum is a comparatively rare material, not mined in that many places, so tantalum capacitors are perpetually expensive and difficult to buy in large quantities. Large electronics companies have at times suffered delays in meeting high demand for their products due to shortages of tantalum capacitors.</p>
<p>Ceramic capacitors tend to be much cheaper and more available.</p>
<p><a href="http://en.wikipedia.org/wiki/Electrolytic_capacitor" rel="nofollow">Electrolytic capacitors</a> have a high ESR in comparison to tantalum and ceramic, as well as being quite a bit larger.</p>
| <p>I'm using the <a href="http://www.ti.com/product/lm2734z" rel="nofollow">LM2734Z</a> (step-down DC/DC converter), which operates at 3 MHz. I'm using it to step down 4.8 V - 20 V down to 3.3 V +/-5%. Is it better to use ceramic capacitors or electrolytic capacitors in this circuit? </p>
<p>They seem to show ceramic capacitors in the datasheet, but would electrolytic capacitors be smaller and better at filtering ripple and handling load transients? Size is critical for this product, and cost is a minor issue. I would like the operational temperature range to be -40 °C to +85 °C, if not that then -20 °C to +70 °C.</p>
| Ceramic or electrolytic capacitors for a switching buck regulator? | 2010-10-15T11:49:41.117 |
5233 | |robotics|dc-motor| | <p>You should not use that driver if you think you'll be pulling that much current. For one, it's rated for 3A for a maximum of 10ms per the datasheet and you'll certainly try to draw for longer than 10ms in a stalled condition. And that is the maximum rating for the device which the datasheet says is not to be exceeded under any circumstance. It sounds to me like you'll be abusing the poor thing. Find a beefier driver, or if you're feeling really adventurous, parallel two of them. Is that a good idea? I've never done it, never heard of it being done, and wouldn't do it myself, but you could certainly try :)</p>
<p>I would just find another motor driver on pololu's site. It looks like there's plenty of them. Make sure their maximum CONTINUOUS current is greater than your stall current. </p>
| <p>I'm thinking of using two of <a href="http://www.pololu.com/catalog/product/1092" rel="nofollow noreferrer">these</a> motors with <a href="http://www.pololu.com/catalog/product/713" rel="nofollow noreferrer">this</a> motor driver. However, one thing concerns me: the stall current of the motor is 3.3A, and the motor driver has a peak current output of 3A.</p>
<p>The motor would be used in a robotics situation involving rapid changes of direction, and potential stalling.</p>
<p>Could this cause an issue, and do I need to get a lower power motor / better driver, or will it still work?</p>
<h3>EDIT:</h3>
<p>What will happen if I DO exceed that thing's current rating, given that it has temperature protection? Will it blow the microcontroller, the motor chip, or the motors?</p>
| How lenient can I be about motor stall current? | 2010-10-15T13:32:11.707 |
5234 | |components|inverter| | <p>The 74AC04E has a rated operating of current of +-24mA. The 50mA is the absolute
maximum rating which you should not be operating at. There is also an absolute maximum
rated current of 100mA into Vcc or GND for the package. </p>
<p>IIRC LVC family form TI has the same +-24mA output currents. TI also has some power logic
devices. Not sure is they have a hex inverter or just a shift register. You could also
try Allegro.</p>
<p>For CMOS devices you can parallel the input and outputs of gates within the same package
to increase the current drive. Do not parallel gates from different packages.</p>
| <p>I am trying to find a hex inverter which has as high output current as 74AC04E (50mA) but surface mounted.</p>
<p>I haven't had any luck so far...</p>
| High output current hex inverter in SMD capsule | 2010-10-15T13:57:04.940 |
5243 | |voltage|voltage-regulator| | <p>what about this
<a href="http://www.analog.com/static/imported-files/Data_Sheets/ADR130.pdf">http://www.analog.com/static/imported-files/Data_Sheets/ADR130.pdf</a>
cheap from digikey circa $2 for single units, wide input voltage range (2-18 V) stable output over temperature a wide temperature range of 50 ppm per degree C, and +/- 0.7% initial accuracy, and small size TSOT package.</p>
<p>Use a voltage divider on the input side to drop your 4.8 V - 25 V to 2.4 to 12.5V which is suitable.</p>
<p>I think that is a tick in every box :)</p>
| <p>For a project, I need a 500mV reference. </p>
<p>Some requirements:</p>
<ol>
<li>Relatively low cost.</li>
<li>Small size. Preferably surface mount.</li>
<li>Supply from 4.8V to 25V.</li>
<li>Accuracy ±5% or better</li>
<li>Stable over voltage (that is, it doesn't change that much with a different supply.)</li>
</ol>
<p>I could use a diode drop but it does not satisfy condition 5, being stable over voltage.</p>
<p>Any suggestions appreciated!</p>
| Cheap 500mV reference | 2010-10-15T17:05:13.943 |
5252 | |switches|automotive| | <p>To answer your question, you just need to convert the low voltage to a high voltage by use of a transistor switch. Using a BJT transistor will work, but I recommend using a MOSFET. They are more efficient and can handle more power without getting hot due to the very low "on" resistance. Consider this circuit:</p>
<p><img src="https://i.stack.imgur.com/6xfyA.jpg" alt="Automotive Voltage Converter"></p>
<p>The P channel MOSFET gate is pulled HI by RA, so it is turned "OFF." Remember, P channel transistors (or PNP) work opposite to that of N channel transistors (OR NPN). Since the FET is OFF, the outputs signal is pulled LO by RB.</p>
<p>If a switch is closed/pressed, then the FET gate is LO, turning the FET "ON." Now, the transistor acts like a switch, connecting the output to the 12V power source. There is a bit of loss in the transistor, but not a lot. Using a "Power MOSFET" is necessary to handle the level of current required to operate an automotive relay - not a problem since many of these transistors can switch dozens of amps.</p>
<p>Since the MOSFET is a voltage controlled device, only a negligible amount of current would be needed to control the transistor (this is the current through your steering wheel wires). A similar circuit could be made using an N channel MOSFET instead. See this website on using a MOSFET as a switch:</p>
<p><a href="http://www.electronics-tutorials.ws/transistor/tran_7.html" rel="nofollow noreferrer">http://www.electronics-tutorials.ws/transistor/tran_7.html</a></p>
<p>But realistically, this is all probably unnecessary. Have a look at the wire gauge table on this website:</p>
<p><a href="http://www.powerstream.com/Wire_Size.htm" rel="nofollow noreferrer">http://www.powerstream.com/Wire_Size.htm</a></p>
<p>You will see that the few hundred mA needed to trip a relay are safely carried in wire size all the way down to 27 gauge (handles 288 mA). You should check those wires to see how big they actually are (usually printed on the side of the wire somewhere).</p>
| <p>Let me start off by saying that I know just enough about electronics to be dangerous (how to solder, follow a simple schematic, and check for connectivity problems and usually figure out what each wire is for).</p>
<p>I've installed a cruise control kit in my car, and I want to use a set of Honda steering wheel controls instead of the stock controls from the kit. The cruise kit controls are expecting 12 volts, but I'm not comfortable running any more than 5 volts through the small steering wheel wires next to the airbag wiring. I'd prefer even less, like 2-3 volts.</p>
<p>So I need to build a switching circuit that will provide the 12 volt signals to the cruise kit. I was thinking of keeping it solid-state, since I don't know of any relays that will switch on 2-3 volts. However, if there's a good reason to use relays then I can.</p>
<p>Here's a rough drawing of what I need:</p>
<p><img src="https://i.stack.imgur.com/2uh9t.png" alt="schematic"></p>
<p>How can I get started with this project?</p>
| How can I build a switching circuit that scales several 12v signals down to <5v? | 2010-10-15T19:08:31.093 |
5260 | |microcontroller|usb|microprocessor|8085| | <p><a href="http://www.ghielectronics.com/catalog/product/6" rel="nofollow">http://www.ghielectronics.com/catalog/product/6</a> This company has some products to allow
interaction between selected usb devices and mcu's and appears fairly adaptable.
Seems like it would be a great addon allowing easy expansion of memory perhaps. </p>
| <p>I wish to expose a usb flash drive and read it as raw binary data, particularly read each byte & simultaneously writing it to another flash drive. </p>
<p>Given that I am working with an 8085 microprocessor, & I am in a position to program it & read data from secondary memory device, how can I start working with the usb.</p>
<p>I have tried to understand USB from this:</p>
<p><a href="http://www.beyondlogic.org/usbnutshell/usb1.shtml" rel="nofollow">http://www.beyondlogic.org/usbnutshell/usb1.shtml</a> </p>
<p>But I still have no idea how I would be writing my program to host flash drives.</p>
| Reading/Writing a usb flash drive | 2010-10-16T07:21:06.163 |
5269 | |batteries|safety|charger| | <p>For a cell phone, the wall adapter just supplies a constant voltage, like any other wall wart, and the phone has all the current regulation and charge monitoring circuitry internally.</p>
<p>If the charger is small, light-weight, and cool to the touch during operation, it probably has a switching regulator inside. If it's heavy, bulky, cheap, and warm to the touch during operation, it's probably a linear regulator.</p>
<p>5 V micro USB chargers <a href="http://www.maximumpc.com/article/news/microusb_way_becoming_cell_phone_charging_standard" rel="nofollow">will be the standard in the future.</a> With any charger, the voltage applied to the phone is fixed, but the phone can adjust the amount of current it draws. Some supplies can provide a lot, but some (like plugging into a laptop's USB) can only supply a little. There are a few different ways to tell the phone how much current it's allowed to draw. The USB-IF <a href="http://www.usb.org/developers/devclass_docs/batt_charging_1_1.zip" rel="nofollow">battery charging standard</a> has the charger short the D+ and D- pins together. iPhones, on the other hand, <a href="http://www.adafruit.com/blog/2010/08/03/the-mysteries-of-apple-device-charging-video/" rel="nofollow">require certain voltages</a> applied to the D+ and D- pins. <a href="http://wiki.openmoko.org/wiki/USB_charger" rel="nofollow">Others use the 5th ID pin</a> to indicate a dedicated charger. Otherwise, without some kind of identification of the charger, a USB-charged phone should only draw 100 mA, in case it's connected to a low-power computer port.</p>
<p>As for "Protection against back current flow", a simple Schottky diode will do. The charger circuitry drives current into the battery by applying a larger voltage than the battery's voltage.</p>
<p>And the phone's internal circuitry takes care of this, as well as switching off power (or applying a float charge?) when the battery is fully charged.</p>
| <p>I would like to know about the workings of mobile phone battery chargers. I know the basic principle, you take a transformer to bring it down to 9/6/3.7 volts then a bridge rectifier circuit and a capacitor input filter to rectify it into DC. Then you apply it to the battery. But I know this should not be enough, I need at least two things,</p>
<ol>
<li>Protection against back current flow</li>
<li>Switch off power when the battery is fully charged.</li>
</ol>
<p>Can someone point me to something simple (apart from this <a href="http://www.extremecircuits.net/2009/07/mobile-phone-battery-charger-circuit.html" rel="nofollow">http://www.extremecircuits.net/2009/07/mobile-phone-battery-charger-circuit.html</a>)</p>
| Mobile phone battery charger | 2010-10-16T15:30:58.537 |
5274 | |capacitor|reliability| | <p>You should actually not be comparing ceramics to electrolytics in terms of lifespan at all, they are actually intended for totally different purposes. Most beginners (I did untill recently) think they are just higher values, but they are as different as inductors are to resistors. Mainly because electrolytic values are more approximate, and their value much more temperature dependant than ceramic, polycarbonates or tantalum. Note: Tantalum are very voltage sensitive.</p>
<p>You answer is that I would also use a 50V cap for a 20V supply, in fact if you glance at the charge curve for electrolytics you will notice that they work better (more farads) at about 1/3 of their rating anyway. As for being for different purpose, you will get heating in an electrolytic if you allow it to completely charge and discharge on a cycle, for instance using a 220uF to service a 10 amp load on a rectifier will tax the cap and cause heating in the leads, and as the other answers alread indicate, heating equals less farads.</p>
<p>I'm just an amateur, so no clever math, sorry.</p>
| <p>Now I know when it comes to electrolytic capacitors it's usually good practice to use a voltage rating 1.5x - 2.5x the maximum rating you ever expect the capacitor to be exposed to, as the lifetime can be significantly reduced by running it near its limits.</p>
<p>But does the same protocol apply to ceramic capacitors? For example, assume a 25V ceramic capacitor - will running it at 24V reduce its lifespan significantly?</p>
<p>I'm currently designing a PSU which needs to be reliable, so at the moment I'm using 50V caps for a maximum 20V input (35V caps aren't available), but I'd like to switch to 25V caps if possible.</p>
| Voltage ratings of capacitors: ceramic vs electrolytic | 2010-10-16T18:04:06.297 |
5284 | |pcb| | <p>I agree Mark, but would like to add some info about cost. If you are looking purely at prototyping in low quantities you can get a 4 layer board from <a href="http://www.4pcb.com/index.php?load=content&page_id=131" rel="noreferrer">Advanced Circuits</a> for $66 and $33 for a 2 layer board.</p>
<p>If you are looking further into the future and want to think about large quantity fab you will need to consider that PCB fab houses will look at everything, more then just number of layers, when they give you a cost. Some items include size, number of vias, special cuts, number of holes... So in this sense, if you are able to get a board to be half of the size and with half of the vias by going to a 4 layer board it may be well worth it.</p>
<p>Also, when you get to higher quantities you will probably need to be looking at FCC testing. Many times in order to pass FCC testing you would need to get a 4 layer board in order to get your unintentional radiators down.</p>
<p>So hopefully by now you can tell that there are many many factors that factor into which way is the smarter choice. It is hard to tell which way to go, but at some point you have to make it.</p>
| <p>I'm wondering at the moment with my Super OSD project whether to go to a 4 layer board.</p>
<p>At the moment, it consists of two micros and some additional circuitry such as a discrete audio amp and switch logic, and a serial EEPROM plus a temperature sensor. There are probably around 40 resistors, 10-15 caps and a few other components (all surface mount 0805 or 0603.) It might get tricky to route it. </p>
<p>Is it worth paying the extra bucks to get 4 layer boards for a relatively simple project?</p>
<p>I'm on the fence, I like 2 layer because it's cheap and if you've got the right equipment you can even do it at home, 4 layer is more expensive, but allows me to squash more stuff into each square millimeter. I've seen a couple of open source projects (Super OSD is open source) using 4 layers but many more using 2 layer.</p>
<p>So, opinions?</p>
| How much more does it cost to fab a 4 layer board compared to a 2 layer board and is it worth it? | 2010-10-16T23:45:26.743 |
5285 | |capacitor| | <p>Another point to consider with decoupling capacitors on op-amps is they need to go from rail to ground, not rail to rail. For example an op amp with +/-5 V rails needs to capacitors one from each rail to ground. This will ensure the op amp has properly decoupled power supplies.</p>
<p>You also need to have them on signal paths also, for example a small capacitor across the feedback resistor will help your op amp circuit transition from a simulator to a real PCB with out noise and oscillations.</p>
| <p>Often 100n to 1µF decoupling caps are placed across IC supply lines for digital logic.</p>
<p>For analog circuitry, are decoupling caps necessary when the environment is also shared by microcontrollers and digital logic?</p>
<p>I have never placed them and haven't had any troubles, but I haven't made production stuff yet, so wouldn't have much experience.</p>
| Are decoupling caps necessary for analog ICs (e.g. LM339, LM324...)? | 2010-10-17T00:05:29.940 |
5286 | |oscilloscope| | <p>All of the existing answers here seem to be answering why you want to connect to the ground of an oscilloscope, not why there would be a <strong>separate</strong> ground terminal, therefore I don't feel too bad about posting the following piece of <strong>speculation</strong>:</p>
<hr>
<p>The presence of a ground binding post is (I hypothesize) a legacy feature arising from the history of oscilloscope input connections.</p>
<p>Once upon a time, coaxial cables and connectors were not so common and cheap, and the frequencies of interest were lower. Oscilloscopes had terminals for <em>individual wires</em>, or banana plugs, such as the binding posts on this unit:</p>
<p><a href="https://i.stack.imgur.com/DsH69.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/DsH69.png" alt="Heathkit IO-12"></a></p>
<p>A later development was the SO-239 or “UHF” coaxial connector. One of the properties of this connector is that it can accept a banana plug. Therefore, if the scope has a SO-239 connector paired with a ground banana jack, it can accept either a coaxial or pair-of-banana-plugs input. An example of such a scope is the BK Precision 1431; note the jack and binding post in the upper right corner, with the same-sized center holes:</p>
<p><a href="https://i.stack.imgur.com/cC3xU.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/cC3xU.jpg" alt="BK Precision 1431"></a></p>
<p>Here's a recent example of such a connection (not to an oscilloscope) actually in use, from <a href="https://www.youtube.com/watch?v=zDcl0-t7ceY&t=18m7s" rel="nofollow noreferrer">one of Dave Jones (EEVBlog)'s videos</a>. (This is a bit of a silly example, since the cable he's using is actually coaxial at the other end, but it was probably handier than digging up an adapter. SO-239/PL-259 is fairly uncommon if you're not an amateur radio operator.)</p>
<p><a href="https://www.youtube.com/watch?v=zDcl0-t7ceY&t=18m7s" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/VY7Tq.png" alt="Two banana plug wires inserted in a SO-239 and binding post."></a></p>
<p>Thus I hypothesize that this feature was simply <strong>not removed</strong> (in some designs) when oscilloscopes transitioned to the BNC connector, which is electrically superior and more convenient to use but does not have the same banana plug compatibility.</p>
<p>This vestigial connector is still <em>potentially</em> useful for banana or wire inputs; one <strong>can</strong> get a single-binding-post-to-BNC adapter (example below), or for that matter a SO-239 adapter, cheaper than the more commonly seen dual-binding-post adapter. But that is a fairly obscure use case and certainly doesn't justify keeping it around when modern oscilloscope use nearly always involves either a probe or a coaxial cable input.</p>
<p><a href="https://i.stack.imgur.com/QdfWe.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/QdfWe.png" alt=""></a></p>
| <p>I just bought my first analog oscilloscope (GoldStar OS-7020A) and noticed it has a port on the front labeled "ground". What exactly is this port for?</p>
<p>I thought it might be for plugging in a ground clip for probes that don't have one included, but there are two channels and only one ground port, so I'm not sure. Is it simply for providing a convenient ground connection for other devices?</p>
<p>Could I, for example, attach my anti-static wrist strap to it? Would the oscilloscope have to be on for that to work? (Electronics newbie here, so please forgive me if this is a stupid question.)</p>
<p><img src="https://i.stack.imgur.com/T2wdB.png" alt="GoldStar OS-7020A"></p>
| What is the ground port on an analog oscilloscope for? | 2010-10-17T00:07:25.590 |
5294 | |light|interference|workbench|emc| | <p>When I record VLF radio onto my Zoom H1 recorder at 96kHz, I use a battery operated LED flashlight (Harbor Freight 27 LED) that I stuck to the ceiling of the room (with heavy duty Velcro) and wired to a 3 AA battery pack (from Radio Shack) with a standard light switch (Bet you didn't know that a 120 volt light switch will also work at low voltages too...) and 47 ohm 1/2 watt resistor in series. Because the power supply is linear (no oscillators or waveform modulation), there is no noise, although it's not very bright, but bright enough to see in color in the room. When I am not recording I go back to a Great Value 40 watt equivalent LED that only makes a narrow band gentle whine at 11 kHz. 3 AA rechargeable batteries can do 96 hours of continuous light on time and can be recharged from flat to fully charged in 1/2 of an hour. Also it's nice having an emergency light when there's a power failure.</p>
| <p>Being a green-oriented treehugger, I've put in all CFL lights in my house. Just as much light for about 1/4 or 1/3 the power. Nice, but flourescent lights put out a lot of EMI. Does this cause trouble for anyone? What are your experiences of CFL or other flourescents versus incandescent bulbs in the room or house where you do sensitive electronics work? Does anyone stick with ol' tungsten just to keep EMI down? </p>
| EMI: CFLs vs Incandescent Lights in Your Lab? | 2010-10-17T04:19:39.930 |
5300 | |temperature| | <p>The materials that the transistor is made out of primarily defines this. Germanium junctions will actually be much lower, more like 70C. Silicon and Gallium-Arsenide can handle 150-200C.</p>
<p>Someone with more semiconductor manufacturing experience can probably give a better answer but I believe that most of these junction limits are imposed due to the transistor crossing a thermal runaway point. Both BJTs and FETs, although for different reasons, have the characteristic that as temperature increases so does power dissipation, which of course creates more heat. As such once you break a threshold, the junction temperature will will rise very fast to the thermal breakdown point of the materials that make up the junction. Which if this occurs for very long results in smoke, and lots of fun smells. </p>
<p>I would venture a guess that 150C in the junction is roughly where normal packaging materials / the junction materials themselves can no longer pull enough heat out of the junction to keep it out of runaway and that the semiconductor materials themselves start to incur physical damage shortly after this temperature. </p>
<p>I don't exactly know what this process is, but it may simply be the point at which the crystalline structure begins to break down. A silicon transistor is normally made with a silicon crystal thats doped with boron (p type) or phosphorus(n type). You may get a more exact answer if you look into the chemistry of those structures.</p>
| <p>As in the title. What limits most integrated circuits to 150°C junction temperature?</p>
<p>I know it's not good practice to run chips very hot (as it shows you are wasting a lot of energy) but I'm curious as to what actually limits them to around 150°C.</p>
| What limits most integrated circuits to 150°C junction temperature? | 2010-10-17T10:42:35.520 |
5313 | |surface-mount| | <p>The difference between a TSOT-23-6 and a SOT-23-6 is the height, apparent from the two PDF files below. The exact dimensions varies between manufacturers.</p>
<p>From <a href="http://www.intersil.com/en/support/packaginginfo.html#PLASTIC/" rel="noreferrer">Packaging Information - Plastic Packages</a>:</p>
<ol>
<li><p>SOT-23-6. <a href="http://www.intersil.com/data/pk/P6.064.pdf" rel="noreferrer">6 Lead Small Outline Transistor Plastic Package (SOT)</a> (PDF, 103 KB). 2.8 x 1.6 x <strong>1.15</strong> mm (body)</p></li>
<li><p>TSOT-23-6. <a href="http://www.intersil.com/data/pk/P6.064B.pdf" rel="noreferrer">6 Lead <strong>Thin</strong> Small Outline Transistor Plastic Package (TSOT)</a> (PDF, 52 KB). 2.8 x 1.6 x <strong>0.87</strong> mm (body)</p></li>
</ol>
| <p>What is the difference between a TSOT-23-6 and a SOT-23-6?</p>
<p>I know one is thinner. But in what dimension? I have looked in my PCB editor and they both have the same footprint.</p>
<p>Any clarity appreciated!</p>
| TSOT-23-6 vs SOT-23-6 | 2010-10-17T22:49:06.980 |
5314 | |wireless|xbee|zigbee| | <p>ZigBee / ZigBee Pro are mesh communication protocols that sits on top of IEEE 802.15.4 PHY.</p>
<p>XBee / XBee Pro are product names for radio communications modules made by Digi. </p>
<p>The modules can be loaded with various firmwares to support ZigBee / ZigBee Pro / DigiMesh and come in several frequency bands.</p>
<p>DigiMesh is an alternative to ZigBee that changes a few things, and adds some features to make it generally better to work with. </p>
<p>But, you sacrifice compatibility with ZigBee devices. </p>
<p>For example DigiMesh allows routers to sleep, has lower overhead, has 1 node type vs zigbee's 3 leading to a more robust mesh, can run at higher data rates, etc. </p>
<p>Frankly its a better protocol all around, in my opinion. I wouldn't use ZigBee unless i needed interoperability with other vendor's nodes. Not that DigiMesh is the only answer, there are other mesh protocols that sit on IEEE 802.15.4 as well.</p>
| <p>It's easy to get an introductory explanation of Zigbee.</p>
<ul>
<li><a href="http://en.wikipedia.org/wiki/ZigBee">Zigbee on Wikipedia</a></li>
<li><a href="http://www.eetimes.com/design/communications-design/4006430/Home-networking-with-Zigbee">Home networking with Zigbee</a></li>
<li><a href="http://www.zigbee.org/">Zigbee alliance</a></li>
</ul>
<p>But technical information on XBee seems harder to find. It's unclear to me what its similarities and differences to Zigbee are.</p>
| What is XBee and how is it different from Zigbee? | 2010-10-17T23:10:24.893 |
5315 | |arduino|audio|adc|arduino| | <p>The solution is to use an Amp-Op</p>
<p><img src="https://i.stack.imgur.com/DtBDg.gif" alt="Pins"></p>
<p>In a circuit like this:</p>
<p><img src="https://i.stack.imgur.com/I33Vp.gif" alt="Circuit"></p>
<p>You can simulate it using the <a href="http://www.falstad.com/circuit/" rel="nofollow noreferrer">Java Circuit Simulator</a> where you can import the following code:</p>
<pre><code>$ 1 5.0E-6 10.20027730826997 57 5.0 50
g 240 240 240 288 0
r 240 112 240 160 0 47000.0
r 240 192 240 240 0 47000.0
R 240 112 240 80 0 0 40.0 5.0 0.0 0.0 0.5
r 272 384 336 384 0 1000.0
R 176 384 144 384 0 1 40.0 0.5 0.0 0.0 0.5
w 176 384 192 384 0
c 192 384 256 384 0 1.0000000000000001E-7 -2.9572014071857935
c 192 176 192 240 0 1.0000000000000001E-7 2.5000000000001608
w 192 240 240 240 0
w 256 384 272 384 0
w 336 384 336 192 0
r 416 240 512 240 0 100000.0
w 512 240 512 176 0
w 192 176 240 192 0
w 416 240 416 192 0
w 240 192 240 160 0
a 416 176 512 176 1 5.0 0.0 1000000.0
w 416 160 240 160 0
w 336 192 416 192 0
o 13 64 0 35 20.0 9.765625E-5 0 -1
</code></pre>
<p>The gain will be proportional to the ratio between the resistance of the 100k resistor and the 1k one.</p>
| <p>I was trying to use the ATMega328 ADC port A0 to read a signal. The hardware I used was:</p>
<ul>
<li><a href="http://www.seeedstudio.com/depot/seeeduino-stalker-atmega-328-p-600.html" rel="nofollow">Seeeduino Stalker</a></li>
<li><a href="http://www.seeedstudio.com/depot/electronic-brick-shield-v4-p-458.html?cPath=48_49" rel="nofollow">Electronic Brick Shield</a></li>
<li><a href="http://www.seeedstudio.com/depot/electronic-brick-microphone-with-amplifier-analog-p-481.html?cPath=48_54" rel="nofollow">Microphone Electronic Brick</a> (I found a <a href="http://item.taobao.com/item.htm?id=1694977260" rel="nofollow">link to the original developer store</a>)</li>
</ul>
<p>The signal I got seems to be only the positive part of a sine wave. Is it possible that this setup isn't suited for audio recording? What I have to change?</p>
| How to read an audio signal using ATMega328? | 2010-10-17T23:13:19.413 |