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9280
|
|voltage-regulator|diodes|zener|
|
<p>Let's assume your input voltage is 10V, the zener is a 5V type and the resistor is 100\$\Omega\$. The zener will set \$V_{OUT}\$ to 5V, so that the current through the resistor will be \$I = \frac{10V - 5V}{100\Omega } = 50mA\$. When you put a load on the output, say 500\$\Omega\$ the zener will still keep the output at 5V, so R will still have 50mA through it, but part of that current will go through the load: \$I_L = \frac{5V}{500\Omega} = 10mA\$, so that there's only 40mA through the zener. For lower load resistances the current though the load will increase, taking away current from the zener diode, until it has too little current left to regulate \$V_{OUT}\$ properly. The 50mA from the example wasn't chosen at random; it's often the current at which the zener voltage is specified (especially for older zeners). <a href="http://www.onsemi.com/pub_link/Collateral/MMSZ4678T1-D.PDF">More modern zeners</a> can work at currents far below 1mA. If \$R_L\$ is less than 100\$\Omega\$ the resistor divider \$R/R_L\$ will pull \$V_{OUT}\$ below the zener voltage, the zener won't play anymore and \$V_{OUT}\$ will drop below 5V.<br>
So far for <strong>load regulation</strong>. </p>
<p><strong>Line regulation</strong> tells how a regulator reacts to variations in input voltage. Let's take our example with the 500\$\Omega\$ load, and decrease the input voltage to 9V. The output voltage is still kept at 5V by the zener, so the current through the load remains 10mA, but the current though R will be \$I = \frac{9V - 5V}{100\Omega } = 40mA\$, and therefore the current through the zener 30mA. Again the input voltage can decrease to the point where the zener has too little current left to operate properly. The upper limit of the input voltage is determined by the maximum current allowed through zener and R. </p>
<p>This type of voltage regulation is very simple, but not very good. <strong>Line regulation is poor</strong>, which means that the output voltage will still vary a bit when the input voltage increases/decreases. Same with <strong>load regulation</strong>: output voltage will vary with varying loads. And compared to the maximum load there's a rather big loss in the zener, so it's <strong>not very efficient</strong>. A small integrated regulator like an <a href="http://www.national.com/ds/LM/LM78L05.pdf">LM78Lxx</a> is always a better choice.</p>
|
<p>I'm having trouble understanding the simple voltage regulator that can be built using a zener diode (from section 2.04 in the Art of Electronics). I know that it would be better to use amplifiers, et cetera, but I'm just trying to understand how this circuit works. </p>
<p><img src="https://i.stack.imgur.com/BFHFl.png" alt="diagram of resistor-diode power supply using zener/avalanche diode"></p>
<p>I don't really understand how the circuit works, but I am guessing that when a load is applied to the output, it drains current from the source (Vin) and thus causes the voltage to drop? How does the zener diode help to maintain the voltage and thus make this circuit act as a regulator?</p>
|
How does a zener diode and a resistor regulate voltage?
|
2011-01-21T18:59:39.607
|
9288
|
|pcb-design|
|
<p>For low-profile SMDs there's not really a limit. I've placed 0402 resistors as close as 0.1mm apart (spacing between pads). Higher components like connectors do require extra attention. You probably can't place a 0402 at 0.1mm from a 15mm high RJ45 connector, the pick-and-place machine may not be able to reach the position. Note that component orientation may matter! Talk to the assembly shop if you want to know what's possible.<br>
Also worth noting is the clearance you have to keep to the board edge, again for the higher parts. If your panel is V-cut you need some space to fold the panel to break it after it's populated, preferably both up and down. RJ45s obviously go on the edge of a PCB, but don't place two of them directly opposite to each other on the panel if possible.</p>
|
<p>I am (still) designing my first PCB and, according to prices listed on websites, the smaller the board the cheaper it is. That is, batchpcb charges per square inch. goldphoenix will print "as many as they can" on an 100 square inch board. Smaller is cheaper. Got it.</p>
<p>So should I try to cram as much as I can in a small space? Obviously one can go overboard doing this, but in all reasonableness, the point stands. Is there a standard guide for minimum distances between components? And are the standards based "this makes it easy to solder" or more technical problems (capacitances, inductances, sparks across components) that are too close together?</p>
<p>For example, one comment on <a href="http://www.sparkfun.com/products/9774">this board from sparkfun</a> says:</p>
<blockquote>
<p>"These don't look like they're spaced
at standard banana jack spacing. Isn't
that important anymore?"</p>
<p>"its low current (5 amps) which
shouldn't be enough to spark across
the terminals at those voltages"</p>
<p>"I think the point is that most double
banana plugs have a spacing of 0.75".
The banana jack spacing on this board
appears to be about 0.5"."</p>
</blockquote>
<p>All implying that there the board has a poor design. But poor based on <em>what</em>?</p>
|
Is there a standard or "safe" distance between PCB components?
|
2011-01-21T23:08:06.967
|
9293
|
|arduino|usb|uart|
|
<p>On mega2560 you can ground reset and bypass avr and use arduino as bridge</p>
|
<p>I have a BluRay player that can be programmed by accessing to a serial console, as described <a href="http://bd560.000space.com/hardware/hardware.html" rel="nofollow">here</a>.</p>
<p>I have an Arduino (a Seeduino, actually), that has a USB interface. According to Arduino's documentation, pins 0 and 1 are RX and TX. Do these pins bypass from what the computer sends? Can I use the Arduino as a USB to serial interface for what I need?</p>
|
Can I use an Arduino as a USB to serial interface?
|
2011-01-22T00:41:18.017
|
9297
|
|spectrum|
|
<p>There are two types of input EMI tests that are done: conducted and radiated.</p>
<p>For conducted EMI, you need special hardware known as a LISN, or line impedance stabilization network which essentially standardizes the line impedance going to the unit under test and provides a connection point to the analyzer.</p>
<p>For radiated EMI, you need a shielded room of sufficient size to hold the unit under test and an antenna sensitive to the frequencies you are testing at.</p>
<p>There are analyzers out there that are pre-programmed with all of the EMI settings you need.</p>
<p>You can take a coaxial cable, bare some of the center conductor and make a loop connection to the shield, hook it up to a scope and use it to sniff for noise - prefab probes also exist on the market.</p>
|
<p>Maybe when I have the cash to buy one, I will. But my question is more related to how to use one once I've got it. I assume I'll need some kind of antenna to receive the EMI. Are there general rules for self-testing? (Before sending it off for proper FCC/CE/etc. validation.)</p>
|
If I buy a spectrum analyser, how do I do an EMI test?
|
2011-01-22T02:14:27.470
|
9303
|
|pic|development|board|
|
<p>Yes, it requires additional hardware to program a new PIC (as indicated in the <a href="http://loginway.com/pdf/manual.pdf" rel="nofollow">manual</a>). <a href="http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=2519&param=en534451&page=wwwdevMPLABEmulatorDebuggers" rel="nofollow">PICkit</a> is one such with good features for the price, including debugging, serial communication and logging. Once you have a way to program your PIC, it can communicate through the serial port; this could be used to implement a <a href="http://www.etc.ugal.ro/cchiculita/software/picbootloader.htm" rel="nofollow">bootloader</a> in self programming capable chips, the way boards like Arduino work. Your Loginway PIC-01 is a pretty good host board to build on, and certainly more featureful than the host board in the PICkit bundle.</p>
|
<p>I have a loginway PIC-01 Development board (it was sat in a cupboard for years).</p>
<p>Does this board require additional adaptor hardware to blow a PIC (ICSP stuff etc), or can the on board serial port be used to do that?</p>
|
Is a loginway PIC-01 development board enough to program a PIC?
|
2011-01-22T10:56:30.317
|
9307
|
|power-supply|usb|usb-device|transient-suppression|
|
<p>The other answers are good but if you prefer a one component solution there exists <a href="http://www.digikey.com/product-search/en/circuit-protection/inrush-current-limiters-icl/656273" rel="nofollow">Inrush Current Limiters.</a></p>
<p>I've used them before to prevent fuses blowing when hot-plugging the power supply. Their operation is really simple. Basically they have a resistance at room temperature, say 5Ω. When you plug in a 5V power source the surge current is now limited to 1A even if there is a direct short on the other side of the ICL. (5V/5Ω = 1A) As soon as current flows through the ICL it starts to warm up and its resistance then drops very close to 0Ω (check the datasheet) and it's like the component is no longer in the circuit. </p>
<p>I like these because they're usually easy to rework into an existing designs and it's only one component.</p>
|
<p>I'm designing a device powered from USB. The device uses FTDI FT2232 chip for USB connection. Upon a command from a computer FT2232 chip should enable power via a MOSFET switch to rest of the circuit. This additional circuit has a capacitance of 50uF (FPGA + aux stuff) and is powered from the same USB port. After the switch is turned on, this additional 50uF capacitance will sink a huge current until it's charged.</p>
<p>How to limit this inrush current 1) to avoid voltage drop on power rails and 2) to avoid USB PTC from disconnecting power to the device?</p>
<p>Is it enough to put a ferrite bead in series with MOSFET switch to limit the inrush current? Or should I use a special chips, like chips for limiting current or chips for slew rate control? </p>
<p>Note: all devices are powered from 3.3V. So a small drop on 5V rail should not be a problem if it does not prevent an LDO to output stable 3.3V.</p>
|
How to limit inrush current?
|
2011-01-22T12:09:47.480
|
9314
|
|microcontroller|floating-point|microblaze|
|
<p>It's been a couple of years, but I believe that one can build a MicroBlaze with or without hardware floating point. If I remember correctly, without took 3 DSP48x blocks and with took 6 DSP48x blocks. I think when you build it, it sets the switches so that the compiler knows what it has.</p>
<p>Part of the decision process in design was how many BRAM blocks to use as well and whether to put these on local bus to the MicroBlaze or on AXI. I think that it is possible to use dual port BRAM and use one port as local bus (1 cycle faster) and the other side as AXI. Something like that.</p>
|
<p>I wonder if I could perform floating point operations in a Microblaze controller?
Thank you to all posible answers with direct references to documentation or articles.</p>
|
Microcontrollers: Can I perform floating point operations in a Microblaze controller?
|
2011-01-22T13:14:22.770
|
9321
|
|identification|
|
<p>There really is a logic in it, but its determined by each manufacturer (unless it is a second source).
There are some organizations (JEDEC, EIA, PRO-ELECTRON) who tried more or less successfully (I believe it more to the less side) to standardize this issue.
Anyway, in the cited example (T and S-something) resembles a european standard managed by PRO-ELECTRON.
Further information see following link <a href="http://en.wikipedia.org/wiki/Pro_Electron" rel="nofollow">http://en.wikipedia.org/wiki/Pro_Electron</a>
It is also helpful consult manufacturer's databooks (major ones are on-line). </p>
|
<p>There are hundreds of prefixes in IC names, <a href="http://en.wikibooks.org/wiki/Practical_Electronics/Manufacturers_Prefix">this page</a> lists a number of them. For some it's easy to see that they refer to the manufacturer's name, like <code>AD</code> for Analog Devices or <code>LT</code> for Linear Technology. Others can be found with several manufacturers, often three letter prefixes: <code>SAA</code>, <code>SAF</code>, <code>SDA</code>, <code>TCA</code> and <code>TDA</code>, to name a few. I wonder if there's some logic in this, like <code>T**</code> being a specific group with subgroup <code>TD*</code>, etc. Is there a logical structure?</p>
|
Is there some logic in IC name prefixes?
|
2011-01-22T15:38:17.367
|
9322
|
|voltage|batteries|battery-charging|lithium-ion|
|
<p>It can in fact be very important!</p>
<p>The charging voltage of a 3.7V LiPo or LiIon is 4.2V, but for a 3.6V one it is only 4.1V! You could easily damage a 3.6V LiIon cell by charging it to 4.2V.</p>
|
<p><strong>1] Voltage: 3.6V or 3.7V</strong><br>
Are <em>all</em> 18650 lithium ion battery cells 3.6 or 3.7 voltsor or are there different voltage Lithium Ion cells in the market as well?</p>
<p><strong>2] Possible Voltage Shortage?</strong><br>
Do all 3.6/3.7V li ions work the same standard way with a <code>+</code> a <code>-</code> and a <code>T</code> or do they really differ? What does the <code>T</code> stand for? Temperature sensor?</p>
<p><strong>3] Physics Voltage Reason</strong><br>
Whats the reason for the 3.6/3.7 Volts per Li Ion Cell? I never saw a 3.0V or 5 Volts... Curious...</p>
<p><strong>4] Parallel Charging of many Li Ion Cells</strong><br>
I was thinking of putting two or four of those Panasonic/Sanyo 18650 Li Ion cells in parallel, soldering together from the instant the are new, that way giving me lots of mAhs. Can I use the same Li Ion charger that was made for charging just 1 cell, and let it be in the charger for longer time?</p>
<p><strong>5] Charging Wiring... How?</strong><br>
I found a nice small cheap charger about 30~40$ called Turnigy Accucel-6 (there is also an Accucel-8 for double price and double weight). Could I attach the + to + of all the cells and the - to all the - poles of the cells without needing any extra in-between-wiring?</p>
|
Combining and Charging multiple Lithium Ion Battery Cells (3.6 V or 3.7 Volts)
|
2011-01-22T17:21:59.757
|
9325
|
|rf|laser|
|
<p>I'm going to make a few assumptions here, due to what I think is right. If you fill in more information, I can give a more specific answer. I'll try to include the math that shows the general case.</p>
<p>The first step will be to estimate the small-signal impedance of the diode. Create a piecewise-linear I-V model for your laser diode. The source data would ideally be in a datasheet, but you may need to measure the curve yourself. It should look something like this:
<img src="https://i.stack.imgur.com/rl5Ua.jpg" alt="Figure from Wikipedia Diode Modeling article"></p>
<p>Find the slope of the active region. In this drawing, that would be approximately 100uA/20mV. Take the inverse of that, and for <strong>THIS</strong> diode the impedance would be 200 Ohms.</p>
<p><strong>Assumption:</strong> The RF input signal is 10 MHz FM with 25 kHz deviation (f_min is roughly equal to f_max)</p>
<p><img src="https://i.stack.imgur.com/38vsQ.png" alt="Bias-T circuit. From Wikipedia"></p>
<p>Now lets calculate what capacitor value we need for the bias-t circuit. The capacitor provides a low impedance path for the RF signal to load (diode), and a high impedance path for DC. When sizing the capacitor, we need to make it large enough to provide a RF short. I'll shoot for a 1:100 impedence ratio. That means that our capacitor needs an impedance of 2 Ohms at our minimum frequency.</p>
<pre><code>Xc = 1/2*pi*f*C; C=1/(2*pi*f*Xc)
C = 1 / (2 * 3.14 * 10MHz * 2Ohms) = 8nF
</code></pre>
<p>Our minimum capacitance is 8nF, assuming a 1:100 ratio. You can make the capacitance larger, but larger capacitors may have worse parasitic characteristics. Use a good ceramic (C0G/NP0) capacitor here.</p>
<p>Next, we need to calculate the inductor value. We want the inductor to act like an open circuit at RF frequencies. Let's design the inductor to have a 100:1 impedance ratio to the diode at RF. We then need our inductor to have an impedance of 20,000 Ohms at the minimum frequency.</p>
<pre><code>Xl = 2*pi*f*L; L = Xl / (2 * pi * f)
L = 20,000 Ohms / (2 * 3.14 * 10MHz) = 318uH
</code></pre>
<p>From these calculations, our minimum inductance is 318uH, which is fairly large. At some point, the stray capacitance in the inductor will begin to look like a short circuit. If you purchase an inductor, look for the self-resonant frequency as the upper limit that it can be used. You would need to comprimise the impedance ratio to find a viable inductor.</p>
<p>Inductors are more complicated to select than capacitors. Taking a Digikey search for "fixed choke", select and apply the parameters in this order:</p>
<ol>
<li>Select all saturation currents greater than your maximum diode current. (apply)</li>
<li>Select all self-resonant frequencies greater than 2-3 times your maximum frequency. (apply)</li>
</ol>
<p>As you decrease your inductor size, less RF power will go to the laser diode. You can compensate this by increasing your input power, but your efficiency will suffer. As with all engineering, you need to decide which trade-offs you make in your design. If you post more information, I can tailor the answer to your data.</p>
|
<p>I need to modulate a diode laser with a RF source. I've found parts on Minicircuits that can do this, but I'd like to have the Bias-T and amp on my own PCB. So, I need to design a bias-T circuit that will mix my constant current source with the RF source to drive the laser. </p>
<p>I'm having a hard time choosing the capacitor and inductor values for the Bias-T, since I don't know the load impedance of the diode laser. How can I find this out? Would it just be better to put a 50 ohm resistor in parallel with the diode and then design the Bias-T for a 50 ohm load?</p>
<p><strong>Update</strong>: After some thought, it seems reasonable to use the I/V characteristics of the diode, after turn-on, to approximate the resistance. This yields a very low value - 5-10 ohms. This, however, doesn't approximate the load while the diode is off - I assume this would be very high. But, the purpose of the Bias-T would be to bias the diode so it's always on, so I presume just the on characteristics would be sufficient. Sound reasonable? </p>
<p><strong>Update 2</strong>: My design needs to supply ~200 mA to the diode. It's a 405 nm diode, so the operating voltage is ~4-5.5 v. I have a wide bandwidth, so anywhere from a Fc of 5 Mhz to 50 MHz will probably work. My transmit bandwidth is about 2 MHz.</p>
|
I need to design a Bias-T circuit for a diode laser - help choosing component values
|
2011-01-22T18:26:59.630
|
9330
|
|arduino|reset|ltspice|
|
<p>IIRC the cap is wired to /RTS not DTR. </p>
<p>When /RTS is high there is 0V across the cap. When /RTS goes low the cap
can not change voltage instantaneously so the reset line goes low.
The cap charges through the 10K resistor. Once the reset line is above
the reset threshold the uC program starts.</p>
<p>@LouisDavis referenced <a href="http://www.arduino.cc/playground/Main/DisablingAutoResetOnSerialConnection" rel="nofollow noreferrer">this page</a>, which states</p>
<blockquote>
<p>The ATmega168 is reset by pulsing its reset pin to GND. ...by setting the DTR line to LOW ... the reset pin gets sucked to LOW until the capacitor is charged through the internal pull up resistor and R1 - which resets the chip.</p>
</blockquote>
<p>Simulated:</p>
<pre><code>Auto-Reset
VDTR 1 0 PWL(0 5 0.5m 5 0.000500004 0 1m 0)
Vcc 3 0 5
C1 1 2 100n
R1 3 2 10k
.control
delete all
tran 10n 5m
plot v(1) v(2)
.endc
.END
</code></pre>
<p>V(1) is <code>DTR</code> or <code>/RTS</code> and V(2) is <code>/RESET</code><br>
<img src="https://i.stack.imgur.com/PNpgm.png" alt="alt text"></p>
|
<p>I'd like to hear some explanations as to how the Arduino Duemilanove resets the ATMega328P over USB through the FTDI FT232R transceiver.</p>
<p>I know it involves the IDE playing some games with the DTR serial handshaking signal. After looking at the schematics, what I'm really interested in getting a better handle on is how the circuit works:</p>
<pre><code> 100nF 10kOhm
DTR -----||------+------^v^v^----- VCC
|
+--/RESET
</code></pre>
<p>The 10k resistor is the usual pull-up on the reset line. So what does the capacitor accomplish in this circuit?</p>
<p>As a sidenote, I used this as an excuse to try and learn/use LTSPICE, so I'm no pro at this tool. I modeled it in LTSPICE as follows, but it looks to me like the /RESET signal just matches the DTR signal exactly, which doesn't really make sense to me. I modeled the DTR signal as a Pulse Voltage source, maybe that's the wrong model. Is it the nature of the FTDI's DTR driver (e.g. perhaps it's open collector) or the internals of the /RESET pin on the MCU that are not present in the circuit I've drawn that make this all hang together electrically?</p>
<p><img src="https://i.stack.imgur.com/xF7td.png" alt="alt text"></p>
<p>Also, here are some of the relevant links to datasheets and schematics for reference.</p>
<ul>
<li><a href="http://www.ftdichip.com/Support/Documents/DataSheets/ICs/DS_FT232R.pdf" rel="nofollow noreferrer">FTDI FT232RL datasheet</a></li>
<li><a href="http://www.atmel.com/dyn/resources/prod_documents/doc8271.pdf" rel="nofollow noreferrer">ATMega328P datasheet</a> [Arduino</li>
<li><a href="http://arduino.cc/en/uploads/Main/arduino-duemilanove-schematic.pdf" rel="nofollow noreferrer">Duemilanove schematics</a></li>
</ul>
|
How does the Arduino Deumilanove Auto-Reset Function work?
|
2011-01-22T22:57:11.527
|
9336
|
|sensor|transistors|cpu|hall-effect|fan|
|
<p>I don't see from datasheet how to use hall sensor separately, but noone should die or explode if you would not connect the load (in the worst case you may connect some resistor as a tiny load).</p>
|
<p>Is it OK if I use the controller from a CPU fan without connecting the motor's coils?</p>
<p>All I want is to use the Hall effect sensor.</p>
<p>The datasheet is posted <a href="http://goo.gl/6atkj" rel="nofollow">here</a>, the driving output circuit uses a darlington pair.</p>
|
Using a 4-pin computer fan controller without the load
|
2011-01-23T09:23:55.380
|
9340
|
|audio|data|
|
<p>If you have a very small amount of data, ( <= 4 bits ) you can simply use DTMF. Easy to encode, easier to decode. works great in noisy environments.</p>
|
<p>I'd like to pass some data over an audio cable (i.e from audio card to my cellphone) with a short cable.</p>
<p>I'm looking for some ideas for algorithms for achieving this. They of course should include the proper modulation technique to transfer the data over audio signal, so the cellphone could interpret it over it's microphone jack.</p>
<p>Ideas? ;)</p>
<p>(P.S - my current idea is using Biphase mark code. is it any good for this?)</p>
<p>Thanks.</p>
|
How could you transfer data over an audio line?
|
2011-01-23T14:59:25.020
|
9350
|
|arduino|cellphone|level-shifting|
|
<p>You could use a resistive <a href="http://www.play-hookey.com/dc_theory/voltage_divider.html" rel="nofollow noreferrer">voltage divider</a> to <em>create</em> the 2.8 Volt source from the 5 Volt supply (<strong>HV</strong> on the level shifter board) available from the Arduino.</p>
<p><img src="https://i.stack.imgur.com/oJwdw.gif" alt="alt text"> (image src: <a href="http://www.play-hookey.com/dc_theory/voltage_divider.html" rel="nofollow noreferrer">Play-Hookey</a>)</p>
<p>Or you could use a linear voltage regulator such as the <a href="http://www.national.com/mpf/LP/LP3987.html#Overview" rel="nofollow noreferrer">LP3987-2.8</a> (SMT) or similar. </p>
|
<p>I am trying to interface a 6150 Nokia cellphone with an Arduino Duemilanove board, as some have already done through the <strong>FBUS</strong> protocol (see <a href="http://www.embedtronics.com/nokia/fbus.html" rel="nofollow noreferrer">here</a> for example).</p>
<p>The FBUS protocol uses <strong>2.8V</strong> logic, so I bought <a href="http://www.sparkfun.com/products/8745" rel="nofollow noreferrer">Sparkfun's <strong>logic level converter</strong></a> to interface with the <strong>5V</strong> from the Arduino, right ?</p>
<p><img src="https://i.stack.imgur.com/wfonb.jpg" alt="alt text"></p>
<p>They say:</p>
<blockquote>
<p>The level converter is very easy to
use. The board needs to be powered
from the two voltages sources (high
voltage and low voltage) that your
system is using. High voltage (5V for
example) to the 'HV' pin, low voltage
(2.8V for example) to 'LV', and ground
from the system to the 'GND' pin.</p>
</blockquote>
<p>Thus</p>
<pre><code>HV <-> Arduino 5V
GND <-> Arduino GND
LV <-> ??
GND <-> ??
TXI <-> Phone TX (Low Voltage)
RXO <-> Phone RX (Low Voltage)
TXO <-> Arduino RX (High Voltage)
RXI <-> Arduino TX (High Voltage)
</code></pre>
<p>The problem I have is with the low voltage source: <em>there is no power output on the phone.</em></p>
<p>Can I power the converter LV/GND from another 2.8V source ? Would it be ok with the Arduino 3.3V source ?</p>
|
Logic Level Converter, Arduino and Cellphone
|
2011-01-23T22:46:59.500
|
9375
|
|resistors|
|
<p>It's a (hand-soldered) quad <strong>resistor array</strong>. The resistors' value is indicated the same way it's done on single resistors: the first two digits for significant digits, and the third for the multiplier (power of 10). So <code>220</code> should be read as \$22 \times 10^0 = 22\Omega\$. </p>
<p><img src="https://i.stack.imgur.com/KSlrN.png" alt="enter image description here"></p>
<p>SMT resistor arrays exist in <strong>dual, quad and octal</strong> versions. They're often used on microcontroller buses, either in series with for example data lines, or as pull-ups for the address bus. Arrays are <strong>space-saving</strong> and <strong>cheaper</strong> than single parts. (Placing a part is several times more expensive than the cost of the part itself, so placing 1 array costs only 1/4 of placing 4 single resistors.) The quads are most often used, even for wider buses because they're easier to layout on complex boards. For the pull-ups there are <strong>resistor networks</strong> with one side of all resistors connected to a single pin. </p>
<p><img src="https://i.stack.imgur.com/Us4I4.png" alt="enter image description here"></p>
<p>Just like single resistors the arrays exist in different sizes, where the size is indicated in tens of mils (hundredths of inches). So a <code>0804</code> package is 80mils x 40mils (2mm x 1mm). <strong>Convex</strong> and <strong>concave</strong> pinouts exist. </p>
<p><img src="https://i.stack.imgur.com/J8Vlv.jpg" alt="concave and convex resistor network"></p>
<p>There are also capacitor networks, as well as combined resistor-capacitor networks.<br>
Manufacturers include Vishay, Yageo and Rohm.</p>
|
<p>What is this component? It's between two ICs, probably on a communication bus. One is a microcontroller and the other is some sort of memory. It's as small as an smd capacitor or resistor.</p>
<p><img src="https://i.stack.imgur.com/0nXjZ.jpg" alt="component written "220" on it"></p>
|
Help identify this component
|
2011-01-24T19:02:46.060
|
9377
|
|integrated-circuit|glue|
|
<p>Red fuming nitric acid is used to dissolve the epoxy resin used in chip packaging, and might work. It's dangerous stuff, though, and will probably dissolve the epoxy used in the PCB.</p>
|
<p>I have a mysterious component covered with yellow "glue" or something. It has very hard surface, but it seems its been poured into the plastic "cage". The shiny cover on the top is some kind of paper, I can rip it off.</p>
<p>Any idea how to remove this goo from the PCB? (Without damaging the components underneath)</p>
<p><img src="https://i.stack.imgur.com/W6LcV.jpg" alt="enter image description here">
<img src="https://i.stack.imgur.com/4MYrb.jpg" alt="enter image description here"></p>
|
How to remove "glue block" from PCB?
|
2011-01-24T19:46:30.203
|
9380
|
|impedance|
|
<p>I assume:</p>
<p>"source amplitude" means "peak" (as apposed to peak to peak)</p>
<p>The load impedance is actually calculated at 60Hz</p>
<p>Ztotal = 1000 + 1000j (really should be using j as sqrt(-1) not i in electronics)</p>
<p>Ztotal = 1414.21 @ 45deg (just rewritten in a magnitude / phase representation)</p>
<p>|Ztotal| = 1414.21 Ohms</p>
<p>Vrms = 10/sqrt(2) ~= 7.07 Vrms</p>
<p>|I| = |Vrms| / |Ztotal| = 7.07 / 1414.21</p>
<p>|I| ~= 5mA</p>
<p>P(true power) = I^2 * R = (5mA)^2 * 1000 = 25 mW (this is what is dissipated in the load, your answer)</p>
<p>Q(reactive power) = I^2 * X = (5mA)^2 * 1000 = 25 mVAR (this is power bouncing back and forth, not dissipated)</p>
<p>S(apparent power) = I^2 * Z = (5mA)^2 * 1414.21 = 35.35 mVA (this is the vector sum of the true and reactive power)</p>
<p>Power Factor = P/S = True Power / Apparent Power = 25mW / 35mVA = 0.714</p>
<p>Hopefully I didn't flub up the math there, my calculators batteries just died so i did it all in google.</p>
|
<p>Problem:
An impedance 1000(1 + i) Ohms (and note it contains an imaginary
part) is connected across an AC voltage source of amplitude 10 V
and frequency 60 Hz. What's the power dissipated during one cycle
within the impedance? </p>
<p>Relevant equations:</p>
<p>P = Re(V*I), where V* is complex conjugate of voltage
I=V/Z</p>
<p>Solution Attempt:</p>
<p>So it's alternating current, so I first take the RMS V: 10/\sqrt{2}. Then I = V/Z, so I get</p>
<p>V*I = V*V/Z = 100/2 1/(1000(1+i)) = (1-i)/(20*2). Then I take the real part of this, which is 1/40. Am I doing this right?</p>
<p>Thanks!</p>
|
Impedance across AC circuit
|
2011-01-24T20:43:17.987
|
9381
|
|skin-effect|
|
<h2>You should use the finest magnet wire with many multiple strands or LITZ WIRE to improve L/R time constant and peak current for lowest loss cable. Your discharge rise time will then drop to xx picoseconds. But for conductor pairs use twisted pair Litz wire to reduce CM emissions.</h2>
<p>Otherwise, you can jam many radios/mobiles with high rep rates of > 1pps affecting AGC. !!</p>
<p>In most conductors R(f) rises fast and L(f) drops slow from skin effect. This R effect increases more with iron content since it is from Eddy Currents. In DSL and cable modem skin effects change Zo, phase shift and group delay.... Tony</p>
<h2>ref wiki</h2>
<p>Although the geometry is different, a twisted pair used in telephone lines is similarly affected: at higher frequencies the inductance decreases by more than 20% as can be seen in the following table.</p>
<p>Characteristics of telephone cable as a function of frequency<br>
Representative parameter data for 24 gauge PIC telephone cable at 21 °C (70 °F).</p>
<pre><code> (Hz) R (Ω/km) L (mH/km) G (μS/km) C (nF/km)
1 172.24 0.6129 0.000 51.57
1k 172.28 0.6125 0.072 51.57
10k 172.70 0.6099 0.531 51.57
100k 191.63 0.5807 3.327 51.57
1M 463.59 0.5062 29.111 51.57
2M 643.14 0.4862 53.205 51.57
5M 999.41 0.4675 118.074 51.57
</code></pre>
<p>The spectrum of your pulse is not at all like a square wave, since it is not repetitive over a small interval. It is a continuous spectrum rolling off similar to The null of 2nd harmonics of the equivalent pulse of a "square" wave and then rolling off above the 0.35Tr rise time. So resonant frequency and group delay calculations of pulses is very poor and affected by skin effects, even in controlled impedances, making Baseband communication much worse than the discrete equalized channel's of a modem for thruput in bps/Hz .....Tony</p>
<p>However hollow copper tubing with interior flash gold plating works wonders in microwave as does ENIG on stripline and gold-plated aluminum cases for RF circuits and enclosures for microwave. I saw this in '77.</p>
<p>Here is a different skin effect from UV on dielectrics (human skin) and how Sodium Bicarbonate helps prevent cancer. ( also reduce causes/reactions of itching). <a href="https://www.cancertutor.com/simoncini/" rel="nofollow noreferrer">https://www.cancertutor.com/simoncini/</a>. :):)</p>
|
<p>I've just bought some 6mm^2 copper wire for my project where I will have large pulse currents - ~500A peak (driving very large Xenon flash bulbs, 1000J pulse in 2ms). </p>
<p>But I know that skin effect make it useless to use thick wires on high frequency, but does it apply to sharp fronts? Is that correct that having multiple non-isolated wires make it even worse? (mine cable have about 20 tiny 'wires')</p>
|
Skin effect for pulse current
|
2011-01-24T20:57:53.813
|
9389
|
|batteries|
|
<p>Generally, this is how I pick batteries:</p>
<p><strong>Create a Power Budget</strong></p>
<ol>
<li><p>This should be the voltage, (average) current, and duty cycle required for each component of your system. For example, if you have a mobile robot that will be driving and processing, you could say 12 Volts, 1 Amp, 80% use for the motors and 5 Volts, 200 milliamp, 100% for the processor. These numbers don't have to be exact, just in the ballpark of what you think that you will need.</p></li>
<li><p>Once you have a list of your power draws, figure out what the total energy each component will use. Find this by multiplying Voltage * Current * Duty, then units will be Watt-Hours.</p></li>
<li><p>For the components not at battery voltage (behind a regulator), factor in the energy lost from converting voltages. Depending on your DC-DC converter, this can be anywhere from 5% - 80% loss (moral of the story, use switching regulators, not linear).</p></li>
<li><p>At this point, I usually fudge a bit and add a 20% margin of error to my average power use. I then figure out how long I want the system to run on average. Multiply your average current at battery voltage by the amount of time that you want the system to run. You can then compare this number to the Amp-Hours available on the batteries that you are looking at</p></li>
</ol>
<p>Remember to oversize your batteries a bit, as the Amp-Hour rating is determined by C/20 in most cases. C being the rated current (a 3.3Ah pack has a C of 3.3 Amps, but tested at 165 milliamp). Picking batteries is not an exact science in most cases, and it may take a few tries to get right.</p>
<p><strong>Choosing Battery Chemistry</strong></p>
<p>As far as picking chemistry, it depends on the project. Weight, size, and cost factor in heavily along with the run time for your system load.</p>
<p>A few questions to ask about your need:</p>
<ul>
<li>Budget</li>
<li>Size and Weight Constraints</li>
<li>Project Lifespan (Charge cycles)</li>
<li>Charger cost, maintenance</li>
</ul>
<p>A few choices:</p>
<ul>
<li>Lead Acid, high cycle count, very reliable, easy to charge, yet they are large and heavy for the capacity.</li>
<li>NiMH and NiCd, go-to hobby batteries, average size and energy density</li>
<li>LiIon and LiPo, super-light, more expensive, high energy density, can be unstable if treated improperly. Good for high-current discharge (20*C and higher).</li>
<li>LiFePo, high cycle count, about the same energy density as LiPo.</li>
</ul>
<p><strong>Brief Example</strong></p>
<p>The attached example is for an autonomous lawnmower project that I worked on. We began by listing all of the components required at each voltage. In the end, we choose to run two different battery stacks to help eliminate some of the noise from the high-current devices.</p>
<p>The 12V battery stack also provided power for the 5V electronics, which we ran through a 80% efficient DC-DC converter. You can see the additional 20% factor in the spreadsheet.</p>
<p>In the end, budget was the main constraint, with size and weight not constraints for the project (300 pound lawnmower, what's a couple batteries?). We ended up using a 64Ah 24V lead-acid stack and a 17Ah 12V stack. Our run times reflected what is in the sheet.</p>
<p>In practice, the 24 Volt battery stack lasted much longer, as we used current figures that were close to worst case (100% full speed forward and cutters in thick grass). As a result, on the next iteration, we combined the 24V and 12V stacks together.</p>
<p><img src="https://i.stack.imgur.com/80xgC.png" alt="Example Power Budget"></p>
|
<p>How do you choose what batteries to use for your projects? Are there a set of criteria that they need to be able to do in order for you to consider them? If so what are they?. The only 2 that come to mind are size and capacity. So do I need a PP3 or could I use 6 AAs? Then capacity AAs are better as they have better capacity. </p>
|
What to consider when choosing batteries for a project?
|
2011-01-24T21:42:45.670
|
9405
|
|multimeter|calibration|
|
<p>Basically, there are lots of adjustable resistors on the multimeter PCB - don't forget to mark original positions of all of them before you start.</p>
<p>You ether get a precision resistor references (read datasheet on temperature coefficient), or find a guy with precision equipment in your city to compare the readings.</p>
|
<p>How can one calibrate a multimeter, like a UT61E or any other multimeter in the 50 ~200 $ pricemark, when one does NOT have an expensive FLUKE nor a friend who has a FLUKE) </p>
|
What Ways to Calibrate a Multimeter?
|
2011-01-25T02:08:48.443
|
9410
|
|analog|digital-logic|ntsc|
|
<p>You may wish to look at a protocol called SDI, totally standard stuff in the broadcast world, but NTSC is about the worst possible place to start, even component would be a better starting point. </p>
<p>Video bandwidth for standard def is actually only about 6MHz tops, but broadcasters like to do much better for production even if it gets mangled by the transmit chain, so standard def SDI is 270Mb/s rising to 2.97Gb/s for high def. </p>
<p>To be honest nearly nobody bothers with analogue video these days, it is a pain in the toot in all ways, and 3Gb/s serdes are not the big deal they once were.</p>
<p>Regards, Dan.</p>
|
<p>I'm interested in capturing analog video in NTSC and transmitting it as efficiently as possible over a digital link, preferably while maintaining as much fidelity to the original signal as possible. My thought was that the video signal might be able to be sampled with a high-speed ADC, the samples transmitted, and the signal reconstructed at the other end with a DAC. Is this possible? If there's a better way of doing this, by all means share!</p>
|
Transmitting NTSC over digital link
|
2011-01-25T07:04:53.133
|
9413
|
|robotics|atmega|
|
<p>Atmeega8L guaranteed to work at 8Mhz at 2.7V, 16Mhz operation at 4.5V is not guaranteed (but in practice it works). </p>
<p>Atmega8 guaranteed to work at 16Mhz at 4.5V.</p>
|
<p>I am recently doing a project on robotics.And am following (societyofrobots) 50$ robot tutorial for that purpose.But i can't find ATmega8 chip anywhere as they told but i did found atmega8L instead.Now,is it possible to replace atmega8 by atmega8L though it has low capacity than atmega8? </p>
|
Can i use ATmega8L instead of ATmega8?
|
2011-01-25T09:08:56.463
|
9418
|
|stepper-motor|servo|
|
<ol>
<li><p>a few examples of heavy duty servos <a href="http://www.active-robots.com/products/motorsandwheels/torxis.shtml" rel="nofollow">here</a> and <a href="http://www.active-robots.com/products/motorsandwheels/industrial-servomotors.shtml" rel="nofollow">here</a>, these will easily swing a 2x4 around. </p></li>
<li><p>Depending on the servo you can just connect the Control line to your servo control and connect the power of the servo to the recommended power source. for the ones linked i would use a lead-acid battery(car battery) or a good power supply.</p></li>
<li><p>Depending on your design a stepper motor probably will not work, and servos are much easier to interface and drive then steppers.</p></li>
</ol>
<p>on a side note a diagram of your design and the estimated weight of the load its moving would help. </p>
|
<p>This is a bit of a general question. I have a project I want to put together similar to the 'sentry gun' projects seen on youtube. I've gathered an SSC-32 servo controller and couple of small servos - i think they're around 76oz-in - and I made a little brace so they are attached at right angles. This basically works as a pan-n-tilt mechanism, and I've plugged the controller board into my serial port, and it all works nicely. The problem is that it's a bit too dainty. </p>
<p>I need way more muscle, and so my question is in several parts.</p>
<ol>
<li>Where is a good place to get hefty servos for a good price? I need something that can easily swing a 2x4 around (around 2')</li>
<li>Can someone point me at a tutorial for hooking this up? I assume the SSC-32 board and it's 4 AAs won't cut it as I'll need more power for those bigger servos. So How do I control the servos with the board but power them separately?</li>
<li>Would there be an advantage to using stepper motors instead? Like, more torque/$? I've never dealt with steppers, but I heard they were similar.</li>
</ol>
<p>Thanks for any advice!</p>
|
High torque servo/stepper setup
|
2011-01-25T14:35:39.373
|
9424
|
|microcontroller|uart|flash|
|
<p>As always these discussions get into lots and lots of different parts. What I like to do is to go to mouser or digikey and search for microcontrollers. Then you'll be presented with a laundry list of options, Memory, speed, price, etc. From there you can narrow down to what you need.</p>
|
<p>I am about to develop a portable device to be interfaced with a computer (so, consumer electronics). I only have experiences with Microchip and Texas Instruments and I would like to have some hint to choose the right MCU.</p>
<p>Key requirements should be:</p>
<ul>
<li>low power (it's a portable device);</li>
<li>16 bit;</li>
<li>RAM>10 kB;</li>
<li>Hardware multiplier;</li>
<li>large program memory (128 kB), and;</li>
<li>available in development kit form or something.</li>
</ul>
<p>Is there any with the possibility of interfacing a on-chip Flash memory (such as the ones in USB keys)? Otherwise, I'll just use an SD card.</p>
<p>Very important, is there any chance I could find one with 3 Mbps (3250000 bps) UART? I need to interface with a Bluetooth module for high speed communication.</p>
<p>What kind of MCU do you think would be a nice compromise?</p>
|
MCU choice, 3 Mbps UART
|
2011-01-25T20:52:50.997
|
9435
|
|power-supply|filter|inductor|
|
<p>For filtering large frequencies I'd recommend the ferrite. The parasitic capacitance of inductors makes them essentially useless for filtering high frequencies.</p>
|
<p>Often I have a 3.3V or 5V mixed-signal circuit with a microcontroller running in the 10 MHz range and some analog circuitry, e.g. audio or analog sensor signals, powered from a wall-wart style supply or USB.</p>
<p>So a problem I often come across is how to filter the supply for the analog signals. Shall I use a ferrite bead or a choke? More inductance or less? Or just an RC filter?</p>
|
Shall I use a choke or a bead to filter analog power supply?
|
2011-01-26T01:44:55.560
|
9437
|
|led|
|
<p>You could use a constant-current supply to set the current yourself. There are well-known ones based off of LM317. Here's another one I sketched up in answer to another question:</p>
<p><img src="https://i.stack.imgur.com/nfuL0.jpg" alt=""></p>
<p>This also has the advantage of making the brightness independent of supply variation.</p>
|
<p>Here's some nice LED's packaged in strips which can be cut apart and used for projects. Voltage is up to 12 volts, and many people are using 3S 11.1 lipo cells to power them.</p>
<p>Some people comment that they are too bright, or that different colors (e.g. red and green) do not match in intensity.</p>
<p>Can I solder a resistor in series to reduce the current flow to match the brighness? Will that improve the battery life? If I get a dial resistor, can I dial in the desired brightness and then measure the amperage flowing through the circuit to determine the needed resistance?</p>
<blockquote>
<p><a href="http://hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=8941" rel="nofollow noreferrer">http://hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=8941</a>
<a href="https://i.stack.imgur.com/UMTUC.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/UMTUC.jpg" width="200"></a><br>
<sub>(source: <a href="http://hobbyking.com/hobbyking/store/catalog/LED-S-RE.jpg" rel="nofollow noreferrer">hobbyking.com</a>)</sub> </p>
</blockquote>
|
How to calculate necessary resistance to dim some LEDs?
|
2011-01-26T02:57:48.370
|
9453
|
|microcontroller|motor|pwm|
|
<p>I'm assuming you only want to use the PWM to determine CW/CCW direction. If you also want to control motor speed then there's no simple solution.<br>
You could filter a DC voltage from the PWM signal using a low-pass filter. Use a comparator to compare with 45% of \$V_{PWM}\$ (indicates 45% duty cycle). If it's lower run CW. Use a second comparator to compare with 55% of \$V_{PWM}\$. If it's higher run CCW. The dead zone between 45% and 55% ensures that it doesn't switch continuously between CW and CCW around 50% duty cycle. The dead zone means you don't need the Schmitt-trigger, which is normally used for this protection. </p>
|
<p>How would I go about detecting at motor controller level, that my PWM signal coming from my microcontroller is at 50% duty cycle. I would like to design a dead band into my motor controller so that I only have a single PWM signal coming from my uC instead of PWM, CCW, CW signals to free up ports.</p>
|
Detect PWM Duty Cycle in Hardware
|
2011-01-26T17:47:24.673
|
9455
|
|measurement|humidity|
|
<p>I'd recommend the Watermark sensors. They're durable and quite easy to read. You need two digital outputs plus one input per sensor.</p>
<p>Connect each meter to your outputs, in series with a 10k resistor. When you want to measure, set one output High and the other Low. Measure the voltage across the sensor. <a href="http://www.irrometer.com/pdf/supportmaterial/sensors/voltage-WM-chart.pdf" rel="nofollow">http://www.irrometer.com/pdf/supportmaterial/sensors/voltage-WM-chart.pdf</a> has a chart for rough calibration; you'll need to establish a "completely wet" baseline. Because you're supposed to thoroughly wet the soil when you bury the sensor, you'd do this anyway in order to make sure the thing is working correctly.</p>
<p>You use two outputs because you should switch polarity in order to avoid corrosion.</p>
|
<p><strong>Background</strong></p>
<p>To kick-start my longstanding ambition of getting back into electronics, I decided to try and make a device that measures the soil moisture of potted plants to determine whether they need to be watered. The aim for the first incarnation is to have a led that shows the plant's current water level (add water is red!), but of course I have wild plans for self-watering plants down the road.</p>
<p>My first stab was based on the <a href="http://www.instructables.com/id/Garduino-Gardening-Arduino/step4/Build-Your-Moisture-Sensor/" rel="noreferrer">Garduino instructable</a>, specifically this circuit here:</p>
<p><img src="https://i.stack.imgur.com/Rc4Ek.jpg" alt="enter image description here"></p>
<p>It is a simple voltage divider using a known resistor and two copper wire electrodes stuck in the soil as measuring device. The voltage measured at <code>A0</code> using the ADC on my <a href="http://www.pjrc.com/teensy/" rel="noreferrer">Teensy++</a> is proportional to the ratio of the resistances, and I can work back to the actual soil resistance.</p>
<p>However, in practice the soil resistance turned out to be subject to a very large drift. Almost immediately after turning on the device, the measured soil resistance started dropping. (This also happens if you stick a multimeter in the plant.) After a few days of measurement, I could find no usable connection between the measurements and the moisture level. Removing the probe and inspecting it revealed considerable tarnish on the anode. To me, this indicates that some sort of chemical reaction is taking place (electrolysis?). A multimeter measures a voltage differential of a few tens of millivolts: I have turned my plant into a battery!</p>
<p><img src="https://i.stack.imgur.com/bRSTy.jpg" alt="Oxidized anode"></p>
<p>To avoid this problem I moved to a probe constructed out of stainless steel screws. As they are considerably less reactive than copper, the oxidation should be less of a problem. Also, to avoid "charging" the soil, i have put the voltage divider between two digital output pins of the Teensy. The measurement happens as follows:</p>
<ul>
<li>Both pins are kept low when no measurement is taking place.</li>
<li>I drive one pin high. I wait one millisecond and I measure the voltage at the center of the divider.</li>
<li>I invert the pin voltages (high<->low), wait one millisecond and measure again. I should now measure the complement of the first measurement.</li>
<li>Both pins are brought low again and the device sleeps until the next measurement.</li>
</ul>
<p>This does reduce the oxidation problem, but the measured soil resistance still seems to start dropping as soon as I start measuring.</p>
<p><strong>Question</strong></p>
<ol>
<li>Can anyone recommend a robust method to measure soil moisture?</li>
<li>Can anyone explain what is really going on here?</li>
</ol>
|
Soil moisture measurement
|
2011-01-26T20:07:14.467
|
9459
|
|pic|adc|
|
<p>Try using a pull down resistor. 1M might be suitable, try out different values. Higher values may tend to not completely ground your ADC input. Lower values may cause a too heavy load on your sensor.</p>
|
<p>I have an ADC input that may be connected to an external sensor (based on how the user configures it). If I leave the input floating, I get a wide range of ADC values.</p>
<p>Is there a way to weakly ground this input to get a stable reading if nothing is connected?</p>
|
How to ground a floating ADC input
|
2011-01-26T21:03:44.410
|
9463
|
|led|usb|
|
<p>Just a touch of nail polish, preferably red, will completely cover the LEDs and since they don't produce heat there is no risk of overheating. </p>
|
<p>I have a 4 port USB hub with 3 INCREDIBLY BRIGHT led lights on the circuit board I would prefer removed.</p>
<p>I've googled a bit and found a user of this site actually describe the process very well.. <a href="http://reviews.bestbuy.com/answers/3545/product/9775443/rocketfish-4-port-usb-2-0-hub-questions-answers/questions.htm" rel="nofollow noreferrer">Here</a> </p>
<p>My knowledge of working with this stuff is next to none, and I do not have a soldering iron.</p>
<p>But, this user suggests soldering off or 'cut off with a knife', a TINY resistor next to each LED. I've poked at it a bit and it doesn't seem to want to budge. I'm worried I will break something or scratch it if I try much harder..</p>
<p>So my main question is, I believe I could much easier pull the led's off with pliers. Would this work as well? Is this dangerous? Or any tips on getting the resistors off without a soldering iron?</p>
<p>Here is a photo of the top with the resistors in question. Click for a high-res version.
<a href="https://i.stack.imgur.com/uQ57b.jpg?4098" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/W5mJD.jpg" alt="https://i.stack.imgur.com/uQ57b.jpg?4098"></a></p>
<p>And here is a photo of the bottom with the LED's I'd like to yank out.
<a href="https://i.stack.imgur.com/JrM8s.jpg?4933" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/1Es23.jpg" alt="https://i.stack.imgur.com/JrM8s.jpg?4933"></a></p>
<p>All help is appreciated. Thank you.</p>
|
I want to remove 3 LED's from a small circuit board. Need a bit of help
|
2011-01-26T21:21:25.660
|
9471
|
|heatsink|
|
<p>Those commercial cases might work, but you'll note that a car amplifier has many, large fins - this dramatically increases the surface area. Those commercial boxes just have some beauty stripes. Also don't forget the volume calculation: I don't know how much thermally conductive epoxy costs, but even, say, a 1 by 3 by 6 inch box has a fair amount of internal volume.</p>
<p>What you also could do is to salvage the heat sinks from the inside on an old PC power supply. These come with screws and insulators and are pretty big in terms of surface area. You might be able to bolt these to the outside of an otherwise flat box (you want to use gap filler between them) to heat sink it. Alternatively, just screw your high temp components to them and the encapsulate over them with your epoxy. </p>
<p>If you're in an environment that can tolerate it, using salvaged heat sinks and salvaged fans inside a salvaged power supply enclosure would likely work well. </p>
|
<p>I am looking for a case that would work well as a heat sink. Thinking that something like a car amplifier case? Anyone know where one could find cases like this? Would be using it to house H-Bridges and fill it with thermal conductive epoxy to water proof it....</p>
|
Where would one find thermal heat sink cases?
|
2011-01-27T13:48:36.530
|
9489
|
|embedded|connector|
|
<p>These type of connectors are usually called fine pitch board-to-board connectors. I doubt that you'll really find a way to connect to them without having to solder small wire leads. With the right tools, it's not as hard as you think. You'll need some fine gauge wire (wire-wrap works great), magnification, and a soldering iron with a sharp tip. With a little practice, I'm sure you can do it!</p>
|
<p>I'm trying to (hopefully) reuse a smartphone LCD and touchscreen controller, among some other components.</p>
<p>The first step is to break out the tiny connectors on the board. It appears to be 2 board to FPC connections. See picture here: <a href="https://i.stack.imgur.com/jctIv.jpg" rel="nofollow noreferrer">https://i.stack.imgur.com/jctIv.jpg</a> (bottom right, sorry for the poor quality)</p>
<p>I found this <a href="http://pewa.panasonic.com/components/connectors/narrow-pitch-board-to-fpc-connectors/a35s/" rel="nofollow noreferrer">resource</a> but it's almost impossible for me to tell which one specifically is used.</p>
<p>Any suggestions for how I could get to those signals or wire it up to a breadboard?</p>
<p>Much appreciated.</p>
|
How to break out Board to FPC connector
|
2011-01-28T04:48:02.243
|
9495
|
|programmer|flash|
|
<p>I've got a <a href="http://www.mcumall.com/comersus/store/comersus_viewItem.asp?idProduct=4282" rel="nofollow">True-USB PRO GQ-4X Willem Programmer</a> with SMD adapters about 150 USD. It can do everything I need:)</p>
|
<p>Can you recommend a programmer for low voltage parallel flash memories like 29LV320?
(around 100 USD max, if possible:)</p>
|
Recommended programmer for parallel flash memory?
|
2011-01-28T12:42:42.310
|
9497
|
|bluetooth|atmel|
|
<p>You may be interested in <a href="http://www.uclinux.org/" rel="nofollow">uClinux</a> (3S's doesn't have MMU), since <a href="http://docs.blackfin.uclinux.org/doku.php?id=bluetooth_over_uart" rel="nofollow">there is BT support in it</a>.</p>
|
<p>I am developing a portable device embedding BT communication to connect it with a computer. I found out that to reach high bitrate (115ks/s) I need to implement the HCI stack. Is it needed or can it be done someway else?</p>
<p>At present, I'm oriented in choosing the <a href="http://www.atmel.com/products/at91/sam3s.asp?family_id=605" rel="nofollow">Atmel SAM3S</a>, do you know whether there is some kind of library available for this family?</p>
|
HCI stack for Atmel
|
2011-01-28T14:01:07.733
|
9499
|
|bluetooth|atmel|
|
<p>your quickest way to communicating would be to use a BT module such as those from bluegiga or a7eng or a host of others. They typically show up (expose "profiles" in BT speak) as bluetooth serial ports to the BT world and give you a standard UART interface. These modules use the RFCOMM BT profile.</p>
<p>You may be able to find some with HID (mouse, kb), HSP, HFP (headset, handsfree) or other profiles, but they will be much rarer.</p>
<p>If you want to do more than RFCOMM you may end up having to buy/write a full HCI stack. I am not aware of any that will fit in the small Atmel uCs. btstack is a free (for non-commercial) stack that was designed for embedded systems. I have personally used it in ARM7TDMI based microcontrollers.</p>
<p>My advice is that unless you're willing to spend a LOT of time with it, stick with the simple RFCOMM-based BT modules. You'll save yourself a LOT of time and anguish. BT is not a simple thing to jump in to.</p>
|
<p>I am building some amauter schemes with Atmel uC. And this time I want to implement bluetooth functionality in my device: I want to be able to connect to device from computer and set parameter/get some readings. </p>
<p>1) While writing communication software on PC side is trivial, I am puzzled on uC side.
What is the easiest way of doing so? Which BT chip is the most simple/wide-spread/easy to use/not deadly expensive in 1-10 quantity (<10$)?</p>
<p>I don't need high speed, even 4800 baud would do at this stage :-)</p>
<p>2) How complex to go further and implement keyboard/mouse/other BT protocols?</p>
|
Bluetooth newbie
|
2011-01-28T14:13:45.017
|
9503
|
|fpga|vhdl|xilinx|
|
<p>This file is commonly called a "bitstream". Xilinx devices' bitstreams have the extension '.bit' and are generated by a program called 'bitgen'. '.bit' files are binaries and those are generated by default; if you want the ASCII representation of the bitstream, run</p>
<pre><code>bitgen -b <your design>.ncd
</code></pre>
<p>and then a '.rbt' file will be generated in addition to the '.bit' file.</p>
<p>For further information about generating Xilinx bistreams, see Chapter 15 in this user guide for ISE version 12.4:</p>
<p><a href="http://www.xilinx.com/support/documentation/sw_manuals/xilinx12_4/devref.pdf">http://www.xilinx.com/support/documentation/sw_manuals/xilinx12_4/devref.pdf</a></p>
<p>For more information about Virtex 4 bistreams specifically, see the configuration guide for that device:</p>
<p><a href="http://www.xilinx.com/support/documentation/user_guides/ug071.pdf">http://www.xilinx.com/support/documentation/user_guides/ug071.pdf</a></p>
|
<p>I wonder what is the file extension that described the functionality of my design and is the file that is loaded in a Virtex 4 FPGA to get the behavior of my VHDL design.
Thank you.</p>
|
What is the file extension of the file that is loaded in a Xilinx FPGA?
|
2011-01-28T18:30:21.130
|
9508
|
|motor|frequency|motor-controller|three-phase|
|
<p>I spent 13 years designing electronics of this exact nature: three phase induction motor reduced voltage soft starters and variable frequency AC drives. I spent the last few of those years as a VFD applications engineer helping customers select and configure this equipment for various loads and industries around the country as well.</p>
<p>You will not be able to build something that is cheap <em>and</em> safe. The voltages and currents involved are well beyond the safety margin of a hobbyiest, especially someone who is openly avoiding buying commercial units in order to save money. Don't do it!</p>
<p>While the theory behind AC motor control is very straightforward, the detail level work (heat sink sizing, snubbering, gate drive requirements, de-sat protection, motor overload calculations, bus capacitor protection, etc.) can be quite tricky to get down, especially with heavy duty cycling and regenerative power modes which a carnival ride will CERTAINLY be generating. I strongly caution you against trying to build something of this nature unless you have significant experience not only in microcontrollers and embedded systems design but also significant experience in power electronics and three phase circuitry. People get hurt and killed building this stuff.</p>
<p>My first question for you is whether speed control is really required, or if you only require a soft start up and slow down. Do you vary the speed of the motor once it is started? If not, you may be able to get away with a MUCH cheaper reduced voltage soft starter. These units act like three phase light dimmers; they only adjust the applied voltage to the motor. You will not have a lot of torque at low speeds, but with the right design of motor (NEMA class D) you can achieve exactly what you're after with a fraction of the cost and maintenance.</p>
<p>If you really do need to vary the full-load speed of the motor then you are more or less stuck using a variable frequency drive. As you are aware these are expensive and if you buy cheap you are likely to replace them sooner due to your high surge current (they call this "constant torque") application. What I would definitely recommend doing if this is the case would be to contact various manufacturers (Allen-Bradley, Cutler-Hammer, SAF drives, Benshaw, Yaskawa, etc.) and ask for reconditioned units. Ask for a drive capable of delivering 150% rated current for 30s (this is usually known as heavy duty) or size the drive 30-50% larger than your nominal current rating. You will also likely be running off of generator power which is notorious for being undersized and prone to brownouts and surges as the load requirements change with the state of the equipment being run. Drives don't like that (voltage sags cause current spikes as the motor starts slipping and surges can cause you to overvoltage the bus capacitors) and have a tendency to either fault out or blow up.</p>
<p>I am all about the little guy building something and saving a buck, but this is not the type of project to do this on. If you really want to build a three phase AC drive, start with a little 10HP 480V motor with a hand brake on a test bench. You have all the potential for experiencing the pants-filling sensation of an H-bridge failure or a bus capacitor explosion two feet from your head but without the potential lawsuits and loss of life (except perhaps your own).</p>
|
<p><strong>Background</strong></p>
<p>If you look at my profile description, you'll see that I'm involved in building and wiring up <a href="http://www.somersetcarnivals.co.uk/image.asp?id=Nor-07-322.jpg&pos=146" rel="nofollow">Carnival floats</a> that are powered by an <a href="http://www.aggreko.co.uk/products---services-overview/power-generation-rental/diesel-generator-hire.aspx" rel="nofollow">800KVA, 415v, 3 phase Generator</a>. Electrically, they generally have about 10 or 15 motors, thousands of light bulbs and a 20KW sound system.</p>
<p><strong>Problem</strong></p>
<p><a href="http://en.wikipedia.org/wiki/Induction_motor" rel="nofollow">3-phase induction motors</a> are used to drive big spinning steel structures which carry a lot of weight and have a lot of momentum, and therefore need to ramp up (and down) the speed over a period of around 10s so as not to put too much stress on gearboxes, chains and bearings, etc. The running speed also needs to be adjusted to fit the float design, which needs to be done electrically as changing gear ratios is not practical once built.</p>
<p>To control the motors, an <a href="http://uk.rs-online.com/web/search/searchBrowseAction.html?method=getProduct&R=7030881" rel="nofollow">Inverter Drive</a> is needed, which is a very expensive piece of kit that has a huge array of parameters that can be adjusted to control motors in all different situations. We have 2 of these units that control a few motors each. So the problem I have is:</p>
<ol>
<li>A big single point of failure - one unit fault causes many motors to fail.</li>
<li>Many of the motors are limited to being driven at the same speed, when individual speed control is sometimes needed.</li>
<li>Costly.</li>
</ol>
<p>As we struggle to raise the funds to build our carnival float every year, we cannot afford to buy any more <a href="http://uk.rs-online.com/web/search/searchBrowseAction.html?method=getProduct&R=7030881" rel="nofollow">Inverter Drives</a> (unless someone is kind enough to donate one as they have with the two we've got).</p>
<p><strong>Solution</strong></p>
<p>I would love to be able to build my own for a fraction of the cost. I don't know if I'm setting myself an impossible task and am setting my sights way too high, or if this is indeed achievable. Looking inside an <a href="http://uk.rs-online.com/web/search/searchBrowseAction.html?method=getProduct&R=7030881" rel="nofollow">Inverter Drive</a>, I can see several SMD circuit boards, some huge capacitors/inductors, and some heat sunk transistors.</p>
<p>I have experience of switching/dimming resistive loads using pic based control circuits, but although I know the theory, controlling a 3 phase inductive load at the moment is beyond my skill level.</p>
<p><strong>Question</strong></p>
<p>Can any one guide me to where I should start with this. I suppose initially I'm looking for a block diagram of the modules (with a little detail) that I would need to build a home-made inverter drive (e.g. PSU, microcontroller, output stages, etc), and how they fit together. I can then work out if indeed its even worth attempting this, and if so work out which parts I can happily design and make myself, and which parts I'll need more help with.</p>
<p><strong>Specs</strong></p>
<ul>
<li>Input: 240v single phase or 415v 3 phase.</li>
<li>Output: 415v 3 phase variable frequency motor drive.</li>
<li>Controls: Stop/Start, Ramp up speed (seconds), Ramp down speed (seconds), Running speed (Hz), Emergency stop.</li>
<li>Display: Current speed (Hz), Load (A)</li>
<li>Motor wiring: Star</li>
</ul>
<p><strong>UPDATE (31st Jan):</strong>
From the information provided by pingswept and bt2 in their answers, I think I've come up with a <a href="http://www.falstad.com/circuit/#%24+1+5.0E-6+6.186780925036789+46+5.0+50%0Av+80+256+176+256+0+1+50.0+339.4112549695428+0.0+0.0+0.5%0Av+80+304+176+304+0+1+50.0+339.4112549695428+0.0+2.0943951023931953+0.5%0Av+80+352+176+352+0+1+50.0+339.4112549695428+0.0+4.1887902047863905+0.5%0Aw+80+256+80+304+0%0Aw+80+304+80+352+0%0Ad+208+224+208+144+1+0.805904783%0Ad+240+224+240+144+1+0.805904783%0Ad+272+224+272+144+1+0.805904783%0Ad+208+448+208+368+1+0.805904783%0Ad+240+448+240+368+1+0.805904783%0Ad+272+448+272+368+1+0.805904783%0Aw+208+224+208+256+0%0Aw+208+256+176+256+0%0Aw+208+256+208+368+0%0Aw+176+304+240+304+0%0Aw+240+304+240+224+0%0Aw+240+304+240+368+0%0Aw+176+352+272+352+0%0Aw+272+352+272+368+0%0Aw+272+352+272+224+0%0Aw+208+144+240+144+0%0Aw+240+144+272+144+0%0Aw+208+448+240+448+0%0Aw+240+448+272+448+0%0Af+368+400+432+400+0+1.5%0Af+368+192+432+192+0+1.5%0Aw+432+144+432+176+0%0Aw+432+208+432+288+0%0Aw+432+288+432+304+0%0Aw+432+304+432+384+0%0Aw+432+416+432+448+0%0Aw+560+416+560+448+0%0Aw+560+304+560+384+0%0Aw+560+288+560+304+0%0Aw+560+208+560+288+0%0Aw+560+144+560+176+0%0Af+496+192+560+192+0+1.5%0Af+496+400+560+400+0+1.5%0Aw+688+416+688+448+0%0Aw+688+304+688+384+0%0Aw+688+288+688+304+0%0Aw+688+208+688+288+0%0Aw+688+144+688+176+0%0Af+624+192+688+192+0+1.5%0Af+624+400+688+400+0+1.5%0Al+816+208+816+288+0+0.5+0.07936331972994357%0Al+816+288+768+336+0+0.5+0.04035416326757956%0Al+816+288+864+336+0+0.5+0.039009156462364004%0Aw+432+288+464+288+0%0Aw+464+288+464+256+0%0Aw+752+256+752+208+0%0Aw+752+208+816+208+0%0Aw+768+336+752+336+0%0Aw+752+336+752+272+0%0Aw+864+336+864+368+0%0Aw+864+368+736+368+0%0Aw+736+368+736+288+0%0Aw+272+144+432+144+0%0Aw+432+144+560+144+0%0Aw+560+144+688+144+0%0Aw+272+448+432+448+0%0Aw+432+448+560+448+0%0Aw+560+448+688+448+0%0Ag+240+448+240+496+0%0AI+304+80+352+80+0+0.5%0AL+304+80+272+80+0+1+false+5.0+0.0%0Aw+352+400+368+400+0%0AL+432+80+400+80+0+0+false+5.0+0.0%0AI+432+80+480+80+0+0.5%0AL+560+80+528+80+0+0+false+5.0+0.0%0AI+560+80+608+80+0+0.5%0Aw+608+400+624+400+0%0Aw+480+400+496+400+0%0Aw+352+80+352+400+0%0Aw+480+80+480+400+0%0Aw+608+80+608+400+0%0Aw+304+80+304+112+0%0Aw+304+112+368+112+0%0Aw+368+112+368+192+0%0Aw+432+80+432+112+0%0Aw+432+112+496+112+0%0Aw+496+112+496+192+0%0Aw+560+80+560+112+0%0Aw+560+112+624+112+0%0Aw+624+112+624+192+0%0Aw+576+272+576+288+0%0Aw+576+288+560+288+0%0Aw+752+256+464+256+0%0Aw+576+272+752+272+0%0Aw+736+288+688+288+0%0A" rel="nofollow">simulation of the bare bones of what I need</a>... Rectify the 3-phase to get 586V DC and use 6 IGBTs controlled by an IRS2330 which is controlled by PWM from a microcontroller.</p>
|
3-phase Motor Speed Controller
|
2011-01-29T01:28:12.630
|
9510
|
|led|diodes|spice|optoelectronics|
|
<p>Great answers, but it is easy to solve the Shockley diode equation algebraicly. Just note that the "minus 1" in the formula is very irrelevant for forward currents that are an order of magnitude greater than Is, which is very small, say, 1E-12 A. Find just two points in the graph with easy to read I and V values, and plug these into the formula. Dividing both formula's eliminates Is, so N is easy to compute. Then fill in N in a formula to find Is.</p>
<p>Here are my LibreOffice Calc macro's in Basic:</p>
<pre><code>Const Q as double = 1.6E-19
Const K as double = 1.38E-22
Const T as double = 300
rem The Shockley diode equation, to build the graph Id(Vd) for hardcoded values of Is and N
Function shockley(Vd as double) as double
Const Is1 as double = 5.94463E-18
rem Note that 'Is' is a reserved word and cannot be the name of a variable
Const N as double = 0.191367
shockley = Is1 * (exp(Vd * Q / (N * K * T )) - 1)
End Function
rem Step 1 in solving the diode equation for N using values from a graph
Function ComputeN(V1 as double, V2 as double, I1 as double, I2 as double) as double
ComputeN = (Q / (K * T)) * (V1 - V2) / (log(I1) - log(I2))
End Function
rem Step 2 in solving the diode equation for Is
Function ComputeIS(V as double, I as double, N as double) as double
ComputeIS = I / (exp(Q * V / (N * K * T)))
End Function
rem for debugging
sub Test
dim N as double
N = ComputeN(1.85, 1.3, 0.1, 1.5E-6)
dim Is1 as double
Is1 = ComputeIs(1.85, 0.1, N)
end sub
</code></pre>
<p>If you look at the formula's, you might recognize simply the description of a straight line with slope of q/NkT but also of delta Log(Id) / delta Vd.</p>
<p>I get a somewhat similar value for Is: 5.94E-18 = 5.94 atto-ampere (W5VO found 1 aA), but much different N = 0.19 (W5VO found 1.8, typo?), still the data also computes back to the same graph:</p>
<p><a href="https://i.stack.imgur.com/VaMqv.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/VaMqv.png" alt="screenshot of my LibreOffice Calc"></a></p>
<p>The column Vd are the voltages, Id is the diode current according to the real formula, Id0 is the current with the simplified formula where the "minus 1" is changed to "minus zero". As Id0 is a true exponential curve, you can take the logaritm in column Id0_log. (You cannot take the log of a curve that becomes zero and negative like Id) The plot is from Id0_Log versus Vd. In this plot I made the lowest part dotted, because there it is NOT the actual diode current anymore, but does show the value of Is at the intersection with the Y-axis.</p>
<p>Following the exponential curve to the left brings you asymptotally to zero. But the "minus 1" subtracts an amount of Is, so that the real diode curve goes through the origin and, with negative voltages, shows a reverse leakage current of amount Is.</p>
<p>If the original manufacturers curve would have been on a really large log plot, we could have simply used a ruler to extend the straight line downwards to easily find Is at Vd=0 and then compute N, instead of compute first N then Is with the above macro's. The ruler method has been described in "The Spice Book" by Andrei Vladimirescu (1994).</p>
|
<p><strong><em>What diode modifiers are used in practice to model LEDs with SPICE (Berkeley v.3f5)?</em></strong> <a href="https://www.macspice.com/ug/sec3.html#3.4.2" rel="noreferrer">These</a> are available to me:</p>
<pre><code># Name Parameter Units Default Example Area
1 IS Saturation current A 1e-14 1e-14 *
2 RS Ohmic resistance Ω 0 10 *
3 N Emission coefficient - 1 1.0
4 TT Transit-time s 0 0.1ns
5 CJO Zero-bias junction capacitance F 0 2pF *
6 VJ Junction potential V 1 0.6
7 M Grading coefficient - 0.5 0.5
8 EG Activation energy eV 1.11 1.11 Si
0.69 Sbd
0.67 Ge
9 XTI Saturation-current temperature exponent 3.0 3.0 jn
2.0 Sbd
10 KF Flicker noise coefficient - 0
11 AF Flicker noise exponent - 1
12 FC Coeff. for for.-bias dep. cap. formula 0.5
13 BV Reverse breakdown voltage V ∞ 40.0
14 IBV Current at breakdown voltage A 1.0e-3
15 TNOM Parameter measurement temp. °C 27 50
</code></pre>
<blockquote>
<p><strong><a href="https://www.macspice.com/ug/sec3.html#3.4.2" rel="noreferrer">3.4.2 Diode Model (D)</a></strong><br>
The dc characteristics of the diode are determined by the parameters IS and N. An ohmic resistance, RS, is included. Charge storage effects are modeled by a transit time, TT, and a nonlinear depletion layer capacitance which is determined by the parameters CJO, VJ, and M. The temperature dependence of the saturation current is defined by the parameters EG, the energy and XTI, the saturation current temperature exponent. The nominal temperature at which these parameters were measured is TNOM, which defaults to the circuit-wide value specified on the .OPTIONS control line. Reverse breakdown is modeled by an exponential increase in the reverse diode current and is determined by the parameters BV and IBV (both of which are positive numbers).</p>
</blockquote>
<p>For example, using this basic, cheap red: <a href="https://www.digikey.com/product-detail/en/osram-opto-semiconductors-inc/LH-N974-KN-1/475-1416-1-ND/1802603" rel="noreferrer"><img src="https://i.stack.imgur.com/wyIh7.jpg" width="50"></a>
<a href="https://i.stack.imgur.com/wIyjZ.gif" rel="noreferrer"><img src="https://i.stack.imgur.com/wIyjZ.gif" width="35"></a>
</p>
<p>I don't care much about high-frequency characteristics -- just would like to be able to match it's IV-curve within its operating specs (-10uA/-5V leakage to +100mA/+2.2<sup>'ish</sup>V forward):
<img src="https://i.stack.imgur.com/SJVLd.png" alt="enter image description here"></p>
|
How do I model an LED with SPICE?
|
2011-01-29T02:42:57.420
|
9517
|
|fpga|xilinx|floating-point|xilinx-system-generator|cordic|
|
<p>From the latency on the cordic block, that looks as if you've chosen to use a single processing element - that will produce results of limited accuracy. Very limited it appears :)</p>
<p>I tried using 10 elements for example, with [zeros (1,9) 1] for the "latency per processing element" - to get back to your 21 tick latency. Making sure I ran the simulation long enough (oops), I then got a result (using UFixed_16_11 inputs) of 0.501953125. Which is closer...</p>
<p>Does that help?</p>
|
<p>He all, I was wondering how should be the parameters fo the CORDIC divider block in order to get proper results.
In this example I´m trying to get 0.1/0.2 = 0.5 but I don´t get it and I don´t know why?
Please, does anyone know how to do it?
Thank you!!!</p>
<p><strong>EDIT:</strong>
To take a look to the parameters of the CORDIC block see this question:
<a href="https://electronics.stackexchange.com/questions/9642/system-generator-how-to-configure-the-cordic-divider-block-understanding-the-bl">System Generator: How to configure the CORDIC divider block. Understanding the block parameters</a></p>
<p><img src="https://i.stack.imgur.com/KKTf8.jpg" alt="enter image description here"></p>
|
System Generator: How to configure the CORDIC divider block?
|
2011-01-29T08:16:21.293
|
9518
|
|microcontroller|xilinx|floating-point|picoblaze|
|
<p>You <em>can</em> do floating point in Picoblaze, but if you try IEEE754 it'll be</p>
<ol>
<li>very slow: it's an 8-bit processor trying to do operations on 32-bit or 64-bit data types.</li>
<li>hard work: nothing's written ready for you to use, so you'll have to do it all yourself</li>
<li>potentially impossible as the amount of code required is probably more than Picoblaze can address</li>
</ol>
<p>Depending on your requirements, you could possibly come up with a custom "small floating point", maybe 2 bytes wide with a 4 bit exponent and 12 bit significand? You'd still have to write your own arithmetic code for it though.</p>
<p>If you must use Picoblaze, fixed-point is going to "fit" it much better.</p>
<p>To be honest though Picoblaze is a weird choice for anything math-related as it doesn't even have a hardware multiplier!</p>
<p>Maybe fall back a step and describe the problem you think you can solve with Picoblaze (as you mention System Generator in another comment, there may be a better way using the tools available)</p>
|
<p>I wonder if I could perform floating point operations in a Picoblaze controller? Thank you to all posible answers with direct references to documentation or articles.</p>
|
Microcontrollers: Can I perform floating point operations in a Picoblaze controller?
|
2011-01-29T11:36:29.983
|
9523
|
|reference|cordic|how-does-it-work|
|
<p>This is an excellent article written by someone on the Parallax forums, called CORDIC For Dummies. Well written and explains things nicely: <a href="https://forums.parallax.com/discussion/127241/cordic-for-dummies" rel="nofollow noreferrer">https://forums.parallax.com/discussion/127241/cordic-for-dummies</a></p>
|
<p>Does anyone know any available reference to learn how works CORDIC algorithm to implement a division?</p>
|
References with explanations of how works CORDIC algorithm for division
|
2011-01-29T12:42:08.777
|
9524
|
|voltage-regulator|buck|
|
<p>You won't find an integrated inductor for these specs and I doubt they exist for smaller currents. You'll need something in the order of 33-100uH and at >1A this is <em>huge</em> from an integration point of view.<br>
<strong>Synchronous</strong> switchers use a MOSFET instead of the Schottky diode, and that's often integrated. They also have higher efficiencies.</p>
<p>Have a look at National's Simple Switcher series, which includes parts like LM22676 which require minimal external components and provide high efficiency (for the LM22676 >90%). National has an online Webench design tool to help you select the right components.</p>
|
<p>I'm trying to minimize part count and cost of my project. It needs to have a 6V power rail with about 1.5A peak current from a 12V input. I'm shying away from a linear regulator because of the power dissipation but I would like to keep cost and part count down.</p>
<p>Do switching regulators exist with internal diode and inductor to match these parameters or would it be less expensive to have a linear regulator with a big heatsink?</p>
|
Inexpensive switching regulator with internal inductor & diode
|
2011-01-29T15:04:16.870
|
9527
|
|spice|transistors|
|
<p>I know of two methods for impedance measurement. The first deals with DC impedance, and the second deals with AC impedance. They work regardless of whether you are looking at the input or output.</p>
<ol>
<li><p>Measuring input impedance: Apply a DC voltage source to the input of your circuit. If any output loading, power supplies, or additional biasing is required, include this in the schematic as well. Sweep the input DC voltage source over the voltage range you expect to use the circuit. Use the equation below to give you the input resistance. Note that it is very possible to not have a flat curve.</p>
<pre><code>R = 1/(Iin dI/dV)
</code></pre>
<p>Explained, this is the inverse of the derivative of the input source's current w.r.t. the input voltage.</p></li>
<li><p>Output impedance (or some other port): Apply the required bias voltages to the inputs to cause the device to be at its quiescent point. Apply a voltage source to the node you want to measure, and sweep the DC voltage over the range of expected node voltages. Calculate resistance in the same method as the first technique.</p></li>
<li><p>AC Impedance: Superimpose a small (1 uV) sine wave on the port you want to measure. Measure the amplitude of the current, and the phase difference between the voltage and current waveform. This will give you a current phasor, which can then be used to solve for a value of Z. You may be able to do this with an AC simulation, but a transient simulation with different frequencies should give the result you are looking for. </p></li>
</ol>
|
<p>How does one measure impedance/resistance using SPICE? I have access to regular SPICE(MacSpice) and HSpice.</p>
<p>The DC current divider circuit at the bottom of <a href="http://www.allaboutcircuits.com/vol_6/chpt_3/5.html" rel="nofollow">this webpage</a> seems to be one method. 0V DC sources are used, and the current through these zero volt sources is measured. Using the node voltage and the current measured, we can deduce resistance. Of course for circuits where we already know the resistance this is only good for measuring the current.</p>
<p>How can one do resistance/impedance measurements for AC circuits, such as the inputs or outputs of transistor amps (e.g. resistance looking into base, output at emitter, etc.)? </p>
|
Measuring Resistance/Impedance with SPICE
|
2011-01-29T16:07:21.650
|
9529
|
|infrared|detection|
|
<p>In case anyone else stumbles upon this IC,</p>
<p>I also just happened to find one of these in an old printer. After some research, i found this datasheet: <a href="http://www.datasheetarchive.com/AEDS-9620-datasheet.html" rel="nofollow">http://www.datasheetarchive.com/AEDS-9620-datasheet.html</a>, which is pin-compatible and looks pretty much the same as the component in question. I tried hooking it up as described in the datasheet and it turns out to be working. I Used a 220 Ohm resistor at 5V for the emitter, and the two outputs show very nice square-waves when the sensor is slid along the printer's code strip.</p>
|
<p><strong>Long Story Short</strong></p>
<p>It's a "linear/rotary optical encoder," or, "incremental encoder," like this one, which costs about \$6:</p>
<p><a href="http://www.mouser.com/Search/ProductDetail.aspx?R=AEDS-9641-P10virtualkey63050000virtualkey630-AEDS-9641-P10" rel="nofollow noreferrer">http://www.mouser.com/Search/ProductDetail.aspx?R=AEDS-9641-P10virtualkey63050000virtualkey630-AEDS-9641-P10</a></p>
<p>You use it with "optical encoder strips," or "codestrips," like this one, which costs about \$.30:</p>
<p><a href="http://www.goldmine-elec-products.com/prodinfo.asp?number=G15602" rel="nofollow noreferrer">http://www.goldmine-elec-products.com/prodinfo.asp?number=G15602</a></p>
<p>It uses a single LED with 2 photodetectors. These are exposed as pins labeled Channel A and Channel B. The pins will output either 0 or Vcc V, which is 5V in my case. Since there are 4 distinct states for A and B, you get 4 times the resolution of your codestrip. Since it can handle up to 150 lines per inch on a codestrip, you get 1 600th of an inch resolution. When monitoring the A and B channels, you can determine which direction you are moving by comparing your current state to your last state. For example if A and B are both high, and then A goes low, you've moved up 1 600th of an inch.</p>
<p>It is a great, accurate, affordable system for determining precise linear position.</p>
<p><strong>Original Post</strong></p>
<p><img src="https://i.stack.imgur.com/BN6qq.jpg" alt="IR emitter / detector pulled off an inkjet printer"></p>
<p>The red arrow points to the ir emitter / detector. The blue arrow points to where I got it. The printed circuit board under the blue arrow would slide back and forth under that gray band, which is transparent plastic with lots and lots of very skinny black lines. That was probably how the inkjet printer kept track of the position of the print head.</p>
<p>The 2 ir diode pins were easy enough to figure out. That's being powered by the fat white wire on the far left. I can't figure out the additional 4 pins on the detector part though. Notice, that's a total of 6 pins. I pulled the cover off the part to get a closer look, and those pins look like this, with the skinny white wire attached to the pin on the far right:</p>
<p><img src="https://i.stack.imgur.com/OdXNC.png" alt="Diagram of what the detector part looks like"></p>
<p>The black cover on the ir e/d has tiny white letters:</p>
<p>9981
C526</p>
<p>and tiny black letters</p>
<p>Agilent
18</p>
<p>I tried Googling around for datasheets, but I didn't manage to find anything. I tried calling Agilent but just got lost in the phone tree, and they hung up on me at some point, haha.</p>
<p>Does anybody have a datasheet for this or a similar component, or have any idea how this 4 pin detector works, or know where to look for a datasheet or who to call, or know a component I could substitute, or anything really?</p>
<p>This is all part of a bigger thing I'm trying to get a handle on, which is precise 1 dimensional movement, and then ultimately precise 2 dimensional movement.</p>
<p><strong>Edit</strong></p>
<p>To be clear, there are 6 pins total. 2 for the diode, and 4 for the detector. I don't understand what all 4 pins on just the detector are for.</p>
<p><strong>Edit 2</strong></p>
<p>I found a very promising blog post about this kind of problem. <a href="http://benkrasnow.blogspot.com/2010/02/linear-position-tracking-with.html" rel="nofollow noreferrer">http://benkrasnow.blogspot.com/2010/02/linear-position-tracking-with.html</a></p>
<p>Here's a 6 pin linear optical encoder with data sheet which I found from this blog post.</p>
<p><a href="http://www.mouser.com/Search/ProductDetail.aspx?R=AEDS-9641-P10virtualkey63050000virtualkey630-AEDS-9641-P10" rel="nofollow noreferrer">http://www.mouser.com/Search/ProductDetail.aspx?R=AEDS-9641-P10virtualkey63050000virtualkey630-AEDS-9641-P10</a></p>
|
Understanding the IR Emitter / Detector I pulled off of an inkjet printer
|
2011-01-29T16:16:32.440
|
9530
|
|dsp|
|
<p>First, collect some of the data you want to process on a PC.</p>
<p>Second, develop your algorithms on the PC. Start with matlab/octave or numpy. </p>
<p>Third, translate the algorithm into C code on the PC. Does it behave well as floating-point? 16-bit fixed-point? Profile it to see how many multiply+accumulates it does per second of sample data.</p>
<p>Now you know the requirements and you have the algorithm ready to go. You are ready to choose a DSP.</p>
|
<p>I have experience with selecting low end PICs, but haven't had to select a controller for DSP before. Initially I thought about the dsPIC line, but the only reason for this because I am comfortable with the microchip line.</p>
<p>So, what options do I have to select from? How can I decide what is best for me? Are there in general differences between lines? Example, the MSP430 line is good for very low power, are there any similar type of things for the DSP lines?</p>
<p>For my specific project I am going to have 3 sets of SPI from ADCs that are 24bit at about 400KHz, but I am find with broad description on how to find the proper platform.</p>
|
Selecting a platform for DSP
|
2011-01-29T17:07:05.000
|
9553
|
|capacitor|inductor|
|
<p>In some situations, inductors and capacitors can substitute for each other. In others, they cannot. Of course, they never <em>directly</em> substitute. What this means is that some circuits can be slightly modified so that an inductor is used instead of a capacitor or vice versa to achieve the same purpose. Some circuits cannot.</p>
<p>An inductor does not store a <em>charge</em> in its magnetic field, but rather energy. When the magnetic field is allowed to collapse, the inductor will spontaneously generate a voltage. The voltage is usually much higher than any voltage which was previously applied to the inductor. A capacitor will never exhibit a voltage which is greater than what was applied to it. So for instance, a capacitor cannot be used to build an ignition coil for a gasoline engine. </p>
<p>A capacitor in series is similar to an inductor in parallel, in some ways. Both approaches can make a filter with the same frequency response. However, the loading effects of these circuits are not the same. A capacitor in series blocks DC, and so to a DC source, it looks like an infinite impedance: the lightest possible load. An inductor in parallel is the exact opposite: a short circuit. The two only look similar from the perspective of the load device: it sees a signal that has been high-pass-filtered, and is free of DC. But the DC is not removed in the same way. Blocking a signal with an open load is not the same as short-circuiting a signal to ground.</p>
<p>Likewise, an inductor in series is similar to a capacitor in parallel, but again, the loading effect is not the same. We can use a capacitor to prevent AC, or AC above certain frequencies, from entering a circuit, by shunting those signals to the return. Sometimes that is acceptable, like when blocking RF noise from entering a device. In some other cases, shunting AC to ground may create an unacceptable load on the source of that signal. An inductor can block AC by creating a high impedance against it.</p>
<p>So even in circuits where we can potentially substitute parallel inductors for series capacitors and vice versa, consideration for the loading differences may require us to choose one or the other.</p>
|
<p>I'm a Trainee electrician and pc hardware enthusiast. I was just wondering why a mixture of inductors and capacitors are used on motherboards? Why not just use capacitor? I thought the inductor stores electrical charge but it uses magnetism. What's so special about storing it as magnetism?</p>
|
Inductor vs a capacitor
|
2011-01-30T17:59:53.100
|
9555
|
|sensor|
|
<p>I believe what you want is called an analogue VU meter, and the mic won't generate enough power to move the needle.</p>
<p>So what you need is a microphone preamp. I found this circuit on the internet which should do the job:</p>
<p><img src="https://i.stack.imgur.com/62ymX.png" alt="Preamp Circuit"></p>
|
<p>My wife and I are planning a Robot themed room for our 1st child which is due in May. My goal for his, yep its a boy, room is to make a wider variety of sensors that will hang on the wall that will each display a different input. </p>
<p>For my first sensor I want to build a simple sound measuring device that will use a moving coil meter and an artsy fartsy backdrop. The problem I'm having is trying to hook up the electret to the moving coil and was wondering if someone out there had a schematic. </p>
|
Moving Coil Circuit
|
2011-01-30T19:14:57.903
|
9556
|
|arduino|x-10|
|
<blockquote>
<p>LED13 is on for 14 seconds, then off for 2 seconds & and repeat. (LED13 is lit to show something has been received)</p>
</blockquote>
<p>Is it located electrically near a switch mode power supply, compact fluorescent or any other device known to generate noise on the power line? That <em>could</em> make it continually receive (noise).</p>
<p>It's an RS232 device so you could hook it to your com port and monitor the transmissions through hyperterm to what is being received. </p>
|
<p>I'm pretty new to the world of Arduino and am trying to get it talking to the CM12U X10 power line interface device. I've seen lots of talk about the US based PSC05/TW523 but nothing for the European CM12U.</p>
<p>I've used the wiring and code found here <a href="http://www.arduino.cc/playground/X10/ReceiveX10" rel="nofollow">http://www.arduino.cc/playground/X10/ReceiveX10</a> and made the suggested changes for 50Hz land, but nothing triggers the receive interrupt.</p>
<p>I've tried reversing the order the pins are connected as there seems to be some confusion as to which way round it should be and that seems to almost continually flood the device - LED13 is on for 14 seconds, then off for 2 seconds & and repeat. (LED13 is lit to show something has been received) </p>
<p>I've triple checked the wiring and continuity tests suggest things are connected ok. (Of course that doesn't help if my assumption that the wiring is the same as the TW523 is wrong!)</p>
<p>Can anyone confirm this device actually works before I dig deeper, or am I'm wasting my time?</p>
|
Has anyone managed to get Arduino talking to the CM12U X10 device?
|
2011-01-30T19:22:51.860
|
9564
|
|can|
|
<p>There are four key elements in CAN specification that allow CAN controllers to detect idle bus state:</p>
<ul>
<li><p><strong>Wired-AND signalling</strong> makes it possible for dominant bit transmitted by one of the nodes to be detected by all other nodes transmitting recessive bit at the same time. So, if any node transmitting recessive bit sees dominant state of the bus it <em>knows that the bus is busy</em>.</p></li>
<li><p><strong>Bit stuffing</strong> makes sure that there are no more than 5 identical consecutive bits. By itself, bit stuffing is used to maintain synchronization. However a side effect of it is that no more than 5 consecutive <em>recessive</em> bits can occur within the frame bits up to CRC delimiter.</p></li>
<li><p><strong>End-of-frame</strong> is a series of 7 recessive bits at the end of a frame. They are not bit-stuffed, so they can be easily detected by controllers. Note, that the bus is <em>not yet idle</em> during this time, as EOF is considered to be a part of the frame. </p></li>
<li><p><strong>Interframe space</strong> is a series of 3 recessive <em>intermission</em> bits between the frames, followed by bus idle state. No node is permitted to initiate a transmission during intermission, unless they want to send <em>error</em> or <em>overload</em> frames. Furthermore, the node that transmitted last frame must also send 8 recessive <em>suspend transmission</em> bits after the intermission before initiating another transmission. This last requirement allows other nodes to start sending pending messages, so no node can "hog the bus" indefinitely.</p></li>
</ul>
<p>From all of the above, here is how nodes detect idle bus state:</p>
<ul>
<li><p><strong>Receiving nodes</strong> <em>simply wait for 10 consecutive recessive bits</em>, which includes EOF and intermission. After that time they consider the bus to be idle and can attempt to begin transmission of their own.</p></li>
<li><p><strong>Transmitting node</strong> <em>sends 11 consecutive recessive bits</em> after EOF of the last frame it transmitted. If no other node initiates transmission during this time it considers the bus to be idle and can attempt to begin another transmission. If dominant bit is detected during this time the node becomes a receiver.</p></li>
</ul>
<p>The above information plus additional info on bit timing can be found in the <a href="http://esd.cs.ucr.edu/webres/can20.pdf" rel="nofollow noreferrer">CAN specification</a> developed by BOSCH.</p>
|
<p>I read a lot of stuff regarding CAN bus arbitration, but it didn't answer my questions.</p>
<p>If one node is already transmitting the data on the bus and in between another node wants to initiate the data transfer, how will that "another node" get to know that the bus is busy?</p>
<p>All the documents (which I read) take condition that both nodes are starting transmission simultaneously and then one with first dominant bit will get the bus but nobody explained the condition which I want to know.</p>
|
How to check the CAN bus is free or not
|
2011-01-31T06:22:26.913
|
9575
|
|batteries|charging|
|
<p>The battery is only being used when the alternator is not running. While the alternator is running (delivering power), the battery is essentially just another load like lights, radio, etc.
For most of the time, the alternator is just maintaining the battery charge and thus supply little actual current into the battery.</p>
|
<p>note and question</p>
<pre><code>* Is it an alternator or dynamo?
</code></pre>
<p>I am not an electrical engineer and neither have any core knowledge but, this is a simple procedure of car battery charging using a dynamo, which is present in all cars and bicycles. But what i don't understand is how can a battery be utilised and charged at the same time?</p>
<pre><code>* That is, head lights drawing current.
* But dynamo is giving current.
* Everything done by using same battery terminals.
* So BHOOM must be a explosion!!
</code></pre>
|
How can a car battery be charged by dynamo (or is it an alternator?) at the same time it is being used by the car components?
|
2011-01-31T16:29:49.823
|
9590
|
|i2c|
|
<p>The resistors you see are called "pull up" resistors; they literally "pull up" the signal to the positive voltage rail.</p>
<p>I2C is a communication bus that allows multiple devices to talk on it. Since there is only a clock and data line there is no way to ensure that two devices won't start talking at the same time, or a device mis-identifies a message as being for it and responds out of turn.</p>
<p>If two devices try to control the data line and one wants it '1' and the other '0' you end up with a condition called contention. Internally a normal digital output is built up out of two transistors: one connects the signal line to +V and the other to ground. The device turns on one transistor or the other to set the output signal to the appropriate level. When two devices are trying to make the same signal two different voltages you end up with +V connected to ground through two transistors. This is known as contention and is something you want to avoid because it causes high currents and can damage one or both of the output drivers.</p>
<p>In order to get around this problem, the I2C specification requires the use of "open collector" or "open drain" (same thing) drivers. This means that the devices on the bus can ONLY connect the signal to ground. The only way for a device to output a '1' is to not drive the line to zero. Something has to bring the line to a logic '1' and that something is the pull-up resistor.</p>
<p>What happens now if two devices try to drive the data line is that one is not doing anything (it wants the line to be '1') and the other device has its output transistor turned on, connecting the signal to ground. The resulting signal is a '0' -- there is no contention because the only thing holding trying to make the line a '1' is a resistor which by design limits the amount of current it allows through. Pull-up resistors are usually selected to offer a bit of resistance to a changing signal but not too much. For I2C the value for a pull up is usually 4700-10000 ohms.</p>
<p>Check out <a href="http://en.wikipedia.org/wiki/Open_collector" rel="nofollow">http://en.wikipedia.org/wiki/Open_collector</a> and <a href="http://en.wikipedia.org/wiki/I%C2%B2C" rel="nofollow">http://en.wikipedia.org/wiki/I%C2%B2C</a> for more information.</p>
|
<p>When reading a manual on using a PICAXE and an I2C device I saw this diagram.<br>
<img src="https://i.stack.imgur.com/H9C6H.png" alt="Picaxe i2c"><br>
I can't work how this would behave as wouldn't it make the connection on the lines constantly high due to the connection to the power rail, so never goes low. I understand that they are open-drain lines and they are needed inorder to make the lines go high but how can it make them go low with that connection to the positive rail?</p>
|
Don't understand how these resistors operate in this circuit
|
2011-01-31T23:17:16.117
|
9595
|
|jtag|
|
<p>At its very basic level, JTAG is a standardized serial protocol. You can build one out of a handful of components for under $20, but it will be slow. Generally speaking the more expensive ones offer higher speed, broader voltage support and even autonomous operation. The software used to drive the particular JTAG interface determines whether you will be able to program the devices you are interested in.</p>
<p>Personally I am happy with the $70ish dollar Olimex JTAG units. They are USB, based on the FT2232, work with 5V and 3.3V devices and have good support for both Linux and Windows (I'm not sure about OSX). I also have an Atmel USB Blaster for programming Altera FPGAs (supports down to 1.0V IO) and an older USB based one for Xilinx devices. Finally, I also have a GNICE+ JTAG adapter used primarily for Analog Devices Blackfin processors.</p>
<p>I have not tried it, but I believe that the Altera USB Blaster should work for anything I connect to, although it does not support RTCK (return clock) support. It is primiarly ARM devices which support RTCK, which is a means for the JTAG interface to detect how fast the JTAG clock can go and still be reliable.</p>
<p>My suggestion is to take a look at the particular devices you wish to use and see if you can find a common JTAG unit that is well supported by all. </p>
|
<p>Althougth I never used one, I know JTAG is a standardized way to program and debug MCUs. But I see a lot of JTAG from various companies. Can I use a particular JTAG to program/debug MCUs from different companies and with diferent architectures?</p>
<p>For example: can I use a JTAG to program/debug STM32 and LPC micros? (all Cortex-m3) Can I use the same JTAG to program/debug MSP430 micros? (16bit MCU from TI)</p>
<p>Which JTAG do you recommend to buy? And why?</p>
|
Particular JTAG to program/debug MCUs from different companies or architectures
|
2011-02-01T01:21:59.363
|
9604
|
|display|cases|mount|
|
<p>Usually LCD displays come in a plastic "cage" that has pins (more precisely, bumps - they are very short) on each corner of its back. The PCB has holes to fit in, but that's just to prevent the display from sliding horizontally on the board. The board is then attached someway (screws, etc.) against the case "top" which has a window for the display, a little smaller than it in each dimension, and that holds it in place. Usually there's no need for an adhesive or glue, which also makes repair easier; just the LCD ribbon is really mechanically attached to the board. But for hobby projects there's nothing that prevents you to do so.</p>
<p>There are other, less popular methods. Displaytech's <a href="http://www.displaytech-us.com/sites/default/files/lcd-design-additional-resources/lcd_panel_LCDDesignCriteria.pdf" rel="nofollow noreferrer">"LCD Connection Methods"</a> document has a few diagrams, but it's not possible to attach a file here in .pdf format. In a roundabout conversion method, it's now on E&R's imgur account <a href="https://i.stack.imgur.com/zKtm7.png" rel="nofollow noreferrer">here</a>, sorry for the low quality.</p>
|
<p>I'd like to mount a small (2.5") graphic LCD or OLED display on a PCB. I believe it should look something like this: </p>
<p><img src="https://i.stack.imgur.com/mBIiL.png" alt="Evalbot pic cropped"></p>
<p>I've seen this done (links to pics) on my <a href="https://i.stack.imgur.com/yAk1C.jpg" rel="nofollow noreferrer">LM3S6965 development kit</a>, on my <a href="https://i.stack.imgur.com/MovT0.jpg" rel="nofollow noreferrer">TI Evalbot</a>, and on <a href="https://i.stack.imgur.com/v9jz2.png" rel="nofollow noreferrer">this Sparkfun breakout board.</a> All of those images show a pane of glass, the screen itself, an FFC folded underneath the board, and very little information about the mounting technique. The LM3S6965 and Evalbot have a bit of foam visible underneath. (I can't speak to the Sparkfun board as I don't own it). </p>
<p>I suspect that the display is adhered to the PCB with double sided tape or an epoxy. </p>
<ol>
<li> Am I correct in my suspicions, or is there another method of doing this? I've considered cutting a relief out of some clear acrylic and screwing that to the PCB as an alternative. </li>
<li> Is it removable? I've considered using a solvent or some force. I'm interested in trying out the screens I already own on other PCBs, and I'm also interested in replacing the screen on my new PCB if I break it or doing edits to the PCB beneath the display. </li>
<li> Is it easy to do? I'd like to distribute the PCB with the components (including the display) as a kit to other engineering students, and I don't want them to have to deal with complex epoxy mixing ratios or risk damaging the LCD in the process. </li>
<li> Is replicating this technique the right thing to do for a development board or in-house tool? I expect users to abuse or break this board, and I expect it to need rework. </li>
</ol>
|
How to affix graphic LCD to PCB?
|
2011-02-01T06:46:40.563
|
9611
|
|temperature|pid-controller|control-system|
|
<p>About applying hysteresis in the OP-AMP case you can add a feedback resistor from OP-amp output to the (+) input. </p>
<p><a href="https://i.stack.imgur.com/loLCO.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/loLCO.png" alt="enter image description here"></a></p>
<p>Increase the 47k for less hysteresis feedback.</p>
<p><em>The original circuit benefits from a better use of the 10K potentiometer. If instead connected in parralell with a resitance similar to that of the PT100 at its highest operating resistance the granularity and useful range of the potentiometer is greatly extended. Another 10K was added in series as well.</em> </p>
|
<p>I want to build an accurate (±2 °C) water heater (<a href="http://en.wikipedia.org/wiki/Sous-vide" rel="nofollow"><em>sous vide</em></a>) that heats water somewhere between 30-100 °C according to user input.</p>
<p>Although I have an engineering background I have no experience whatsover with building controllers and have no clue on how to start. I don't want to spend to much money on the project (< 100 €) thus money is an issue. The good thing is that I already have a power thyristor.</p>
<p>What I (probably) need:</p>
<ul>
<li>Temperature sensor PT100</li>
<li>Input device to define water temperature (digital?)</li>
<li>Controller (PID?)</li>
<li>Resistor to heat the water (can be taken from old water cooker I assume)</li>
</ul>
<p>My question is how I can best make the link between the sensor and the heating element. I of course need to build/program a circuit that does this but do I make an analog or digital circuit? </p>
<p>I have a thyristor but is this really necessary or should an on/off regulation also work? Don't forget that I also should be able to define the water temperature.</p>
<p>Any help is greatly appreciated (also useful links).</p>
|
Building a temperature-controlled water bath
|
2011-02-01T10:54:57.247
|
9618
|
|switches|multiplexer|terminology|
|
<p>I think you're confusing terms. It sounds like what you want is to connect a SRAM and Flash to a microcontroller. This has nothing to do with crosspoint switches.</p>
<p>I also see you deleted an answer stating the same about 2h ago; if you care to comment why this is wrong we can try to help you out. Otherwise I believe W5VO has answered your question about nomenclature quite well. (edit: nevermind, deleted by owner appears to me the owner of the answer, not the owner of the question.)</p>
<p>Run the address lines together, the data lines together, tie the RD (read strobe) lines together (if the flash has an OE, tie RD to OE as well). The WR lines should be tied together, and now you should be left with two CS (chip select) lines. Either run these to dedicated output enables on the microcontroller (many have built in address decoders) or build up some select logic that gives you a an OE for accesses to one memory range and another OE for another memory range. There are PLENTY of examples online, and the 74HC138 is a great chip for this. Googling for "memory address decoding" or "chip select decode" or even "microcontroller external memory interface" may get you started.</p>
<p>There are some different ways of going about this (Motorola-style bus vs Intel-style bus) but any book or articles on the older microprocessors or microcontrollers will give you plenty of information.</p>
|
<p>I'm looking through Digikey's <a href="http://search.digikey.com/scripts/DkSearch/dksus.dll?Cat=2556671" rel="nofollow">Interface - Switches, Multiplexers, Demultiplexers</a> section (and, thanks to W5VO, the <a href="http://search.digikey.com/scripts/DkSearch/dksus.dll?Cat=2556595" rel="nofollow">Logic - Signal Switches, Multiplexers, Decoders</a> section as well), and I'm having trouble deciphering what circuit/topology I need. </p>
<p>I've got a processor with a 32-bit coprocessor interface, and I'd like to interface it with a parallel Flash or RAM chip. Ideally, I would have both, and could swap between the two in software. I imagined (wrongly, it appears) that this would be a fairly common need, and that I could buy a pair of ICs that would each break out 16 inputs into 2 banks of 16 outputs, with power, ground, a single channel select pin, maybe an enable/high impedance pin. This would ideally come in a 54-pin TSSOP or 64-pin QFP or something of that size. A 32-switch chip would also work, but I imagine that two switches would make routing the a bit easier. The interface would be digital (I don't really need an analog switch), and I'd like to keep up with the 150MHz maximum speed grade of my processor (but will settle for 72MHz or so of actual performance). I am confident that I don't need some of the $200+ crosspoint switches!</p>
<p>I imagined that this would be a simple task, but it seems that my idea of what AxB:C should mean is different from Digikey's idea. I thought that the options would include 1x16:32 or 16x1:2, but (1) these options are not available at reasonable prices (I don't see why this device should cost $70 or $234!), and the other options (like 8x2:1, which seems popular) are designed for analog switching of Ethernet signals.</p>
<ol>
<li> Where can I learn about the mux nomenclature? (An answer on this site would be ideal :) Also, where can I learn about the various functions listed, like AV/crosspoint/Ethernet/USB?</li>
<li> What topology or function should I use for to do this task (digital, ~100MHz, 32 or 16 lines)? </li>
<li> If all else fails, how can I build a switch out of discrete components or transistor arrays?</li>
</ol>
|
Deciphering Mux/Demux/Switch Nomenclature: AxB:C?
|
2011-02-01T15:18:24.627
|
9623
|
|batteries|voltage-regulator|camera|
|
<p>The camera likely has a voltage regulator on board between the batteries and the main circuitry. If you're able to find a part number on that, you should be able to find a datasheet for the part and that will tell you what the max / min input voltages are.</p>
<p><strong>EDIT:</strong> I did some googling, and it looks like there is a power adapter you can purchase:</p>
<p><a href="http://rads.stackoverflow.com/amzn/click/B000EVLS3S" rel="nofollow">http://www.amazon.com/Canon-ACK-DC30-Adapter-SD700IS-SD800IS/dp/B000EVLS3S</a></p>
<p>It's bloody expensive, but if you can find some specs on that power adapter, you should have a better idea of what you can supply the camera with safely.</p>
<p><strong>EDIT2*</strong> I did some more searching, and it appears as though unit expects around 4.3 volts, so you should be good to go.</p>
<p><a href="http://www.studio3d.com/download/canon_870_user-guide.pdf" rel="nofollow">http://www.studio3d.com/download/canon_870_user-guide.pdf</a></p>
<blockquote>
<p>4.3V DC 1.5A</p>
</blockquote>
<p>I would think it would be easiest / most robust to just plug your power supply circuit into the DC jack.</p>
|
<p>I have a Canon SX210 IS which has not a connector to use a external power supply. So I wanted to connect "my" power source to the pins the battery usually touches.</p>
<p>In the back of my camera, it says 4.2 V but the battery has 3.7 (model NB-L5).</p>
<p>Right now, I have in my hands a voltage regulator (7805) and a diode which would drop 0.7 V.
I plan to connect the 7805 to a car battery so there is no line noise. Do you know if it safe to feed my camera with those 4.3 V?</p>
<p>Should I use less voltage? Would the camera be damaged if I pass 4.2 V?</p>
<p>I haven't tried anything yet just for precaution.</p>
<p>Thanks in advance!</p>
<p><strong>EDIT</strong></p>
<p>Does somebody know about a voltage regultor with arround (3.8 - 4.3)V of output?</p>
|
Is this a good way to power my camera?
|
2011-02-01T16:47:58.820
|
9628
|
|current-measurement|voltage-measurement|multimeter|
|
<p>It's because of the circuit used inside of the multimeter to create a virtual ground at approximately Vbat - 6.2V, or about 2.8V for a 9V battery; this basically means the COM terminal on the meter is at 2.8V relative to battery ground and readings will be offset by this.</p>
<p>I tried with another meter to measure its 9V battery - it read 6.08V, which is very close to the predicted 2.8V drop.</p>
|
<p>Well I finally obtained another multimeter, so now I have a Mastech MS8226T and a Ben Electronic M92A. I decided to measure at which voltages would the low battery warning appear and how much current each of them consumes. </p>
<p>So here's my setup: Power supply->M92A->9V plug->MS8226T->other end of the 9V plug->power supply.</p>
<p>I used M92A to measure current and wanted to use MS8226T to measure voltage. Unfortunately, I couldn't measure the supply's voltage using MS8226T. I always got 0 V. When I swithched the meters, M92A would show voltage out of range for every scale. </p>
<p>So I decided to use the powered on meter to measure current and the second meter to measure voltage. I got zero as result on both meters, when I wanted to use them to measure their own curent consumption. </p>
<p>Why is that so?</p>
<p><strong>EDIT</strong>
Here are the schematics.<br>
<img src="https://i.stack.imgur.com/BRPB4.png" alt="first image">
On this image, XMM1 is the meter measuring current and it is powered by its battery. Meter XMM2 is powered by the power supply V1. I used R1 as the meter's power plug. When I use MS8226T as XMM2 in such a set-up, I get zero volts on the supply. When I use the M92A, I get out of range on all ranges. The XMM1 meter shows expected values.</p>
<p><img src="https://i.stack.imgur.com/R9ECz.png" alt="second image">
On this image meter XMM1 is powered by its internal battery, is measuring voltage and shows expected values. Meter XMM2 is measuring current and reads zero. I'm using resistor R1 instead of meter's power plug here. </p>
|
Why can't a multimeter measure its own current and voltage?
|
2011-02-01T18:48:15.630
|
9631
|
|ground-loop|low-pass|
|
<p>As you have tried the monitor on two different cards, one it works with, the other smears the signal - this would indicate that the Monitor is OK and the video card is faulty.</p>
<p>I have seen this smearing effect on a very old video card, and it was caused by either a faulty DAC (Digital to Analogue Converter) or the smoothing caps around the DAC (And as the caps were quite old - the printing looked grey/brown instead of silver/white - an indication of age or overheating - When Caps get old - they loose capacitance and the ESR (Effective series resistance) increases.</p>
|
<p>Okay, I know this is an electronics Q&A site, and this question is mildly computer related. But I've got this problem with my VGA monitor, a graphics card and a computer. The problem is the video output is blurred in one direction quite badly. This looks very similar to a low pass filter - i.e. parasitic capacitance. </p>
<p>The confusing part is - this only occurs with one card, an Nvidia 9800 GT. I have a somewhat broken ATI card (GPU started melting and now all 3D games have misplaced polygons), and this doesn't occur. So I'm thinking something else is up with either the card or some configuration involving it. I've also noticed that there is an odd ripple to the black in the image. Could it be a ground loop? I'm using a cheap DVI to VGA adapter which could also be suspect.</p>
<p>I've attached an image of the problem.</p>
<p><img src="https://i.stack.imgur.com/5Vza5.jpg" alt="Blurred in one direction"></p>
|
Do I have a ground loop or another problem?
|
2011-02-01T19:20:17.633
|
9635
|
|video|ntsc|programmable-logic|
|
<p>Use <strong><a href="http://www.raspberrypi.org" rel="nofollow">Raspberry Pi</a></strong> with a supported frame grabber and extract needed info with <strong><a href="http://opencv.org" rel="nofollow">OpenCV</a></strong> library. Alternatively, if you can use onboard camera instead of external video signal, you can use <strong><a href="http://www.jrobot.net/Projects/AVRcam.html" rel="nofollow">AVRCAM</a></strong> for up to 8 objects 30fps color tracking.</p>
|
<p>I want to process a PAL or NTSC video signal and pick up colors, like green, orange, blue and red. Is there any way to decode RGB from NTSC/PAL easily, and then detect these colours? I'm looking for a small and cheap solution. The end goal is to build up an array of pixels matching a colour, then filter this to decode shapes and locate targets on a camera. </p>
|
Image processing on PAL/NTSC
|
2011-02-01T22:07:35.287
|
9637
|
|motor|brushless-dc-motor|
|
<p>When starting up a brushless motor will turn in a random direction determined by the position of it's windings and magnets. For an ESC to make it turn for example clockwise, it will apply a pulse of current, read the Back EMF from the windings, and if the BEMF matches the right direction it will continue, if it doesn't match, it will reverse the polarity of the circuit.</p>
<p>Hope this clears it up :)</p>
|
<p>When connecting a brushless motor to an ESC, we are taught to apply power and switch two of the wires if the blade is spinning in the wrong direction.</p>
<p>Is it possible to predict the blade rotation by examining the ESC and motor?</p>
<p>(note: learning-style question, I don't have a practical problem with switching wires)</p>
|
predicting brushless motor rotation direction?
|
2011-02-02T00:58:33.970
|
9638
|
|laser|motion|mechanical|
|
<p>The galvanometers are rated in terms of how many different angles they can point at per second. The smaller the angle the mirror has to swing through, the more times per second it can do it, which is reflected in the specs for the second galvanometer you pointed to. For a light show application, the desired patterns and level of detail would determine both the required deflection and the number of points.</p>
<p>The generic component selection process is applicable here and goes something like this:</p>
<ol>
<li>figure out a performance requirement for the component</li>
<li>find some components that meet the requirement</li>
<li>cheap enough? you're done!</li>
<li>too expensive? try adjusting your design to work with a cheaper version, go to 1.</li>
</ol>
|
<p>I am currently looking to purchase laser galvanometers like <a href="http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&hash=item19c28a1677&item=110638012023&nma=true&pt=LH_DefaultDomain_0&rt=nc&si=ykIfbnG6rxMQVKB7tfa6%252BniDziU%253D" rel="nofollow">this</a> and <a href="http://cgi.ebay.com/Laser-Galvo-Scanning-30Kpps-for-laser-show-light-ILDA_W0QQitemZ220550668048QQcategoryZ29944QQcmdZViewItemQQ_trksidZe11014.m263QQ_trkparmsZalgo%3DSIC%26its%3DI%26itu%3DUCI%252BIA%252BUA%252BFICS%252BUFI%252BDDSIC%26otn%3D10%26pmod%3D110638012023%26ps%3D63%26clkid%3D6562780343974550774#ht_2653wt_1168" rel="nofollow">this</a>. However, as I'm not familiar with lasers, I'm not sure the criteria I should use to evaluate whether a given product is a good buy. What are your suggestions?</p>
<p>Thanks in advance!</p>
|
How to choose laser galvanometers
|
2011-02-02T02:16:19.827
|
9639
|
|stepper-motor|torque|
|
<p>Well, since I have physics exam in a cople of hours with problesm such as this one, I decided to make a more or less detailed solution. </p>
<p>First let's take a look at the diagram. On it we have 3 major points: weight, pulley wheel and the shutter.<img src="https://i.stack.imgur.com/AeUrU.png" alt="wheel image"></p>
<p>I'll start with the wheel and assume that it will rotate in the negative mathematical direction. Wheel's radius is R and its mass is Mw.
First we should take a look at the forces acting on it. We have the weight of the wheel Qw=Mw*g actung downward and we have the rection of the surfece, N acting upward. They cancel eachother out. Next, we have rope tension forces. S1 is the force which tenses the rope from the weight side and S2 is from the shutter side. </p>
<p>Now we need to write the moment equation for the system.</p>
<p>Wheel's moment of inertia is Iw=Mw*R^2/2 and its angular acceleration is α.</p>
<p>Iw*α=S1*R-S2*R</p>
<p>For the system to work, we need the α to be greather than zero. So we get the obivous α=(S1*R-S2*R)/Iw from which we can deduct that S1 should be greater than S2. We also know that α=a/R. We'll need that later. Next interesting thing which we can find from the wheel is the ratio between two forces. S1=S2+Iw*α/R. Also, the force S2=S1-Iwα/R</p>
<p><img src="https://i.stack.imgur.com/TPYhT.png" alt="shutter"></p>
<p>Next, let's take a look at the shutter. Let's say that the length of the rod is L2. We have force S2 which is pulling the rod upwards and it's creating the moment of force (torque) which gives us: M2=L2*S2. We also know that we have a minimum moment of force needed to trigger the mechanism and we'll calculate that later.</p>
<p><img src="https://i.stack.imgur.com/EQYOx.png" alt="weight"></p>
<p>Lastly we have the weight side. We want to replace the weight with a motor and we need to calculate its moment of force. The motor has axle whose radius is r. We know that mass of the weight is m=12.8g. We can see that the force S1 which tenses the rope in the wanted direction is S1=Q1=m*g=0.125568 N or 125.568 mN. To achieve such a force, we'll need moment of force which is equal to M1=Q1*r, where r is the radius of the motor's axle. </p>
<p>Now let's take a look at what we can tweak. It would be good is we could get the needed moment to operate the shutter. If we know it, we can twaek the rest of the system. </p>
<p>So by taking a look at the wheel equation, Iw*α=S1*R-S2*R, we see that the wheel should be as light as possible and that that its diameter should be as small as possible in order to minimise the losses. </p>
<p>After that, if we take a look at the moment equation for the shutter, we have M2=L2*S2. We can increase the length of the rod in order to minimize the needed force. </p>
<p>In the end, let's take a look at the weight side. We know that Q1=125.568 mN and that M1=Q1*r. So if we divide the torque of the motor from the list by the axle diameter, we can get the force it will produce and check if it will be good enough for our needs. Q1=M1/r If we take for example, ADM_1220, we see that it has torque of 4.1 mNm and axle diameter of 12mm. So we get F=4.1mNm/12*10^(-3)m=341.67 mN, which is enough to close the shutter.</p>
|
<p>I'm working to design a motor to control a mechanical shutter. After considering some other possibilities I have decided to try using a stepper-type micro motor. We're using a <a href="http://www.edmundoptics.com/onlinecatalog/displayproduct.cfm?productID=1461" rel="nofollow noreferrer">shutter from Edmond optical</a>. I'd like to pair it with one of the <a href="http://catalog.micromo.com/db/service?domain=micromo&command=locate&category=2_phase_stepper_motors" rel="nofollow noreferrer">Micromo stepper motors</a>.</p>
<p>The critical datasheet specification seems to be the holding torque which is rated as nMn. I take this to be Millinewton/meter. I rigged up the shutter with a simple pulley and found that a weight of 12.8 grams was sufficient to turn the shutter's lever (which opens and closes the aperture). </p>
<p>This explanation might benefit from a diagram, so I drew up one to illustrate the experiment:</p>
<p><img src="https://i.stack.imgur.com/MQ9e9.png" alt="pulley experiment"></p>
<p>If <strong>w=mg</strong> then the weight exerts a force of 126 mN on the lever...ignoring the geometry of the pulley and that the lever turns on a circular orbit. My naive self imagines that I need a motor which provides a torque of more than 126 nMn. Is this a correct estimate?</p>
<p>If so it seems all the Micromo stepper motors are too weak to turn the shutter.</p>
|
Calculating the amount of torque needed to turn shutter
|
2011-02-02T05:34:05.773
|
9640
|
|sourcing|
|
<p>I lived in China for several years. If you're looking for specialized electronics pieces (as opposed to consumer or computer pieces such as hard drives), you will probably have difficulty finding retail places to look at them. Most of the electronics vendors sell to other manufacturers, so if you don't have a certain quantity you wish to buy you will not be able to find many people to talk to.</p>
<p>What part of China are you going to? If it's Shenzhen or one of the other manufacturing cities in the south of China you will have much better luck than if you're going to Beijing, etc.</p>
|
<p>I found a few specialized electronic parts that I am interested in buying from eBay and/or Alibaba. However, knowing that I will be traveling to China soon, I felt checking the purchase in person would lower my risks of getting a lemon. What do you think and why?</p>
<p>Thanks in advance.</p>
|
What're the benefits of checking electronics in person over the exclusive online stores?
|
2011-02-02T08:12:24.140
|
9642
|
|xilinx|floating-point|xilinx-system-generator|arithmetic-division|cordic|
|
<p>The cordic block is split up into a bunch of processing elements (PEs). Each PE is a bunch of logic operations. There is some latency associated with each PE already.</p>
<p>You can add additional registers at any point in the pipeline by putting non-zero values into the vector you have highlighted. The vector should have as many elements as you have requested PEs. In your case, you've requested one PE so it will only look at the first value of the vector, resulting in an additional latency of zero.</p>
<p>As regards notation - [] is standard Matlab for a vector (or matrix, depending on how it's used, but I'll not go into that here!). It's a bit like an array in other languages.</p>
<p>so</p>
<pre><code>a=[5 6 7 8]
</code></pre>
<p>creates a 1x4 vector called <code>a</code>. Element 1 (which you can access in matlab by doing <code>a(1)</code> ) has the value <code>5</code>. Element 4 has the value <code>8</code>. </p>
<p>Note that Matlab starts its numbering from '1' not '0' like many other languages!</p>
|
<p>I have some dudes about the block parameters of the CORDIC DIVIDER.
<strong>I would like to someone explain me the parameter called "Latency for each processing element".</strong>
(See the parameters inside the red rectangle)</p>
<p>I don't understand the notation that is used, some zeros or ones between two brackets.</p>
<p>By the way, this question is realted with one I asked before:
<a href="https://electronics.stackexchange.com/questions/9517/system-generator-how-to-configure-the-cordic-divider-block">System Generator: How to configure the CORDIC divider block?</a></p>
<p><img src="https://i.stack.imgur.com/iFXsS.jpg" alt="enter image description here"></p>
|
System Generator: How to configure the CORDIC divider block. Understanding the block parameters
|
2011-02-02T08:55:45.290
|
9644
|
|fpga|floating-point|architecture|
|
<p>The first step in performing a floating-point exponential operation is to scale things so that you're trying compute 2^(someInteger / powerOfTwo). This will easily reduce the problem to one of converting a value between 0 and 1, into a value between 1.00 and 1.99+. Let's suppose that we have a 32-bit integer and a scaling factor of 2^24. The upper 8 bits of that integer can easily yield the exponent for the result. As a rough approximation (to show how things are done), scale things so that the bottom 20 bits of the exponent will yield a value between 1.0 exactly and 1.04427378. Use bits 20-21 of the exponent to pick an entry from the table (1.0, 1.04427378, 1.09050773, 1.13878863) and multiply by that, and then use bits 22-23 to pick an entry from (1.00, 1.18920711, 1.41421356, 1.68179283) and multiply by that.</p>
<p>Note that this approach won't yield precise results, but it can achieve reasonably fast results with a reasonable amount of hardware. Using more lookup table steps can increase precision at the expense of time and hardware. Using larger lookup tables can increase precision at a given speed at the expense of hardware.</p>
|
<p>does anyone knows how is the fast way to perform a floating point exponential operation? (like this y = 2.71^(3.45))
Thank you to all posible links to references or articles.</p>
<p><strong>EDIT:</strong></p>
<p>I am pondering several possibilities:</p>
<p>Doing by System Generator (I am using the 9.2.01 version)</p>
<p>Using some Free Xilinx IP</p>
<p>Using some open libraries like:</p>
<ul>
<li><a href="http://www.vhdl.org/fphdl/old_index.html" rel="nofollow noreferrer">VHDL.org</a> </li>
<li><a href="http://optngn.com/place/index.php?option=com_virtuemart&page=shop.browse&category_id=2&Itemid=53&TreeId=2&vmcchk=1&Itemid=53" rel="nofollow noreferrer">OptNgn</a></li>
</ul>
<p>Using <a href="https://electronics.stackexchange.com/questions/9662/looking-for-a-open-source-alu">an open-source ALU</a></p>
|
Digital Architecture Design Question: Fast way to perform a floating point exponential operation
|
2011-02-02T11:34:16.183
|
9647
|
|analog|digital-logic|ground|
|
<p>Divide your board into those discrete sections: PLL, Analog, Digital, and IO. Try to keep all of the copper (signal & power) for each section separate except where they require interconnect. Join the power to each sub-circuit only at near the power supply, within the sub-circuit and at chip when possible. Bypass each at the chip grounds with a cap or two (you might leave an extra footprint here for test). </p>
<p>You may find that the layout doesn't permit total separation of sub-circuits. If so, at least try to use a wider trace to supply the split and filter where necessary.</p>
|
<p>I am considering using a chip, but the datasheet is confusing me as it has several distinct power pins. </p>
<p>It has:</p>
<ul>
<li>PLL_VDD</li>
<li>PLL_GND</li>
<li>AVDD</li>
<li>AGND</li>
<li>DVDD</li>
<li>DGND</li>
<li>DVDD_IO</li>
<li>DGND_IO</li>
</ul>
<p><a href="http://focus.ti.com/docs/prod/folders/print/tvp5150am1.html" rel="nofollow">This is the chip</a>.</p>
<p>How do I hook up each? Do I connect AVDD straight to DVDD, and what about PLL_VDD, and the ground pins? The suggested schematic seems to show them all connected to the same potentials (with different symbols for both types of grounds); from a cursory glance it doesn't mention anything about PCB layout. So how should I wire it up?</p>
|
AGND/AVDD on a chip
|
2011-02-02T12:22:45.843
|
9652
|
|pcb|timing|
|
<p>In addition to the good answers by others, there's still things you can do if you've got functional failures due to trace mismatch on your board (though at 27 MHz, there's not much to worry about). Most modern FPGAs from Xilinx (and maybe Altera, not sure) have reconfigurable delay element inside of the I/O pin so you could adjust with very fine resolution when the signal is captured. Look for the 'IDELAY' and 'ODELAY' primitives.</p>
|
<p>I'm considering using a chip which outputs 8-bit data on a 27 MHz clock. The data will go from the chip to a FPGA, a distance of a few cm max. Do I need to be concerned about timing differences between traces on a PCB, and if so, how can I mitigate these? I've often seen motherboards with traces in small coil shapes, presumably to act as little delay lines.</p>
|
Timing differences with a 27 MHz data clock
|
2011-02-02T13:30:36.470
|
9653
|
|interconnect|
|
<p>This is another option: <a href="http://buckeyeshapeform.thomasnet.com/item/bmx-bmu-rackmount-desktop-enclosures/bmu-series-cases/bmu-10-100-13" rel="nofollow">http://buckeyeshapeform.thomasnet.com/item/bmx-bmu-rackmount-desktop-enclosures/bmu-series-cases/bmu-10-100-13</a>.</p>
<p>They look very 1980s, but they.</p>
|
<p>I'm looking for some chassis and cases to put my electronics projects in. My projects tend to involve at least one microcontroller and/or fpga. My boards are often very "verbose" and I put few major features on each board so I often end up with several boards. I would like an easy way to both reuse some of the boards across projects but also have a structured way to connect the boards, not just lay them out on my desk as I do now.</p>
<p>I would like something like this <img src="https://i.stack.imgur.com/dWpQH.jpg" alt="http://www.errock.co.uk/motherboard%20rack%20photo%20high%20res.jpg"> except that it shouldn't cost me my first born. It doesn't have to be as big, but I would like something that can hold a handful of boards and have a "useful" backboard. It would be nice if uses standard VME connectors or something similar (even ISA would be useful). Hopefully each board be 100mmx160mm in size, but that's not critical either.</p>
<p>Also, does anyone have an alternate way of organizing the few boards that make up a project?</p>
|
Chassis / case for electronics projects
|
2011-02-02T13:38:55.940
|
9662
|
|architecture|floating-point|open-source|alu|
|
<p>There are several open-source ALUs available.
In particular, there is at least one open-source ALU somewhere in every open-source CPU.</p>
<p>The <a href="http://opencores.org/projects" rel="nofollow">Open Cores website</a>, under the "Arithmetic core" tab, has a bunch of projects -- some of them involve floating point.
It also has a bunch of CPUs under the "Processor" tab,
some of which apparently include FPUs -- OpenFire, S1 Core (OpenSPARC), Zet (x86), and probably a few others.</p>
<p>This <a href="http://www.1-core.com/library/digital/soft-cpu-cores/" rel="nofollow">table of embedded CPU soft cores</a> has a column that indicates which ones have a FPU and another column that indicates which are open source; several of them are both.</p>
<p>Pretty much any ALU <em>can</em> perform any floating-point operations.
There are several approaches, including:</p>
<ul>
<li>use a CPU with only an integer ALU;
emulate all floating-point operations
in software. Perhaps you can
compile your code with the
<a href="http://gcc.gnu.org/onlinedocs/gccint/Soft-float-library-routines.html" rel="nofollow">-msoft-float option</a> or
--without-fp option. Or perhaps you will want to manually port a
floating-point library such as
<a href="http://gcc.gnu.org/wiki/Software_floating_point" rel="nofollow">fp-bit.c, ieeelib, or soft-fp</a> or
other <a href="http://en.wikibooks.org/wiki/Embedded_Systems/Floating_Point_Unit" rel="nofollow">floating point emulation
library</a>.</li>
<li>use a CPU with a simple
floating-point ALU (aka FPU) that only does
add, subtract, multiply, and a few
utility operations; emulate more
complicated operations such as divide
in software.</li>
<li>use a CPU with a more complicated
floating-point ALU (aka FPU); only emulate
really complicated operations such as
cosh(), asin(), etc.</li>
</ul>
<p>As other posters have already pointed out, doing floating-point calculations in a FPGA may not be the be the easiest or lowest-cost way to achieve your goals.
Many people using FPGAs prefer to use fixed-point calculations if at all possible.
Often an off-the-shelf microprocessor is a better fit than a FPGA.</p>
|
<p>I am looking for a open ALU to compute several equations like these:</p>
<pre><code>y1 = e^((constant1 - x)^2/(2*x))
y2 = constant2/y1
y3 = y2*constant3 + x*constant4
</code></pre>
<p>Where x is the input of my system and y3 is the output. </p>
<p>I would prefer that the ALU supported floating-point operations. Where can I find an open or free floating-point ALU?</p>
|
Looking for a open-source ALU
|
2011-02-02T16:37:27.070
|
9663
|
|fpga|xilinx|xilinx-system-generator|
|
<p>Well, I found the how-to.
Just click on the System Generator token block on the simulink scheme and configure its parameters. In the parameter compilation it´s neccesary to select 'bitstream'.</p>
|
<p>I am using System Generator and I would like to generate a .bit file in order to load into my FPGA. Does anyone know how to generate a .bit file with SG?
Thank you.</p>
|
System Generator: How to generate a .bit file?
|
2011-02-02T16:48:54.917
|
9671
|
|audio|cables|
|
<p>Speakers are relatively high power devices with very low impedance. This combination won't pick up any noticeable noise.<br>
Use just <em>any</em> low resistance cable and you'll be fine. Low resistance is needed to achieve a good <strong>damping factor</strong>. Anybody paying 100 euros and up per meter of oxygen-free copper cable and the like just <em>knows</em> he's being swindled.</p>
|
<p>Sorry if this is the wrong place but I'm interested in a scientific and electrical explanation and not some HiFi voodoo magic.</p>
<p>I guess you all have seen the discussions about expensive audio cables and "improved" sound quality.</p>
<p>My question is, what's the best cable for an audio signal? Loudspeaker cables are usually a pair of ~12 AVG cables terminated with banana connectors. </p>
<p><img src="https://i.stack.imgur.com/9Jxn0.jpg" alt="enter image description here"></p>
<p>As far as I understand this must be affected by all sorts of noise. To minimize noise it's normal to use coax cable for "radio" signals (LF, MF, HF, ...). Wouldn't coax with proper connectors like APC-7 or equivalent be the best for audio too? Or are the frequencies too low for coax somehow?</p>
<p>Internet was a bit vague on this topic. </p>
<p>What I'm really wondering is why don't we use coaxial cables for loudspeakers in average home stereos?</p>
<p>Lets say a signal level of 50 dBm (100W).</p>
|
What's the best cable to transfer audio signal?
|
2011-02-02T20:52:18.700
|
9692
|
|microcontroller|atmega|board|
|
<p>I wanted to do something with microcontrollers for some time now, but it wasn't until yesterday that I collected enough courage to actually buy one. </p>
<p>Since you said that you're absolute beginner, here are some very basic pointers.</p>
<p>First site you may want to visit it Atmel's website for the microcontroller you have. <a href="http://www.atmel.com/dyn/products/product_card.asp?PN=ATmega16" rel="nofollow">Here</a> it is. There, you'll need to visit the documentation section and get the 2 datasheets. You should read the summary and take a look at the datasheet. While you can read the whole datasheet, I think it may be better to just keep it as a reference. You might want to download AVR Instruction Set and keep it as a reference too, but to me at least, it looks more interesting to assembly fans and compiler writers. </p>
<p>By now you should have an idea of what the device you have is capable of. Next step would be to set up the needed toolchain. On the site I linked, go to tools section and look under design software. There you'll find a link to AVR Studio 4, which is one of the available programming environments. Some of the other IDEs are <a href="http://winavr.sourceforge.net/" rel="nofollow">WinAVR</a>, IAR Embedded Workbench for AVR(non-free, but there's a program size limited demo), ImageCraft, CodeVisionAVR, CrossWorks for AVR.</p>
<p>For a beginner, AVR Studio and WinAVR seem to be the easiest to obtain.</p>
<p>After that, you can start programming. There's a simulator in AVR Studio, so you can try out and debug programs before you burn them on the controller. </p>
<p>Next step which needs to be overcome is how to get program from your computer to the microcontroller. On the tools page, you'll find a list of officially blessed development boards and programmers and debuggers. Problem with them is that they are usually too expensive for a beginner. On the other hand, they should work without any problems and there's a lot of documentation on how to use them. </p>
<p>If you want to save some money, but suffer potential headaches, you can get one of the many alternative programmers. Just search for AVR programmer and you'll get countless results. Unfortuantley, I can't recommend you any specific programmer, since I'm looking for one too. </p>
<p>The other option is to build one yourself. There are countless schematics available for AVR programmers and many of them can be very cheap to make. On the other hand, there's the problem with finding specific parts (some programmers need Russian transistors, which are now difficult to obtain and then you'll have to look for compatible replacements and so on) and that you have to build it yourself. Still, building a programmer yourself can be a good learning experience.</p>
<p>After you have a programmer, you'll need a circuit which can power up the controller and provide the basics. You should know by now that AVRs run on 5 volts, so that's what you'll need. There are lots and lots of examples on the Internet for basic boards, so again search. Some sites with programmer schematics will have most basic target boards too. For most basic system, you'll need a 5 V source and that's pretty much it, as ATMega 16 has its own clock source. If you can't make a basic board, feel free to ask for specific instruction. </p>
<p>Next step is to make a basic program which will do something. For microcontrollers, hello world programs are a bit more complicated and are a good project for a bit more advanced users. Instead, the most basic program will turn on an LED. After that comes flashing LED and after that button controlled LED and so on. Circuits for such project are very simple. In addition to the most basic AVR board, you may only need one resistor and LED. I think that ATMega 16 can source enough current to power a LED, but I'm not 100% sure. You can always check the datasheet. If you're feeling a bit more advanced, you could make a circuit which will use a transistor to control the LED.</p>
<p>In the end, here are some interesting links for beginners:</p>
<p><a href="http://www.avrfreaks.net/" rel="nofollow">http://www.avrfreaks.net/</a> They have a nice forum and they have a list of projects which could be interesting.</p>
<p>Here are several interesting tutorials:<br>
<a href="http://imakeprojects.com/Projects/avr-tutorial/" rel="nofollow">http://imakeprojects.com/Projects/avr-tutorial/</a><br>
<a href="http://avrbeginners.net/" rel="nofollow">http://avrbeginners.net/</a><br>
<a href="http://www.avr-asm-tutorial.net/avr_en/" rel="nofollow">http://www.avr-asm-tutorial.net/avr_en/</a><br>
<a href="http://www.ladyada.net/learn/avrdevtut/" rel="nofollow">http://www.ladyada.net/learn/avrdevtut/</a> </p>
<p>Another interesting thing worth mentioning is <a href="http://en.wikipedia.org/wiki/Arduino" rel="nofollow">Arduino</a>. It's an electronics prototyping platform which is based on AVR microcontrollers. The plus side of them seems to be that you'll be able to skip the background stuff, such as getting a programmer, getting a basic board for the microcontroller and so on. There's an IDE for Arduinos and a simple programming language too. The minus side of them is that you'll be able to skip the background stuff, such as getting a programmer, getting a basic board for the microcontroller and so on. There’s also the problem with the fact that there's an IDE for Arduinos and a simple programming language too.</p>
|
<p>First of all, I'm a newbie regarding electronics&robotics so please bear with me.</p>
<p>I have been working as a programmer for a few years but I just got interested in playing with microcontrollers.</p>
<p>Can anyone recommend a book/tutorial for building a development board based on ATMEGA16-16PI
.</p>
<p>As of yesterday I own a breadboard and a atmega16 microcontroller.</p>
<p>Where do I go from here?</p>
<p>Thanks</p>
|
Build ATMEGA16 Board
|
2011-02-03T09:56:06.127
|
9697
|
|power-supply|diodes|
|
<p>The current will be the same for all parts of the circuit, and in this case be about 90A as the diode can be considered to be a low resistance 10V drop.</p>
|
<p>The rule of thumb is that when a diode is fully on, it looks like a short circuit (ideally). So (to make this easy), say I have 100 V source and a diode which breaks down at 10V. If my power supply/source impedance is 1 Ohm, will the current through my diode be:</p>
<ol>
<li>I = (Vsupply - Vdiode)/Rsupply = (100 - 10)/1 = 90/1 = 90 Amps, or</li>
<li>I = Vsupply/Rsupply = 100/1 = 100 Amps?</li>
</ol>
|
What is the diode current when used in clipping/clamping
|
2011-02-03T16:30:58.913
|
9701
|
|arduino|dc-motor|
|
<p>Not possible...</p>
<p>The Arduino can not drive that type of motor - the start up surge would damage the chip, also a diode is needed to handle the 'back emf' when the motor is turned off.</p>
<p>A servo has internal electronics to switch the motor. you just provide a repeating pulse of the correct length.</p>
|
<p>I have three small motors, and I know you should use a motor shield or driver when working with the arduino, but would it be safe to use these with the arduino by themselves without a shield? And if so, what would be the best way to work with them and control their speed?
<img src="https://i.stack.imgur.com/BN5tW.jpg" alt="the motors"></p>
|
Using motors with arduino without external hardware
|
2011-02-03T17:01:42.293
|
9703
|
|microcontroller|bus|sharedbus|
|
<p>There is a "daisy-chain SPI protocol" ("JTAG-like protocol") that requires a total of 4 pins on the bus master, no matter how many slaves are in the chain.
The daisy-chain SPI never has conflicts on the bus,
because each bit of wire has only one driver connected to it.
See
<a href="http://en.wikipedia.org/wiki/Serial_peripheral_interface#Daisy_chain_SPI_configuration" rel="nofollow noreferrer">Wikipedia: Daisy-chain SPI</a>
and
<a href="https://electronics.stackexchange.com/questions/5188/help-with-device-identification-in-a-chain">Help with device identification in a chain</a>
.</p>
|
<p>I want a master node consisting of a TI Stellaris Cortex M3 core connected to what can be up to 32 slave nodes of TI MSP430 (or possibly more Stellaris slave nodes). These will be maximally 0.5 meters between master to most distant slave. Bit rates of around 0.5-1mbps will be needed. What kind options are available for internal communications? </p>
<p>From docs they both seem to support SPI, UART and I2C. </p>
<ul>
<li>SPI will from what I find, need 1 selector wire pr node. Way too many wires. </li>
<li>I2C seems easy, but for from docs I get the max speed is 400KHz. Too slow without degrading quality or maximum number of nodes.</li>
<li>UART seems to acheive the speed, but can it be used outside of A to B communication?</li>
<li>Did I miss anything?</li>
</ul>
<p>Update: As noted in comments, updated I2C speed for msp430 to 400KHz. Still too slow though. Also the network is purely one master and n slaves.</p>
|
Multi node bus options
|
2011-02-03T17:19:08.530
|
9709
|
|connector|cables|
|
<p>Are those jumpers beside the connector? Then probably the connector can be connected using the common <a href="http://www.sparkfun.com/products/9140" rel="nofollow">jumper wires</a> (available with up to at least 10 pins in one housing).
Servo cables usually have a different kind of connector (rounded corners).</p>
<p>To make your own jumper leads, you can buy <a href="http://pololu.com/catalog/product/1904" rel="nofollow">crimp connector housings</a> from <a href="http://pololu.com/" rel="nofollow">pololu</a>. They also sell <a href="http://pololu.com/catalog/category/71" rel="nofollow">pre-crimped wires</a>, if you don't want to crimp them yourself.</p>
|
<p>I have a <a href="http://www.luminarymicro.com/jaguar" rel="nofollow noreferrer">Jaguar</a> motor controller that has a set of 5 inset male header pins to connect an encoder. The encoder has only loose wires coming out.</p>
<p>What type of connector should I be buying to solder/crimp onto the end of these?</p>
<p>Also, there're a couple of sensor boards with a similar arrangement of 0.1" male headers. The control board also has male headers. However, every compatible cable I can find is male to female.</p>
<p>Do servo cables with sockets at both ends exist?</p>
<hr>
<p>This is what the controller looks like. Encoder slot is on the front, as the freehand-circling below shows</p>
<p><img src="https://i.stack.imgur.com/nNEIM.jpg" alt="Jaguar"></p>
|
What cable do I need to connect rows of male header pins together
|
2011-02-03T18:51:28.103
|
9714
|
|power-supply|
|
<p>An LDO may not be powered directly from the battery. Often the battery goes to a switching regulator that's very efficient at getting the battery voltage down to the main power rail (say 3.3V), good enough for digital but a bit noisy for sensitive circuits, especially RF and probably audio. So an LDO would be added for each sensitive subsection to re-regulate the main rail to a slightly lower voltage that's much cleaner. The linear regulator doesn't have to throw away the whole voltage difference between the battery and the main rail as efficiency loss.</p>
|
<p>Analog Devices <a href="http://www.analog.com/en/press-release/01_25_2011_500-mA_LDOs_Double_the_Power_Rejection/press.html" rel="nofollow">just brought out several LDO regulators claiming double the power supply rejection ratio of competing devices, and targeting these devices at battery powered devices</a>. </p>
<p>However, I thought that batteries were quite noiseless, as opposed to powering up your device via a switchmode power supply where (i would have thought) a very good PSRR would be handy.</p>
<p>Why would PSRR be a crucial factor in battery powered systems?</p>
|
Power Supply Rejection Ratio for Battery Powered Systems
|
2011-02-03T23:03:07.383
|
9718
|
|batteries|safety|automotive|battery-charging|
|
<p>Lead acid batteries, like those used in vehicles, create hydrogen gas from the sulphuric acid. If the gas concentration is high enough and you get a spark, it explodes, the acid goes everywhere including in your eyes. </p>
<p>You almost always get a spark when completing the circuit, sometime even if the charger if off. By making the last connection away from the battery this lessens the chance of an explosion. If the battery is still in the vehicle, attach the positive to the battery terminal then attach the negative to a ground point away from the battery. Many people use a point on the engine block. With the battery removed, you don't have a ground point to connect to, so make the last connection away from the battery by using an extra ground cable. </p>
|
<p>If you go to: <a href="http://www.battery-chargers.com/charging_instructions.htm" rel="noreferrer">http://www.battery-chargers.com/charging_instructions.htm</a></p>
<p>...Under "Operating Instructions" part "B: Charging battery outside of vehicle", it says you have to attach an extra jumper cable to the negative battery post, that is then clamped to the charger's actual negative cable. See below:</p>
<p><img src="https://i.stack.imgur.com/0ESB3.gif" alt="enter image description here"></p>
<p>Both my charger's instructions and these look identical on this point (Indeed, they might be the same instruction sheet). </p>
<p><strong>Why is this extra cable needed?</strong></p>
<p>(Not like I don't have one, just rather curious...)</p>
<p>Thanks!</p>
|
Extra negative battery cable when charging outside car?
|
2011-02-04T01:05:47.110
|
9732
|
|pcb|
|
<p>I've done an LGA without a stencil. But that was a small low pad count part (BMA180). I had to tin the pads with flux and solder, then placed the chip on top, then used hot air reflow to solder it.</p>
|
<p>I have come across a chip which is only available in <a href="http://en.wikipedia.org/wiki/Land_grid_array" rel="nofollow">LGA</a>. I wouldn't touch <a href="http://en.wikipedia.org/wiki/Ball_grid_array" rel="nofollow">BGA</a>, but what about LGA? How possible is it to design for one with little experience? Are there any gotchas? I'm planning to reflow solder these using a hot plate.</p>
|
Difference between BGA and LGA
|
2011-02-04T13:10:00.177
|
9740
|
|schematics|
|
<p>I've looked into it and this seems to be an open bug issue that just hasn't been fixed yet: <a href="http://sourceforge.net/tracker/index.php?func=detail&aid=2859909&group_id=47763&atid=450703" rel="nofollow">http://sourceforge.net/tracker/index.php?func=detail&aid=2859909&group_id=47763&atid=450703</a></p>
<p>If you can use a different type of netlist output that might help but I'm guessing it's not an option for you. Your best bet at this point is to just abandon hierarchical designs until it gets fixed. Sorry.</p>
|
<p>I've got a design (PIC microcontroller that uses transistors to turn on banks of LEDs). I have 2 instances of the LED array, so I made a hierarchical design - I have a separate schematic for the LED array, and I put 2 instances of it into my main project.</p>
<p>The LED arrays are just a bunch of resistor/LED pairs, labeled R1/D1, R2/D2, etc.</p>
<p>The problem comes when I generate a netlist - the netlist appears to include everything, but it doesn't differentiate between the R1 from the first instance of the array and the R1 of the second instance. So I get things like this in my netlist file:</p>
<pre><code>*SIGNAL* _HN_1_!ON
Q1.3 D1.1 D14.1 D2.1 D15.1 D3.1 D16.1 D4.1 D17.1 D5.1 D18.1 D6.1 D19.1 D7.1 D20.1 D8.1 D21.1 D9.1 D22.1 D10.1 D23.1 D11.1 D24.1 D12.1 D25.1 D13.1
*SIGNAL* _HN_2_!ON
Q2.3 D1.1 D14.1 D2.1 D15.1 D3.1 D16.1 D4.1 D17.1 D5.1 D18.1 D6.1 D19.1 D7.1 D20.1 D8.1 D21.1 D9.1 D22.1 D10.1 D23.1 D11.1 D24.1 D12.1 D25.1 D13.1
</code></pre>
<p>Q1 feeds the first LED array, Q2 feeds the second LED array, but you see that D1 is referenced in both. If I feed that into FreePCB, I'm only going to get one LED array and it's going to be wired ALL wrong.</p>
<p>Is there a way to make TinyCAD do the right thing here?</p>
<p>Update: I tried putting the LED arrays on separate sheets, but that didn't help.</p>
<p>Update again: I suppose I could just copy the LED array design onto separate sheets and then number their reference designators appropriately, but that's giving up the hierarchical design altogether.</p>
|
How to get TinyCAD to output correct netlist when using hierarchical design?
|
2011-02-04T14:40:15.623
|
9741
|
|fpga|xilinx|pins|xilinx-system-generator|configuration|
|
<p>If you double-click the Gateway block and click to the "implementation" tab, there's a box you can tick to "Specify IOB location constraints".</p>
<p>You can then enter something like this in the IOB pad locations box underneath:</p>
<pre><code>{'P22', 'P12'}
</code></pre>
<p>(if you have 2 bits, repeat as needed if you have more!). This is for a leaded package with simple numbers on each pin. If you're using a BGA device, the pins will be named alphanumerically. It's explained quite well in the HELP for the Gateway blocks.</p>
<p>You can check this has worked by looking at the .pad file in the same directory as your .bit file was created - you should be able to find the IOBs named and see which pin they were mapped to. (There's two versions of the pad file, one is a CSV file the other is a text table which looks fine in a monospaced font)</p>
|
<p>I am programming a FPGA by System Generator. I have done this design:
<img src="https://i.stack.imgur.com/wxt2e.jpg" alt="enter image description here"></p>
<p><strong>I don´t know what are the respectives pins of my FPGA for the blocks of my design called 'Gateway In' and 'Gateway Out'</strong>. I would like to check I would check the design made in my FPGA through a generator waves and a oscilloscope.
Does anyone know how to assign pins of your design if you made it using System Generator?
Thank you so much.</p>
|
System Generator: How to configure the pins for the signals of your design?
|
2011-02-04T15:51:38.523
|
9748
|
|microcontroller|audio|
|
<p>What you need is:</p>
<ul>
<li>Soldering Iron</li>
<li>A desoldering tool or some solder wick</li>
<li>Some solder</li>
</ul>
<p>First you need to locate where the pins are soldered to the board. You need to remove all the solder from these joints.</p>
<p>If you have a desoldering pump (it looks a bit like a syringe with a sprung piston inside it and a release button on the side), this is the easiest way. Heat the pins until the solder has melted, keep the soldering iron on the joint, then at the same time touch the tip of the desoldering pump to the pin and press the button. This will instantly suck all the solder off the pin and into the tool.</p>
<p>If you have solder wick, this absorbs the solder by soaking it up into the wick. This won't remove it all though.</p>
<p>When you've got most of the solder off all the pins, nudge the pins with the tip of a screwdriver to release them from any final solder bonds, and you should be able to lift off the socket unharmed.</p>
<p>Do the same to the faulty socket, replace with the good one, and resolder.</p>
<p>Job done.</p>
|
<p>My Roland cube has stopped working, the guitar input connector for the main channel has been faulty for a while but now its gone completely. I opened it up and it looks like the connector is badly damaged.</p>
<p>I want to take the connector from the clean/line in channel at the back. Its the same connector as the main channel. I have a soldering iron. I am a noob. </p>
<p>Here is a photo of one of the sockets:<br>
<img src="https://i.stack.imgur.com/HtYY0.jpg" alt="photo of PCB"></p>
<p>How do I remove these connectors? Can I do it with just a soldering iron?</p>
|
Roland Microcube modification, need a hand
|
2011-02-04T19:05:37.500
|
9750
|
|sensor|light|
|
<p>Certainly there are microbolometers for this spectral range. They are called PIR sensor and are cheap and readily available as they are used in motion detectors.
See for example <a href="http://www.futurlec.com/PIR_D203B.shtml">this</a> (first Google result) sensor: 5-14µm</p>
|
<p>I want to detect light near 10 micrometer wavelength. It seems like photodiodes are mainly targeted for 1 micrometer range. Is there any detector/sensor for 10 micrometer wavelength ?</p>
|
IR-near visible light detection
|
2011-02-04T20:14:04.707
|
9757
|
|transistors|counter|
|
<p>It's possible to design a T flip-flop using two transistors, some capacitors, and some resistors. Start by wiring the transistors in a classic bistable multivibrator. Next, put small capacitors in parallel with the feedback resistors. The effect will be that if the circuit is sitting with one transistor on it will remain that way (the capacitors will enter a steady state where the cap that's in parallel with the feedback resistor that's passing current will be charged, and the cap in parallel with the other one won't be). If the circuit is disturbed slightly (e.g. by reducing the supply voltage by a volt) the charged cap will render its associated feedback resistor momentarily ineffective, causing its transistor to turn off. This will in turn cause the output of that transistor to float to its rail, turning on the other transistor. Depending upon the exact requirements, there are many variations of the circuit which may be used.</p>
<p>If your goal is to divide down a known frequency, another approach you could use would be to use some relaxation oscillators which can be "nudged", and then have each stage nudge the succeeding one. For example, suppose one wanted to output one high-going pulse every 3600 high-going pulses of a 60Hz signal (3600 counts). One could design a two-transistor circuit which would output a high pulse and discharge a cap every time the cap voltage reached 3.0 volts, or any time an input pulse was received and the cap voltage was over 2.0 volts. One could then cascade six such circuits which would cycle when fed pulses after delays of 75ms, 208ms, 875ms, 4.5s, 12.5s, and 52.5s (effectively yielding divide ratios of 5, 3, 4, 3, 5, 4). This approach might require some tweaking to ensure reliable operation, but it would a divide-by-3600 using twelve transistors rather than using twenty-four or more.</p>
|
<p>I am playing around with real implementation of basic logic schemes from transistors.</p>
<p>Could you suggest any compact implementations of T-trigger? Obviously, classic "CMOS" way eats way too many.</p>
<p>Other nonlinear elements are allowed (like tunnel diodes), diodes and other components does not counts.</p>
<p>I will need this to implement binary counter.</p>
|
T-trigger: minimum transistor count
|
2011-02-04T23:52:01.927
|
9769
|
|resistors|adc|impedance|
|
<p>How fast is your signal changing and how fast does your sample rate need to be?</p>
<p>If you have a slow (DC) signal, you can add a capacitor between the divider resistors which will supply the sample capacitor as a capacitor's impedance is very low. The capacitor just needs to be big enough to hold a steady voltage during the sample time. This limits your bandwidth significantly though as you now have an RC filter. It also limits your sample rate as sampling too fast can drain the capacitor. It needs time to stabilize between samples, the larger the resistor values the longer this time.</p>
|
<p>I'm using a maxim ADC in my application from this family: <a href="http://datasheets.maxim-ic.com/en/ds/MAX1304-MAX1314.pdf" rel="nofollow">http://datasheets.maxim-ic.com/en/ds/MAX1304-MAX1314.pdf</a></p>
<p>The devices have relatively low input impedance. If you look at Figure 5 in the above datasheet, on page 19, you can see the equivalent input circuit. My ADC is 0-5V range. My input signal however is in 0-10V range, so i have to reduce it to match the ADC.</p>
<p>If I use a resistive divider at the ADC input, it seems to me that I can not get a proper reading from the ADC due to the interaction between my 2 resistors, and R1 and R2 in figure 5. For example:</p>
<pre><code>| Vdiv
| Vin------Rdivider--------Rdivider---------> GND
| |
| |
| |
| R1 (3.33k)
| |
| | Csample
| |-------/ ------| |-------
| |
| R2 (5K)
| |
| |
| |
| v
| 0.9V
</code></pre>
<p>In the above figure, no matter what Rdivider values I chose, it seems to me that Vdiv will not be Vin/2.</p>
<p>Do I have to use an amplifier in the input for this case?</p>
|
ADC input circuitry and source impedance
|
2011-02-05T11:22:38.277
|
9772
|
|batteries|beagleboard|
|
<p>Because of regulator dropout, it will be hard to find an ideal regulator that can deliver >1A from four NiMH cells. Low dropout regulators typically have modest power, high power regulators typically have larger dropout.</p>
<p>I recommend you switch to 6 cells (7.2v); however I just don't use NiMH any more, lithium cells are so much better. Search for "protected 14500" on dealextreme.com, these AA-sized 3.4v laptop cells are awesome. The larger 18650 size is good too. </p>
<p>For 5v regulation, try the "Battery Eliminator Circuit" from a model helicopter (search for BEC or battery eliminator on dealextreme.com or a hobby site such as hobbyking.com). These regulators can handle way more current than you will use. eg <a href="http://www.dealextreme.com/p/8s-5a-switch-mode-ultimate-bec-ubec-45214" rel="nofollow">http://www.dealextreme.com/p/8s-5a-switch-mode-ultimate-bec-ubec-45214</a></p>
<p>Don't forget you can use your multimeter to measure how much current your beagleboard
is actually using, which will let you know both how beefy a regulator you will need, and
how long a battery life you can expect (factoring in the efficiency of your regulator).</p>
|
<p>I'm looking for a battery solution for the Beagleboard XM, which requires a 5V power supply. I currently have a simple 4x1.2V AA battery pack, but I'm not particularly satisfied with it:</p>
<p>1) It gets overcharged (~5.2V) and activates the overvoltage detector of the machine.</p>
<p>2) I have to remove the batteries from the pack to put them on a charger every time I need to charge them. I'd much prefer a solution that with no separate parts and one in which you don't need to move the batteries around.</p>
<p>The <a href="http://www.liquidware.com/shop/show/GL000149/BeagleJuice" rel="nofollow">BeagleJuice</a> is the closest thing I've found to what I'm looking for, but there's no version out for XM yet. </p>
<p>I'm embarrassingly electronics-illiterate, so I don't really know how to go about this. Any help?</p>
|
Battery-powering up a Beagleboard XM
|
2011-02-05T18:58:26.223
|
9774
|
|usb|esd|
|
<p>I have found this to be a good article that explains ESD protection: <a href="http://www.ti.com/lit/ml/sszb130b/sszb130b.pdf" rel="nofollow">System-Level ESD/EMI
Protection Guide</a></p>
|
<p>I am using a microcontroller (PIC32) with a USB interface. The USB interface will be often exposed to human body ESD discharges. Should I protect against these, and if so, how?</p>
|
USB ESD protection
|
2011-02-05T21:44:49.137
|
9777
|
|power-supply|
|
<p>A simple model of a real current source is an ideal source I_S in parallel with an internal resistance R_S. The current and voltage at the load R_L is as follows:</p>
<pre><code>I_L = R_S/(R_S + R_L) * I_S
and
V_L = R_L*I_L
= R_S*R_L/(R_S + R_L) * I_S
= (R_S // R_L) * I_S
</code></pre>
<p>As long as the load resistance R_L is much smaller than the internal resistance R_S, the load receives most of I_S. In this case the equivalent resistance of R_S in parallel with R_L is approximately R_L, and the source voltage is approximately <code>I_S*R_L</code>. In the extremely non-ideal case, the load resistance R_L is much larger than the source resistance R_S, and the load current I_L is then approximately zero. Also, the equivalent resistance in this case is approximately R_S, so the source voltage reaches its maximum of <code>I_S*R_S</code>. To make a current source as ideal as possible, it needs a large internal resistance to be able to source a high voltage.</p>
|
<p>How do constant current power supplies work? For example I have a power supply that is constant voltage that can supply up to 5A and I have a 12V motor that takes ~500mA so I crank up the supply to 12v and my motor pulls ~500mA from the supply. But how does this work for a constant current power supply? Would it determine its own voltage output depending on the resistance of the load(ohms law)?</p>
|
How do constant current power supplies work?
|
2011-02-05T22:51:16.020
|
9781
|
|laser|
|
<p>Maybe you will get direct links in other answers. I'd suggest googling for the particular components of a CD drive: CD focus, tracking, decoding, etc...</p>
<p>An even better method is probably to open a CD player (preferably an Audio CD because of low data rates) and to look at the signals using a scope. I have even done this with hard disks and it is pretty informative.</p>
|
<p>Can you point me some technical resources on how cdrom works and is it possible or lets say how easy to make a diy cdrom ? I am interested in reading and processing raw data from cd, not using a chip to decode EFM etc.</p>
|
reading raw data from a cdrom
|
2011-02-05T23:32:34.533
|
9784
|
|surface-mount|assembly|pcb-assembly|
|
<p>I've had a little job at an internship of soldering 250 small boards. It consisted of about 3 resistors, 1 SOT23, 1 chip and 1 capacitor (all SMD). It took a total of about 3 work days (x7 hours) to assemble them. Doing it by a company was expensive (very small run - only 1500 components) and we were interns, so you know how things work out.</p>
<p>That was about 12 boards per hour, but I am not an incredible good/fast solderer either. So expect 45 - 1 minute per component. Note that the chip was only a 6 pin device.</p>
<p>Unless you have a board that consists of 25x resistors of the same value right next to each other, it sounds that 9000 components is going to take you at least 10 workdays. </p>
<p>I can hardly imagine that sparkfun does their work by hand. It only is worth it in China when loans are a few dollars per hour. If you need to pay someone in a company environment and costs $10 - $15 per hour (which is cheap I suppose), that's still 15 - 20cts per component added.</p>
|
<p>What would be the average speed (an experienced) person would assemble surface mount components on to a PCB? Assuming they have desk that is correctly set up (pick and place station) and the PCB has solder paste already applied.</p>
<p>Reason for the question:</p>
<p>Pick and place machines talk about components per hour (CPM) speed, interested to know how to compare this against a person. Looking into doing small runs (100 units) of a product, need to determine if I hire staff or purchase a small scale pick and place machine instead.</p>
<p>I know Sparkfun say they do this sort of work by hand, but I have a part count of 90! </p>
|
what is an average CPH speed for hand SMD assembly?
|
2011-02-06T01:13:22.857
|
9792
|
|connector|
|
<p>There's generally only two important variables in spade connectors:</p>
<ol>
<li><strong>Blade</strong> (not socket) width (the thickness may vary as well, but it should be prescribed by whatever the width is), </li>
<li>and if it's on a wire (versus a board), wire gauge it accepts.</li>
</ol>
<p>Measure the blade width (I've only ever seen them specified in inch sizes, 0.187, 0.250...), and see if there's a good match on some parts catalogs (<a href="http://search.digikey.com/scripts/DkSearch/dksus.dll?Cat=1442842" rel="nofollow">here's</a> the Digi-Key category). After that, pick the one that fits a wire gauge that will safely carry your current.</p>
|
<p>I need to replace a plug on a mains powered device. It uses a specialised connector (to make it difficult for hobbyists, I guess) so I want to replace it with a standard mains plug. Unfortunately the cable connects to the PCB using some kind of spade/Faston connector, but there are millions of different variants of these and I have no idea which parts to buy! Does anyone know what it might be, from the photo below? It's kind of hard to get a good view, so let me know if a particular angle would help. The plastic cover is 9mm wide, and the metal receptacle is about 7mm wide. The device is rated at 24A, so I'm not sure if that means there is a special high-power variant needed.</p>
<p>Any ideas?</p>
<p><img src="https://i.stack.imgur.com/Juyr3.jpg" alt="In housing">
<img src="https://i.stack.imgur.com/Ks5Fc.jpg" alt="Alternate view"></p>
|
What kind of spade connector is this?
|
2011-02-06T04:21:55.610
|
9807
|
|arduino|stepper-motor|cnc|
|
<p>I know I'm a bit late to the forum but interestingly enough I have been working on a open source project called EMC-2-Arduino that can do exactly what you speak of and more...
ie:
Up to 9-axises of non-blocking synchronous stepper motor control.
Allow basic E-Stop, Power, Srart, Stop, Pause, Resume and Program Step inputs.
Software selectable microStepping down to 1/16th step
Basic serial interface control makes it easy to command via serial a link.</p>
<p>You can find the code at <a href="https://github.com/dewy721/EMC-2-Arduino" rel="nofollow">https://github.com/dewy721/EMC-2-Arduino</a></p>
|
<p>I'm building a CNC mill based on <a href="http://buildyourcnc.com/default.aspx" rel="nofollow">Patrick Hood-Daniel's machines</a></p>
<p>I'm also playing with Arduinos, and I'm beginning to wonder if I have this right:</p>
<p>I have 5v 1A steppers.</p>
<p>I'll be using <a href="http://linuxcnc.org/" rel="nofollow">EMC2</a> (Linux-based CNC) to run the whole thing and I had intended to feed the output from the Ubuntu box that's running EMC2 into an Arduino that then splits the data and sends it to three stepper drivers, probably built with sn754410ne h-bridges. </p>
<p>I had thought of possibly building the controllers with an ATtiny2313 per motor. </p>
<p>Is this overkill? Is the Arduino even required or can I feed the h-bridges directly from the EMC2 output?</p>
<p>My main worries are that the Arduino won't be able to control three motors concurrently, although there is a new library available: <a href="http://www.open.com.au/mikem/arduino/AccelStepper/" rel="nofollow">http://www.open.com.au/mikem/arduino/AccelStepper/</a> that purports to achieve this, and also that I won't be able to get half-stepping (or finer) with this setup.</p>
|
EMC2, Arduino & stepper motors - Have I got this right?
|
2011-02-06T18:50:19.633
|
9813
|
|bom|
|
<p>Here is a good online example of <a href="https://ciiva.com/bom-analyzer/bom/28b95450d55d4d7e9d34829cfc1419d5" rel="nofollow">Bill of Materials</a>. You can export the BOM to excel and save to local as a BOM template.</p>
|
<p>I'm an electronics newbie, and recently purchased empty PCBs for GoodFET and Ubertooth.</p>
<p>While trying to put together an order for all the parts in the bill of materials, I realized I'd very much like to have a computer parseable format I could dump into a parts search engine like octopart.</p>
<p>I started hacking up a simple website to do this using the octopart API but I can't find any sort of xml standard for a BoM.</p>
<p>Has anyone heard of such a thing? I'd be particularly interested in some sort of standard format that's available from gEDA, EagleCAD, etc</p>
|
Is there a text or markup standard for describing a Bill of Materials?
|
2011-02-07T02:41:39.260
|
9819
|
|spi|pcb-design|
|
<p>It depends on the edge rate. If it is driven by a fast general-purpose chip, e.g. a FPGA, then you might care. But at 25 mm you are ok unless the rise time is so very fast.</p>
<p>As @bt2 said, vias hurt signal integrity, but I wouldn't worry about it at this distance.</p>
|
<p>In my schematic, I have 4 SPI devices to hook together. I am going to operate the SPI up to 8MHz. Should I be concerned with installing damping resistors? source termination resistors? Should I route them in a star formation, or in a serial fashion? Does adding lots of vias hurt the signal integrity?</p>
<p>I also have to add that these devices are quite close together, within 25mm of each other.</p>
|
How should I route SPI lines?
|
2011-02-07T09:30:01.370
|
9824
|
|arduino|netduino|mbed|production|
|
<p>Generally speaking there is nothing wrong with using off-the-shelve products. We all do this at some level, I guess the Arduino-haters don't design their own chips, even tough at <em>some higher volume level</em> that would make economic sense.</p>
<p>It always boils down to cost, schedule and quality (and maybe long-term availability too). If an Arduino meets these criteria better than a custom board, the choice is a no-brainer.</p>
<p>The difficult part is to get the right figures, especially for your volume. But using the correct figures and little math will give you the break-even volume for the choice between uising let's say the Arduino versus a custom board. If that is way beyond what you expect, or way below, the choice is easy. So forget all advices that say either "by all means use an Arduino" or "always go for a custom board", they are both locked into a mindset that belongs to a specific volume level. Do your own calculations.</p>
<p>Note that I have no specific knowledge of the Arduino. You will have to decide for yourself whether it meets for instance your quality requirements.</p>
|
<p>Let's assume that the cost of goods is an insignificant factor. If a company lacks a team to produce a custom board for a particular product, but has success with an off-the shelf development platform like Arduino / Netduino / mbed, what sorts of things should be considered before going forward?</p>
<p>If I'm not mistaken, Arduino was originally targeting university students because of its low price and ease of use. It naturally became a popular platform for artists and makers. I see the Netduino as a logical extension of Arduino -- it allows people to use a robust and rich IDE (Visual Studio 2010) and get things done quickly via the .NET Micro Framework. mbed is another nice hobbyist platform because of its ease of use, free tools (online compiler), and hardware peripherals.</p>
<p>So my question is, why shouldn't companies adopt these development platforms for production usage? In other words, is it a bad idea to just buy several boards from Sparkfun, program each of them with the code, and then deploy the product to customers?</p>
<p>I'm specifically interested in Netduino, but arguments for / against Arduino and mbed are also welcome. On the flip side, would you, or have you done this before?</p>
<p>I personally look at the Netduino development as a "core module" that other processor manufacturers sell for product integrations, but maybe I'm missing something important here.</p>
|
What makes a particular platform suitable or unsuitable for production use?
|
2011-02-07T14:32:09.030
|
9850
|
|computers|
|
<p>It's simply for covering the back of the computer, and for shielding your inputs and outputs from being jarred around and damaged when you're plugging in and unplugging things. Some people on this thread seem confused. Because it has "shield" in the name, people think it's shielding against current or EMF. It has nothing whatsoever to do with current, or EMF interfering with radios or anything else. I use radios, I also have no covers on my computer, side front or back. To add to that, the radio I have right now is inside my computer. It's really only aesthetic, there to look good because as a shield for your inputs and outputs most of them are fairly useless without being actually attached to the board and solid rather than thin and flimsy.</p>
|
<p>What purpose does the IO shield on computers serve? I have been reading a lot of articles (mostly forums) on the internet and can't seem to find a definitive answer.</p>
|
What is the purpose of an IO shield on a computer case?
|
2011-02-08T07:49:22.840
|
9855
|
|rs232|emc|antistatic|
|
<p>A simple, although not cheap, solution is something like the ADUM1447 and its family members. I don't think you can top that.</p>
|
<p>My company sells devices many devices that use RS-232 line transceivers like the MAX232 chip. In many cases our users run their RS-232 cables in the range of 30 to 50 feet to connect our device to their PC. Over the years we have seen many boards come in for repair because the serial communication stops working and the problem can often be fixed by simply replacing the MAX232 line transceiver. </p>
<p>My guess is that the long serial cable is acting as a giant antenna for EMI or static and the transceiver can only take so much. In our next board design we want to go with a surface mount chip which will be much more difficult to "pop-out" and replace if the problem occurs again. Is there a way that I can protect this chip against such problems without increasing the cost of the board/components greatly?</p>
|
Is there a way to protect RS-232 Transceiver IC from static death
|
2011-02-08T15:02:02.663
|
9865
|
|radio|emc|
|
<p>The other answers here are mainly on track, but one aspect they haven't mentioned is <em>proximity</em>. When I hear interference from a GSM device, it's usually when someone is standing within 2-3 feet of a land-line telephone or telephone-related device (my home answering machine and the conference phones at my office are the main victims I've noticed). </p>
<p>However, the radiated emission limits (both FCC and CE) are based on limiting the emissions from the radiator at a distance of 10 m or more. This means the regulations are not designed so much to ensure that two devices sitting right next to each other won't interfere, but to sure that your phone doesn't interfere with a device in the next room, or in your neighbor's house. </p>
<p>In part, the specification at 10 m distance is simply meant to ensure a uniform test condition, because it gives a reasonable distance for "near-field" radiation effects to have fallen off and ensure the measured radiation pattern will be consistent with the interference effects at any distance in the far field. </p>
<p>But also, the regulations were developed in consultation with electronics manufacturers and they would have considered that trying to reduce radiation to a level where they won't interfere with each other at 0-1 m distance would increase costs (as alluded to in Leon's answer) to a point that would make many consumer electronic products unsaleable. </p>
|
<p>It seems that to sell a GSM mobile phone, companies like Apple, Motorola, Sony Ericsson and many others invest a considerable amount of money in EMI testing them. Yet they still interfere with my stereo, radio, computer speakers, and other devices. Why?</p>
|
If mobile phones have to go through such extensive FCC/CE/EMI testing, why do they interfere with my radio?
|
2011-02-08T17:15:51.463
|
9873
|
|avr|power-supply|decoupling-capacitor|
|
<p>Your solution is way overkill, and if you would use this in a professional design, the review team should disapprove of it for cost reasons. </p>
<p>Decoupling capacitors are there to cover minor dips in the power supply because of fast switching in the controller. The more complex the controller (i.e. the more transistors switch simultaneously) and the faster the switching the deeper the dips. That's because the PCB's traces' inductance prevents the power supply to deliver the extra power quickly enough. So the decoupling capacitor acts as a local power buffer. You can calculate and measure what capacitance is needed but everybody gets away with just placing 100nF. The smaller ones are not necessary. </p>
<p>The inductor's task is to filter ripple from the power supply, but unless you have a very poorly designed power supply this isn't necessary either. As a matter of fact, a few mV ripple are less harmful to the microcontroller's operation than the switching dips.<br>
An inductor or small series resistor is recommended however if your digital supply is also used to power analog parts like an ADC, which often has separate power pins.</p>
|
<p>I've read the datasheet and the application notes elated to AVR Hardware Design Considerations and EMI. From them and various Internet sources I came up with pictured design for power supply circuit for <a href="http://www.atmel.com/dyn/products/product_card.asp?PN=ATmega162" rel="nofollow noreferrer">ATmega162</a>. AVR would be connected after C3. Right now, I plan to run the device form its internal clock source, but later I plan to try with external 16 MHz crystal.</p>
<p><img src="https://i.stack.imgur.com/8hA2E.png" alt="Image 1"></p>
<p>There are few things I'm not certain about. First, I'm I overdoing it with 4 capacitors near the microcontroller? Some sources say that decoupling capacitors should be placed in decades while some say that the 100nF is enough. I was thinking about using multilayer capacitors for 100 nF and 10 nF and ceramic disk for 1 nF. Would that work? </p>
<p>Next point is the inductor. In one document, it is placed between the electrolytic capacitor and in the other document between last capacitor and power supply. Which location would be better? I'm thinking about placing it after last capacitor close to the microcontroller, but the HDC document made me uncertain about that. As far as I understand it, coils do their best to keep current constant, so the coil should prevent spreading of pulses as the controller switches states.</p>
<p>AVR Hardware Design Considerations recommend tantalum electrolytic capacitor. Is there any special reason for that? </p>
<p>On the board, I'd place a MAX232, couple of 20 mA LEDs and 2*16 character LCD screen. What decoupling capacitor should I use near the power connector of the board?</p>
|
Would pictured circuit be good enough to power ATmega162?
|
2011-02-08T18:58:38.357
|
9877
|
|wire|
|
<p>If space is tight check out Alpha's Ecowire, which has thin but very tough insulation, so the overall diameter is less than PVC wire of the same copper cross-section.</p>
|
<p>I have an 11.1v lithium polymer battery pack which has 1300 mAh capacity and has a 20 C rating. Therefore I figure the maximum amperage the battery can supply is 26 A. (C * mAh / 1000<sup><a href="http://www.cheapbatterypacks.com/?sid=764526&apage=faq.asp" rel="nofollow" title="See: 'What does the C mean in 10C, 20C etc ?'">1</a></sup>) To be safe, I figure the wiring I use with it should be able to handle 30 A in case a higher capacity battery is used later. I figure that I can safely use an ~11.1 V, 1500 mAh, 20 C battery at that current.</p>
<p>The circuit this will be used in has a momentary switch (trigger) and a DC motor. (<a href="http://i235.photobucket.com/albums/ee12/aces31767/MOSFET-WiringDiagram.jpg" rel="nofollow" title="Wiring diagram, see: 'Stock Wiring' (top left)">Airsoft gun wiring diagram</a>) There will be about a foot and a half of wire from battery terminal to battery terminal. The circuit under nominal conditions would be under load for no more than half a second every few minutes. However it could potentially be under continuous load for up to 5 seconds with an average of those cases being 3 seconds.</p>
<p>The problem is, the wiring has to fit through small passages. And I need to use the smallest possible wire gauge that will handle the current. I currently have some stranded copper 18 AWG wire for automotive use. I'm pretty sure that this will not handle the current this battery is likely to supply<sup><a href="http://www.powerstream.com/Wire_Size.htm" rel="nofollow" title="AWG Table">3</a></sup>. From memory, (without measuring the clearance of the passages) 18 gauge wire seems to be an ideal size, though I think I really need 14 gauge wire to handle the current if it's just stranded copper.</p>
<p>I have trouble finding any easily understood documentation on the subject and there are so many variables to consider. Such as the length of the wire, the diameter of the strands (if stranded), the number of strands, the coating (if any), the ambient temperature, etc.</p>
<p>My research leads me to believe that if I were to get some 18 or 16 gauge wire with silver coating and a thin insulator (teflon?) that it would fit the bill. <strong>What is the proper gauge (solid or stranded), coating, and/or insulation for this application?</strong></p>
<p><strong>Update</strong>: I added "duty cycle" information to paragraph 2.</p>
|
What wire do I need to carry 30 A for 18"?
|
2011-02-08T19:42:48.210
|
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