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11823
|
|sensor|temperature|linux|
|
<p>If you don't want to use a solder iron, these might be of some interest:</p>
<p><a href="http://www.yoctopuce.com/EN/products/usb-sensors/yocto-temperature" rel="nofollow">http://www.yoctopuce.com/EN/products/usb-sensors/yocto-temperature</a></p>
<p><a href="http://www.phidgets.com/products.php?category=6" rel="nofollow">http://www.phidgets.com/products.php?category=6</a></p>
|
<p>I'm looking for a temperature sensor, that can be connected to a computer over an interface that is ubiquitous, like USB. I'd like to read the temperature data over the command line.</p>
<p>Any suggestions what I could use?</p>
<p>All I plan to do, is measure the ambient temperature in the vicinity of the computer, for instance 2m above it.</p>
<p>I can access internal sensors with <code>sensors</code>, of the <code>lm_sensors</code> package. If possible, I'd like a similar interface.</p>
|
Temperature sensor for Linux
|
2011-03-22T11:24:49.187
|
11825
|
|design|digital-logic|
|
<p>I think what you're asking is for a method to build an reversible/bidirectional circular/ring shift-register. </p>
<p>The main concept behind the shift-register is to shift all bits in a direction. You may accomplish it by using some flip-flops as here:</p>
<p><img src="https://i.stack.imgur.com/0oxSW.png" alt="http://en.wikipedia.org/wiki/Shift_register"></p>
<p>You may see that the data in is shifted to the right each time the clock ticks. The main concept is that the flip-flop keeps its status while the clock is down and transfers it to its output when the clock is up. In order to make it reversible you need to insert some digital circuitry that choose if the input (D) of the flip-flop will be: 1) the output of the flip-flop before itself or 2) the output of the flip-flop after itself.</p>
<p>One example of bidirectional shift register is presented in this site</p>
<pre><code>http://eelab.usyd.edu.au/digital_tutorial/part2/register06.html
</code></pre>
<p>In order to make any shift-register circular you just need to connect the output wire to the input.</p>
<p>If the pattern to be shifted needs to be pre-set to an specif value you may act in the R/S lines, resetting or setting each flip flop to the desired value.</p>
|
<p>I have :</p>
<pre><code> four outputs :
a, b, c, d ( four output pins )
</code></pre>
<p>Assume I have one insect, let us say it jumps one step at a time and I can control its direction.<br>
If input <code>DW = 1</code> it goes right to left; else it goes left to right. </p>
<pre><code> clock clk :
DW = 0
( clock goes left to right )
0 1 1 0 ( means b,c = 1, assume rightmost-1 is head of the insect and it goes right )
0 0 1 1 ( now, c and d are 1 )
1 0 0 1
1 1 0 0
after operation on combinational and sequential circuit
DW = 1
clock clk :
( now, it goes right to left )
1 1 0 0 ( a, b = 1 ) ( assume leftmost-1 is now head of the insect and it goes left )
1 0 0 1 ( a, d = 1 )
0 0 1 1
0 1 1 0
1 1 0 0
</code></pre>
<p>How can I construct that circuit ? To construct it, which topic I should (re) read or Can you recommend any web-page?</p>
|
manipulation on clock output
|
2011-03-22T11:32:04.937
|
11827
|
|audio|operational-amplifier|
|
<p>This morning, the device works, as far as I can tell, just as expected. I think it has to do with extensively bathing the PCB in alcohol. I use this flux which is conductive and has proven quite hard to remove, and it's also called "FU". No, really. The 3.5V at the + input of the opamp is probably due to my DMM's input impedance. Clipping is because of my amp, and the volume is OK. Made a lot of silly mistakes, haven't I? There's still a lot to learn before I can call myself an electronics engineer.</p>
<p>Thanks everyone for the advice, you've given me some useful insights. Now, onto the bottom half of the schematic (relays), which I built beforehand, which previously worked, and which is probably going to give me some more hell until I get it to do what it has to...</p>
|
<p>I'm building a circuit that allows me to blend a guitar effect in and out, based on <a href="http://www.geofex.com/Article_Folders/panner.pdf" rel="nofollow noreferrer">>this<</a> (page 2, bottom circuit). I have, however, replaced the 10k pot and the 15k and 51k resistors with 100k, 150k and 510k.</p>
<p>The blending works fine, however the volume is too low, and the blend pot is prone to noise when in the middle position, which makes me think of an impedance problem. Do I have to replace the 1M resistors at FX in and FX out with 10M ones?</p>
<p>Also, the circuit clips quite early. I checked the voltages at the opamp's pins, and, while the second half is OK, the first half has 3.5 at the non-inverting input and 4.5 at the inverting one and at the output. Those should all be within 10mV from each other, right? Try as I might, I couldn't make it right.</p>
<p>I'm in kind of a hurry, and this pedal has already taken me more time than I could possibly give. I'll be immensely thankful if somebody pointed me in the right direction.</p>
<p>Here's my schematic. Right click and choose "view image" to see it in full.
<img src="https://i.stack.imgur.com/TQ7uX.png" alt="schematic"></p>
|
troubleshooting GEOFEX guitar effect panner
|
2011-03-22T11:54:17.617
|
11833
|
|spi|sd|
|
<p>Part 1 of the "<a href="https://www.sdcard.org/downloads/pls/" rel="nofollow noreferrer">Physical Layer Simplified Specification</a>" of SD Cards, Version 8.00 on page 263 (Figure 7-1: SD Memory-Card State Diagram (SPI mode)):</p>
<blockquote>
<p>Note: SDUC card, card can stay at busy status and does not reply ready
to host during ACMD41 to let host know SDUC card cannot use SPI mode.</p>
</blockquote>
<p>EDIT: ...and thick and underlined on page 262:</p>
<blockquote>
<p>SPI Mode is not supported by SDUC cards.</p>
</blockquote>
<p>So at least Secure Digital Ultra Capacity (SDUC) cards (that is > 2TB I think) do not have to support SPI.</p>
<p>I experienced the same phenomenon with several SDHC cards as well and try to figure out what's the issue at the moment. In a project about 5 years ago, I also had the problem that with a FatFs library, some cards simply couldn't be used.</p>
<p>In a nutshell: I wouldn't bet on it. Try different cards and also consider using other types of memory.</p>
<p>EDIT, a few days/weeks after: Ok, finally got all of the three SD cards I had from different manufacturers working. I shared the initialization steps here: <a href="https://electronics.stackexchange.com/questions/602105/how-to-initialize-use-sd-cards-with-spi/">How to initialize/use SD cards with SPI?</a></p>
|
<p>Have you ever encountered an SD card which does not support the SPI mode?</p>
<p>I read microSD are not required to but I believe all do support SPI.</p>
<p>EDIT: The information about optionality of SPI seems to come from Wikipedia and was recently removed (<a href="https://en.wikipedia.org/w/index.php?title=Secure_Digital&diff=415230469&oldid=415228902" rel="nofollow noreferrer">here</a> and <a href="https://en.wikipedia.org/w/index.php?title=Secure_Digital&diff=412862593&oldid=412855668" rel="nofollow noreferrer">here</a>).</p>
|
Do all microSD cards support SPI mode?
|
2011-03-22T13:09:41.143
|
11840
|
|connector|ffc|
|
<p>Manufacturers' crimp tools are precision-engineered for their connectors, and actually create a cold weld between the terminal and the wire. It's impossible to make a reliable connection without the correct tool. Distributors will usually make up cables for customers, using the correct tooling, even in prototype quantities.</p>
|
<p>After much experimentation and some <a href="https://electronics.stackexchange.com/questions/5620/mechanical-connectors-for-flexible-pcbs">helpful</a> answers <a href="https://electronics.stackexchange.com/questions/9147/tips-for-wire-to-pad-and-wire-to-wire-soldering">here</a> I've decided that <a href="http://portal.fciconnect.com/res/en/pdffiles/datasheets/950500-025_FPC-Clincher2.pdf" rel="nofollow noreferrer">FCI "Clincher"</a> (.pdf link) parts are the right answer for adding connectors to the ends of <a href="http://www.alibaba.com/product-gs/318410435/ZJ168_Dream_color_strip.html" rel="nofollow noreferrer">flexible ZJ168 RGB LED strip</a>.</p>
<p>The parts themselves are cheap enough (< $2 each) but the crimping tool appears to <a href="http://parts.digikey.com/1/parts/356767-tool-hand-crimp-clincher-series-ht270.html" rel="nofollow noreferrer">cost almost USD$2500</a>! I certainly can't afford that and in any case Element 14 here in Singapore (from whom I got the connectors) don't have any crimpers in stock and can't hire/lend me one.</p>
<p>I've had a modicum of success crushing the crimps down with the tip of my pliers but can someone suggest something more elegant and/or foolproof? Are there any un-obvious flaws with attempting to crimp these without the proper tool?</p>
|
Ghetto crimping tool for FCI "Clincher" connectors?
|
2011-03-22T14:50:22.660
|
11844
|
|power|mosfet|ups|
|
<p>I think Magic Sinewaves is essentially the sames as "selective harmonic elimination", a well known method in Power Electronics.</p>
<p><a href="http://web.eecs.utk.edu/~tolbert/publications/trans_pe_mar_2004_complete.pdf" rel="noreferrer">This paper</a> has a description of the theory and some experimental results.</p>
|
<p>For several years now Don Lancaster is promoting <a href="http://www.tinaja.com/glib/sinquest.pdf">magic sinewaves</a>. They are strings of binary digits (like 420 bits for a full sine cycle) that, when used to drive a digital switch (MOSFET/IGBP), result in quite a clean sinewave (only very high harmonics remaining). For more details, please read the linked article or any other he wrote on that matter.</p>
<p>Had anybody actually used these for anything? The idea seems quite useful but I cannot find any information about these (that did not come from Lancaster himself).</p>
|
Don Lancaster's Magic Sinewaves
|
2011-03-22T15:45:21.243
|
11847
|
|voltage|generator|
|
<p>Almost all are piezo-electric. Check <a href="http://en.wikipedia.org/wiki/Piezo_ignition" rel="nofollow noreferrer">this Wikipedia page</a> for info:</p>
<p>Piezo ignition is a type of ignition that is used in portable camping stoves, gas grills and some lighters. It consists of a small, spring-loaded hammer which, when a button is pressed, hits a crystal of PZT or quartz crystal. Quartz is piezoelectric, which means that it creates a voltage when deformed. This sudden forceful deformation produces a high voltage and subsequent electrical discharge, which ignites the gas.</p>
<p>And as Christopher Biggs commented: </p>
<blockquote>
<p>the dielectric strength of dry air is about 33kV/cm, so if the spark jumps 2mm it has to be at least 6600v</p>
</blockquote>
|
<p>On some gas grills, there is a button you push which creates a spark to ignite the gas (propane, natural gas etc.)</p>
<p>My questions are probably pretty simple: </p>
<p>How does the button create the spark?</p>
<p>What voltage is this spark?</p>
|
How does a gas grill starter spark work?
|
2011-03-22T17:53:51.753
|
11850
|
|radio|receiver|transmitter|
|
<p>All of this assumes you are in the US. </p>
<p>My understanding of the associated FCC rules is: You cannot modify or create an FRS, GMRS or MURS radio without going through FCC certification (legally, Part 95 rules). You can create up to 10 ISM band transmitters (Part 15 rules) for research and development or experimentation as long as the transmitters meet the FCC technical requirements for part 15 ISM transmitters. This means you can use parts like the AT86RF212 (which is available in modules) and an audio codec like G.711, G.729 (now patent free) or SILK/OPUS to convert the analog audio to a digital stream. G.711 can be implemented on any microcontroller, G.729 or SILK generally require an ARM running at 72Mhz (or equivalent in other processors like the PIC32s).</p>
<p>Using a codec and a digital transmitter is a little more difficult but much more interesting from a project perspective. You can also transmit data including GPS, inertial sensor data, biometric data, etc. If you do go with the AT86RF212 or a module using that chip, you can expect most of a mile @ 100Kbps (line of sight) or several miles @ 40kbps or with an external power amp.</p>
<p>If you want to experiment, take a look at the <a href="https://freaklabsstore.com/index.php?main_page=product_info&products_id=211" rel="nofollow noreferrer">FreakDuino 900Mhz boards</a>. You will only be able to do G.711 with the processor on that board but you can get started really quickly. G.711 required 64Kbps, do you'll need to run at least 100kbps for your on-air data rate. The board also has an RF power amp, and the two boards I have did meet FCC rules for part 15.</p>
|
<p>I'd like to build a set of miniature two-way (half-duplex) radios that operate on the FRS band. It seems that transceivers for this band would be widely available. However I've not been able to find any. Ideally they would be controlled digitally (I'm thinking to use a PIC controller) and have analog inputs and outputs for earbuds and a microphone. Where can I find a transceiver?</p>
<p>I was planning to use <a href="http://www.sparkfun.com/products/9582" rel="nofollow">this transceiver from Sparkfun</a> but it doesn't look like there will be an easy way to get an analog output and input. </p>
<p>I'd actually not mind building a basic transceiver from scratch but I can't find a good tutorial or set of schematics.</p>
|
Walkie-talkie transceiver
|
2011-03-22T19:18:05.020
|
11859
|
|lcd|repair|
|
<p>Isopropanol didn't work for me to clean the rubber remains of the zebra stripes on the LCD glass..
Instead I used Nitro thiner on a cotton bud and it worked like a charm!!!</p>
|
<p>To repair something, I had to disassemble it. Unfortunately, it had an LCD, and that used an <a href="http://en.wikipedia.org/wiki/Elastomeric_connector" rel="noreferrer">elastomeric connector</a> to connect to the LCD. Now I have an LCD, a PCB, and a spare elastomeric connector. I can occasionally get the LCD to work if I put them together, but it will not stay there, and the connection is very dodgy. Is there an easy fix?</p>
<p><img src="https://i.stack.imgur.com/hDKgv.jpg" alt="enter image description here"></p>
|
I took apart an LCD module. How do I fit it back together again?
|
2011-03-22T21:45:33.240
|
11861
|
|eaglecad|
|
<p>In eagle 6.4 and I assume newer versions also, you have the dimension button (2 vertical parallel lines with arrow between them). When you click on it, you can measure the distance between the centers of 2 objects.</p>
|
<p>How do I easily measure how far apart two objects are in EAGLE 5.11.0 Light? Is the easiest way to record the coordinates and subtract?</p>
|
How to measure component distances in EAGLE PCB
|
2011-03-22T22:31:00.063
|
11868
|
|gps|
|
<p>The rules known as CoCom are discussed here: <a href="http://en.m.wikipedia.org/wiki/CoCom" rel="nofollow">http://en.m.wikipedia.org/wiki/CoCom</a></p>
<p>Australia is a signatory.</p>
<p>There is a nice discussion of GPS units suitable for High Altitude Balloons (HAB) at not surprisingly the UK High Altitude Society (UKHAS) here:
<a href="http://ukhas.org.uk/guides:gps_modules" rel="nofollow">http://ukhas.org.uk/guides:gps_modules</a></p>
<p>By the way the Geohelix GPS cited is no longer produced as the company has gone out of business.</p>
|
<p>I have a problem concerning GPS units. I have been studying on a project for a weather balloon which will go about 30 - 40km up. Now I do know that some GPS units have a limit on how high they can receive/show you the location whether it is a limitation made by the military to stop random production of cruise missiles and others which just don't work above a certain height. This is a problem as my weather balloon does go to a height which could be considered as a "GPS fail zone". At the moment I am using a 50 Channel D2523T Helical GPS Receiver - <a href="http://www.sparkfun.com/products/9566" rel="nofollow noreferrer">http://www.sparkfun.com/products/9566</a> . It’s a great product but I am worried with problems with height etc. Could anyone give me some ideas on GPS units or give me advice....Any help is greatly appreciated....P.S - The unit has to have the standerd GGA protocol.</p>
|
GPS Units - Weather Balloon
|
2011-03-22T23:43:49.263
|
11879
|
|capacitor|resistors|math|laplace-transform|
|
<p>Using the Laplace transform in circuit analysis works just like normal complex analysis. You just plug \$s\$ instead of \$j\omega\$ everywhere.</p>
<p><img src="https://i.stack.imgur.com/ze4js.png" alt="Laplace circuit analysis rules from Wikipedia"></p>
<p>The interesting part comes after you calculate one thing or another since you can use Laplace transfer function to <a href="http://en.wikipedia.org/wiki/Bode_plot#Rules_for_hand-made_Bode_plot" rel="nofollow noreferrer">draw a Bode (frequency and phase response) plot</a> or to <a href="http://en.wikipedia.org/wiki/Laplace_transform#Example_3:_Method_of_partial_fraction_expansion" rel="nofollow noreferrer">calculate the circuit's response to any stimulus</a>.</p>
|
<p>I'm expecting a midterm question about the circuit below that involves the equation t=RC and using a Laplace transform. We won't actually be using differential equations. Memorizing a certain equation is all we need, but we're not told what it is. I've found a lot of equations when looking up Laplace transforms. Which equations would be helpful for analyzing this circuit, and where in the circuit could they be applied?</p>
<p><img src="https://i.stack.imgur.com/KO8me.png" alt="enter image description here"></p>
|
How would a Laplace transform be useful in analyzing this circuit?
|
2011-03-23T05:54:27.407
|
11884
|
|gps|
|
<p>Why more than 12 channels?</p>
<p><strong>The number of channels inside a Navigation receiver is definitely more than a marketing gag.</strong> It is the question how many data you can and want to handle to use a wide spectrum of different navigation systems of similar kind. Please keep in mind that this satellite systems are useful for a big variety of applications (ship - , car-, rail- and airplane navigation, geodesy, timing, monitoring of earth, buildings ionosphere, weather forecast, so on and so on....) and therefore also the variety of receivers (supporting different channels) is wide. </p>
<p>Current high-end geodetic GNSS receivers (for multi-constellation) come around with more than 216 and up to 440 channels. Receivers used for mobile applications uses 66-200 channels. The number of channels has also noting to do with the number of correlators. Each channel can have his own number of correlators. It is true that the number of correlators to reduce the seach space is importens to get a good and stable TTF (time to first fix).</p>
<p>Very important - and thats is described in answer of adam davis: you need one channel per signal per satellite. Since the design of the navigation signals varies (diferent singal strength, modulation, bandwith etc.) you have to prepare the receiver to be capable for any navigation system you would like to add for your position solution. </p>
<p>Lets make a small overview of differnt kind of Navigation systems:</p>
<p><em>Navigation Systems:</em></p>
<ul>
<li>GPS (America)</li>
<li>GLONASS (Russia)</li>
<li>Beidou/COMPASS (China)</li>
<li>Galileo (Europe)</li>
</ul>
<p><em>... and furhtermore Augmentation Systems and regional navigation Systems, which use same/similar frequencies and Navigation messages, which can be used by the same signal aquisition technique:</em></p>
<ul>
<li>QZSS (regional System: Japan, Quasi-stationary)</li>
<li>IRNSS (regional System. India)</li>
<li>EGNOS (augmentation system Europe)</li>
<li>WAAS (augmentation system America)</li>
<li>OMNISTAR (private augmentation system) </li>
</ul>
<p>So lets count and come back to the per satellite/per signal discussion (exzerpt): </p>
<ul>
<li>GPS: L1,L2,L5 (L5 counts 2 times since there are subchannels inside the signal - the I (in-phase) and Q(quadphase) component for example)</li>
<li>GLONASS: L1 L2 L3 (also GLONASS uses subchannels for code division multiple access (CDMA) signal aquisition) </li>
<li>Galileo (E1, E6 (secure signal), E5a E5b E5a+b (wideband signal))</li>
<li>please refer to the current signal plan for each system and also to the reciever overview (furhter reading)</li>
</ul>
<p>So if you like to track one GPS Satellite with L1 and L2 and L5a+b you need 4 channels. For a first fix you need 4 Satellites which menas, you need 8 channels only for a direct poisiotn solution without any redundance. The more GPS satellites the more the redundance (and integrity). <em>To speed up:</em> in this configuration you are only able to track 5 GPS Satellites with L1/L2 and L5. For my understanding a weak solution. But if you only consider L1 measurements - than of corse, you are able to track 12 satellites. So the more the channels the more the receiver (or baseband processor) has to work. This belongs on the capability of your chip - ... and definitely the number of useful observations and data for your application. At any time the quastion has to be: </p>
<ol>
<li>What do I want for my application?</li>
<li>How many data I need to get a reliable solution?</li>
<li>How much processing capabilities I have to get reliable solution?</li>
<li>How much I want/have to control my solution?</li>
</ol>
<p>for further reading:</p>
<ul>
<li><a href="http://www.navipedia.net/index.php/Generic_Receiver_Description" rel="nofollow">a very good receiver description from ESA</a> </li>
<li><a href="http://gpsworld.com/wp-content/uploads/2014/02/GPSWorld_2014ReceiverSurvey.pdf" rel="nofollow">2014 GNSS reciever survey</a></li>
<li><a href="http://gpsworld.com/multi-constellation-dual-frequency-single-chip/" rel="nofollow">Article of Multi-constellation receiver on one single board (GPS World)</a> </li>
<li>Aviala-Rodriguez et al. (2007): The MBOC Modulation, Indside GNSS, 2(6):43-58 (<a href="http://www.insidegnss.com/node/174" rel="nofollow">online</a>)</li>
<li>Guo et al. (2013): Building a Wide-Band Multi-Constellation Receiver, GPS World, 24(3):36-42</li>
<li><a href="http://www.navipedia.net/index.php?title=Galileo_Signal_Plan&oldid=12522" rel="nofollow">Galileo Signal Plan</a></li>
<li><a href="http://www.navipedia.net/index.php/GPS_Signal_Plan" rel="nofollow">GPS Signal Plan</a></li>
<li><a href="http://www.navipedia.net/index.php/GLONASS_Signal_Plan" rel="nofollow">GLONASS Signal Plan</a></li>
<li><a href="http://www.navipedia.net/index.php/COMPASS_Signal_Plan" rel="nofollow">COMPASS Signal Plan</a></li>
</ul>
|
<p>You need 4 channels to determine your position (including elevation), and I can understand that a few extra channels increase accuracy. However, there are maximum 12 satellites in view at any time, so why have receivers with more channels? I've seen receivers with 50 or even <a href="http://www.sparkfun.com/products/8975">66 channels</a>, that's more than the number of satellites up.<br>
I don't see any advantages in this explosion of number of channels, while I presume that it does increase the receiver's power consumption.<br>
So, why do I need 66 channels?</p>
|
How many GPS channels make sense?
|
2011-03-23T08:25:08.883
|
11886
|
|matlab|
|
<p>Besides SCAM in Matlab, there is also a slick online symbolic circuit analysis tool at <a href="https://circuitnav.pythonanywhere.com/" rel="nofollow noreferrer">CircuitNAV</a>, which uses netlist files (from LTspice, Micro-Cap, TINA-TI, PSpice, etc) as the input and generates the algebraic solution for each circuit parameter.</p>
<p>CircuitNAV also provides a <a href="https://www.youtube.com/watch?v=mVk6TzEtQYE" rel="nofollow noreferrer">demo</a> and a <a href="https://www.youtube.com/watch?v=iLSRXXUobSE&t=8s" rel="nofollow noreferrer">tutorial</a>.</p>
|
<p>I often hear of people using Matlab for circuit analysis, but I never actually figured out how it is done. I assume that there is something more to it than just setting up equations by hand and solving them in Matlab.</p>
<p>I'm looking for a good starting point.</p>
|
How to do circuit analysis using Matlab?
|
2011-03-23T08:45:30.020
|
11895
|
|power|resistors|ratings|
|
<p>I cannot say for sure who the manufacturer of this part is. I've used many of these sorts of resistors in my career, so my speculation below is made with a fair degree of confidence.</p>
<p><a href="http://www.renfrewelectric.com/prod_resistors_2.html" rel="nofollow">Renfrew wire-wound resistors</a> that are 8" long and 1 1/8" in diameter are rated at 160W, which correlates with the 160D marking on the part. I'd hazard to guess that it's rated 160W (or very close to that). </p>
<p>R5 on these sorts of parts usually implies 0.5 ohms. The other marks are probably tolerance and packaging codes. If you measure higher, and your meter is OK, the resistor may be somwhat fried.</p>
|
<p>I have this wire-wound power resistor that appears to be either ceramic or porcelain in construction with a soft brown plastic or vinyl like coating. I want to find out its power rating. My meter shows about 5.2 ohms. A Google search for 160DR5WL returns nothing. </p>
<p><img src="https://i.stack.imgur.com/CyCct.jpg" alt="enter image description here"></p>
<p><img src="https://i.stack.imgur.com/EQMLl.jpg" alt="enter image description here"></p>
<p><img src="https://i.stack.imgur.com/B3SZd.jpg" alt="enter image description here"></p>
<p><img src="https://i.stack.imgur.com/g3qIB.jpg" alt="enter image description here"></p>
|
Need help identifing the power rating for this resistor
|
2011-03-23T13:42:32.013
|
11899
|
|power-supply|power|energy|
|
<p>Another point not yet mentioned is that energy-conversion devices (be they electronic, mechanical, chemical, or whatever) lose energy through a number of mechanisms. Some mechanisms waste energy proportional to the amount of energy being converted, while others waste energy largely independent of the energy being converted. A device which could convert 0-100W of power with 0.1W of waste would appear to be 99.9% efficient when used to convert 100 watts, but less than 1% efficient when being used to convert 1mW. In reality, most devices lose energy through a combination of mechanisms, some of which are proportional to the amount of energy converted, but there are design tradeoffs. For example, suppose the above device is used for a minute a day, and one could change the design to reduce the "constant" energy loss to 0.05W in exchange for accepting a 50% loss in conversion efficiency. Saving 0.05W continuously would make up for the loss of 50W during the minute of use, but dissipating 50 watts for a minute in a small device would cause it to get very hot, which might cause problems in and of itself.</p>
|
<p>Each electronic device consumes electric power when it is "idle" unless it has a mechanical switch. I can understand that for example a TV with a remote control needs to "be ready" to receive a command from the remote control. But even a cell phone charger consumes power when it is connected to the outlet and not connected to the phone.</p>
<p>For example, Nokia claims that one of its new chargers <strong><em>consume less that 30 milliwatts</em></strong> when not connected to the phone and they say it is very cool. I don't understand - the charger is a very simple device, what does it do with those 30 milliwatts?</p>
<p>Why can't this standby consumption me made lower when we already have microprocessors with gazillions of transistors fitting onto a plate size of fingernail? What's the fundamental problem here?</p>
|
Why is it so problematic to have close to zero standby power consumption?
|
2011-03-23T14:47:25.090
|
11914
|
|batteries|battery-charging|
|
<p>Your dumb charger is just providing a slightly regulated voltage. It works due to the combined resistances of the charger and battery limiting the current. As the battery voltage gets close to the charger, the voltage potential is less. So with a fixed resistance, the current drops.</p>
<p>I doubt that you can modify your current charger to push 38 A up to 14.4 V. This could only happen if the combined resistances and voltage difference allow sufficient current flow. </p>
<p>Most likely you will need a higher voltage source and then circuitry to make a constant current source to provide a fixed amperage. Shutting it off can be done with a simple comparator circuit. Put a 10k trimmer pot across the battery voltage and run it into a comparator along with voltage from a zener regulator. Then you just adjust the voltage divider from the pot till it trips at the correct battery voltage. Use that to turn off a high current MOSFET or something similar. (Might use the same MOSFET to control the constant current.)</p>
|
<p>I have a huge, cheap and dumb battery charger which can charge a 12 V lead-acid battery with 70A, but it only outputs anything near (by "near" I mean over 30A) that value if I give him a completely empty, dead battery. As soon as it starts charging it, the current drops, quite quickly well below 20A, and most of the charging is done at about 10A, in fact it decreases linearly all the time. AFAIK this is called a "taper charger" and is the cheapest, most dumb lead-acid battery charger common on the market.</p>
<p>The battery I want to charge has in the specifications that you can charge it with a maximum of 38A in the "Constant Current" phase of CCCV charging, in which 80% of the battery capacity can be filled. I want to modify my cheap charger to actually do that - to charge with a constant current of 38A up until the voltage at the battery terminals reaches 14.4V, and then just turn-off (I can do this manually, I won't leave it for unattended charging anyway).</p>
<p>Any idea how such cheap taper chargers are commonly made, and what could be done to modify one to a constant current charger?</p>
|
how to modify a taper charger of lead-acid batteries to be a constant current charger?
|
2011-03-23T18:49:33.273
|
11919
|
|voltage-regulator|lm317|
|
<p>One way to ensure a minimum load is to make sure the feedback network draws the minimum load. For example 240 ohms and 75 ohms gives a 5.25V output and draws 16mA. Tweak the resistors to get it perfect.</p>
|
<p>I just built a small 5.1V regulator with LM317, using 220 and 680 ohm resistors. However, I measure 8.6V at the output without a load connected. Is this normal, i.e. under a load (about 120 ohm) it would drop to 5.1V? The input is a 9V/300mA unregulated wall wart, which reads about 13V without a load.</p>
|
Is it normal for LM317 to give a higher voltage without a load?
|
2011-03-23T20:35:18.950
|
11938
|
|rf|spread-spectrum|
|
<p>While having 24-bits would be great lots of useful work can be done with only 14-bits. As an example, see the USRPs from Ettus Research used worldwide by researchers in conjunction with GnuRadio software.</p>
<p><a href="http://www.ettus.com/downloads/ettus_ds_usrp_n200series_v3.pdf" rel="nofollow">http://www.ettus.com/downloads/ettus_ds_usrp_n200series_v3.pdf</a></p>
|
<p>I have a modern microprocessor (Cortex-M3) with a decent ADC (10-bit 400kSPS or 12-bit 200kSPS).</p>
<p>How to design and build a simple DSSS system for learning purposes? What is the simplest RF front-end that would be needed for this?</p>
<p>The bandwidth is not very important but the system should demonstrate high noise resistance since this is one of the big selling points of DSSS.</p>
<p>EDIT:</p>
<p>I hoped I would get more information on how to proceed on the software side. Like should I do blind correlation of the whole buffer at every sample or are there any "magic" tricks. Maybe I should ask another, more focused question.</p>
|
How to build a simple DSSS (direct sequence spread spectrum) transceiver?
|
2011-03-24T02:47:38.730
|
11945
|
|repair|tv|
|
<p>What makes me curious is the 50 Hz noise whenever the picture is bright. Tow possible reasons come to mind:</p>
<p>1) Interference from the (broken?) vertical deflection stage or backwards from there to the power supply and then on to the audio amp</p>
<p>2) Ripple from the power supply (should be 100 Hz, though.) The total power increases for bright pictures, hence the ripple voltag would increase as well.</p>
<p>Does the TV have a traditional power supply that uses a 50 Hz transformer or does it have a switch-mode power supply?</p>
<p>Do you have a scope? Are you able to probe the various supply rails, especially the one that powers the vertical deflection circuit?</p>
<p>Here's an extremely good app'note with tons of typical oscillograms and ICs that are likely very similar to the ones your TV uses: <a href="http://www.nxp.com/documents/application_note/APPCHP4.pdf" rel="nofollow">http://www.nxp.com/documents/application_note/APPCHP4.pdf</a></p>
<p>...</p>
<p>Some more hints after I have checked my old funny book that has pages after pages with pictures of ill TVs and list their possible causes (ISBN 978-3772350580); parts refer to Fig 4 in the <a href="http://www.alldatasheet.com/datasheet-pdf/pdf/77335/PHILIPS/TDA3653.html" rel="nofollow">TDA3653 data sheet</a>:</p>
<ul>
<li>Check electrolytic cap in the vertical amp's supply (220 µF). Also check the decouplig resistor (4,7 Ohm)</li>
<li>Check electrolytic cap in the vertical oscillator or flyback circuit (100 µF).</li>
<li>Check big cap at deflection coil (1500 µF) and 1,2 Ohm resistor.</li>
<li>Check feedback circuit (4,7 µF)</li>
</ul>
|
<p>I found a TV-Set in a dumpster, and checked if it's still working.</p>
<p>Indeed it is somewhat functional, but the picture is distorted:</p>
<p><img src="https://i.stack.imgur.com/vRdBo.jpg" /><em>(screenshot of the TV)</em></p>
<p>Depending how bright the picture is, it get's more or less vertically "compressed", where the upper half is more compressed than the lower part.
The brighter the picture, the more compressed it becomes.</p>
<p>There is also a combing effect, and the picture seems horizontally slightly shrunk.</p>
<p>When the picture is very bright, as in almost white, the screen flashes, and sound disappears.</p>
<p>Also, the brighter the picture, the more 50Hz noise I can hear from the speakers.</p>
<p>I suspect either the V-control IC to be broken (TDA3653B), or one of the capacitors connected to it.</p>
<p>Or, some of the AC/DC capacitors might be dried out or otherwise broken.</p>
<p>Any suggestions?!</p>
|
V-control broken on old (CRT) TV-Set?
|
2011-03-24T08:37:31.627
|
11946
|
|power|data|pov|
|
<p>Besides having a lot of "chatter" and there being limited power handling capabilities in the contact another alternative is to use a rotating transformer. The primary and secondary can be used on the stationary vs the rotating platform and transmit energy across an air gap.</p>
<p>One key aspect is to ensure that there is not a lot of "run out" in air-gap as this presents itself as a variable reluctance.</p>
<p>Here is one instance taken from Wikipedia:
<a href="https://i.stack.imgur.com/Vg9IY.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/Vg9IY.png" alt="enter image description here"></a></p>
<p>and another taken from <a href="http://ref.scielo.org/xvqx74" rel="nofollow noreferrer">here</a>
<a href="https://i.stack.imgur.com/peQiz.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/peQiz.png" alt="enter image description here"></a></p>
<p>These can even be used to transmit signals ...</p>
<p>How I've made them in the past is to use pot cores Which are like inside out toroids. Here is a picture from dexter magnetics:
<a href="https://i.stack.imgur.com/AhMEI.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/AhMEI.jpg" alt="enter image description here"></a></p>
<p>You use two bobbins to wind your primary/secondary on. cast them with epoxy and then mount the two open faces close together.</p>
|
<p>I want to build a small <a href="http://en.wikipedia.org/wiki/Persistence_of_vision#Persistence_of_vision_displays">POV display</a>, but how is the power (and if possible a communication line) transmitted to the spinning part?</p>
<p>I've looked at some POV project, but they usually don't explain that part much...</p>
|
Power for POV display
|
2011-03-24T08:51:24.470
|
11952
|
|current|safety|protection|
|
<p>The key here is AC - alternating current - vs DC - direct current. They are different - AC oscillates while DC doesn't. That means, as the answer above notes, that AC breaks contact easier that DC and DC creates greater arcing across the contacts - AC doesn't to the same degree - use a DC circuit breaker - they are available..... </p>
<p>Same applies to standard switches. A 230v switch will fail very quickly if used in a DC circuit because of the arcing.</p>
|
<p>Will a standard home automatic circuit breaker, designed and sold as to work on 230V AC (alternating current), and for example 16A, or 25A etc, will it work (break the circuit if it exceeds the rated amperage) on 12V direct current (DC)?</p>
<p>If not, are there any automatic circuit breakers for over-current protection, which work on DC? I mean besides fuses which blow, I want the thing to be reusable with a click, not one-time-use.</p>
|
will a circuit breaker designed for 230VAC work for 12VDC?
|
2011-03-24T11:42:59.457
|
11953
|
|avr|
|
<p>I've had good luck with this online <a href="http://www.engbedded.com/fusecalc" rel="nofollow">AVR Fuse Calculator</a> in the past. Might be useful for ya.</p>
|
<p>I have an atmega16 which I need to clock to at least 16MHZ. How do I know what fuses to set? The fuse calculator gives you a choice of low, medium and high frequency. What does that mean?</p>
<p>Is there a limit to how fast the chip can go despite you put a crystal in?</p>
|
AVR and external crystals
|
2011-03-24T11:48:03.150
|
11957
|
|arduino|avr|
|
<p>The <code>const char javascript[] PROGMEM = "..."</code> is a >5,000 character string. It's possible that the Arduino IDE doesn't support line lengths of this size, you can break it up using the continuation character <code>\</code> at the end of your line: </p>
<pre><code>const char javascript[] PROGMEM = "<script type=\"text/javascript\">function" \
" getScrollY(){var scrOfX = 0,scrOfY=0;if(typeof(window.pageYOffset)=='number')" \
"{scrOfY=window.pageYOffset;scrOfX=window.pageXOffset;}else if(document.body&&" \
[Many more lines]
"setCCbldSty2('colorpicker201','ds','block');" \
"document.getElementById('colorpicker201').innerHTML=mid;}</script>";
</code></pre>
<p>Note that you can't have // comments at the end of these lines. </p>
<p>If this is what you meant by "broke into 2 parts" you should be fine. Otherwise, I think your reassembly at runtime is suspicious.</p>
|
<p>I'm trying to build RGB led color picker from ladyada.net tutorials.
<a href="http://www.ladyada.net/make/eshield/examples.html" rel="nofollow">http://www.ladyada.net/make/eshield/examples.html</a></p>
<p>I build ethernet shield, installed on my Arduino Duemilanove with ATMEGA328 and then load the sketch from ladyada web site.
<a href="http://www.ladyada.net/make/eshield/LEDcolorpicker.pde" rel="nofollow">http://www.ladyada.net/make/eshield/LEDcolorpicker.pde</a></p>
<p>This code dosent's work for me, until I break line into two separate and re-merge at runtime.
I need to remove some piece of code to make it works.</p>
<p>After burning 3 times this sketch on my Arduino, it seems not to responde anymore.
On extensive log I see:</p>
<pre><code> avrdude: Version 5.4-arduino, compiled on Oct 9 2007 at 11:20:31
Copyright (c) 2000-2005 Brian Dean, http://www.bdmicro.com/
System wide configuration file is "/Applications/Arduino.app/Contents/Resources/Java/hardware/tools/avr/etc/avrdude.conf"
User configuration file is "/Users/emaaaa/.avrduderc"
User configuration file does not exist or is not a regular file, skipping
Using Port : /dev/tty.usbserial-A9007MIy
Using Programmer : stk500v1
Overriding Baud Rate : 115200
avrdude: Send: 0 [30] [20]
avrdude: Send: 0 [30] [20]
avrdude: Send: 0 [30] [20]
avrdude: ser_recv(): programmer is not responding
avrdude: stk500_recv(): programmer is not responding
avrdude: Send: Q [51] [20]
avrdude: ser_recv(): programmer is not responding
avrdude: stk500_recv(): programmer is not responding
</code></pre>
<p>Anyone have some ideas ?
I tryed on 2 different arduino 2009, same results</p>
<p>Thanks.</p>
|
Arduino killed trying to load a sketch?
|
2011-03-24T12:41:19.710
|
11960
|
|batteries|battery-charging|automotive|
|
<p>"moy" or "moyenne" most likely refers to "average" and "eff" or "effusion" is most likely put here to signify "burst"... as in some sort of vehicle jump mode.</p>
<p>(idea stolen from my dinky battery charger at home that has 10A continuous and 30A "burst" capability for helping to jump a car)</p>
|
<p>I have a huge (28 kg mass) automotive high-current battery charger, and its current delivering capabilities are described like that:</p>
<pre><code>70A moy/arit 90A eff
</code></pre>
<p>What do these mysterious abbreviations "moy", "arit" and "eff" exactly mean, and how much current can this beast really deliver, 70A, 90A, what's the difference between the first and second number?</p>
<p>Here is a photo, so you have an idea what kind of device it is:
<img src="https://i.stack.imgur.com/7WIW0.jpg" alt="http://telto.nazwa.pl/allegro/15.10.2010/d/dscf1313.jpg"></p>
|
what does "70A moy/arit 90A eff" on a high-current automotive lead-acid battery charger mean?
|
2011-03-24T13:28:39.470
|
11965
|
|stepper-motor|
|
<p>I would suggest driving the motor with 72% of rated current, or about 310mA. That should yield the same power dissipation as would be expected from unipolar drive at 440mA. When the motor isn't moving, the voltage would have to be about 31 volts. I wouldn't expect insulation problems at 31 volts, or even 50, but I don't know how far one could safely go. Perhaps measure the AC voltage when hand-spinning the motor quickly to see if there seems to be a limit.</p>
|
<p>I have in my possession two stepper motors that are clearly marked as 50 ohm, 22V motors. They have six leads each, which I believe makes them unipolar stepper motors.</p>
<p>It is my understanding (and experience) that unipolar stepper motors can be driven as bipolar stepper motors by ignoring the center lead, and that is what I am doing. When I measure the resistance between leads to determine which lead is the center of each winding, however, I find that the resistance between each "edge" lead and the center lead is 50 ohm, and the resistance between the two "edge" leads is actually 100 ohms. It is my guess that this is because when driven by a unipolar driver, current is never passed between the "edge" leads, and only ever from the center lead to one or the other "edge". This arrangement would make the 50 ohm rating make sense. Is this correct?</p>
<p>Because I am driving these motors as bipolar motors, however, I see double the resistance that a unipolar driver would see. I am also using a "chopper" driver, or constant-current driver, and I have the ability to select the maximum current for the motor. How do I calculate this? Is it a simple question of ohm's law, using the 100 ohm value I measured between the "edge" leads?</p>
|
How do I determine the power rating of a stepper motor?
|
2011-03-24T15:02:46.353
|
11972
|
|communication|books|
|
<p>On my shelf I have
B. P. Lathi. "Modern Digital and Analog Communication Systems". 1983. (Should I upgrade to a later edition?)</p>
<p>In section "3.2: Line Coding", it has a description and frequency spectrum for a few line codes: on-off, polar, bipolar (pseudoternary), duobinary, split-phase (Manchester), high-density bipolar (HDB3). It mentions "A list of codes ... can be found in Bylanski and Ingram.".</p>
<p>P. Bylanski and D. G. W. Ingram, "Digital Transmission Systems", Peter Peregrinus Ltd., Herts., England, 1976</p>
|
<p>Would you recommend any good book dealing with line codes (i.e. <a href="http://en.wikipedia.org/wiki/Line_code" rel="nofollow">http://en.wikipedia.org/wiki/Line_code</a>).</p>
<p>I mean a book that goes a little bit deeper into properties of each encoding (e.g. spectrum). I believe this topic is discussed in many digital communications text books, but there are too many of them</p>
|
Books on line codes?
|
2011-03-24T16:38:28.503
|
11973
|
|battery-charging|
|
<p>The charger circuitry is usually not as extensively built as a power supply circuit. Things such as filtering, and well regulated circuits for both current and voltage. I don't know what you are trying to do with it, so it may satisfy your basic needs for devices such as motors, etc...</p>
<p>To test the charger you can connect an ammeter in series with the output, and monitor the voltage output with a dvm. Then apply different loads to the output while monitoring the current and voltage meters. If the voltage deviates a lot, it shows poor or no voltage regulation. You mentioned you have 10 ohm resistors, but you did not say what the power rating in watts were. Using ohms law I=E/R tells you that 12 volts/ 10 ohms = 1.2 amps. Them P = I*E tells us that 1.2*12 = 14.4 watts that the resistor must be rated at. Providing the resistors are 15 watts or greater, you could use these as a load test. Adding other 10 ohm resistors to the load will increase the current additive, so to achieve 10A you could get close with 8 resistors 8*1.2=9.6.</p>
|
<p>How can I safely detect output of a car battery charger?</p>
<p>It has a OS/MP switch and for output it lists 12 V and 10.1 A. Unfortunately I have no idea what OS/MP means and I of course have no manual. The charger also has a single 5x20 glass slow fuse rated at 2 A and a 10 A standard household circuit breaker. </p>
<p>I'm hoping to use the charger as a power supply for a project. Either constant current or constant voltage would be OK, but I can't determine right now which one the charger is. It looks low-tech, so I doubt that it has both output types.</p>
<p>On the equipment front, I have two multimeters and I could easily obtain various 5 W and 11 W ceramic resistors. I have several 10 $\Omega$ resistors available right now. </p>
|
Safely detecting lead-acid battey charger output?
|
2011-03-24T17:34:25.333
|
11975
|
|battery-charging|
|
<p>Here are some more articles to mention ...</p>
<p><a href="http://www.ti.com/general/docs/lit/getliterature.tsp?literatureNumber=slus066" rel="nofollow">http://www.ti.com/general/docs/lit/getliterature.tsp?literatureNumber=slus066</a></p>
<p><a href="http://www.maximintegrated.com/app-notes/index.mvp/id/3388" rel="nofollow">http://www.maximintegrated.com/app-notes/index.mvp/id/3388</a></p>
<p>Most reliable:
- use separate battery pack with wire and connector
- or single alkaline batteries in the same compartment</p>
<p>This completely differs the two chemistries</p>
|
<p>I'm looking at making a universal battery charger. And I am interested in seeing whether I can get it to detect the chemistry so if a non rechargeable had been put in it won't charge. </p>
|
Is it possible to detect battery chemistry?
|
2011-03-24T18:17:59.400
|
11988
|
|atmega|pwm|gyro|
|
<p>AREF is defined as as the analog input voltage-reference. I looked in a few places and I can't find any discussion of changing the PWM voltage. Not a definitive 'no' but that would be my guess. I'd be reaching for my meter, right about now.</p>
|
<p>I'm have a project which is using an ATMega 328 which is powered by 5 volts. It is connected to an accelerometer/gyro breakout board through a 3.3 voltage regulator and supplying the 3.3 volts to the ATMega's AREF pin. I want to control a Jaguar speed controller via PWM, which I believe expects a 5 volt signal. My question is, when I set the AREF pin to 3.3 volts, is that going to change the upper limit of my PWM output from 5 volts to 3.3 volts?</p>
|
ATMega 328 AREF and PWM/analogWrite()
|
2011-03-24T20:57:19.360
|
11993
|
|enclosure|
|
<p>Get the right size drill bit(or one size smaller), and a wire nut. Screw the wire nut to the end of said drill bit. for more holding power, use epoxy JB weld. Then you have a hand(finger)held bit that will last as long as you don't lose it. Or use pliers to twist it and break loose the epoxy. In which case it would no longer be a finger bit, but a pliers bit.</p>
|
<p>A good deal of projects I see have their inputs and outputs neatly aligned in to plastic enclosures. I wish to do the same, however, I do not own a drill or anything similar.</p>
<p>What is a cheap but effective way to drill neat holes in my cases?</p>
|
Cheap method to drill neat holes in plastic casing?
|
2011-03-24T22:34:00.127
|
11996
|
|lcd|
|
<p>Some four-row LCDs are actually two controllers with separate enable inputs. </p>
<p>Try writing to all the locations in the data RAM, the memory-address to character-location in these LCDs is not always what you think it is. For example I have a weird 16x1 display that is actually laid out as two disjoint 8-column memory ranges.</p>
|
<p>I'm wondering if I've blown my lcd by accident. It's supposed to be a 20 * 4 rows lcd however only row 2 and row 4 seem to light up. Should they not all light up</p>
|
LCD rows not all lighting up
|
2011-03-24T23:04:35.943
|
12009
|
|rectifier|
|
<p>It's a power diode (20A) manufactured in the past by Czech company Tesla, and the package is called DO-5/1.</p>
|
<p>The device is called KY 717 and from what I've been able to find out, it's some sort of rectifier. The solder tab is insulated from the rest of the body.</p>
<p><img src="https://i.stack.imgur.com/4Fe4j.jpg" alt="KY 717"> </p>
<p>I was unable to make a better picture. The major division on the paper is 10 mm and the device appears to be 37 mm long. The screw is from what I can see M4 type screw. The soldering hole has diameter of around 3 mm, but is deformed so my measurements could be bad. </p>
|
What's the name of this component's package?
|
2011-03-25T08:34:43.463
|
12014
|
|rectifier|
|
<p>One thing I haven't seen in the other answers:</p>
<p>This is a centre-tapped rectifier. It uses a centre-tapped transformer to create a full-wave rectifier.</p>
<p>Its biggest positive is that you only need 2 rectifiers to do this. Because of this, these were used when solid state rectifiers were still very pricey or you had to use valve rectifiers. Its not used often today because the cost of creating two secondary windings in a transformer is much higher than adding 2 more rectifiers to create a full-wave rectified signal from a simple transformer.</p>
|
<p>In a car battery charger, I found a strange rectifier. Can someone explain to me how does it work?
<img src="https://i.stack.imgur.com/VulyL.png" alt="Rectifier"></p>
<p>Here I have a transformer which is unmarked. By measuring resistance between its output terminals, I determined that the plus cable is connected to the center of the transformer. The two outer connections both have a diode connected as shown on the image. To me it looks similar to this:<br>
<img src="https://i.stack.imgur.com/O6aLi.png" alt="wikipedia rectifier"><br>
rectifier, but the diodes are turned backwards. I checked their orientation several times with two different multimeters and I'm sure that I've drawn them correctly.</p>
|
How does this rectifier work?
|
2011-03-25T10:43:40.350
|
12031
|
|power|
|
<p>I have built such AC/DC source by salvaging a transformer, there were more than 4000Amp at 4 Volt DC. I have rewind a 10/16kVa 400V to 220V transformer, the primary winding has been kept as it is, and the secondary has been rebuilt with a copper strip capable for such current.
To adjust the output current I have used variac in the primary side. It was to detect any crack inside an workroll of Rolling Mill.</p>
|
<p>I'm not an electrical engineer. I have an unusual need and would like suggestions as to how to proceed. I have an application that needs very high currents at very low voltages. I'm trying to heat a thin strip of aluminum to temperatures near 100C quickly and then control the temperature. My calculations suggest about 150 to 200 amps at less than 0.1 volt. About the only idea I have is using a toroidal transformer with maybe 1000 turns and thick copper bar passing through the center of the toroid connected to the aluminum strip. I can use either AC or DC current and if AC, I'm not necessarily limited to 60hz.</p>
<p>Any and all good suggestions are welcome.</p>
|
Very high current very low voltage application
|
2011-03-25T15:55:32.047
|
12048
|
|arduino|servo|
|
<p>All servos require a repeating pulse to work</p>
<p>depending on the servo, they require a 1 to 2ms pulse repeat about 50 times a second.</p>
<p>What is done is this...</p>
<p>a reset pulse sets the counter IC back to 0
Output 0 on the counter goes high,</p>
<p>A timing loop is run for the first servo (on output 0),
e.g. 1 ms,</p>
<p>then a pulse is applied to the clock input, this sets the counter IC to 1
Output 0 goes low, and output 1 goes high</p>
<p>A timing loop is run for the second servo (on output 1)
e.g. 1.5ms</p>
<p>then a pulse is applied to the clock input, this sets the counter IC to 2
....</p>
<p>I first came across the method of using a counter IC in "Theory and practice of model radio control" - second edition... (c) around 1975</p>
<p>A reset pulse, then variable length sequential pulses applied to the clock pin to both control the servo and select the next servo.</p>
|
<p>I have just become aware that people are using 4017 decade counters and an Arduino to drive relatively large numbers of servos from relatively small numbers of pins. Not being an Arduino connoisseur myself, however, I have not been successful in my attempts to decode the software that makes the magic happen.</p>
<p>My question is, in non-code, what exactly is going on <a href="http://www.auv.co.za/blog/atmega128servocontrol4017" rel="nofollow">here</a> that makes this possible?</p>
|
How does the 4017 decade counter drive a set of servos?
|
2011-03-25T21:08:26.660
|
12050
|
|ground|
|
<p>Both sides of the resistor are connected to the same point: ground. Since there is no voltage across the resistor, no current will flow through it.</p>
|
<p>Referencing <a href="http://www.falstad.com/circuit/#%24+1+5.0E-6+1.0312258501325766+48+5.0+50%0Aw+304+144+544+144+0%0Aw+544+144+544+160+0%0Ar+544+160+544+224+0+100.0%0Aw+544+224+544+256+0%0Aw+544+256+304+256+0%0Av+304+256+304+144+0+0+40.0+5.0+0.0+0.0+0.5%0Ar+304+144+224+144+0+100.0%0Ag+224+144+192+144+0%0Ag+304+256+304+320+0%0Ar+544+256+544+320+0+100.0%0Ag+544+320+544+336+0%0A" rel="nofollow">ground circuit simulator</a>(link launches a simulator applet)</p>
<p>Why doesn't current flow in the resistor in the bottom right? What do I need to read about electric theory to be able to correctly trace current flow and solve problems like this?</p>
|
Simple current flow
|
2011-03-25T21:53:38.640
|
12060
|
|555|ham-radio|
|
<p>This circuit is going to generate square waves into your antenna. As a licensed ham, you are responsible for transmitting a clean signal. I'm all for trying stuff, but it's best that you put this into a dummy load instead of an antenna, and see if you can hear it on your receiver. Then tune around and look for harmonics and other spurious output. As a matter of fact, the article states that the 555 is running at a fraction of the desired frequency, and you are picking up one of the harmonics on your radio.</p>
<p>This is not as off-the-wall as it sounds. It's a very common practice to "multiply" the frequency to get a higher frequency that the oscillating circuit can't reach by itself. It's also common to build RF amplifiers that are anything but linear. What's needed, though, is a filter to remove all but the desired signal. What you'll need is at least a tuned tank circuit before the antenna. The result won't be a very strong signal, but it may be legal.</p>
<p>Note that a perfect square wave has only odd harmonics. It should be interesting to tune through the bands and see if the odd harmonics are stronger than the even ones. This also suggests that you don't try to, say, run at 500 kHz trying to get 2 MHz. You'd be better off with 400 kHz or 667 kHz. Now, your square wave won't be perfect, so there will still be some energy at the even harmonics. But still, there's a lot to play around with here.</p>
<p>One final note. Almost everything about this circuit will be unsuitable for AM. The original article even said so. But if you get that far, I think that should be discussed in another question.</p>
|
<p>I'm a general class ham, and am just starting to do my own homebrewing. I was planning on basing a QRP transmitter off of <a href="http://www.instructables.com/id/Easy-AM-Transmitter/" rel="nofollow">this instructables project</a>, seeing as I have a veritable plethora of 555 ics in my shack toolbox. </p>
<p>The problem is, this transmitter is designed to operate a bit below the commerical AM band. How is the general operating frequency being set? I'd like to get it set around the 1.8 mhz band (160 meters).</p>
<p>Help is much help appreciated, as I'm going to use this to teach the other kids in the ham radio club at my school how to build basic transmitters. Picture of circuit:
http://www.instructables.com/image/FD38QHUGIKL42D3/Schematic.jpg"></p>
|
What determines the transmit frequency in this 555-based transmitter?
|
2011-03-26T02:24:22.120
|
12072
|
|connector|wire|identification|
|
<p>A connector with wires/cable pre-attached is often sold as a "pigtail", "preassembled cable","cable assembly"; if it is a spare part for a specific device, esp with multiple connectors attached, it might also be called a "harness".</p>
|
<p><img src="https://i.stack.imgur.com/mT7xo.jpg" alt="From the "Half the battle is knowing what to search for on DigiKey" deptartment"></p>
<p>What are these connectors commonly called, and what would I search for if I wanted to buy sets of male/female pairs with a specific gauge of wire pre-attached?</p>
|
What are these wires with pre-attached connectors called?
|
2011-03-26T08:51:07.270
|
12078
|
|microcontroller|programming|
|
<p>You can use <code>avr-size</code> to check the real size of your program:</p>
<pre><code>[jpc@jpc sepack] avr-size sepack.elf
text data bss dec hex filename
4396 6 277 4679 1247 sepack.elf
[jpc@jpc sepack] avr-size sepack.hex
text data bss dec hex filename
0 4402 0 4402 1132 sepack.hex
</code></pre>
<p>As you can see it works better with <code>.elf</code> files since it can also show you both how much ram you need (<code>data</code>+<code>bss</code>) and how much flash will be used (<code>text</code>+<code>data</code>). With the <code>.hex</code> file only shows you the second figure (labeling it <code>data</code>)</p>
|
<p>I have a hex file with a size of 42 kB. Does the size matter while loading it in a microcontroller? Can I load 42 kB hex file in a ATMEGA32 chip which has a memory of 32 kB?</p>
|
Will my HEX file fit in my microcontroller?
|
2011-03-26T13:48:33.693
|
12085
|
|integrated-circuit|buying|
|
<p>All of the other answers are fairly good, but you all forgot one important thing: simulation! Analog circuits are often somewhat tweaky, and spending a little bit of time with a simulator can often save hours or days of headaches later on. </p>
<p>Many of the manufacturers have some level of support for simulations, but they all have issues. In my opinion, Linear Tech's <a href="http://www.linear.com/designtools/software/#LTspice" rel="nofollow">LTSpice</a> is probably the best free tool available for simulations. </p>
|
<p>I'm an electronics beginner and I find myself often needing to pick an IC for an analog application with no prior knowledge.</p>
<p>In the domain of microcontrollers, it's very clear that I should use Atmel AVR since many hobbyists use the ATMega8/128/168/32u4 etc. due to Arduino + I've got the toolchain setup for that now. I've familiarized myself with the line at this point and I don't bother looking elsewhere.</p>
<p>But when I'm researching something like signal conditioning, I'm always finding myself asking: so do I get an IC from Analog, Linear, TI or Microchip? Especially these three companies have a lot of overlap in the signal conditioning domain, but I'm sure you can find other groups of companies with similar overlaps in other domains.</p>
<p>When you're picking an IC, do you have a favorite or "go to" company that you'll start with? Or do you compare the specs from all the main companies and go with the "best" one? Do you leave it up to chance and go with the first thing you find that satisfies the requirements?</p>
<p>Do things like the general quality of datasheets, customer service, website UX and marketing influence your decisions?</p>
|
How Do You Decide Between Analog Chip Manufacturers?
|
2011-03-26T17:37:31.550
|
12087
|
|avr|
|
<p>The AVRISP mkII can program the tiny44 in the latest version of AVR Studio (4.18 SP3 or 5 beta). Make sure your version is either up-to-date or check the help files/release notes that came with it to verify. Also allow AVR Studio to update the firmware in your AVRISP mkII if it needs to.</p>
<p>Verify the following conditions:</p>
<ul>
<li>Programmer is connected to PCB (GND, RESET, MOSI, MISO, and SCK)</li>
<li>Target is powered.
<ul>
<li>Not sure how much power the AVRISP MKII can provide, but don't rely on it if your board takes more than 50 mA.</li>
<li>You do <em>not</em> need to connect the programmer's VCC line to the chip power if you provide it externally.</li>
</ul></li>
<li>MOSI, MISO, SCK have pullups to GND/VCC no stronger than 820 Ω.</li>
<li>RESET pullup should be no stronger than 4.7 kΩ and have a decoupling capacitor less than 10 µF.</li>
</ul>
<p>Follow the troubleshooting guide in the <a href="http://www.atmel.com/dyn/resources/prod_documents/AVRISPmkII_UG.pdf" rel="nofollow noreferrer">AVRISP mkII user guide</a> [PDF] if you experience problems as a first step:</p>
<p><img src="https://i.stack.imgur.com/stJQx.png" alt="enter image description here"></p>
|
<p>It's not responding to the programmer at all in avr studio.</p>
<pre><code>avrisp attiny44
mosi -- - mosi
miso ---- miso
sck ---- usck
reset ---- reset
</code></pre>
<p>Or can it not be programmed by an mk2? I assumed all chips can be programmed by it</p>
|
ATtiny44 not responding to AVRISP mkII programmer
|
2011-03-26T18:50:19.970
|
12093
|
|rfid|telephone|
|
<p>This is a tough and subtle problem. I wouldn't discourage you from trying to find a cool, clever, "good enough" hobbyist solution. In fact if you can do so it might even justify starting your own company to market it.</p>
<p>What you are talking about is an RTLS (<a href="http://en.wikipedia.org/wiki/Real-time_locating_system" rel="nofollow">Real Time Locating System</a>).</p>
<p>RFID can be used to solve this problem, but at a very limited resolution and requires an extensive sensor grid. Basically with RFID, since the range is very short and there is no timestamp, position, or other useful information transmitted, the best you can do is sprinkle your volume with a sensor grid and see which readers can see a tag, which will allow you to narrow down the possible locations to the proximity of active triggers. This could be fine if you want to know what room something is in and keep track of the path it followed through the volume (by watching the history of sensors that could pick up the tag).</p>
<p>If you want something that will tell give you x, y, z coordinates for the object's position, things get a lot more complicated. If you want to get an idea conceptually of how such a system might work, look up <a href="http://en.wikipedia.org/wiki/TDOA" rel="nofollow">multilateration</a>. The basic idea is that you have a set of receivers with a common clock and known positions, and your locator tags chirp (emit a sound/light/whatever pulse) periodically. The receivers and transmitters do not have a common clock, so they cannot directly determine distance by time of flight. But by comparing the difference in arrival times between the transmitter and each receiver and grinding through some math it is possible to solve for the position of the transmitter.</p>
<p>There are some cool hobbyist opportunities for building multilateration systems using ultrasound or even audible sound, because ultrasound hardware is pretty cheap and there is plenty of existing audio processing software for PCs.</p>
<p>Another type of RTLS is Trilateration, which is what GPS uses. This depends on the transmitters (GPS satellites) transmitting very accurate synchronized timestamps and position information, as well as a receiver that is (at least sort of) synchronized with the transmitter's clocks. Since the receiver knows where and when each satellite was when it chirped, it can directly determine distance from each satellite, and the set of possible positions relative to each satellite is the surface of a sphere. With multiple satellites and multiple sphere's of possible positions, the position is the intersection of the spheres.</p>
<p>The problem with trying to build anything like this is that you're not going to get a tiny little passive tag that you can put on sunglasses or keys without adding obvious bulk. There is a company called <a href="http://www.plus-ls.com/" rel="nofollow">Plus Location Systems</a> that makes turnkey systems that essentially meet your requirements, but they are quite expensive and even with all the work they have done the asset tags are roughly 1.4 x 1.3 x 0.5 inches.</p>
<p>There is a company called <a href="http://www.decawave.com/" rel="nofollow">DecaWave</a> that is developing a system based on peer-to-peer transmitter/receiver chips. Their chips are tiny (although they still need to be powered, etc.), and they are not quite commercially available, but are probably about as close as we currently are to tech that allows us to put little tags on everything and know exactly where it is.</p>
|
<p>I'd like to be able to put something small on items (eg glasses, car keys, etc) and have an Android or iPhone app that will tell me the direction or proximity of a certain item. Current phones usually just communicate via cell, wifi, and bluetooth, but for these the other end of the communication has to be powered, which increases the size of what I attach to my items. Is passive RFID what I'm looking for? (In which case I'd have to wait for phones to come out with better RFID readers.) If yes, what size passive tags have what ranges? For range I'd like to be able to find a device a couple floors away, but even just within a room would be useful. For size, the smaller the better, with maybe a quarter the size of a dime as the minimum practical/usable size. Do you think that the RFID readers in phones will be able to take advantage of those maximum ranges? (Currently the ones I've looked at, eg Nexus S, have to be inches away.) And finally, where do you recommend I buy such tags?</p>
|
How can I locate items from a phone? RFID?
|
2011-03-26T20:13:12.147
|
12102
|
|microcontroller|video|mbed|rca|
|
<p>By "RCA output" I assume they mean a composite video output. In order to convert that into some sort of digital image that a microcontroller can use, you would need an extremely fast ADC, or simply a video decoder (i.e. one from <a href="http://www.maxim-ic.com/products/video/decoders.cfm" rel="nofollow">Maxim IC</a>, <a href="http://www.analog.com/en/audiovideo-products/video-decoders/products/index.html" rel="nofollow">Analog Devices</a>, <a href="http://focus.ti.com/paramsearch/docs/parametricsearch.tsp?family=analog&familyId=375&uiTemplateId=NODE_STRY_PGE_T" rel="nofollow">TI</a>) to tease out the image data. Better yet, just get a camera with a digital output, as the digital-to-analog-to-digital path is a waste, as it's costly and performs worse.</p>
<p>NTSC scanlines are transmitted at 15.734 kHz with frequency content up to 4.2 MHz, impossible to handle with a standard microcontroller ADC which have sample rates of 1 Msps at the high end (NXP LPC1768 only has 200 ksps). Furthermore, as Leon points out, your memory is extremely limited. If you read just <em>one</em> QVGA (320 x 240) frame into memory at 8 bits/pixel, that's 76.8 kB, which exceeds the mbed's (NXP LPC1768's) on-board 64 kB RAM.</p>
|
<p>I'm wanting to buy this <a href="http://www.sparkfun.com/products/8773" rel="nofollow">IR camera</a> but it says it has RCA output. Is it possible to read this into an mbed without external components(aside from a 12v power source)? If so, how?</p>
|
How to read RCA output from an mbed?
|
2011-03-27T02:40:43.067
|
12120
|
|digital-logic|
|
<p>You should only consider drawing the state machine for the actual 2-complementer with serial input, and forget about the shift register (drawing a state diagram for a shift register of a given length is perfectly possible, but makes hardly any sense). </p>
<p>Said that, the task boils down to a single-input/single-output state machine with 2 states. Look here: <a href="http://k5rec.blogspot.com/2006/12/digital-electronics-serial-twos.html" rel="nofollow">http://k5rec.blogspot.com/2006/12/digital-electronics-serial-twos.html</a></p>
|
<p>If I understand correctly, the state diagram of a sequential circuit simply shows the different states the circuit goes through. However, if I'm trying to build a 2's complementer using a shift register and a flip-flop, how does the state diagram look? Seeing as what goes through the flip-flop depends on the digit put in the register, I'm not sure how to draw it.</p>
<p>Thanks</p>
|
Problems deriving state diagrams
|
2011-03-27T16:00:03.940
|
12125
|
|pcb|prototyping|
|
<p>Sometimes, such a QFP device will have either a demo board that you can buy with headers broken out, or have a family equivalent device in a smaller/bigger package (which either is available in DIP or have an easy to prototype demo board).</p>
<p>This will let you get started in a hurry and validate your design, and let you get on the software while you are still working on designing/building the "real" PCB.</p>
|
<p>I'm starting to design a circuit that includes a QFP-38 component. I'm accustomed to using DIP components and prototyping on a breadboard, but in this case I won't be able to acquire a DIP version of the component.</p>
<p>Is it normal practice for electrical engineers to have a PCB fabricated without prototyping? Or do you always acquire breakout boards for small components at first?</p>
<p>(In my case, I would just go ahead and order a QFP-38 to DIP adapter, but it will cost me $20 including shipping. It seems like I may as well just have a PCB made and hope for the best.)</p>
|
How Do You Prototype with QFP-Only Components?
|
2011-03-27T19:35:23.307
|
12130
|
|switches|stepper-motor|
|
<p>Looking at th PCB those 2 DPDT switches are being used as SPST ones - one pin (the middle one) is wired to +V, the other is connected to an input on a chip with a pulldown resistor to ground (R6/10).</p>
<p>If the switches are off then the pin furthest from the panel will be pulled down by the resistor to ground - you could then drive it externally (run that pin and ground to the external controller.</p>
<p>Some caveats: if you accidentally turn the switch on bad stuff could happen - best to drive the signal through a small diode for protection - you also need to be careful about voltages - don't drive the circuit from something with a higher voltage than expected (perhaps snarf the power from that other pin assuming it's 5v)</p>
|
<p>Anyone familiar with the SMD1 Stepper Motor Driver Kit ?
I am trying to figure out how to connect external control to the lugs on the switch assembly (DPDT push switches). </p>
<p>The lugs already have the leads soldered so leads for the following </p>
<ul>
<li>run/hold</li>
<li>Counter and Clockwise</li>
<li>Power</li>
</ul>
<p>Really new to the electronic stuff though (Two months in). It could be that I am not understanding how to control the leads so that they behave in a similar fashion to the switches. The kit has already been pre-built the only missing piece is the external controls.</p>
<p><img src="https://i.stack.imgur.com/Li3Km.png" alt="Illustration of the SMD1"></p>
<p>Interestingly (at least for me... still grasping), a lead is soldered to the right end of Resistor 3. The <a href="http://www.ramseyelectronics.com/downloads/manuals/SMD1.pdf" rel="nofollow noreferrer">manual</a> says the only requirement is that the control's state is equal to 5 vdc when energized. So ... in simple (new to electronics) layman terms how does one connect it say to a breadboard with a 5V supply.</p>
<p><img src="https://i.stack.imgur.com/wcXGb.png" alt="Switch"></p>
|
Connecting an external control to a DPDT switch
|
2011-03-27T21:25:41.007
|
12136
|
|soldering|
|
<p>I have used with much success the Micro-care Pro-Clean alcohol enhanced flux remover. Comes in a spray which is very handy especially for stencil printed wipe down pcbs.</p>
|
<p>At college we have to use a colophony-free solder, but over heating the solder leaves the flux residue on the boards(light amber in colour). Multicore recommend there own <a href="http://www.prime-electronics.com.au/datasheets/data/Multicore/Wave%20Soldering/Solvents/Prozone/Tech%20Data%20Sheets.pdf" rel="nofollow">Multicore Prozone cleaner</a>(this is some datasheet on what it is) to remove this residue from the board, but I can't find it on RS, Farnell or Rapid Electronics. Is there another alternative? Is there another industrial alternative as it looks like a generic PCB cleaner. </p>
|
Multicore Prozone Alternative
|
2011-03-27T23:52:27.353
|
12145
|
|arduino|
|
<p>Wikipedia <a href="http://en.wikipedia.org/wiki/Water_meter" rel="nofollow">has a page</a> on different methods of measuring water flow. If you wanted to build the sensor yourself, then the <a href="http://en.wikipedia.org/wiki/Ultrasonic_flow_meter" rel="nofollow">ultrasonic flow meter</a> would be probably the easiest.</p>
|
<p>I recently purchased an Arduino Uno and I've had lots of fun tinkering with it. I'm now interested in measuring the amount of water that flows into my house through the water line.</p>
<p>I'm having trouble finding an appropriate device that will let me measure the flow of water from my well and capture it with my Arduino. Can you guys please recommend a specific component or some general search terms so I can start looking?</p>
<p>Thanks in advance!</p>
|
Measuring Home Water Flow
|
2011-03-28T05:57:17.273
|
12150
|
|temperature|measurement|
|
<p>Thermocouples are not stable enough to measure human body temperature (you want 0.05C accuracy there). It only gives about 1-2C long-term stability.</p>
<p>Platinum PT100/1000 RTD ones are much more suitable and way way more procise.</p>
<p>When you have this extra-accuracy, you can measure target temperature while ovserving how it's rising by extrapolating... This would allow some 1-5sec measurement.</p>
<p>The only way to be faster - IR sensors.</p>
|
<p>Is there anything I need to he aware of when using K-type thermocouples?</p>
<p>I got the idea by touching the probe. I can get a reading when measuring temperature for 30 seconds using a DMM. A commercial electronic thermometer needs around minutes for the same result. </p>
<p>This gave me an idea to make a device which will use K-type thermocouple to quickly measure temperature. On the other hand if it was so simple to measure temperature, why don't the commercial thermometers produce their result faster.</p>
<p>I have a feeling that I'm missing something important here.</p>
<p>So my question is: Are there any non-obvious problems I could face when using a K-type thermocouple to measure measure human body temperature?</p>
|
Using K-type thermocouple to measure human body temperature
|
2011-03-28T08:45:32.270
|
12175
|
|ethernet|interface|cables|shielding|
|
<p>No, you do not need to do anything special. We have X-ray generators and Digital Imaging devices everywhere at my place of work, we run cable around them, in front of them sometimes(tie comes loose) and all around them. We have never had issues.</p>
<p>Other forms of radiation can have very negative affects on materials and electronics, but on ethernet cable we do not see negative affects from these either.</p>
<p>X-Rays are not that terrible, it is just not a good idea to get a dose from them repeatedly throughout the day. This is why the therapist is placed behind a bit of lead.</p>
|
<p>My mother runs a small veterinary clinic. She is getting a new X-Ray machine that will need a network connection to send digital copies of the X-Ray to the server. I will be installing a wall plate with a few Ethernet jacks in the X-Ray room. </p>
<p>Do I need to do anything special like shielded cabling for this install? I am not worried about transmission errors that may occur during the split second the X-Ray is active, TCP can fix those, I am concerned about damaging the NIC card on the computer or router in the wiring closet due to some form of current induction.</p>
<p>The cable will not be running in the direct path of the X-Ray beam just be in wall leading to the room. Am I being overly cautious or is this a legitimate concern? Also if I need to route under the path of the beam for some reason are there any consequences for that?</p>
|
Running network cable near X-Ray equipment
|
2011-03-28T19:03:15.813
|
12176
|
|microcontroller|pic|c|microprocessor|
|
<p>Firstly, lets check that you have connected your LDR up correctly, it should be something like this...</p>
<p><img src="https://i.stack.imgur.com/YW0B3.gif" alt="LDR wiring"></p>
<p>To read the value of PIN RA0/AN0, you need to do some initialisation to make sure the port is setup correctly. The <a href="http://ww1.microchip.com/downloads/en/devicedoc/39632c.pdf" rel="nofollow noreferrer">datasheet</a> explains how all this works, but these values should work:</p>
<pre><code>TRISAbits.TRISA0 = 1; // Set RA0/AN0 to input
ADCON0 = 0b00000000; // Set channel select to AN0
ADCON1 = 0b00001110; // Configure RA0/AN0 as analogue
ADCON2 = 0b10101010; // Right justified result
// TAD 12 and FOSC 32 - may need to adjust this
// depending on your clock frequency (see datasheet)
ADCON0.ADON = 1; // Enable ADC
</code></pre>
<p>Now the port should be set up, you can now read the LDR value:</p>
<pre><code>ADCON0bits.GO = 1; // Set the GO bit of the ADCON0 register to start
// the conversion.
while (ADCON0bits.GO); // Wait until the conversion is complete.
</code></pre>
<p>You can now read the result of the LDR as a 10-bit value in <code>ADRESH:ADRESL</code>. If you only need 8-bit resolution, then set <code>ADCON2.ADFM = 0</code> for left justification of the result, then you only need to read the <code>ADRESH</code> to get your result.</p>
|
<p>I'm using the picdem 18F4550 with microchip v8.63 with the C18 compiler.</p>
<p>I will enable PortA to set as input, I will connect a LDR on port RA0. Which is as following (I think):</p>
<pre><code>TRISAbits.TRISA0 = 1; //<= set RA0 as input.
</code></pre>
<p>Now I want the value of the LDR (voltage/value if a led is on), can I say: </p>
<pre><code>int colorLed = PortAbits.RA0;
</code></pre>
<p>And now in the variable of type int there is the value/voltage of my Led.</p>
<p>Correct me if I'm wrong.</p>
|
Enable port RA0 as input and retrieve value LDR from led
|
2011-03-28T19:31:16.130
|
12179
|
|pcb|inductor|
|
<p>If you were to build a "super-component" out of 4 identical inductors (or 4 identical resistors) in 2 chains of 2 components each,</p>
<pre><code> +--X1--X2--+--
| |
---+--X3--X4--+
</code></pre>
<p>(assuming negligible mutual inductance, which is true for many common "shielded" inductors), and if each of the four components has identical impedance X, then all 4 of them may be considered as a whole to be a single super-component, which will have the same net impedance X and can also handle twice as much current and dissipate 4 times as much power.
(This is related to the idea of measuring <a href="http://en.wikipedia.org/wiki/Sheet_resistance#Units" rel="nofollow noreferrer">sheet resistance in "Ohms per square".</a>)</p>
<p>There may have been times ;-) ;-) where I've already bought a bulk bag of exactly the impedance I need, and then discover that it can't handle the power. If I use the square arrangement, it allows me to continue prototyping with the components that I have on hand, where each component has exactly the desired net impedance X, while I'm waiting for the "right" component(s) to ship.</p>
<p>Sometimes the current rating is limited by thermal considerations -- higher currents will make the wires overheat and something will melt and cause permanent damage or melt the solder. In those cases, the power dissipated is proportional to the surface area. Using N components rather than one big component makes it easier to cool and can save net space. (Sometimes N components in parallel, each with N times the desired impedance X, use the least space. And N components in series, each with 1/N of the desired impedance X, has the least parasitic capacitance).</p>
<p>Sometimes the current rating is limited by core saturation -- higher currents will saturate the ferrite core, causing the inductance to drop out of spec.
In those cases, the maximum energy (temporarily) stored in the core is proportional to the volume of the core. Using one big component that holds all the necessary volume usually uses less board area than using the same volume of core divided up into a bunch of smaller components.</p>
|
<p>I am doing a space constrained board layout, in terms of surface area. So I found an inductor which is \$15\mbox{ }\mu H\$, \$2.3\mbox{ }A_{RMS}\$. I need about \$3.5\mbox{ }A_{RMS}\$, so I was thinking of paralleling two \$8.2\mbox{ }\mu H\$ (\$2.7\mbox{ }A_{RMS}\$) to get \$16.4\mbox{ }\mu H\$ at \$5.4\mbox{ }A_{RMS}\mbox{ (max)}\$, with each inductor on opposite sides of the board. Is this a viable solution?</p>
|
Is parallelling inductors a viable solution?
|
2011-03-28T20:16:31.880
|
12187
|
|capacitor|resistors|ground|
|
<p>One purpose for such a circuit is to take a speaker level output (balanced) from the head unit and attenuate it so it can be used as the line level input to your amplifier or active crossover system. So the resistive divider matters in order to get the proper line level input based on the maximum power capability of the head unit. You will also want to make sure the resistors are rated properly for the power from the head unit. For example let's say the resistors total ~5.3k ohms and your head unit can deliver, say 30 watts RMS into an 8 ohm load. Typically the maximum voltage of the output of the head unit is what matters as you spec the resistors. V^2/R = Power, so in this example 30 watts = V^2/8, solve for V and you get Sqrt(240)= 15 volts RMS. So how much power is going through your divider? 15^2/5.3k = 45 mW. So 1/8 Watt resistors would work great. If you pick smaller resistors in the divider, say 470 and 68, you get the same ratio but you need 1/2 watt resistors instead. Line level inputs are high impedence and prefer the sources to be low impedence to minimize noise. So lower value divider resistors are better. I use the 470 ohm and 68 ohm, 1/2 watt resistors to make this. The smaller cap will also result in better low end response. Z(cap)=1/(2*PI<em>freq</em>C) When the freq is such that Z(cap) = Rtot, that's where your low end starts to cut off. So 1uF, 530 ohms, means low cut at 300Hz. Go with 10uF and you get a 30Hz low cut. If you have 5.3k ohms, you have to go with 100uF to get that low end. Hope this helps. </p>
|
<p>I'm coming from a stock Dodge headunit, which has regular analog output that goes up to 10 volts. Nothing fancy, when I had it going straight to the amp it worked fine. It's going into a regular JL amplifier, with a max input of 4v. I was sold a Raptor LOC15 converter to bring the voltage down. </p>
<p>Here's a diagram of what I'm working with. On the left, we have the inputs. They're coming from the source unit. To the right are the outputs, that are heading to the amplifier. This board is supposed to bring the 10v from the source unit down to something more acceptable:</p>
<p><img src="https://i.stack.imgur.com/p6CKG.png" alt="https://i.stack.imgur.com/nNCIo.png"></p>
<p>Ground... I can't figure out where I should ground it to. Chassis ground? Input ground? No ground?</p>
|
Stereo line-level converter: Odd grounding?
|
2011-03-28T22:06:01.550
|
12195
|
|pcb-fabrication|heat|
|
<p>This is just a crazy idea I got, but...</p>
<p>Build your own little contraption consisting of two sheet of metal, say aluminum, and drill 4 wholes in the corners. Add some nuts and bolts through said wholes to apply pressure, and lastly apply heat. This could be with a big-ass heat gun, or even a (domestic) oven. </p>
<p>Report back with the results if you try it. :)</p>
|
<p>Is it possible/practical to use a heat gun instead of an iron to transfer toner when making your own PCBs? Can you get a uniform heat pattern without for a small board? Is enough heat applied from the heat gun to actually transfer the toner?</p>
|
Using a heat gun to transfer toner onto DIY PCB?
|
2011-03-28T23:16:14.900
|
12198
|
|capacitor|
|
<p>AFAIK electrolytic capacitors (like any other capacitors) will work in both polarizations, but DC voltage of the wrong direction will degrade (like in electrolysis) the oxide layer. After being degraded for a while the oxide layer will cause short and a violent explosion.</p>
|
<p>I've got a 1 F electrolytic capacitor and it seems to have developed a short. </p>
<p>I never used it before and its brand new. It reads zero resistance only when I connect positive lead of my DMM to its negative lead and negative lead of my DMM to its positive lead. In the other direction, there's no short. </p>
|
Is it possible for electrolytic capacitor to develop a short in one way only?
|
2011-03-29T00:26:07.347
|
12202
|
|voltage-regulator|dc-motor|
|
<p>The 10 uf 50V capacitor you are talking about looks like its connected to the Power rails, and it is used to smooth out the power lines. Depending on your power supply and voltage you are using you can switch out the cap for another value, I would suggest at least double the voltage and a similar capacity. Check out this question for a better explanation.
<a href="https://electronics.stackexchange.com/questions/2262/smoothing-capacitors-what-size-and-how-many">Decoupling capacitors: what size and how many?</a></p>
<p>the kickback that you are talking about is usually quite high and is taken care of by the motor driver, not something you need to worry about in this example,but double check the datasheet to be sure. when creating your own motor driver you will need to consider these conditions.</p>
<p>as for your 4V motor, best way to measure is hook it up to a 4V source with an multimeter in series and turn it to measure milli amps and run it for a few seconds and get the running current, next if possible stall the motor for no more then 2 secs and read the current. That will tell you your running current and stall current. </p>
|
<p>I have set up a circuit similar to the one <a href="http://luckylarry.co.uk/arduino-projects/control-a-dc-motor-with-arduino-and-l293d-chip/" rel="nofollow">here</a>. I was wondering instead of the 10 uf 50V capacitor, would A 100 uf 16 V or a 47 uf 6.3V capacitor work? I am asking because I don't know how much kickback into the hbridge there is. I know there can be enough to damage it, but how much is that? Also, how would I determine the amount of current used by a 4v motor?</p>
|
Amount of kickback from dc motor
|
2011-03-29T01:16:19.757
|
12207
|
|filter|
|
<p>I'd use a small MCU, like a PIC, which has a comparator. The software will be quite trivial. It has the advantage that it's a one-chip (and two resistors) solution, and should be cheaper than the other proposed techniques. It would also be a lot more compact, if one of the tiny PIC10F200 six-lead devices was used.</p>
|
<p>I'm trying to create a circuit that will pulse out (short pulse) whenever it passes a certain threshold going upwards and another one to detect going downwards. I was thinking of using delay to achieve this... but I dont know how to really go about it.</p>
<p>Any help would be appreciated, thanks in advance!</p>
|
Threshold activated circuit
|
2011-03-29T04:00:13.013
|
12210
|
|ethernet|
|
<p>As Ranieri pointed out, we don't know if you need 10/100/1gig or half/full duplex. We also don't know what kind of CPU you are using. And we don't know how many of these you want to make (I'm assuming 50+, for various reasons). So this answer is sort of a stab in the dark, but...</p>
<p>There are four different approaches you can take. 1. Use a passive hub. 2. Use a 3-port switch chip. 3. Use a CPU that has two Ethernet ports on it. Or 4. forget the 2-port requirement and use commercially available Ethernet switches instead.</p>
<p>I've done enough PCB's with Ethernet to tell you that a passive hub isn't all that great. It might work in some one-off situations, but for a real product they stink. They will limit network bandwidth in weird ways, limit your max cable length, etc. </p>
<p>There are several companies that make Ethernet switch chips. Micrel is one of them, and more importantly Digikey has them in stock. I haven't read the datasheets to know now suitable they are, but it looks promising.</p>
<p>Using a CPU with two embedded Ethernet controllers can be a good option, and would be the option that most companies would choose. But for this to work well, the CPU should be at least a 32-bits, like an ARM or PowerPC. The CPU needs to be running a reasonable TCP/IP stack and be setup to route packets between the two Ethernet controllers. Companies like AMCC and Freescale make these. TI has one on their roadmap, although I don't know if it's available yet. </p>
<p>So I don't know which one will be a good solution for you. My guess is that you'll have to choose between the lesser of three evils, but that's frequently the way engineering works.</p>
|
<p>I am designing a board with Ethernet input, but would like to have the Ethernet re-routed.</p>
<p>So the board should have two RJ-45 connectors, one which is the main Ethernet (board is using this port for accessing the network), and another which is just re-routing of Ethernet signal.</p>
<p>(Ethernet) --> My Board --> (Ethernet) --> PC(or another board).</p>
<p>I have looked around for a description, circuit or chip for doing this, but with no luck.</p>
<p>I have found the passive 3-port Ethernet hub, but I'm not sure whether that circuit is any good for my application.</p>
|
Ethernet two-port hub (re-routing)
|
2011-03-29T07:43:13.417
|
12213
|
|sensor|
|
<p>have you considered finding a cheap gram scale and taking out the load cell out? usually I see them accurate down to +-.1 grams</p>
<p>As stevenh pointed out, cheap scales may not be that accurate, compared to there "box values" If you are just using a load cell from it you should be able to get at least the same and or better accuracy if you have a sufficient design for your ADC and cell combo.
To get even better results i would suggest getting a small set of standard weights to calibrate your device.</p>
|
<p>In a project, I want to measure weight with the resolution of 1 gram. Things I want to weigh, are max of 6 grams and I need to diffrentiate between a 5 gram thing and a 6 gram thing.... So I would require a Load cell with resolution of 1 gram.</p>
<p>I searched in Local Market as well as online but I couldn't find a good one.... Can anybody have suggestions what can I do?? Or Links where such load cells are available will be way good....If anyone used such load cells then...then I would be the happiest person on earth! :)</p>
<p>Thanks!</p>
<p>P.S. I been to <a href="http://www.omega.com/guides/loadcells.html" rel="nofollow">omega.com</a> but these are very costly.... If no other alternative.... I have to choose them or close the project.... Second option would be easy for me! :(</p>
|
Load cell required with resolution of 1 gram
|
2011-03-29T10:17:45.870
|
12215
|
|voltage-regulator|
|
<p>You could do it, for just a few milliamps, with two zeners and a resistor.</p>
<p>If you did it this way you could probably get away with a 1206 SMD resistor (0.5W) and a dual series SOT23 zener, in total smaller than most linear regulator packages. Here is a possible circuit (output is 9.1V per rail):</p>
<pre><code> ____
48V -|10k_|-+-- 9V
|
|__|__
/ \ | 9.1V
/___\
|
|
+-- GND
|
|__|__
/ \ | 9.1V
/___\
|
Source COM -+-- -9V
</code></pre>
|
<p>I need to save space on PCB and have to convert voltage from +48 to +9, -9 and virtual ground. Is there a single IC that could do that?</p>
|
Voltage regulator IC with positive and negative voltage output
|
2011-03-29T11:05:49.587
|
12219
|
|arduino|sensor|components|piezoelectricity|
|
<p>A cheap vibration sensor such as SW-18010P consisting of a fine spring wire coiled around a rigid wire in a sealed package may well be sensitive enough. They act as a momentary switch contact when jolted, and cost a few pennies.</p>
|
<p>What's the cheapest way to detect vibration with Arduino?</p>
<p>What's the vibration sensor that I need?</p>
<p>I want to detect PING PONG NET vibration and light on led if touched.</p>
|
What's the cheapest way to detect vibration with Arduino?
|
2011-03-29T12:24:13.750
|
12230
|
|components|
|
<p>When tin, a common plating on components, is left exposed to the air, it will oxidize over time, forming tin oxide, a white powder that is insoluble in water. I believe that if your components are bright tin, the oxide layer will be fairly smooth and not "powdery", which may be the case if you have components plated with matte tin.</p>
<p>The flux in your solder (paste or rosin-core wire) should be able to remove a fair bit of the oxides, but if they are extremely oxidized you may have to add additional flux, or clean the parts somehow.</p>
|
<p>I can't post a picture, since I don't have a good camera.</p>
<p>I've noticed white powder on leads of some components. What could it be?</p>
<p>I'm sure that it isn't just dust, because there isn't any on the component bodies and was on some components which were stored in their own sealed bags. </p>
<p>I've seen it on all types of components, but not all components have it. I was unable to find any mention of it in any datasheets. I've seen in on for example Fairchild DB237 transistors, Piher potentiometers, various no name resistors and so on.</p>
<p>I did notice that most components which have the powder have flat leads. </p>
|
What is white powder on component leads?
|
2011-03-29T15:20:36.683
|
12237
|
|battery-charging|
|
<p>It sounds like what you're building is a dock that will accept multiple phones and power them all at the same time. A block of plastic with a micro-USB connector sticking up for each phone? </p>
<p>If every phone has a wall adapter that puts out 5V, or has a USB connector that accepts standard USB output (which is 5V at 0.5A), you can add up all the currents and make sure the power adapter for your dock can supply at least that much current at 5V. It's fine if it can supply more current, because the phones will only take as much current as they require. The official USB spec (thus most ports) only offers 0.5A, although some manufacturers give the device more current when connected to the wall adapter, notably the iPad. Making the power adapter unnecessarily large does add some extra risk in the case of a mishap like an accidental short circuit.</p>
<p>A fuse on each line might be a good idea. Ian suggested adding a diode between the main power supply and each phone's connector, but I'd be wary of that because 5V - 0.7V = 4.3V, which does not leave a lot of room for the phone's internal battery charger to step down to the 4.2V the battery will require to be fully charged. The phone is expecting to see 5V, not 4.3V, and is designed accordingly.</p>
<p><a href="http://en.wikipedia.org/wiki/Universal_Serial_Bus#Mobile_device_charger_standards" rel="nofollow">http://en.wikipedia.org/wiki/Universal_Serial_Bus#Mobile_device_charger_standards</a></p>
<p>If you are only powering the phones and not the batteries directly (removed from the phones), you don't need to worry about 4.2V, 1C, or how the battery is being charged. The phone will handle that for you.</p>
|
<p>I have a cell phone that has a 1500 mAh 3.7 V battery. It comes with a 700 mA charger but I've sucessfully used a 1 A charger with no problems. I'm now trying to make my own multi-device charging station and my first problem if figuring out the maximum amount of current I can use at 5V?</p>
|
How do I determine the maximum current for charging a li-ion battery?
|
2011-03-29T17:31:39.690
|
12239
|
|i2c|pwm|ultrasound|
|
<p>Thank you for linking to exactly what you are talking about -- it makes it much easier to get to the data sheets.
The question <a href="http://www.maxbotix.com/MaxSonar-EZ1__FAQ.html#How_can_I_use_more_than_one_MaxSonar_EZ1_in_the_same_system" rel="noreferrer">"How can I use more than one MaxSonar®-EZ1™ in the same system?" in the MaxBotix MaxSonar FAQ</a> lists several ways of using a bunch of them at one time (and some pitfalls to avoid).
Some of them use 2 pins of the MCU -- the same number of pins as I2C, but a completely different protocol.</p>
<p>If I understand <a href="http://www.sparkfun.com/products/9491" rel="noreferrer">the data sheet</a> correctly, one of those 2-pin methods is:</p>
<ul>
<li>wire pin 1 low the MaxSonar to enable chaining</li>
<li>Wire an output pin from your MCU to the RX pin of the first MaxSonar in the chain.</li>
<li>Wire TX of each MaxSonar to RX of the next in the chain</li>
<li>Combine the signals from all the MaxSonar PW pins (AND? OR? NAND? diodes?).</li>
<li>Wire that combined signal to a timer input pin on the CPU.</li>
</ul>
<p>Then software on the MCU</p>
<ul>
<li>pulse the RX pin of the first MaxSonar</li>
<li>Time the first pulse width to give the distance the first MaxSonar sees</li>
<li>Time the second pulse width to give the distance the second MaxSonar sees</li>
<li>...</li>
<li>After getting the pulse from every sonar (or timing out at 49 ms per sonar), do something with the data.</li>
<li>repeat.</li>
</ul>
<p>Perhaps one of the other methods listed in the FAQ would work just as well or better for you.</p>
|
<p>I'm thinking about getting a bunch of <a href="http://www.sparkfun.com/categories/84" rel="nofollow noreferrer">Maxbotix Ultrasonic rangefinders</a>. I'd like to use as few pins on my controller as possible. Since I don't think you can have multiple devices on an RS232 serial connection, I'd quite like to interface their PWM output with the controller using I²C.</p>
<p>Is there some I²C device I can buy that accepts around 8 PWM inputs, and stores a representation of <span class="math-container">\$\frac{\text{pulse width}}{\text{period}}\$</span> in its registers?</p>
|
Is there an I²C device out there for reading a set of PWM inputs?
|
2011-03-29T17:55:19.073
|
12242
|
|current|wire|wiring|fuses|
|
<p>Fusible links in automotive use are normally made with a short length of wire (25-35 mm) that is two wire gauge sizes smaller than the wire supplying the load. For example, if the wire is 12 AWG, use 14 AWG wire for the fusible link. (Convert American Wire Gauge, AWG, to whatever system of measurement you are using in your part of the world.) This will prevent a fire that destroys the vehicle, but the wiring in the system may still overheat and be permanently damaged.</p>
<p>If super-fast response is not required, consider replacing the fuses with an appropriately rated thermal circuit breaker. A thermal-magnetic circuit breaker, such as those used in house wiring, can be used for faster response to overloads. You may find that replacing the fuses two or three times costs more than the circuit breaker and its enclosure.</p>
|
<p>If I would like to use a piece of copper wire as a 150A fuse, what size of wire should I use?</p>
<p>It doesn't have to be 150A very accurately, the parameters I need the wire to meet are:</p>
<ul>
<li>it needs to conduct continuously 70A 10V-30V DC without getting red or overheating</li>
<li>it needs to conduct 120A sometimes for 15 seconds without melting</li>
<li>it needs to surely be melted before the current reaches 200A</li>
</ul>
<p>Easily available wires over here are: 0.5 mm^2, 0.75 mm^2, 1.0 mm^2, 1.5 mm^2, 2.5 mm^2, 4 mm^2, 6 mm^2, 10 mm^2. Will any of these do the job? I can combine a few if the required value is not in the above series.</p>
<hr>
<p>Edit: now I read more into the specifications of the device, and it is in fact rated to be fine with 600A for 5 seconds. Besides that I will be only ever using it continuously with 50A. Is that gap (50A - 600A) large enough to make a fuse out of copper? </p>
<p><a href="http://en.wikipedia.org/wiki/American_wire_gauge#Table_of_AWG_wire_sizes">This table of AWG wire sizes</a> suggests that a 2.5mm^2 copper wire will melt with about 750A in 1s, and with a little under 200A in 10s, so it looks like it will melt in time for the device not to be damaged. The device itself is wired with 10mm^2 insulated wire, and I mostly worry about that wire not to be damaged.</p>
<p>Now I only need to find out to what temperature will a short piece of uninsulated 2.5mm^2 copper wire heat-up with 50A continuous current flow, and will it not melt the thing it is secured in at that temperature.</p>
<p>By "continuous" use I mean max 1 hour at a time, with full attendance of me, so it will not run unattended like this.</p>
<hr>
<p>More info: The machine came originally with two 50A fuses wired in parallel. In fact I want to use a wire, because the fuses blow so often it starts to get expensive, on average I need 1 fuse per 1 hour of charging, so the fuses cost more then the electricity to power this. I don't know why they blow, because I have an ammeter wired in series with the fuse, and I never seen anything over 60A on the ammeter! The fuses don't blow randomly, I just can see the fuse slowly get red, it stays red for some time, and at one point it just melts. I've been watching this process and I didn't see over 60A while the fuse was melting, I was watching the ammeter all the time in the slow process of the fuse being melted. So if I need 1 fuse per hour, so be it, but I need some cheaper option then 50 cents a fuse if I am to use them at that rate.</p>
|
what size of copper wire can act as a 150A fuse?
|
2011-03-29T18:16:55.927
|
12248
|
|energy|fuses|
|
<p>Fuse resistance is dependant on temperature. In some case standards give (ENA 12.6 <em>The resistance of each rating of time fuse-link shall be measured at 60% of the melting time when carrying a direct current which causes melting in 0.2 seconds. The resistance values so measured shall not exceed the values given in Table 1.</em>
A more day to day approach is to measure the resistance (or divide volt by amp with a less than 25% rated current to avoid heating) in worst case the resistance will increase by a <strong>factor 6 to 8 just before fuse blow</strong> this can last for minutes, values found in literature & checked. This can be interesting to know how many watt to consider for an enclosure for instance
example of "special" TLF fuse Table 1</p>
<div class="s-table-container">
<table class="s-table">
<thead>
<tr>
<th style="text-align: right;">Time fuse-link rating(A)</th>
<th style="text-align: right;">Resistance ( )</th>
</tr>
</thead>
<tbody>
<tr>
<td style="text-align: right;">3</td>
<td style="text-align: right;">0.073</td>
</tr>
<tr>
<td style="text-align: right;">5</td>
<td style="text-align: right;">0.043</td>
</tr>
<tr>
<td style="text-align: right;">7.5</td>
<td style="text-align: right;">0.031</td>
</tr>
<tr>
<td style="text-align: right;">10</td>
<td style="text-align: right;">0.028</td>
</tr>
<tr>
<td style="text-align: right;">12.5</td>
<td style="text-align: right;">0.020</td>
</tr>
<tr>
<td style="text-align: right;">15</td>
<td style="text-align: right;">0.017</td>
</tr>
</tbody>
</table>
</div>
|
<p>If you have a common fuse, is there way quantify the power consumption which is flowing through this fuse, or could you replace the fuse with something that measures the power consumption but still works as a fuse?</p>
<p>If it is not possible, could you explain it is impossible?</p>
|
Is it possible to quantify electric power consumption on a fuse?
|
2011-03-29T19:46:48.723
|
12255
|
|arduino|microcontroller|pic|microprocessor|
|
<p>If you want something well supported by free (as in freedom) tools, Atmel's AVR line is probably the way to go. A working development environment is packaged in every major Linux distro, Mac OS packages are easily available, and I bet Windows packages are, also.</p>
<p>I'd advise that you stay away from Arduino. It's a platform designed to appeal to the amateur computer programmer who wants to make LEDs blink, not aspiring engineers. The software libraries and development tools will shield you from learning anything (except possibly how to get a JVM working on Linux...have fun!) and probably teach you some bad habits in the process. It's also very expensive. It's little more than an AVR with the reference circuit in the datasheet, a USB programmer attached permanently, and a pair of headers for "shield" modules which are for some reason not mounted at an interval of 100 mil, so you can't connect it to a breadboard. Of course, there's a breadboard shield you can buy, and it's expensive. Get yourself a reusable USB AVR programmer for the price of an Arduino and buy a $1 ATMega instead.</p>
|
<p>Here's my story: I got my electrical engineering degree BUT I do not have a lot of experience with circuits (OMG, right? O_O). Most of my education was about communication theory, so I really feel incomplete and want to apply my knowledge somewhere and start making something on a microprocessor. It would also be a good skill to develop for the workforce. Do you folks have any recommendations as to what type of microprocessor I should be working with? PIC? Arduino? Others? What is used most in the market and for production purposes? Does it matter? I hear Arduino has a very good community for help, but I hear it is more for "hobbyists"? Is that necessarily a bad thing? Any insight is much appreciated. Thanks!!</p>
|
Want to apply EE knowledge -- which microprocessor would you recommend?
|
2011-03-29T21:07:11.763
|
12260
|
|avr|usb|
|
<p>If I were you I would study the reference project for using the internal clock with a 5v design carefully. It's the <a href="http://www.obdev.at/products/vusb/easylogger.html" rel="nofollow">EasyLogger</a>.
You can download the schematic from the archives at the bottom.</p>
|
<pre><code>ar 29 22:12:14 stevendesktop kernel: [ 4265.290019] usb 5-1: device descriptor read/64, error -62
Mar 29 22:12:15 stevendesktop kernel: [ 4265.572782] usb 5-1: new low speed USB device using ohci_hcd and address 52
Mar 29 22:12:15 stevendesktop kernel: [ 4265.990018] usb 5-1: device not accepting address 52, error -62
Mar 29 22:12:15 stevendesktop kernel: [ 4266.160020] usb 5-1: new low speed USB device using ohci_hcd and address 53
Mar 29 22:12:16 stevendesktop kernel: [ 4266.580018] usb 5-1: device not accepting address 53, error -62
Mar 29 22:12:16 stevendesktop kernel: [ 4266.580032] hub 5-0:1.0: unable to enumerate USB device on port 1
</code></pre>
<p>These are the messages that appear in the logs when I connect my avr. What could of caused these errors.</p>
<p>pin D-
I have D- connected to a 68R resistor in series. The other end goes to my avr. I wired a 1.5K pull in parallel to the 68ohm resistor. A zener 0.5w 3.6v parallel to pin 2 of the type A socket.</p>
<p>pin D+
Wires in series to a 68ohm resistor. The other end to avr. A zener in parallel to the D+ pin. Also wired to int0 pin.</p>
<p>It's self powered at the moment so therefore I don't need to connect the 5v and gnd pins right?</p>
<p>When I connected the D+ pin to my scope I could see a square wave being generated. I tested the frequency it's bang on 16MHZ. Though I did notice occasionally it went down to 15.98.</p>
<p>So what could be wrong?</p>
|
USB connection not working VUSB
|
2011-03-29T21:26:40.500
|
12280
|
|gps|navigation|
|
<p>With no filter at all the most error you should ever see is 30 meters/second, but this will only last for 1 sample. In my past experiences, you should expect to see an error more around less than 1 meter a second, but with 0 mean. This equates to about +/- 2.25 miles per hour. However, for consumer GPS modules you will never see an error like this. There are several reasons for this, but it all comes down to filtering.</p>
<p>GPS systems like the Garmin and Tom Tom employ filtering algorithms to give you the most accurate position it can. One of the things that these systems do is they assume you stay on the road until they are very sure that you didn't. With the filtering on the position, it forces the velocity calculations to already be much more accurate then using the raw data. Then with the filtering on the velocity calculations you get a very accurate measurement.</p>
<p>NOTE: I should probably quantify what I mean by "very accurate". I thinking about the situation of you having a GPS in a car and comparing its accuracy to what the car says it is at.</p>
|
<p>How exact is the velocity that is showing in a GPS Navigation System like Navigon or TomTom?</p>
|
Velocity showing in GPS-Navigation Systems
|
2011-03-30T10:46:21.930
|
12283
|
|transistors|led|basic|
|
<p>Imagine that R2 were omitted, and suppose the left side transistor (which I'll call Q1) started out being turned on. Then the right side transistor (Q2) would have nothing to turn it on, and the left side transistor would be held on by current through R3, while the R4 and the LED would charge C2. The effect would be that the left LED would come on and stay on, while the right LED would never light.</p>
<p>Now add R2. This will cause C1 to charge to -0.7 volts, until Q2 turns on. Once that happens, the charge on C2 would cause the base of Q1 to go negative, turning it off. When that happens, left-side LED current will start flowing through C1 and the base of Q2, turning it on even harder. Once Q2 has turned on, it will keep Q1 off until C2 charges to -0.7 volts.</p>
<p>Note that while the circuit would have a stable state with both transistors on and both capacitors reverse-biased by 0.7 volts, in practice the winky-blink circuit always starts oscillating rather than entering such a state.</p>
|
<p>I am a beginner in electronics. I come to know about the oscillator using RC circuits (capacitor charge and discharge and time constant tells the behavior of circuit).</p>
<p>Then I saw the following circuit that blinks 2 LEDs timely in sequence.
Will somebody explain its working? I know that capacitor will charge and during charging the LED will be off and when they discharge they will turn on the LED.</p>
<p>But why are the transistors there?</p>
<p><img src="https://i.stack.imgur.com/G6Bx6.png" alt="This Circuit will blink LEDs timely"> </p>
|
How does an astable multivibrator LED blinking circuit work?
|
2011-03-30T11:42:20.837
|
12286
|
|pcb-design|decoupling-capacitor|
|
<p>What drives your concern about PCB real-estate? 0.1 uF and 1 uF caps are physically small, and usually adds only small routing complication. </p>
<p>Doing surface mount devices? Try adding the caps on the back side of the board. </p>
<p>Doing socketed-DIP's? You can get sockets with built-in capacitors, so you could design without the caps, and change your socket if you find that you need them.</p>
|
<p>I know it's good practice to use bypass capacitors near the power pins of your ICs, but I'm now moving on from the breadboarding stage to the PCB-design stage, and I'd like to know if there are any good rules of thumb for when the caps are actually needed (I don't want to waste any PCB real-estate).</p>
<p>For example, what if I have a simple counter IC fed by a 250KHz clock signal? 31.25 kHz? If all input and output signals of an IC are changing at sufficiently low frequencies <em>and if the IC doesn't draw much current</em>, can I leave off the bypass caps? </p>
<p><em>Edit: inserted text in italic.</em></p>
|
Bypass capacitors needed in low-frequency digital logic systems?
|
2011-03-30T12:57:35.560
|
12291
|
|psoc|capsense|
|
<p>Some years ago we were going to do a project with another company and their design engineer wanted to sell us the idea of the PSoC, which he seemed to think of as the best thing since bread came sliced. My colleagues and I had a look at it and dismissed it.
Cypress sales engineers stress on the idea that you can reconfigure your PSoC in during runtime. Is that so great? No! If I have configured blocks as timer that's because I need a timer <em>all the time</em>. Other microcontrollers <em>do</em> have timers which are available all the time.<br>
And talking about timers. IIRC one building block could be used as an 8-bit timer. For a 32-bit timer you needed 4 blocks, and with that most of those great reconfigurable blocks were used up.<br>
Maybe things have changed since, and there may be more resources on recent parts, but at that time PSoC certainly wasn't an added value over other microcontrollers to us. (We were using for example NXP LPC2100 at the time.)</p>
|
<p>Hey, yesterday I saw a demo (which was actually meant for my seniors) of a PSoC 5 board by cypress at my college. They demonstrated how to use the capsense built into the board and one of the PSoC chips to turn an LED on and off. This is basic Hello World stuff.</p>
<p>Although I thought it was cool and all, I really couldn't figure out in what way could I use those boards. Yes they eliminate all the need for making my own hardware, but how would I use this capability?</p>
|
What exactly is the use of PSoC?
|
2011-03-30T13:53:07.040
|
12294
|
|avr|compiler|avr-gcc|
|
<p>A little explanation of what's really going on:</p>
<p>The <code>-l</code> argument order does not normally matter on computers since most libraries are dynamically loaded (.dll, .dylib or .so) and are truly <em>linked</em> only at program startup time.</p>
<p>OTOH on the AVR all libraries are static. When linking with static libraries the linker adds to the program only the functions he currently needs from the library.
If you pass <code>-lm</code> on the command line before a file that needs a particular function you will get unresolved symbols errors.</p>
|
<p>So this seems to be a generic issue. "libc.a" is associate with some sort of incompatibility with floating point math and/or the correct library used.</p>
<p>I've added the "-lm" as suggested on the forums, but still unable to link/compile correctly?</p>
<p>Any other suggestions? </p>
<p><code>
/opt/local/lib/gcc/avr/4.0.2/../../../../avr/lib/avr5/libc.a(cmpsf2.o):../../../libm/fplib/cmpsf2.S:58: multiple definition of <code>__ltsf2'
/opt/local/lib/gcc/avr/4.0.2/avr5/libgcc.a(_lt_sf.o):/opt/local/var/macports/build/_opt_local_var_macports_sources_rsync.macports.org_release_ports_cross_avr-gcc/work/build/gcc/fp-bit.c:1272: first defined here
/opt/local/lib/gcc/avr/4.0.2/../../../../avr/lib/avr5/libc.a(floatsisf.o):../../../libm/fplib/floatsisf.S:44: multiple definition of</code>__floatsisf'
/opt/local/lib/gcc/avr/4.0.2/avr5/libgcc.a(_si_to_sf.o):/opt/local/var/macports/build/_opt_local_var_macports_sources_rsync.macports.org_release_ports_cross_avr-gcc/work/build/gcc/fp-bit.c:1334: first defined here
/opt/local/lib/gcc/avr/4.0.2/../../../../avr/lib/avr5/libc.a(modf.o):../../../libm/fplib/modf.S:88: relocation truncated to fit: R_AVR_13_PCREL against symbol `__subsf3' defined in .text section in /opt/local/lib/gcc/avr/4.0.2/avr5/libgcc.a(_addsub_sf.o)</p>
<p></code></p>
|
avr-gcc(4.4.2)/avr-libc linker issues
|
2011-03-30T14:41:38.293
|
12300
|
|arduino|
|
<p>I have just solved this type of problem on my Arduino Mega.
I had uploaded the program given in Example →communication →MIDI and the Arduino went on transmitting data to serial port and <strong>I could't upload any new program</strong>.</p>
<p>What I did to solve:</p>
<ol>
<li>My Computer(Right Click) →<strong>Properties</strong></li>
<li><strong>Device Manager</strong></li>
<li>Found Arduino in Port List and open properties of it. (only available when it is connected to PC)</li>
<li><strong>Port Setting →Advanced</strong></li>
<li><p>Uncheked the <strong><em>Use FIFO Buffers</em></strong></p></li>
<li><p>Then uploaded</p>
<ul>
<li>I think the continuous receiving of data for computer can full the FIFO Buffers</li>
<li>I wish it works for all Arduino</li>
<li>I just tested on Arduino Mega 2560 ADK and worked</li>
</ul></li>
</ol>
|
<p>I've got a big problem with my new Arduino. I made a big mistake, and now I can't anymore connect to my arduino. Is there any possibility to recover the Arduino, or to <strong>stop</strong> the execution of code definitly?</p>
<p>Here my code:</p>
<pre><code>void setup () {
Serial.begin(9600);
}
void loop () {
Serial.write("Hello World!");
}
</code></pre>
<p>My problem is, that this code is executed so immediatly after booting the Arduino, and I can't upload something different to the Arduino...</p>
<p>Please help me. </p>
|
Arduino - Stop execution of code definitly
|
2011-03-30T16:40:24.540
|
12302
|
|microcontroller|microprocessor|assembly|
|
<p>my suggestion is any one who is going to start studying about microcontrollers and processors should read the book naming "code the hidden language of computer" if you study that almost you are expert with processors and for programming avr better use poney prog programmer and program from atmel studio6.1 from atmel official site</p>
|
<p>So I'm wanting to learn Assembly first on an MP, then move onto C (since it seems like that's what most of them use).</p>
<p>I'm wanting to get into Embedded Programming, I really love low level C stuff (Kernels/Modules for Linux is mainly what I've done), but I love the idea of being able to program even lower level than that (Microcontrollers/Microprocessors).</p>
<p>I know about Arduino, and that's great and all, but I can't find many resources for using Assembly with them. Atmel AVRs seem to be very popular (and cheap), but when it comes to the actual hardware portion (hooking them up on a breadboard, etc.), I'm not finding much information.</p>
<p>Any suggestions/information or resources that you guys/gals know about please let me know.</p>
<p>Edit: Another thing:
It seems like all the Microprocessor books I read (Usually AVRs) talk about the microprocessor itself, and programming it. But I have yet to see a book that actually talks about installing all the components yourself (microprocessor, memory, power, etc.). If I could find something that walks me through that I'd be in business. (I want to learn from the ground up.) Not to mention I have no idea how you would communicate between them.</p>
|
What is a Good Starter Microprocessor to learn Assembly?
|
2011-03-30T17:36:49.390
|
12305
|
|wiring|automotive|negative|
|
<p>You can connect the grounds in one point or leave them separate. As long as the only common point between the two circuits is the isolated power supply you are free to do as you wish.</p>
<p>If OTOH you want to connect them somewhere (to use the car antenna or sth.) then you should carefully choose the connection point (or even points) to avoid ground loops and ground noise.</p>
|
<p>Normally in a car's DC installation the negative is on the car's body. Is it just to make it cheaper by not having to provide two wires everywhere, but just one and use the car body as negative, or is there another more important reason it is done that way?</p>
<p>I ask, because I want to make a secondary DC installation in the car, with another battery, different voltage, to be used for my electronics, computers, etc. The second installation will have a separate battery, but that battery will be charged off the main installation - not directly, but through a charge controller, basically a DC-to-DC converter with current limit, which will have separate positive and negative terminals for both input and output.</p>
<p>How do you recommend to wire the negative of this secondary DC circuit, should I keep it separate, isolated from the car body, or should I also connect its negative wire to the car body, so use a common ground for both installations?</p>
|
Is it a good idea to make a second DC installation in a car with its negative separate from the car body?
|
2011-03-30T18:16:54.080
|
12312
|
|datasheet|hysteresis|
|
<p>One point not yet mentioned about hysteresis: any circuit with hysteresis has some possibility of exhibiting metastability on either the rising or falling edge (circuits may be designed to eliminate the probability of metastability in one direction, at the expense of increasing it in the other). For example, if an input is designed to switch high at precisely 2.10 volts and low at precisely 2.00 volts, one can pretty well figure that if the input goes to 2.15 volts, it will be regarded as high until it goes below 2.00 volts. If, however, the input goes to precisely 2.10 volts and then down to 2.05, it's possible that the registered value might never go high, go high and stay high, go high and then low, or even start going randomly high and low until such time as the input goes above 2.10 or below 2.00 volts.</p>
<p>There are a variety of ways to minimize the risk of an input gate going into a metastable state, but the possibility cannot be totally avoided. One could have a three-state output with "clean high", "clean low", and "uncertain" states, and guarantee that if "clean high" was asserted, "clean low" could not be asserted unless the input fell below 2.0 volts, and likewise if "clean low" was asserted, "clean high" could not be asserted until the input rose above 2.10 volts. Unfortunately, there'd be no way to prevent oscillation between "clean high" and "uncertain", or between "clean low" and "uncertain". One could try to latch the "clean high" and "clean low" signals, but there'd be no way to guarantee that they wouldn't violate the setup/hold times of whatever latching circuit one tried to use.</p>
|
<p>I'm looking at a datasheet for a digital circuit and it specifies that the typical input hysteresis is 100 mV. What does this mean exactly? </p>
|
what is "input hysteresis"?
|
2011-03-30T19:41:56.583
|
12316
|
|sensor|wireless|
|
<p>You could use a simple Infra-red LED, and a photo diode. You may have to adjust the LED intensity with a potentiometer to calibrate the range.</p>
<p>This will sense proximity providing there is line-of-sight.</p>
|
<p>I'd like to create a small device that can tell when it's near another created device or sensor. When it detects the other device, it lights up an LED. </p>
<p>Maybe maximum detection range of a few feet. No need for any unique ID values or complex data exchange, just a simple "Yes I detect one, no I don't" sort of control.</p>
<p>Any suggestions on how this could be done in a low power, portable sort of way? Because its requirements are so simple, something like RFID seems overkill (even if it could be made to work).</p>
|
WTB (Build): Low power "proximity to a device" detector
|
2011-03-30T20:43:08.473
|
12343
|
|pcb|pcb-fabrication|toner-transfer|
|
<p>I use a GBC Creative 9 laminator with great results and I performed the exact modification you're trying to make! (except I followed these instructions: <a href="http://frikkieg.blogspot.com/2009/08/us-pcb-laminator.html" rel="nofollow">http://frikkieg.blogspot.com/2009/08/us-pcb-laminator.html</a>)</p>
<p>I just went ahead and swapped out the parts as the tutorial said, and it's worked great. You can see <a href="http://www.robotenthusiasts.com/tutorials/?p=46" rel="nofollow">my pcb making method and results here</a>.</p>
|
<p>After receiving a ton of feedback from <a href="https://electronics.stackexchange.com/questions/7003/best-one-off-diy-pcb-creation-technique">this post</a>, I decided to give the old toner method a try once again. I grabbed a GBC Creative 9 laminator off of <a href="http://rads.stackoverflow.com/amzn/click/B000MBLW90" rel="nofollow noreferrer">Amazon</a> for $23 and am now looking to modify it to produce more heat for the transfer.</p>
<p>I ran across <a href="http://ultrakeet.com.au/index.php?id=article&name=fritzHack" rel="nofollow noreferrer">UltraKeet Australia</a> where PodeCoet modified a similar GBC laminator for the same purpose. I got the laminator in the other day and quickly took it apart only to realize that my model was slightly different. Unlike his model, I only have one thermal switch in my unit.</p>
<p>Here is a picture of the thermal switch and thermal fuse that comes with the Creative 9 laminator.</p>
<p><img src="https://i.stack.imgur.com/LnSUL.jpg" alt="Thermal Switch (left) and Thermal Fuse (right)"></p>
<p>One thing that I noticed on PodeCoet's laminator, he has a switch on the front of his unit which allows 3mm and 5mm items to be inserted. He also labeled the two thermal switches noting that one was for 3mm and one for 5mm. This may explain the missing component on my system.</p>
<p>I am wondering if and how I can safely modify my unit to produce more heat for the Toner Transfer method. Also, if anyone can point me in the direction of a component that will put out around 200-220 celcius, I would be much appreciated as I have not found anything cheaper than $35 (on Mouser).</p>
<p>Any help is appreciated. Thank you in advance.</p>
|
Toner Transfer + GBC Creative 9 Laminator: GBC Mod Question
|
2011-03-31T07:37:42.017
|
12346
|
|power|audio|dc-dc-converter|power-line-communication|
|
<p>You would need to use a modulated signal, not the baseband audio because the low frequencies will be heavily attenuated by capacitance on the d.c. voltage, and because of the rate of change of your d.c. voltage could be at low audio frequencies (rumble). I'm sure you could get reasonable audio quality if you use a suitable modulation that could be seperated out from the d.c./low frequency signal.</p>
|
<p>I have multiple generators that are producing a variable DC voltage between 0 and 18volts each that are being sent to an inverter for an AC output used to power various devices.</p>
<p>I really need to be able to transmit an audio signal back to each of the generators, and would really like to avoid having to add additional wires. Would it be possible to piggyback an audio signal of a usable quality over these variable DC lines?</p>
<p>I've searched around and suspect <a href="https://electronics.stackexchange.com/questions/1654/injecting-a-communication-signal-over-dc-power-supply-lines/1661#1661">this answer</a> might be appropriate, but they're mostly talking about communication signals, and I'm not sure if the required fidelity for an audio signal would be possible. I'm also not sure the effect a highly variable DC voltage would cause.</p>
<p>Thanks</p>
|
Transmitting audio over variable voltage DC power line?
|
2011-03-31T09:00:30.447
|
12360
|
|power-supply|power|adapter|
|
<p>I add to the 8pins answer. Iam interested too, to fix a tool with broken battery. i retrieved the thread from archive.org and the circuit is here <a href="https://gofile.io/d/xYVFlB" rel="nofollow noreferrer">https://gofile.io/d/xYVFlB</a> . Is a SMPS small to fit inside the tool (in the battery case) with toroid transformer. I will try it with a simple PSU.</p>
|
<p>I have a dewalt 18V cordless drill. I am wondering if it is feasible to build an adapter that can power the drill from a standard US wall socket?</p>
<p>A typical DeWalt drill needs 2.6 amps with no-load. I am assuming this jumps significantly higher under load. Most DeWalt motors have a stall current over 250 amps...</p>
<p>Any insight would be greatly appreciated!!</p>
|
Is it possible to power a cordless drill from wall socket adapter?
|
2011-03-31T13:58:36.723
|
12362
|
|microchip|
|
<p>The term "tri-state" is often used informally to refer to the act of floating a pin; I know that National Semiconductor used to have a trademark on the term, though its widespread usage as a common term may have rendered it unenforceable.</p>
<p>Incidentally, in case anyone's curious why the OPTION instruction is so called, and the settings aren't controlled via a register, on the original General Instruments PIC devices, there were no TRIS or OPTION instructions; instead, the selection of which pins should be floating, as well as the settings for the timer/watchdog prescalar and modes, were part of the factory specification (the devices used mask ROM, so the whole program would be a factory spec).</p>
|
<p>When reading/writing/talking about electronics, I like to understand the acronyms and mneumonics for abbreviations used for registers, functions, filenames, pin names, etc. Usually, the first time the abbreviation is used, either the context or a parenthetical note sets it off, or it's blatantly obvious. </p>
<p>On the Microchip dsPIC parts, the TRIS register controls the data direction. I can't find a note which uses the full word/phrase that would be abbreviated or have the acronym TRIS. ('The Register Input/output Settting' is about the best I can come up with, although 'TRIS Really Is a Silly abbreviation' is a close second guess).</p>
<p>How do you remember this? I've heard it pronounced as a word, but I'd like to know what it means to make it easier to remember, read, and write.</p>
|
What is the meaning of Microchip's acronym TRIS for data direction registers?
|
2011-03-31T14:44:35.483
|
12383
|
|audio|fpga|verilog|spartan|
|
<p>The interface to an AC97 codec is a bit more complicated than straight digital audio. The serial data consists of 256-bit data frames; each frame contains several channels of 20-bit samples. The overall data rate is 12.288 MHz; dividing by 256 gives the sample rate of 48 kHz. Part of the 256-bit frame is dedicated to control messages, e.g. to set mixer registers. You may need to do this once after power up/reset to set the volume.</p>
<p>The AC97 spec is available <a href="http://download.intel.com/support/motherboards/desktop/sb/ac97_r23.pdf" rel="nofollow">from Intel</a>. Writing your own master is not unreasonable but it will take some time. You may also be able to find one you can reuse. <a href="http://opencores.org/project,ac97" rel="nofollow">OpenCores has one</a>. There's a very barebones AC97 controller and some general information about the protocol <a href="http://www-mtl.mit.edu/Courses/6.111/labkit/audio.shtml" rel="nofollow">here</a>.</p>
<p>I can't remember how many of the AC97 registers are standardized. The manual I found online for your board says it has an LM4550 codec. Assuming that's right, you may want to refer to the <a href="http://www.national.com/opf/LM/LM4550.html" rel="nofollow">LM4550 datasheet</a> for a complete list of configuration registers.</p>
|
<p>I'm a beginner to FPGA programming. I just started programming an Atlys Spartan 6 board and so far have written one program to blink LEDs in a counter pattern.</p>
<p>Now I'm trying to send the clock signal down-sampled to audio frequencies to the AC97 codec. Here is the Verilog program I've written:</p>
<pre><code>module music(
input clk,
output ac97_sdo
);
reg [25:0] count_aud;
reg clk_aud;
assign ac97_sdo = clk_aud;
/* down-sample the 100MHz system clock to 1kHz */
always @(posedge clk)
begin
count_aud <= count_aud + 1;
if (50000 == count_aud)
begin
clk_aud <= !clk_aud;
count_aud <= 0;
end
end
endmodule
</code></pre>
<p>The bit-file generation is fine, but the code doesn't seem to work - I don't hear anything either on Line Out or on HP Out (I don't know how to control the output, either), and I don't have enough experience with the AC97 specification to figure this out. The audio part of the UCF is:</p>
<pre><code>NET ac97_bitclk LOC = L13;
NET ac97_sdi LOC = T18;
NET ac97_sdo LOC = N16;
NET ac97_sync LOC = U17;
NET ac97_reset LOC = T17;
</code></pre>
<p>Do I need to use the bit clock, sync, reset, etc. to make this work? If yes, how can I go about it?</p>
<p>I couldn't find any detailed information on the Atlys Reference Manual.</p>
<p>Please help!</p>
<p>Thank you.</p>
|
Using the AC97 Codec on an Atlys Spartan 6 Board
|
2011-04-01T00:46:57.587
|
12385
|
|arduino|serial|computers|
|
<p>You can use <code>Serial.print("DATA")</code> and on your pc build a program that listen on serial port.</p>
<pre><code>if (Serial.value == "DATA") {
doWork()
}
</code></pre>
<p>When you get correct value, do anythink. </p>
<p>Like <a href="http://www.albertopasca.it/whiletrue/2011/03/arduino-mail-notifier-cs/" rel="nofollow">gMail notifier</a>.</p>
<p>hope this helps.</p>
|
<p>How can I send data to the arduino from the computer? I'm thinking sort of a prompt on the command line and some commands like "led1 on". Then, the arduino would process that and light up a certain led.</p>
|
How can I send data to the arduino from the computer?
|
2011-04-01T01:42:50.597
|
12388
|
|frequency|generator|counter|
|
<p>You can use several methods:</p>
<p>1) PLL - for example <a href="http://www.analog.com/en/rfif-components/pll-synthesizersvcos/adf4002/products/product.html" rel="nofollow">ADF4002</a> works up to 400 MHz. The resolution is limited, because it works by multiplying reference frequency. This chip will work with your VCO.</p>
<p>2) Integrated PLL synthesizer - <a href="http://www.analog.com/en/rfif-components/timing-ics-clocks/adf4350/products/product.html" rel="nofollow">ADF4350</a> can generated frequencies within 137-4400 MHz range with fairly good resolution. However, within your range the result will be more square wave rather than sine. </p>
<p>3) DDS - direct digital synthesis - <a href="http://www.analog.com/en/rfif-components/direct-digital-synthesis-dds/ad9910/products/product.html" rel="nofollow">AD9910</a> can generate frequencies up to 400 MHz with resolution under 1 Hz. </p>
<p>Trying to tune wideband VCO without any stabilization and measuring the result will not provide stable frequency.</p>
<p><a href="http://www.analog.com/en/rfif-components/pll-synthesizersvcos/products/index.html" rel="nofollow">Here is a list</a> of PLL chips and PLL synthesizers made by ADI. Other vendors have some too, but usually working within GHz range. </p>
|
<p>I want to generate a precise frequency in the 500MHz range, and have therefore purchased a VCO (200MHz to 400MHz).</p>
<p>To measure the VCO output frequency, I'm trying to build a high frequency counter up to 500MHz.</p>
<p>The way I have been trying to do it, is using the MC100E016 (ECL Synchronous Binary Up Counter). Take the Q6 (/64) output and feed this into my oscilloscope (and later MCU). But this seems hard to get to work, because the PECL logic sets high demands on the input.</p>
<p>Do you have any good and easy way to build a frequency counter, or even just a divider would be fine (my 100MHz oscilloscope can measure the output from the divider).</p>
<p>Or even better, generate a 200MHz to 400MHz range frequency, who's frequency can be set (digital or what ever).</p>
|
frequency generator / counter
|
2011-04-01T07:43:11.360
|
12390
|
|transformer|
|
<p>If you need 12 VDC, it may be simpler to use an off-the-shelf wall wart with a 12 VDC output. Such devices <em>do</em> convert to DC for you. A few of them use exactly the circuit BG100 shows, but nowadays many of them use a switching regulator technique that requires <em>more</em> parts, but has a lower net cost.</p>
|
<p>My circuit uses main electricity in parts of the circuit. However my AVR and other components only need 5V. So I'm using a step down transformer to generate 12V. It's then regulated to 5V. </p>
<p>The transformer won't convert it to dc for me will it? </p>
<p>It just steps it down then outputs a certain voltage depending on it's coils. So I would need to convert it to dc myself right?</p>
|
Using a transformer to step down 230V to 12V
|
2011-04-01T10:38:48.683
|
12395
|
|signal|rectifier|
|
<p>The short answer is that this is the "magic" of capacitive coupling. The signal voltage is superimposed on top of the node "bias" voltage (which is 0.6V). Therefore the voltage at C,D2,R1 is 0.6V + Vin, not just Vin. And therefore the diode D2 must turn on, have a 0.6V drop across it (assuming D2 and D1 identical), and the output voltage must then be basically equal to Vin. It is important to note that just the AC part of Vin gets through the cap. The DC part is blocked, if there is a DC part.</p>
<p>The longer answer goes like this:</p>
<p>In your response to my comment, you wrote "C, D1, R1" but I think you meant "C, <strong>D2</strong>, R1". So I will continue with that assumption. </p>
<p>First, note the node D1, R1, R3 will basically be clamped to 0.6V at all times. This will not change no matter what the input signal is. </p>
<p>Second, remember that the I-V relationship for a capacitor is </p>
<p>$$i_c = C\frac {dV} {dt}$$</p>
<p>What does this mean? It means that if your input voltage source changes, then the voltage across the cap changes. Therefore you have a nonzero $\frac {dV} {dt}$. Therefore you will have a nonzero current. (It's easy to get confused about signs at this point... bear with me) This is the differentiator action that you mentioned in your question.</p>
<p>So let's assume an increase in input voltage which would cause a current to flow "through" the cap into the circuit (to the right). Where does the current go? It can either go through R1 or D2 or both.</p>
<p>We started with the assumption that D2 is off, so let's first assume that the current flows only through the resistor R1. That causes a voltage to be developed across R1. So the voltage at C,D2,R1 becomes 0.6V + I*R1. <strong>Here is kind of the key part</strong> for you to see, I think... see that the voltage at that node must have an 0.6V offset? That is because the change in input voltage causes a current to flow through the capacitor, not a voltage. So the current causes an additional voltage to be developed across the resistor R1, which adds to the voltage at that node due to the diode D1.</p>
<p>Okay, so continuing on, this means that the voltage across D2 would be greater than 0.6V, since the cathode ("line side") of the diode is presently at 0V. If the diode forward voltage is 0.6V, then we have an extra voltage (equal to I*R1) that would cause the diode D2 to turn on--which would mean that the diode would present a very low resistance compared to R1, which means current would flow through the diode D2, also. </p>
<p>So, our initial assumption that the current flows <strong>only</strong> downward through R1 must be incorrect--instead, the current must also flow through D2 and then through R2. Note that the current that flows through D2 is then limited by the 10K resistance R2, so it will indeed be small compared to the current that flows through R1 (by a factor of about 1/10, in fact). But regardless of the amount of current that flows, the output voltage still effectively "follows" the voltage at C,D2,R1, just shifted down by one diode drop (0.6V). <em>EDIT: except of course for negative input swings, in which case D2 blocks. But I think that part is already understood.</em></p>
<p>That came out pretty lengthy. I hope it was clear. It's tough to talk about circuits without a chalkboard or something to draw on...</p>
<p><em>EDIT: I reread your comment, and you mention a square wave input. In the case of the square wave, the voltage at C,D2,R1 is not going to look like a square wave. It is going to look like a series of positive and negative spikes. This is due to the differentiating action of the capacitor. The square wave signal is "constant in the short term". It just switches polarity periodically. It is during those switching times that a signal will appear at the C,D2,R1 node, because only during switching is $\frac{dV}{dt}$ nonzero. This is all assuming several "idealities" which I will not list out at this time, in order to keep it simple. It's easier to think about if the input signal were a sine wave (easier for me, anyway).</em></p>
|
<p>I was reading an electronics book and came upon this circuit. </p>
<p><img src="https://i.stack.imgur.com/ZguAL.jpg" alt="enter link description here"></p>
<p>I am having a difficult time understanding why the voltage across D1 is 0.6V. I understand that that the reason is because the input signal's pp voltage is lower than 0.6v C and R1 make a differentiator then D2 rectifies that but none of that would work if the signal is less than 0.6v. I just don't understand why D1 is at 0.6V and how that makes D2 be higher than 0.6V. I was going to post a diagram but I don't have enough reputation.</p>
|
Help Understanding a signal rectifier
|
2011-04-01T13:51:50.687
|
12396
|
|communication|filter|digital-logic|
|
<p>It's a bandwidth-saving measure. Consider if instead of raised-cosine waveforms you used square waves (the beta = 1 case) - lots more harmonics, more bandwidth required. The raised-cosine limits the bandwidth at the expense of making the baseband signal more difficult to produce and detect.</p>
|
<p>This is in regards to digital communications. I have a link I've set up using <a href="http://www.gnuradio.org" rel="nofollow">GNURadio</a> that's sending BPSK modulated data through water via a LED. I can control the roll-off factor, $\beta$, of the <a href="http://en.wikipedia.org/wiki/Raised-cosine_filter" rel="nofollow">root-raise cosine filter</a>. What are the practical implications of this number? It seems that any value should work fine, since it fulfills the nyquist criteria (adjacent symbols have zero energy at the current symbol's sample point) and the energy/frequency is constrained. Is it mostly just a way to control the affects of jitter vs. slight savings in bandwidth?</p>
|
What are the practical implications of changing the rolloff factor of a root-raise cosine filter?
|
2011-04-01T13:55:52.487
|
12404
|
|arm|compiler|keil|
|
<p>This is the best method I have come up with recently:</p>
<p>In the build options, select create batch file.</p>
<p>When you initiate a build from the IDE, a batch file along with several text files are created based on the options set in the IDE. You need to track these IDE generated files in source control:</p>
<ul>
<li>*.bat</li>
<li>*.ini</li>
<li>*.__i</li>
<li>*._ia</li>
<li>*.lnp</li>
<li>*.sct</li>
</ul>
<p>Then foo.bat can be launched from a build script.</p>
<p>While this does create extra files that need to tracked in source control if you want to build reliably from the generated batch file, it does remove the need to rely on the Keil project file (foo.uvproj) and the IDE. I find it easier to compare differences, and thus track changes, to the generated text files (*.__i) that contain compiler flags than to the .uvproj file. Additionally, the batch file calls the various tools, armasm, armcc, armlink, directly. This gives you the direct output of each of those steps as well as a seemingly better potential for migrating a project to a different tool chain in the future if necessary.</p>
<p>I realize this answer sounds a lot like my original question, but I genuinely don't know of a better way of running a scripted build with Keil's tools. I asked to see what might come up from others. I don't completely disagree with the answer from @digikata, but I prefer to have compiler flags and the memory map in an easier format for tracking and to use more unix-style tools for compilation rather than launching an all-in-one compilation with the IDE. I think the all-in-one compilation from the IDE works well at my workstation, but not for the build server.</p>
<p><strong>EDIT</strong>: The build server runs on Windows Server 2003. I must confess that I have relented to using the IDE command line interface rather than a batch file. This just became too difficult to manage.</p>
|
<p>I would like run daily builds, or check-in/commit triggered builds of Keil MDK-ARM based projects. So far I've gotten things going with the batch file feature of the IDE. This does require you to build the project at least once with the IDE, then check-in the batch file and associated <code>.__i</code> and <code>._ia</code> files created by the IDE.</p>
<p>Additionally, the IDE puts lots of user specific things into the batch file like the Windows PATH variable. This could become a problem with multiple developers, because the batch file for building could be changed at each commit from a different developer.</p>
<p>Ultimately, one just needs to keep track of the various switches for <em>armcc</em>, <em>armasm</em>, and <em>ArmLink</em>.</p>
<p>Is there a way to use a more standard makefile to build Keil uVision projects? Is there a method of translating a uVision project file into a more maintainable build script?</p>
|
How can I use a build server with Keil uVision4 (MDK-ARM), script a build, use a makefile?
|
2011-04-01T14:38:58.410
|
12405
|
|power-supply|resistance|inductive|
|
<p>I would venture that any inductance in the resistors would be swamped by the output inductance of the power supply, so the likelihood that they'd cause any disturbance would be low.</p>
<p>I have a hard time believing that the inductance in a small cement wire-wound resistor could store enough energy to do any damage to the output of a power supply, especially one that doesn't have ORing (e.g. an ATX computer supply, which isn't intended to operate in parallel with another supply) - the output capacitors will do their best to absorb any energy kicked back from the inductance.</p>
<p>Imagine that you have 1 microhenry of inductance, and 1 A of current. The energy is:</p>
<p>\$\; E = \frac{1}{2} \mbox LI^2 = 0.5 \mu J \$</p>
<p>If that 1 A were to dissipate in 1 microsecond, the voltage would be:</p>
<p>\$\; V = L \frac{di}{dt} \mbox = 1V \$</p>
<p>The risks are minimal. </p>
|
<p>I'm doing my second ATX-to-bench supply conversion, and this time, I've decided to follow the "book" and place the correct minimum loads on all the rails instead of merely the 5V rail. This involves fairly small loads on the 3.3V rail and 5V rail (under 2W each), but a fairly sizable load on the 12V rail (12W). I've sourced very cheap cement resistors to provide the loads, but I understand that they are inductive loads, and I would like to know, will that cause a problem?</p>
<p>I assume it will not, because many of the loads in a normal computer are already inductive (HDD motors etc), but I would like confirmation from someone who knows a lot more about switching power supply design than I do.</p>
|
Can I use an inductive load in an ATX-to-bench supply project?
|
2011-04-01T14:40:47.180
|
12407
|
|dsp|
|
<p>I'll try to explain this in another way. Non 2^n numbers may help.
First of all, it's helpful to remember what the FFT (the DFT, basically) does: it multiplies a -windowed- signal with <em>the fundamental cosine (and sine) and the next N harmonics of it</em> that the algorithm creates. In a digital computer, the algorithm creates the cos(2 pi t n) [+ j sin(2 pi n t) but let's leave the sine aside], where <em>t</em> (and not n - n is the harmonic order) is the number of bins. This is the most important part: in a digital computer, t, the time, is quantised <em>in the provided bins</em>. So the computer calculates the cosine of the a -scalar- time value, x harmonic order x 2 pi.</p>
<p>Let's assume a sampling rate of 1kHz; this means that you get one value (voltage, usually) every 1 ms. If we set the bins number to 200, then the <em>longest</em> cosine that is created has a temporal length of 200 x 0.001 = 0.2 s, thus its period is 0.2s, thus its frequency is 5 Hz. This is the cosine that has only one peak and one trough in the entire bins set; it's the f_min. The next harmonic will have two peaks and two troughs, the next harmonic three of each etc. The harmonics will be multitudes of 5, 10, 15 etc. Hz. </p>
<p>If though we had selected 500 bins, then the fundamental cosine would be more expanded: it would have a temporal length of 500 x 0.001 = 0.5 s => f_min = 2 Hz. So in the latter case, the cosines are built up as a series of 2,4,6,8... Thus, we see that increasing the number of bins increased the resolution of the algorithm.</p>
<p>The resolution was increased because the <em>investigating tools</em> of the algorithm, the cosine (and sine) coefficients, are more dense. The input signal is affected only by the sampling rate.</p>
<p>If we invert the multiplications and convert the periods to frequencies, the types of the first post come out.</p>
|
<p>If I have sampled a signal using proper sampling methods (Nyquist, filtering, etc) how do I relate the length of my FFT to the resulting frequency resolution I can obtain?</p>
<p>Like if I have a 2,000 Hz and 1,999 Hz sine wave, how would I determine the length of FFT needed to accurately tell the difference between those two waves?</p>
|
What is the relation between FFT length and frequency resolution?
|
2011-04-01T15:23:02.963
|
12409
|
|capacitor|resistors|surface-mount|
|
<p>For assembling by hand I offer the following suggestions:</p>
<ul>
<li>Capacitors: For the ubiquitous 0.1uF ceramic decoupling caps go with 0603. They're nonpolar and unlabelled so the small size is not that much of an issue. You could buy a whole reel and be set for life. Every tantalum and electrolytic SMT cap is big enough that handling is not an issue. If you are following a datasheet recommendation to put down 2 or 3 decades of caps near a pin of a high-density package even 0805 will feel very big.</li>
<li>Resistors: They are labelled down to 0603 (usually). If you care about reading the markings it's worth checking a few with your own eyes to see what you can read. I find 0805 much more readable than 0603. A nice tradeoff for density vs handling is 4 resistor arrays. A 1206 array is basically 4 0603 resistors side-by-side. The package is much bigger and the label is much easier to read but the density is even better than 0603 (because there is no gap) and the soldering is only slightly trickier. These are great for pullups, series/stub terminations, LED arrays, etc.</li>
<li>Jumping over tracks: It's easy to home-etch a board with a trace going under (between the pads) of a 1206 or 805. You can manage nearly 10/10 rules cutting under 0603 but you will probably have to make your own land pattern for 0603 to do it (otherwise the pads will be too close).</li>
<li>LEDs: I find the ones in the tantalum-capacitor style A, B, C, D cases the easiest to orient and solder. Ones sized like resistors (0603) can be quite hard to orient without magnification. I usually use a setup where I can probe the LED to light it up to verify which way it's going in.</li>
<li>Other ICs: SOT-223 and SO-89 are nice for voltage regulators. SOT-23 is fairly easy to work with in 3-lead packages and slightly trickier in 5 or 6 lead. SO-8 is easy to work with. QFP with pitch 0.8 or 1.0mm is pretty easy but fine-pitch QFP (0.65, 0.5mm) requires a lot of flux and good technique. QFN, MLF, BGA and the like are very tricky to work with at home and can be difficult to route on 2-layer boards (especially without plated through-holes). I avoid PLCC when I can because it's neither small nor that easy to solder (it's very easy to bridge pins under the chip and very hard to desolder them).</li>
</ul>
<p>Mind your ground relief when connecting to surface mount pads. If you let your plane simply merge with a pad it can be very hard to solder even with a very good iron.</p>
<p>Remember that putting SMT components in your PCB <em>design</em> is almost free. There's no hole to drill and it's just a modification of the copper and silk masks. It won't affect the cost of the PCB at all. If you think you might need another cap or an indicator LED or a pullup resistor just put them all in the design. You can always DNI them.</p>
|
<p>So I need design a prototype PCB circuit and need to decide on using what kind of surface mount resistors and capacitors to use. But looking at digikey, there are so many types with many variations in size, manufacturers, etc.! </p>
<p>Since there is not really any strict requirements for my project, I'm assuming most of them would work fine. Cost and precision is not a huge issue for my case. </p>
<p>But what are some deciding factor on choosing which size/packaging/manufacturers to use? </p>
|
choosing surface mount resistor/capacitors
|
2011-04-01T15:55:36.003
|
12423
|
|pcb-design|esd|
|
<p>To start with I would use special <a href="http://www.vishay.com/diodes/protection-tvs-esd/arrays/" rel="nofollow">ESD suppression diodes</a> instead of common zener diodes; they're faster and withstand the high voltage better. </p>
<p>Your concerns about the relative placement are justified. The current may indeed split up and reach both protection diode and the controller. Therefore alway place the diode between the connector and the controller, and don't place them on a stub trace, because you will create the same problem. Place the ESD diode on the trace itself. </p>
<p>Make sure the distance and resistance to a ground plane are as short as possible. The larger the ground area the larger its capacity, and the lower the remaining voltage.<br>
Don't count too much on earth, that's too far away; a discharge can zap all you CMOS before it reaches earth. </p>
<p>If possible try to make some kind of "lightning rod", this can be a bare trace ending at 0.1mm from an also bare ground trace, so that an ESD discharge can spark over the gap.<br>
For one project we had a small slit in the enclosure which exposed the PCB to a distance of 2.5mm to the outside of the enclosure, at a place which would be touched by the user (button). So I feared that ESD discharges might pass through the slit. I removed all copper nearby, and placed an 0603 resistor, with one end connected to ground, the other under the slit. The idea was that, if we can't avoid a discharge, we at least know where it passes, so the resistor should work as a lightning rod. A resistor instead of a 0\$\Omega\$ jumper reduces the discharge current, which otherwise would couple to nearby traces and induce excessive voltages there. ESD tests results were fine.</p>
|
<p>I have a DB25 I/O connector, thru-hole. The pins connect to an SMT MCU, which I want to protect from ESD, specifically IEC 61000-4-2. I want to use SMT Zener diodes to protect the pins.</p>
<p>I am considering various layouts. I imagine the optimal layout would have the diodes between the DB25 and the MCU. In this way, an ESD event can be shunted to ground before it gets to the MCU</p>
<p>MCU <-> Diodes <-> DB25</p>
<p>However, I would like to take advantage of the thru-holes in the DB25 to simplify routing and reduce the number of vias that I would need. However, in doing so, the diodes will end up on the "other side" of the DB25.</p>
<p>MCU <-> DB25 <-> Diodes</p>
<p>Is this a bad idea? I'm slightly concerned about whether a sufficiently fast ESD strike could "split up" and reach the MCU before the diodes begin fully conducting.</p>
<p>If this is the case, would it be mitigated if the MCU <-> DB25 traces were run on bottom-layer, while DB25 <-> Diodes traces were on the top layer? Would the added vias between the MCU and DB25 encourage the ESD current to go through the diode instead?</p>
|
ESD Diode layout recommendations
|
2011-04-01T19:58:01.617
|
12432
|
|fpga|xilinx|vhdl|spartan|
|
<p>Here is an example for an IP STACK, written in VHDL. Is simulated, RTL and net-list post NGD:
<a href="http://bknpk.ddns.net/my_web/IP_STACK/start_1.html" rel="nofollow">http://bknpk.ddns.net/my_web/IP_STACK/start_1.html</a></p>
|
<p>I'm struggling with WebPack's bloat and random broken pieces when running in Linux. So, I'm thinking it may just be easier to use a different compiler/simulator. </p>
<p>Is it possible to use something different? Note, all I need to do is get a <code>.bit</code> file. I have the <a href="http://gadgetforge.gadgetfactory.net/gf/project/butterfly_one/">Butterfly One</a> which has an external programming application. (which only requires a .bit file)</p>
|
Can I use ghdl or some other VHDL compiler/simulator than WebPack with a Spartan 3E?
|
2011-04-01T22:58:57.100
|
12453
|
|voltage|diodes|high-voltage|rectifier|
|
<p>If the definition of <em>calculate</em> is by drawing with pen and paper, you can draw 230VAC lines 120 deg apart and multiply the phase-phase voltage by SQRT(2) drawing a box with equal sides.</p>
<p>The diagonal of the box is the rectified voltage.</p>
<p><a href="https://i.stack.imgur.com/1jrLT.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/1jrLT.png" alt="enter image description here" /></a></p>
|
<p>If a standard (in Europe and a large part of the world except North America and Japan) three-phase 400V AC (three lines having 230V RMS voltage if measured to neutral each) mains supply is rectified with a standard 6-diode rectifier like this:</p>
<p><img src="https://i.stack.imgur.com/w7RYk.png" alt="Three-phase, full-wave bridge rectifier circuit"></p>
<p>What DC voltage value will come out of the rectifier? How to calculate it having the RMS AC source voltage given?</p>
<p>Are there any other ways to wire diodes to get a different voltage (without using any transformers or anything else then just diodes), what are they and what DC voltage will come out then?</p>
|
if a standard three-phase 400V AC connection is rectified what DC voltage comes out of it?
|
2011-04-02T18:08:41.357
|
12459
|
|soldering|dc-motor|glue|
|
<p>With really small hobby motors, the usual scheme is to go for an 'interference fit', which is basically the 3rd option you mentioned. Even when the shaft is completely round and smooth, this works b/c the power and torques are so low. You will find this done in inexpensive toys, for example.</p>
|
<p>I don't know if this is the best place, but it seems the best out of the exchanges. How do you attach a plastic (or metal) gear to the little pole/nub that sticks out of a dc hobby motor? I have come up with 3 ideas: gluing, it doesn't seem like it would hold well; soldering, maybe but what about plastic gears; and making the hole on the gear slightly smaller so there is enough friction to hold it well, the most likely solution. Has anyone tried these or any other?</p>
|
Attach a gear to dc motor pole
|
2011-04-02T23:57:16.757
|
12462
|
|led|spectrum-analyzer|
|
<p>Since FFT is linear in frequency and you most probably want a logarithmic display you may also check the <a href="http://en.wikipedia.org/wiki/Goertzel_algorithm" rel="nofollow">Goertzel filter algorithm</a>. It may be faster if you only need the values of several frequency bins.</p>
|
<p>I want to design a simple LED audio spectrum analyzer kinda like <a href="http://www.youtube.com/watch?v=LIOUXr9v2RI" rel="nofollow">this</a>.</p>
<p>Which method would be less expensive to do:</p>
<ul>
<li>Use many filters for each frequency band, depending on how much bands and LEDS I want to use</li>
<li>Use a microprocessor to do FFTs</li>
</ul>
<p>Clearly, doing FFTs will have a certain lag, but would that lag be significant enough to overcome the expensive of the many filters of the first bullet? Which method would be most power efficient? Or is this extremely dependent on the hardware? Any input is much appreciated. This is the first time I am taking on such a project, and I want to get as much feedback as possible. Thank you!!</p>
|
Designing a Audio Spectrum Analyzer
|
2011-04-03T00:36:28.323
|
12464
|
|design|digital-logic|vhdl|
|
<p>It certainly does seem as though there should be a simplification -- after all one of the inputs is limited to a fixed value that is the same every time!</p>
<p>Unfortunately, that's only enough to get a small reduction in number of gates, but not much of a reduction in time to complete. That is because you do get simpler adders -- they only have 1 input plus carry, so the base adders have about 1/3 fewer gates. But the delay is determined by the carries, which are not reduced, they still must ripple up the whole chain. So, you don't get much meaningful speedup. And, if you want to go fast, at least half the gates are dealing with the carries, so that 1/3 gain reduces to about 1/6 fewer gates overall. In the end, roughly the same speed, and 85% of the size of a full adder.</p>
|
<p>I'm designing a very simplistic microprocessor as a project to help learn VHDL. So I'm needing something to increment the 8 bit program counter. I will need to increment it by two. Is there a better (either faster or less logic required for equal speed) design than using an 8 bit full adder? I'm also interested for the same thing for if you only needed to increment the PC by 1. </p>
|
Is there a more optimized way of making an incrementer than a full adder?
|
2011-04-03T02:32:57.327
|
12468
|
|arduino|power|electromagnetism|inductive|
|
<p>I would consider using four MOSFETs in an H-bridge configuration. Connect the top of the bridge to the 9V supply, the bottom to return, and drive the diagonally-opposite MOSFETs with PWM to alternate the current flow through the ringer.</p>
<p>The body diodes of the MOSFETs will clamp any kickback, so ensure that you choose robust-enough parts for the task. Trying to use discrete diodes is tricky when MOSFET body-diodes are in parallel with them.</p>
<p>You will need to generate high-side drive for the upper bridge FETs, perhaps with another wall-wart supply having it's return referenced to the 9V high side. (You need to bring the top MOSFETs several volts above +9 in order for them to turn on.)</p>
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<p>I'm currently working on a project that involves hooking up an arduino, a cellular shield, and an electromagnet (in this case, one of those old fashioned ringer boxes with a bell powered by electromagnets). I need the arduino to be able to power the ringer - presumably via a relay, and the power supply for the arduino and the ringer electromagnet will be the same 9v wall wart.</p>
<p>I know the arduino and the cellular shield have their own regulators, but should I be concerned about effects the inductive load of the electromagnet might have when it's turned on and off? What precautions should I take besides the obvious reverse-biased diodes?</p>
<p>Further, in order to use the ringer effectively, I need to be able to pass current through the electromagnet in both directions (each polarity moves the striker in a corresponding direction). Can anyone suggest a simple circuit that will achieve this with a minimum of external componentry?</p>
<p>Edit: Does this look like a reasonable interface circuit? It seems involved to use two relays to control a third electromagnet, but I can't think of another way to achieve what I need.</p>
<p><img src="https://i.stack.imgur.com/ECVRV.png" alt="Ringer interface circuit"></p>
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Safely connecting an solenoid/electromagnet to a switch-mode supply
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2011-04-03T04:43:23.553
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