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electronics.stackexchange.com

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648

|memory|books|system|

<p>After some searching, I found a website that gives a very good overview of memory: <a href="http://www.pcguide.com/ref/ram/index.htm" rel="nofollow">http://www.pcguide.com/ref/ram/index.htm</a>. Also has some good info on other components of a PC.</p>

<p>Is there a good book that talks about memory (SDRAM, DDR, NVRAM, flash etc) from a hardware/system perspective? Most of what I've been able to find deal with memory at the transistor level. I am looking for overview of the different types of memories, power requirements and PCB guidelines.</p>

Book on memory from hardware perspective?

2009-11-24T19:25:43.637

661

|solar-cell|voltage|

<p>Modern silicon solar panels provide 100 to 150 Watts per square meter of panel when pointed directly at the sun at midday. (9 to 14 Watts per square foot of panel). For a model size panel that's 10 to 15 <strong>milliWatts</strong> per square centimetre. </p> <p>This will be reduced to about 20% - 50% for bright cloudy conditions, 5% - 10% when very "overcast" but still somewhat bright. You will get almost no power from indoor lighting. </p> <p>On your model, if you managed a 100 mm x 150 mm (4" x 6") panel - same size as a typical small photograph - that would be 10 x 15 = 150 square centimetres or 1500 to 2250 milliWatts - say 1.5 atts in practice. That's large compared to the panels you see on most small portable device.</p> <p>If you could save all this energy to battery at 100% efficincy (you can't) and retrieve it with 100% efficiency (same) then you'd get "1 Watt hour" of energy per hour of sunlight. </p> <p>On a sunny Sydney December day <a href="http://www.gaisma.com/en/location/sydney-au.html" rel="nofollow">the wonderful Gaisma solar data site</a> says you effectively get 6 hours of full sunshine. </p> <p>So, on Australia's best days you'd get 1.5 Watts x 6 hours = 9 Watt-hours of energy. Let's call that 10 Watt-hours to make arithmetic easier.</p> <p>This means that after a day of Sydney summer sun charging you can run</p> <blockquote> <p>A 100 milliWatt motor for 100 hours<br> A 1 Watt motor for 10 hours<br> A 10 Watt motor for 1 hour<br> A 100 Watt motor for 0.1 hours = 6 minutes.<br> A 1 kiloWatt motor for 0.01 hours = 36 seconds.</p> </blockquote> <p>In the real world things don't scale quite so nicely - the faster you take energy from a battery the less efficient it gets. Lets ignore that for now.</p> <p>A 100 mW (milliWatt) motro can be useful but is too small for driving a model car.<br> A 1 Watt motor will allow a small toy with efficient gearbox etc to wander around slowly.<br> 10 Watts starts to get energetic but is far from RC racing style. 100 Watts is very capable and would hake many people happy - probably below the very top RC power level.<br> 1 KiloWatt :-) !!!!!</p> <p>So - to get RC levels of performance you get about 1 minute of running per hour of charging.<br> A 10 Watt motor will run for about 10 minutes per hour of charging. And a 1 Watt or so motor wild run in direct sunlight - as would be expected with a 1.5 Watt panel. </p>

<p>I'm looking to power a remote controlled car with a solar panel on its back. </p> <p>What size to power am I going to get? Is there one light enough that it wont slow the car down?</p>

Size to power trade off with solar panels

2009-11-25T09:51:31.393

688

|arduino|avr|atmel|programmer|

<p>I'm pretty sure that you can. All the schematics for the AVR910 programmer that I have found show it with a 6 pin interface. </p> <p><a href="http://microcontrollershop.com/product%5Finfo.php?products%5Fid=1918" rel="nofollow">10 Pin to 6 Pin Converter</a></p> <p>A converter ought to do it. Some programmers come with both interfaces, for instance the Adafruit Attiny USB programmer. Loooking at its schematic, I can see that the 10 pin programmer has the same connections on it as the 6 pin, just a few not connected pins. I assume that the 10 pin connectors pinout is standardised. You of course could convert it yourself or build a similar converter as above without too much difficulty.</p>

<p>Hi I've done some dev using AVR's. </p> <p>I'd really like to use the arduino but continue using atmel tools. </p> <p>Is this straightforward? </p> <p>Is there a converter that I can use my 910 programmer with? I think it's a 10 pin connector</p>

Arduino with atmel tools

2009-11-26T05:13:16.090

693

|atmega|avr|usb|

<p>The problem is that the AVR-GCC library file "iom88p.h" for the ATmega88P (and similar files for ATmega168P and ATmega328P) is broken. It doesn't define the SIG_INTERRUPT0 interupt vector handler and only defines the alternate handler name of INT0_vect. The V-USB assembly code uses SIG_INTERRUPT0 and for some reason avr-as doesn't pick up the null define. </p> <p>This library problem is also why you can no longer use defines like "PC3" in Arduino and must instead use "PORTC3".</p> <p>The solution in the case of V-USB is to go into the "usbconfig.h" for your project and add:<pre> #define USB_INTR_VECTOR INT0_vect </pre></p>

<p>I'm working on a <a href="http://www.obdev.at/products/vusb/index.html" rel="noreferrer">V-USB</a> (aka AVR-USB) -based circuit running at 5V (i.e. two 3.6V Zeners across D+ &amp; D-) and at 12MHz. I tried an ATmega88P instead of the ATmega88 chips I normally use and I can't get the circuit to enumerate. The Atmel appnotes on mega88->mega88P migration don't describe any obvious gotchas. </p> <p>Anyone have any experience/tips with the differences in ATmega88P chips?</p>

Issues migrating from ATmega88 to ATmega88P, with V-USB/AVR-USB?

2009-11-26T09:22:19.893

695

|arduino|avr|atmel|timer|

<p>You could use one of the built in timers. Get everything set up for prescaller=1 and TCNT=0 before the block. Then enable the timer on the line before the block and disable it on the line after the block. The TCNT will now hold the number of cycles the block took, less the fixed cycles for the enable and disable code. </p> <p>Note that the TNCT will overflow after 65535 clock cycles on a 16 bit timer. You can use the overflow flag to double run time. If you still need longer, you can use a prescaler, but will get less resolution. </p>

<p>Is it possible to monitor a block of code and determine the number of processor clock cycles that code took on an Arduino and/or AVR atmel processor? or, should I rather monitor microseconds passed before and after code run? Note: I'm not concerned with real time (as in, how many real seconds passed) as much as I am in "how many clock cycles does this code require from the CPU"</p> <p>The current solution I can come up with is from time.c:</p> <pre><code>#define clockCyclesPerMicrosecond() ( F_CPU / 1000000L ) #define clockCyclesToMicroseconds(a) ( (a) / clockCyclesPerMicrosecond() ) </code></pre> <p>wiring.c adds:</p> <pre><code>#define microsecondsToClockCycles(a) ( (a) * clockCyclesPerMicrosecond() ) </code></pre> <p>By this account i could calculate clock cyles passed by monitoring microseconds passed and then pass that to microsecondsToClockCycles(). My question is, is there a better way?</p> <p>sidenote: are there good resources for performance monitoring of the AVR. lmgtfy.com and various forums searches do not provide any obvious results, other than exploration of timers</p> <p>thanks</p>

Monitor clock cycles for code on arduino/AVR?

2009-11-26T10:56:40.500

700

|atmega|

<p>I use this: <a href="http://www.engbedded.com/fusecalc/" rel="nofollow">http://www.engbedded.com/fusecalc/</a></p>

<p>How would I need to set my fuse bits on a ATMega328p to use a 16MHz crystal? I tried this on my own and killed the last atmega I had. I'd like some advice this time.</p> <p>The crystal I am using is <a href="http://www.sparkfun.com/commerce/product_info.php?products_id=536" rel="nofollow noreferrer">this one</a> </p> <p>I am assuming this is a "Full Swing Crystal Oscillator" as listed in the datasheet, so CKSEL3..1 should be 011</p> <p>Then I need to set the startup time. I'm assuming the "Crystal Oscillator, slowly rising power" is the safer option so CKSEL0 should be 1 and SUT1..0 should be 11.</p> <p>I don't want to divide the clock by 8 so CKDIV8 should be 1</p> <p>CKOUT I will leave at the default of 1</p> <p>If my assumptions are correct (and how do I verify that?) my lfuse bit settings will be 0xf7.</p> <p>Am I doing this right?</p> <hr> <p>This didn't work. See <a href="https://electronics.stackexchange.com/questions/717/troubleshooting-an-atmega328p-clock-setting">here</a></p>

Using a 16 MHz crystal on a ATMega328p

2009-11-26T22:49:42.460

708

|arduino|voltage|i2c|digital-communications|

<p>There are ICs available specifically for level-shifting I2C:</p> <ul> <li>LTC4300A-2 (<a href="http://www.linear.com/pc/productDetail.jsp?navId=H0,C1,C1007,C1070,P2296">http://www.linear.com/pc/productDetail.jsp?navId=H0,C1,C1007,C1070,P2296</a>)</li> <li>PCA9306 (<a href="http://focus.ti.com/docs/prod/folders/print/pca9306.html">http://focus.ti.com/docs/prod/folders/print/pca9306.html</a>)</li> </ul> <p>I don't know what kind of constraints you have on your design, but I would think using a dedicated IC would be easier then coming up with your own solution.</p>

<p>I'm trying to interface a 3.3V I²C device to a 5V Arduino. </p> <p>I don't have any problem with SCL line. I can use a simple voltage divider but I have an issue with the SDA line as this is bi-directional. </p> <p>I'm not at all sure how to handle this. I have though of adding a pair of diodes, with a voltage divider on the slave input side and nothing extra on the master input.</p> <p>Are there any other solutions?</p>

I2C 3.3 to 5.0 V conversion

2009-11-27T20:45:08.053

710

|board|layout|pcb|

<p>As already mentioned you can use a fast processor with a PLL and still have only your 10kHz signals + a 12MHz quartz oscillator (close to the CPU) on your board. To lay this out will not be a problem.</p> <p>Many people (me included) did 48kHz stereo audio output on an ARM7TDMI (streaming from an SPI connected SD card in my case). I even saw mp3 decoding in software on a 50MHz ARM7 running from RAM (there may be wait-states when working from Flash).</p> <p>Maybe buy an mbed LPC1768 board (100MHz, very fast ADC/DAC and PWMs on-chip, cheap: 50€) and make a prototype? Only if this is not sufficient start playing with other (more costly and difficult) stuff.</p>

<p>I'd like to design a PCB for an analog loop controller.. something with an A/D, D/A, and processor on board. (Either DSP or FPGA, I haven't decided.) Since this should modulate analog signals at 10 kHz, it needs to be quite a fast processor.</p> <p>From what I understand, designing a board for processors running above 150 MHz or so can be very challenging due to RF problems. What are some advice you can provide in designing such a board? What problems due to layout can occur? Are there any good online resources that have knowledge bases for this?</p> <p>Thanks.</p>

What are some 'gotchas' of high-frequency board design?

2009-11-27T21:09:38.487

718

|power-supply|switch-mode-power-supply|solar-cell|

<p>Over at <a href="https://electronics.stackexchange.com/questions/170/5v-800ma-to-at-least-3v">Electronics Exchange</a>, <a href="https://electronics.stackexchange.com/users/14/rex-logan">Rex Logan</a> had a great answer - the <a href="http://www.dimensionengineering.com/lvboost.htm" rel="nofollow noreferrer">LVBoost</a> is exactly what I'm looking for.</p>

<p>I have a project where I'd like to convert a 0.5 V, 800 mA supply (a solar cell) to at least 3 V with as much efficiency as possible. I've seen DC boost converters, but all the ones I've seen are designed for a higher voltage.</p> <p>Any tips on a good low voltage one?</p>

DC boost for low voltage?

2009-11-28T01:00:08.897

724

|arduino|

<p>Electonic's very own <strong><a href="https://electronics.stackexchange.com/users/1307/tronixstuff">tronixstuff</a></strong> has a huge, very informative <a href="http://tronixstuff.wordpress.com/tutorials/" rel="nofollow noreferrer">Arduino tutorial at his website</a>.</p> <p>Jeremy Blum also did a <a href="http://www.youtube.com/watch?v=fCxzA9_kg6s&amp;feature=list_related&amp;playnext=1&amp;list=SPA567CE235D39FA84" rel="nofollow noreferrer">10-part YouTube series</a> on the basics of working with Arduino that I found extremely informative, if a little slow-paced at times (but never lacking in detail).</p>

<p>I'm looking for some cheap beginners projects that show the uses of an arduino.</p> <p>things like turning on and off an LED</p> <p>getting back sensor data</p> <p>...</p> <p>if anyone has come across useful youtube video tutorials that would be perfect!</p> <p>that sort of thing</p>

What are the best beginner project using an arduino

2009-11-28T04:21:04.377

725

|flash|storage|

<p>I assume you are looking for an embedded solution, since you could easily get a reader for a desktop or laptop computer.</p> <p>People have written SPI IDE interfaces, which you might be able to run on an AVR. I will link to one that runs on an ATMega32. It may be too big for an ATMega168, but it should fit on a 328, though it may need a bit of cleanup to account for the Arduino bootloader if you go that route: <a href="http://forum.6502.org/viewtopic.php?p=8343&amp;sid=a06dc948bd456b223cf8a93d175d37e1" rel="nofollow">http://forum.6502.org/viewtopic.php?p=8343&amp;sid=a06dc948bd456b223cf8a93d175d37e1</a></p> <p>I have seen a lot of work on this for the PIC series of microcontrollers as well. A simple search on PIC and CF should return plenty of details, though the hardware and article linked above by zklapow should be more than sufficient to complete the project. I just wanted to add in an AVR solution for those who are looking since I know there is a big Arduino community here.</p>

<p>Does anyone know how to create a cf controller in order to read data from cf card?</p>

Creating a compact flash controller

2009-11-28T04:24:08.057

742

|robotics|encoder|

<p>I've played with these a bit and found some useful documents in the past.</p> <p>Have a look at the <a href="http://www.robot-forum.com/robotforum/empty-t417.0.html" rel="nofollow">robot forum</a> on it. </p> <p>Basically run the 'home' job on the robot, you need the absolute position from each axis and this is found on a sticker on the inside of the controller. At the home position you should have all the ref arrows alligned.</p> <p>If the home position has been lost the encoder memory is lost. It counts 4000 points for each revolution - if the encoder memoery is lost it doesnt know how many have passed. </p> <p>Take the difference between the new and old encoder home position and divide by 4000 - this will give you how many it is out by.</p> <p>the example given was:</p> <p>Original home encoder count: -119771 New home encoder count (after lining up reference marks and setting the data for that axis): -95834 Difference: -23937 Divided by 4000: 5.98425 Therefore, number of revolutions out was 6 My new home position should then be -119771 + (6)x(4000) = -95771</p>

<p>I've been using a Motoman and I'm wondering what is the best way to recover when the encoder position has been lost.</p> <p>I've tried lining up all the reference marks on the joins but this can be a bit dodgy.</p>

Robot Encoder Position

2009-11-28T22:27:18.637

758

|audio|frequency|sampling|arduino|

<p>Are you interested in a 64K sampling rate? Have a look <a href="http://didier.longueville.free.fr/arduinoos/?p=1134" rel="nofollow">here</a></p> <p>Now raised to 150 kHz, 10 bits, no additional components!</p> <p>Have a look <a href="http://didier.longueville.free.fr/arduinoos/?p=2366" rel="nofollow">there</a></p>

<p>G'day all!</p> <p>I have an Arduino Duemilanove hanging around spare at the moment and thought I might try a few audio interfacing projects. I'm just wondering what sort of sampling frequency I can achieve using a single analog input and applying some simple algorithms on chip, then reporting using a few digital outputs tied to LEDs.</p> <p>I'd like to sample in at ~44.1 kHz if possible.</p> <p>For reference the first thing I want to try is a simple guitar tuner.</p>

Maximum sample rate of Arduino Duemilanove?

2009-11-30T03:03:53.963

761

|atmega|uart|low-power|

<p>From my observation it's not viable to run ATMega328p below 1Mhz to save the power (because you will need more time running to finish the calculation). However reducing voltage will result in high power saving. Running at 1Mhz and 1.8V consumes only 1% of power if run at 16Mhz and 5V. I made this <a href="https://docs.google.com/spreadsheets/d/1v2LGArlAkp5wiknlZEDknqD65P9FCHSeSo-Op2iwd0I/edit?usp=sharing" rel="nofollow">ATMega328 power consumption chart</a></p> <p>According to this <a href="http://wormfood.net/avrbaudcalc.php?postbitrate=9600&amp;postclock=1" rel="nofollow">AVR UART Calculator</a> if you run your AVR at 1MHz (default speed without external crystal) you can UART up to 4800</p>

<p>I am looking at designing a low-power project that will have an ATMega328 running at a low speed for lower power consumption.</p> <p>The current plan is to have the UART hooked up to a <a href="http://www.littlebirdelectronics.com/products/rf-link-2400bps-receiver-315mhz" rel="nofollow">RF Link Receiver</a> for communication at 1200baud.</p> <p>What I'm wondering, though, is what the minimum speed is that I can run an ATMega328 at and still have a 1200baud UART running. Is 1MHz fast enough?</p>

Minimum ATMega328 speed with UART

2009-11-30T05:08:22.000

765

|microcontroller|measurement|sensor|

<p>Please check the following link:</p> <p><a href="http://www.edgefxkits.com/contactless-liquid-level-controller" rel="nofollow">http://www.edgefxkits.com/contactless-liquid-level-controller</a></p> <p>I think it may be useful to you.</p>

<p>How do i measure the level of a water tank with a microcontroller?</p>

Level of a water tank with a microcontroller

2009-11-30T11:00:08.153

778

|arduino|power-supply|

<p>That thing is a Ferrite Filter. It's there to dampen Electromagnetic Interference (EMI) or high frequency noise from your power lines from interfering with your circuit. If you're not doing audio (or radio) work or you're not picky you can cut it off. If you are and it gets in the way, you can cut it off and add a ferrite bead elsewhere in your circuit.</p> <p>Better than cutting it would be to add a proper plug to your circuit, but you've probably already considered that. If you're using a breadboard, this type of terminal block works well: <a href="http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;name=ED2580-ND" rel="nofollow">http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;name=ED2580-ND</a></p> <p>A bit of warning: That looks like a laptop power supply, so it's probably capable of sourcing a fair amount of current. It's a little more powerful than a typical "wall wart". Be careful not to short anything, and don't work on your project while it's powered up.</p>

<p>I have no vocabulary for this, so forgive my clumsiness in explaining.</p> <p>I need to hook up a power supply to use with solenoids and an Arduino, but I'm not sure where to cut it. Just before the power plug there is a thing (not sure of the name, bottom right of picture in the link below), do I need to cut before or after it? </p> <p><a href="http://www.allelectronics.com/mas_assets/image_cache/height.500_width.500_modified.1237373195.3188.PS-1233.jpg" rel="nofollow">Here is a link to the picture</a>, I'm a new user so I can't embed it. </p> <p>If you know the name of the mystery thing, I'd also love to know.</p>

Where to cut my power supply for Arduino?

2009-12-01T05:33:38.630

782

|arduino|timer|

<p>I had written a little while back a detailed guide to implementing one's first arduino intervalometer. The link is here: <a href="http://openmoco.org/node/88">Arduino Intervalometer Basics</a></p> <p>The difference between this and other examples, is that it provides not only the standard "pinmode, delay, pinmode"-style control, but also introduces the reader to non-blocking timing concepts, and discusses the benefits and drawbacks of each programming method. In addition, it walks the reader through a series of tests to make sure they understand the concept well before they try to hook up the camera.</p> <p>Of course, no one can tell you how to control your camera, unless you tell us what kind of camera you are using. But, in most cases, it is pretty simple. </p> <p>Then, once you really get into it, check out the whole openmoco project, which does a lot more than just interval shooting. =)</p>

<p>How would i set up an Arduino to do time lapse photography?</p>

Arduino for time lapse photography

2009-12-01T09:53:19.223

795

|display|light|

<p>The <a href="http://opencircuits.com/Multi-touch_display" rel="nofollow">open-circuits wiki lists many multi-touch technologies</a> and techniques:</p>

<p>We have been given a project at uni to create a multi touch display.</p> <p>I've done some research into this and a lot of them call for special film on the glass or use a <a href="http://www.instructables.com/id/interactive-Multitouch-Display/" rel="nofollow">projector</a> (meaning it needs a certain amount of darkness).</p> <p>I want to make a multi touch screen that can be used in full daylight (outdoors) and not more than a few cm behind glass - has anyone come across such a project?</p> <p>It needs to be about a 42" screen size - so not a small pre-made one.</p>

Create multi touch display for full light

2009-12-01T21:40:06.523

800

|microcontroller|lpc|nxp|

<p>If you're talking about connecting the processor's UART to a PC's serial port, you can now get USB to RS232/TTL converters. One end goes into your PC's USB socket, and appears as a normal serial port; the other comes out to 5 V or 3.3 V signals that can be connected directly to your processor, with no level-shifting required.</p> <p>We've used <a href="http://www.ftdichip.com/Products/EvaluationKits/TTL-232R-3V3.htm" rel="nofollow">TTL-232R-3V3</a> from FDTI Chip, which works perfectly for this kind of application.</p>

<p>I can't get data off my ARM <a href="http://www.nxp.com/documents/data_sheet/LPC2377_78.pdf" rel="nofollow">LPC2378</a> microcontroller - does it need UART or can any GPIO be used?</p>

Reading a LPC2378 microcontroller

2009-12-01T23:46:31.113

824

|pic|rtos|embedded|microcontroller|

<p>One thing I've found useful on a number of machines is a simple stack switcher. I haven't actually written one for the PIC, but I would expect the approach would work just fine on the PIC18 if both/all threads use a total of 31 or fewer stack levels. On the 8051, the main routine is:</p> <pre> _taskswitch: xch a,SP xch a,_altSP xch a,SP ret </pre> <p>On the PIC, I forget the name of the stack pointer, but the routine would be something like:</p> <pre> _taskswitch: movlb _altSP >> 8 movf _altSP ,w,b movff _STKPTR,altSP movwf _STKPTR,c return </pre> <p>At the start of your program, call a task2() routine which loads altSP with the address of the alternate stack (16 would probably work well for a PIC18Fxx) and runs the task2 loop; this routine must never return or else things will die a painful death. Instead, it should call _taskswitch whenever it wants to yield control to the primary task; the primary task should then call _taskswitch whenever it wants to yield to the secondary task. Often, one will have cute little routines like:</p> <pre> void delay_t1(unsigned short val) { do taskswitch(); while((unsigned short)(millisecond_clock - val) > 0xFF00); } </pre> <p>Note that the task switcher doesn't have any means of doing any 'wait for condition'; all it supports is a spinwait. On the other hand, the task switch is so fast that a attempting a taskswitch() while the other task is waiting for a timer to expire will switch to the other task, check the timer, and switch back faster than a typical task-switcher would determine that it doesn't need to taskswitch.</p> <p>Note that cooperative multitasking has some limitations, but it avoids the needs for a lot of locking and other mutex-related code in cases where invariants that are temporarily disturbed can be reestablished quickly.</p> <p>(Edit): A couple caveats regarding automatic variables and such:</p> <ol><li>if a routine which uses task-switching is called from both threads, it will generally be necessary to compile two copies of the routine (possibly by #including the same source file twice, with different #define statements). Any given source file will either contain code for only one thread, or else will contain code which will be compiled twice--once for each thread--so I can use macros like "#define delay(x) delay_t1(x)" or #define delay(x) delay_tx(x)" depending upon which thread I'm using. <li>I believe that PIC compilers that can't "see" a function being called will assume that such a function may trash any and all CPU registers, thus avoiding the need to save any registers in the task-switch routine [a nice benefit compared with preemptive multitasking]. Anyone considering a similar task switcher for any other CPU needs to be aware of the register conventions in use. Pushing registers before a task switch and popping them after is an easy way to take care of things, assuming adequate stack space exists. </ol> <p>Cooperative multitasking doesn't allow one to completely escape issues of locking and such, but it really does greatly simplify things. In a preemptive RTOS with a compacting garbage collector, for example, it's necessary to allow objects to be pinned. When using a cooperative switcher, this isn't necessary provided that code assumes GC objects may move any time taskswitch() is called. A compacting collector which doesn't have to worry about pinned objects can be much simpler than one which does.</p>

<p>I have seen many articles that tell me I should be using RTOS for time management and resource management. My time has not permitted my own research, so I come to chiphacker for advice.</p> <p>I use low resource microcontrollers(MSP430, PIC) and was looking for RTOSs I can use.</p> <p>To the point:</p> <ol> <li>Resource cost of system</li> <li>Advantages of system</li> <li>Disadvantages of system</li> <li>Implementation Tricks</li> <li>Situations the RTOS should/should not be used in.</li> </ol> <p>I do not use systems like the arduino, the projects I work with cannot support the cost of such a system.</p>

RTOS for Embedded Systems

2009-12-02T20:59:25.127

825

|usb|serial|rs232|

<p><a href="http://www.silabs.com/products/interface/usbtouart/Pages/default.aspx" rel="nofollow">CP210x</a> from Silabs is a great product. It's difficult to solder, but have lots of tutorials teaching this on Google.</p> <p>The advantages is that don't need crystal and uses only some capacitors.</p>

<p>Anyone have any recommendations on a good rs232-to-usb converter. There are a lot out there and from the looks of it some are hit or miss. </p> <p>Good driver support is a must.</p>

RS232-to-USB Converter

2009-12-02T21:17:17.587

848

|sensor|serial|rs485|

<p>I think the big difference has to do with how far away your sensors are on your network.</p> <p>If they're close, and likely not to be affected by electrical noise, then I don't think it matters too much. <strong>USB, RS-232, SPI, I2C, parallel, Bluetooth</strong>... all would be good options.</p> <p>If they're far away, and likely to be around electrical noise, a system that utilizes a differential communication scheme (like <strong>CAN, RS-485, Ethernet</strong>) is probably a better route to go.</p>

<p>I am planning on an automation project that will be using several different sensors including but not limited to: Temperature, Barometric Pressure, Air flow, Humidity, etc. </p> <p>As I was talking with someone they mentioned that I should look into RS-485 as a means to connecting my sensors to my controller. Then ultimately to the PC.</p> <p>After a quick search I gathered some information about RS-485 but now I am wondering if it's over kill or if it's even used now a days?</p> <p>Couldn't I just use a microcontroller that has enough inputs and interface with the PC using USB?</p> <p>Thoughts? </p> <p>EDIT: Ok if distance to controller and environment (in my case an industrial application) then RS485 might be useful. Are there other bus alternatives that might be more useful?</p>

Should I consider using RS-485 for my next project

2009-12-04T06:26:07.350

851

|prototyping|development|manufacturing|

<p>If it's a small batch, and you're using an approved wall transformer as mentioned by Jason S, you probably don't have to worry about anything. I've seen all sorts of sites selling little gadgets they make in small quantity, that I am 99% sure they didn't do any kind of certification. It all depends on the scale...does 'small batch' mean 20 or 2000?</p>

<p>I'm thinking about selling a small batch of a simple gadget that would have some electronics inside.</p> <p>If I want to use an online shop and sell it worldwide, what are the certifications and licenses to be aware of? </p> <p>If I qualify something for the UE, can it be sold to the USA?</p>

Manufacturing, qualification and sale

2009-12-04T10:31:25.477

864

|arduino|software|

<p>While using 10 of the Decimalia units in a large sensor array, I had 2 of them from different manufacturing runs die in the course of development. The inputs and outputs were externally opto-isolated, so it wasn't because of current or stray voltage. I put the failures down to two possible sources. One is that they bricked because of manufacturing failures, probably internally in the I.C.'s. The second was because it might have been possible to brick the unit by damaging the boot loader. After the failures the units failed to be recognized as a legitimate device by the programming computer. I still use them for sensor and data logging. I haven't had any further troubles on any other project.</p>

<p>Can you brick an Arduino just through code?</p>

Frying an Arduino

2009-12-05T04:55:08.833

865

|arduino|library|mac|osx|

<p>Libraries should go to <em>~/Documents/Arduino/libraries/</em> folder. This way when you upgrade Arduino IDE it wont overwrite your libraries. If Arduino IDE does not show your recently added library you need to restart the IDE.</p>

<p>Where do i put the Arduino "Library" folder on a Mac?</p>

Arduino Libaries folder

2009-12-05T04:59:03.087

866

|arduino|wiring|

<p>Wiring was an older attempt at what the Arduino has succeeded in doing. It was designed to be an educational platform for learning about microprocessors, software, and physical computing.</p> <p>The Wiring board has a different processor and more robust hardware then the Aduino Duemilanove. It has more I/O pins, more memory, more interrupts, etc (although fewer then an Arduino Mega). It is also quite a bit more expensive.</p> <p>The language is essentially the same, and each has an IDE based on the one written for processing. </p> <p>Here is a page comparing the Wiring board to (older) arduinos and other platforms.</p> <p><a href="http://wiring.org.co/hardware/compare.html" rel="noreferrer">http://wiring.org.co/hardware/compare.html</a></p>

<p>What are the key differences between Wiring and Arduino?</p> <p>What would you recommend?</p>

Wiring vs Arduino

2009-12-05T05:01:20.867

868

|rgb|led|resistors|

<p>The provided answers are incorrect. Connecting to either the common pin (If there are 4 terminals) or simply shorting all of the cathodes or anodes together (to make a common pin) and using 3 signal lines will let you use a single resistor. Choose the smallest resistor which can be connected continuously to any one pin without blowing the LED. The supply voltage must not be too close to the highest voltage, (e.g. a 1.4V red LED and 2.5V blue LED will have manageable current differences at 5V, but 3.3V might make it hard to get a full spectrum over your brightness options.</p> <p>Now, the software. If you PWM each pin at a different time, the current difference in voltage can be compensated for in software. </p> <p>For example: </p> <pre><code>Naive White: R --__________ G ____--______ B ________--__ More accurate white (V_red &lt; V_green &lt; V_blue, so I_red &gt; I_green &gt; I_blue, and the eye sees some colors brighter): R --____________________ G ________----___________ B ________________-------- Bright Red-yellow, whitened: R ----___ G___---_ B_____- This causes current drops (probably wouldn't turn on). Don't do this: R ___---- G _----__ B----____ </code></pre> <p>Etc.<br> The maximum brightness will be the same as PWMing them independently, because you're limited by the power dissipation of the single component.</p>

<p>Do you need to use different resistors against each of the colours on an RGB LED?</p>

Red Green Blue LED

2009-12-05T05:05:39.420

869

|kits|tools|

<ul> <li>A pencil (and sharpener). Molten tin won't stick to the carbon of the pencil, so you can use it to open a solder pad or solder bridge. It is in the same category as desoldering braid and a solder sucker. </li> <li>I like to use one small and cheap breadboard for soldering. It holds pins nicely in place while I solder them. I use it only for soldering to prevent flux and resin from ending up on other components. Same category as a third-hand rig.</li> <li>Antistatic foam to keep IC's safe.</li> <li>A drawer full of old power supplies (SMPS, that came with telephones, monitors, network equipment, ... at various voltages and currents) saved from the junk yard.</li> <li>Order components in bulk: 10, 50, 100, 500+ pcs. prices can drop incredibly if you find the right shops. </li> <li>Couple universal heat sinks and mounting material.</li> <li>Pin headers, lots of them. I often push the pins out to reuse them by pushing them eg. into a breadboard (or female header on a breakout) so I can easily connect a multimeter to it. </li> <li>Lots of single pin 2.54mm Dupont male and female connector wires to make interconnections between male headers.</li> <li>Battery holders for 1 and 4 penlights.</li> <li>IC sockets.</li> <li>Account credentials to <a href="https://electronics.stackexchange.com/">https://electronics.stackexchange.com/</a></li> </ul>

<p>What are the items you have in your personal electronics tool kit?</p>

Personal electronics tool kit

2009-12-05T05:08:23.893

875

|avr|measurement|robotics|servo|

<p>Sounds like a cool project.</p> <p>Some motor drivers already measure current in order to provide "overload protection". If you can't tap that signal, there are <a href="http://opencircuits.com/current_sense" rel="nofollow">several ways to measure current</a>. Start with the simplest and cheapest method, and if that won't work, try the next one.</p>

<p>I'm building a hexapod robot using simple servos and I was wondering how feasible it was to measure the current flow to each servo (5-6V DC to a maximum of 0.25-1A (I haven't found the spec for the servo's stall current yet)) using, say, an ATMega168. What kind of circuit would I need to build in series with each of the servo's power lines to give me a useful readout? I assume I'd get a voltage drop across this circuit, what's it likely to be? etc. </p>

How do I measure the current flow to a component?

2009-12-05T09:04:58.050

878

|arduino|temperature|1-wire|

<p>This can be due to the controller mis-reading one or more bits of the temperature response under certain high-load conditions, or due to electrical interference corrupting one or more bits.</p> <p>Take a close look at the data sheet here <a href="http://www.rentron.com/Files/ds18b20.pdf" rel="nofollow">http://www.rentron.com/Files/ds18b20.pdf</a></p> <p>On page 5, it shows that the exact binary sequence for 85C is:<p> <code>+85°C 0000 0101 0101 0000</code> <p> Likewise, for 25C, it is:<p> <code>+25.0625°C 0000 0001 1001 0001</code></p> <p>In some cases, if the controller misses a bit, you'll get a value that is the actual temperature, expressed in binary and bit-shifted. Often this is 1/2x the target value in C.</p> <p>Sometimes you can get electrical interference on the line, and the controller reads an entire nibble of 1s, In that case, you'll get some number like 15.64, which expressed in binary is actually very close to numbers between 65 and 70F, except with a bunch of 1s at the beginning.</p>

<p>I'm using Maxim's DS18x20 (I've actually got more than one variant) 1-Wire temperature sensors to log the temperatures in various rooms in my house once a minute. About one reading in a thousand, I get something completely bogus back. In the middle of a sequence that's gradually rising from 65F to 70F I get something like -32.1F or 15.64F.</p> <p>Has anyone else had that kind of problem, or is this something wrong with my setup? If this is just a known issue with these things, I'll have to do something like taking three readings and throwing out the outlier.</p> <p>Just a few statements about my setup:</p> <ul> <li>I'm running at 3.3V</li> <li>I'm checking the checksum of the reading as it comes back to the arduino, and it matches (or I think it does - there could always be a bug in that code).</li> <li>These are running off of normal power, not parasite power.</li> <li>I have the 4.7K pullup resistor in place.</li> <li>I'm only using a single sensor on each sensing platform.</li> <li>The sensor is on a PCB attached to the arduino that's reading it.</li> <li>I see the same problem reading from a variety of different arduinos (diecimilla, pro-mini, homemade custom)</li> </ul>

Reliability of DS18x20 temperature sensors

2009-12-05T15:13:17.883

884

|arduino|ftdi|reset|

<p>What I did to get my breadboard arduino to reset was to go into the device manager (Windows 7) and highlighted the FTDI device (A virtual COM port) and then went to Properties, Port settings, Advanced. I then checked off the box that said "Set Rts on close". After I did this my arduino reset itself no problem. Hope this helps.</p>

<p>How do you get the <a href="http://www.sparkfun.com/commerce/product_info.php?products_id=9115" rel="nofollow noreferrer">SparkFun FTDI Basic Breakout</a> board to auto reset?</p> <p>I still have to hit the reset button for any Arduino clones when I use the breakout board. I have tried connecting to the DTR pin and other methods of trial and error but I am just not getting it.</p>

Arduino reset with FTDI breakout question

2009-12-05T18:46:31.313

893

|switches|transistors|current|voltage|

<p>If you want the relay to close when the DS2406 output closes:</p> <pre><code>replace the NPN transistor with an equivalent PNP, tie the PNP's base to the +12V supply through maybe 10k to 50k ohms. tie the PNP's base to the DS2406 output through maybe 4.7k to 5.1k ohms. </code></pre> <p>When the DS2406 is high impedance, the first resistor biases the PNP off. When the DS2406 output goes to zero, it pulls about 2mA of current through the base of the transistor and the relay should close.</p> <p>If you want the relay to close when the DS2406 output opens:</p> <pre><code>tie the base of the NPN transistor to +12V through about 5k ohms. connect the output of the DS2406 directly to the base of the NPN </code></pre> <p>When the DS2406 is high-Z, the resistor should dump about 2mA into the NPN, turning it, and the relay both on. When the DS2406 goes to ground, it will 'steal' that 2mA from the base of the NPN and turn it and the relay off.</p> <p>The above resistor values are all calculated assuming that 1.5 or 2mA of base current is enough to drive the transistor into saturation. The collector-emitter drop should either be the full supply voltage in the OFF state, or something around 0.2V in the ON state. If not, resistor values should be changed.</p>

<p>I have a relay operated by an NPN transistor that needs some voltage applied to the base. I'm working with an arduino and if I give it a digital port, all's well. The circuit looks like this one: </p> <p><img src="https://i.stack.imgur.com/qHDPE.gif" alt="enter image description here"></p> <p>Now I want to replace the arduino port with a <a href="http://www.maxim-ic.com/datasheet/index.mvp/id/2907" rel="nofollow noreferrer">DS2406</a> (the TO92 kind).</p> <p>This seemed to get really complicated fast. <a href="http://github.com/dustin/arduino-2406" rel="nofollow noreferrer">My library</a> for operating the 2406 is fine, but I can't figure out how to wire it.</p> <p>Now that both pieces independently work, my goal is to get some current fed into the base of the transistor so it throws the relay.</p> <p>I've run into the following issues:</p> <p>The DS2406 closes to ground. That's the only option, so I can't map it directly to the base pin of the transistor.</p> <p>The TO-92 package doesn't have a vcc pin, so I have to have a pull up resistor between vcc and the data pin. This causes stuff to get hot and smelly when I power it up hooked up to the collector of the transistor with the base wired to the relay power. I could be using the wrong kind of resistor, but I don't have a strong sense of what's right here.</p> <p>I <em>may</em> be able to run the relay strictly off the DS2406, but I'm afraid it will have too much draw, which is why I want it to go through the transistor.</p> <p>What's the easiest way to go from a switch that opens and closes ground to a transistor base that wants current?</p>

Need help operating a transistor

2009-12-06T01:02:42.253

902

|led|light|detection|

<p>This site: <a href="http://www.users.waitrose.com/~robinjames/LED_as_light_sensor/LED_as_light_sensor.html" rel="nofollow noreferrer">http://www.users.waitrose.com/~robinjames/LED_as_light_sensor/LED_as_light_sensor.html</a> shows how to measure light levels using an LED and an opamp, to give a voltage proportional to the light level. It gives a wide range of readings and works from complete darkness to full sunlight. It can be used to feed the ADC of a microcontroller such as an Arduino.</p>

<p>How do I detect light with an LED?</p>

Detecting light with an LED

2009-12-07T06:57:42.730

922

|resistors|voltage-regulator|

<p>Does this simplified circuit help?</p> <p><img src="https://i.stack.imgur.com/eSHpF.png" alt="schematic"></p> <p>^{<a href="/plugins/schematics?image=http%3a%2f%2fi.stack.imgur.com%2feSHpF.png">simulate this circuit</a> &ndash; Schematic created using <a href="https://www.circuitlab.com/" rel="nofollow">CircuitLab</a>}</p> <p>The specifics of the internals is basically the above and is published in the data-sheets. If you can't recognize common circuits in the actual 7805 schematic, and figure out the details of the complex internal circuitry, then I am afraid it is far too complicated to detail here.</p> <p>There are numerous links already given in the other answers and comments, that should get you well on your way though.</p>

<p>How do most voltage regulator ICs work? Are they the same as hooking up a variable resistor and a voltmeter and turning the knob until you get the desired voltage?</p>

How does an LM7805 voltage regulator work?

2009-12-07T21:22:52.240

927

|arduino|ethernet|

<p>Wiznet have stated that it is not possible to disable the trailers.</p> <p><a href="http://wiznet.co.kr/rg4%5Fboard/view.php?&amp;bbs%5Fcode=en%5Fqna&amp;bd%5Fnum=21321" rel="nofollow">http://wiznet.co.kr/rg4_board/view.php?&amp;bbs_code=en_qna&amp;bd_num=21321</a></p>

<p>I have an <a href="http://arduino.cc/en/Main/ArduinoBoardDuemilanove" rel="nofollow">Arduino Duemilanove</a> (ATmega328) and Ethernet shield (based on the <a href="http://www.sparkfun.com/datasheets/DevTools/WIZnet/W5100_Datasheet_v1_1_8.pdf" rel="nofollow">WizNet W5100</a>). My network gateway is a <a href="http://en.wikipedia.org/wiki/D-Link_G604T_Network_Adaptor" rel="nofollow">D-Link DSL-G604T</a>.</p> <p>Using this setup, I can contact computers on my local network fine. However, when I attempt to contact computers on the public Internet, the device times out. I traced the packets going back and forward using <a href="http://en.wikipedia.org/wiki/Wireshark" rel="nofollow">Wireshark</a> and the problem appears to be that the gateway is not responding to the W5100's ARP request.</p> <p>I saved the ARP packet that the W5100 is sending and the ARP packet that my computer is sending and compared them. The only thing different is that it is not a timestamp, address, length or sequence number that the W5100 is sending a trailer at the end of the Ethernet II frame.</p> <p>According to <em><a href="http://www.faqs.org/rfcs/rfc1122.html" rel="nofollow">RFC 1122 - Requirements for Internet Hosts - Communication Layers</a></em>, section 2.3.1, a trailer may only be used if both hosts have previously agreed to use them. I suspect that my gateway is not able to handle trailers and is ignoring the packet.</p> <p>Is there a way to disable trailers in the W5100?</p> <p>Here are the ARP packets that are sent by a computer on my network that is able to make Internet connections and the Arduino device. I have also provided a diff of the two packets. In the case of the packet that is sent by the computer, the gateway responds, in the case of the packet sent by the Arduino, the gateway does not respond. Note that I have changed the hardware addresses, but that's all.</p> <ul> <li><p><em><a href="http://chiphacker.pastebin.com/f37faeff5" rel="nofollow">Computer Packet</a></em></p></li> <li><p><em><a href="http://chiphacker.pastebin.com/f779740ba" rel="nofollow">Arduino Packet</a></em></p></li> <li><p><em><a href="http://img38.imageshack.us/img38/8179/packetdiff.jpg" rel="nofollow">Diff</a></em></p></li> </ul>

Disabling trailer protocol when using this W5100-based Ethernet shield

2009-12-08T04:48:47.253

933

|usb|operational-amplifier|atmel|biopotential|

<p>In the 70's we developed 8 and 16 chan eeg telemetry units for hospitals. Need to keep input leads twisted, shielded and away from the transmitter antenna. Foor safety, We used the very first lithium cells to supply isolated power. Used L113 micro-power, flat-pack opamps for signal amplification. The outputs were multiplexed to the transmitter input. The fun part of this design was the method of de-multiplexing required to separating the 8/16 eeg signals. Have fun - this is a neat project!</p>

<p>this is my first post, and I need some help/advice finding the right integrated circuits. I'll start by describing the project background a bit. I've received a fellowship to develop an open source electroencephalograph, the finished hardware will provide a platform for people to develop various creative and therapeutic uses for an EEG system i.e music controllers, game controllers or brain training programs. I want to use an Atmel MCU for the analogue to digital conversion, I'd like it to connect to a computer via USB and I'd also like the unit to be powered by the USB connection. I need help finding a suitable op-amp IC to amplify the signals from the electrodes prior to the MCU. The finished device will be 16 channels, so I'd like to find an IC with multiple op-amps. The electrical activity picked up by the electrodes will be in the region of 200mV and less, so I'll need a lot of gain. Is it possible to adjust the gain of an op-amp circuit with an MCU by using a digital resistor program? It would be nice if the hardware could be reprogrammed to work with various audio and sensor inputs. Any help or advice would be fantastic.</p> <p>Jim.</p>

RnD on an EEG, Help required, what op-amp?

2009-12-08T21:36:04.020

937

|arduino|sensor|

<p>You need two things: to use a differential input to compare against a 1.9v standard (or close to it), and an amplifier to increase the resolution of that difference.</p> <p>For the best results you should use external high quality instrumentation amps or op amps. But you could try using facilities built into the microcontroller. The Arduino Mega (ATMega2560 chip) and Arduino Leonardo both include the option for differential, amplified inputs to the ADC right on the chip. (The Uno does't have this). An ATMega2560 could do multiple channels (multiplexed) of amplified differential ADC for multiple sensors - read the datasheet to see which pin combinations are possible. It has a 200x amplification option, which would put the full 1024 step resolution across 25 mv. You just have to position that 25 mV window where you need it!</p> <p>That may or may not be sufficiently noise free for your purposes - it's not as high quality as you could build externally for more $$. </p> <p>The harder part may be getting a stable and accurate 1.9v reference to compare against.</p>

<p>I've recently built some fiber-optic bend sensors and I want to read the values I get from them into a computer via an Arduino. I'm measuring the light with <a href="http://i-fiberoptics.com/pdf/IFD91.pdf" rel="nofollow noreferrer">this photodiode</a> from <a href="http://i-fiberoptics.com/Fiber_optic_led_photodetectors.php#photodetectors" rel="nofollow noreferrer">Industrial Fiber Optics</a>. Currently, I'm giving the LED on the other end as well as the photodiode 2.2V. My question has to do with the fact that the voltage fluctuations as measured by a multi-meter on the photodiode are linear, but rather small as the fiber is deformed, even quite radically. With the fiber straight, depending on the fiber (its hard to score them identically), the voltage hovers around 1.92V, for instance, and with bending it will it will go up to, say, 1.93-1.94V. I'm not worried about getting the voltages identical as I can scale in software.</p> <p>What I am worried about is losing resolution when doing A/D with the Arduino. If my voltage fluctuations are on the order of 10mV, won't the Arduino's 10-bit A/D quantize the hell out of it, even if I step the voltage up to 5V with a voltage divider? What I'm looking for is an analog scaler. How can I stretch out that range between 1.92 and 1.94 to cover the full range, from 0V to 5V so that I can take advantage of the full range of the Arduino A/D?</p> <p>I feel like this has got to be a common operation in electronics, but I've never studied it formally, so a lot of things are lost on me. </p> <p>(You may be thinking, as davr was, "why are you using fiber optics for bend sensing? Why would you expect a voltage change when the fiber is bent?" The trick is to remove the cladding on one side of the fiber optic cable. This lets light spill out. When the cable is bent away from the scoring, even more light is let out of the cable, causing a voltage drop in the receiver, and vice versa.)</p>

Scaling Voltage for Arduino Analog In, Beyond Voltage Dividers

2009-12-09T05:18:18.990

940

|arduino|pins|spacing|

<p>I found a couple of interesting points on the adafruit forum on this when i started looking into it.</p> <p>On this one the guy soldered another header on to the arduino as an '<a href="http://forums.adafruit.com/viewtopic.php?f=25&amp;t=13666" rel="noreferrer">outrigger</a>' - so that the new header lines up.</p> <p>And this one.... the guy has created his own <a href="http://www.adafruit.com/index.php?main%5Fpage=product%5Finfo&amp;cPath=17%5F21&amp;products%5Fid=187" rel="noreferrer">bent header</a> which slots in so that you can make your own shield.</p>

<p>How do you get around the annoying pin spacing on the Arduino? </p> <p>Where pin 7 and pin 8 are not standard spacing.</p> <p>Why is it set up like this?</p>

Arduino pin spacing

2009-12-09T08:12:33.267

958

|usb|uart|ftdi|

<p>Also noteworthy is that the <a href="http://lxr.free-electrons.com/source/drivers/usb/serial/ftdi_sio.c" rel="nofollow">Linux driver</a> presently supports speeds (only?) up to 460800 baud. </p>

<p>Anyone used one of the <a href="http://www.ftdichip.com/Products/FT2232H.htm">FT2232H</a> chips from FTDI?</p> <p>Specifically, how do you figure out the permissible baud rates?</p> <p>The data sheet is kind of vague, and I have to pick something in the 1-3 MBaud range but need to know what my options are.</p>

FTDI FT2232H (USB <-> UART) baud rates?

2009-12-09T22:37:36.933

984

|serial|lcd|

<p>I had the same problem with my sparkFun LCD, and found Termite by CompuPhase, and it worked fine. On linux i just used stty and echo from bash. </p>

<p>I just recently started using a Sparkfun serial LCD. I am able to control it through an arduino, but I want to be able to control it through a terminal on my computer. To be able to move the cursor or clear the screen, you need to be able to send hexadecimal code to it, for example, 0xFE. I am unable to find an open source terminal program for Windows that will give me this functionality. An example of a program that works very well is <a href="http://www.eltima.com/products/serial-port-monitor/">Eltima serial port monitor</a>, although it is rather expensive for just a student. I have a USB to serial FTDI breakout board to get the signal to the LCD. Any suggestions as for programs, under Windows 7, will be greatly appreciated.</p>

Best serial monitor?

2009-12-10T22:32:15.080

992

|analog|sampling|

<p>Components are always a big cost. When you need high accuracy resistors, you can run up your BOM cost quickly. Add in some pricey op amps (which are also my favorite, unfortunately), and you can have a 100 dollar board in no time. If you want to match the high speed A/D technology of the AC coupled circuits you speak of and want to do it at a high resolution you also will be paying through the nose. Just the other day I was looking at an 18 bit, 1 MSPS A/D that topped 25 dollars. You could build a lot of cool stuff with that same 25 bucks.</p> <p>Also, a key thing to remember is 1/f noise. As you go towards (absolute) DC noise goes through the roof. DC is a tough field, but I work with it everyday so if you have any other questions, give me a shout.</p>

<p>I've noticed that in analog signal acquisition hardware you see two paradigms: AC-coupled and DC-coupled. Typically AC-coupled hardware is less expensive, and basically has a 20 Hz high-pass filter to remove the DC component. DC-coupled hardware, which is good for reading sensor signals for example, tends to be in the hundreds or thousands of dollars, whereas AC-coupled hardware like computer sound cards is very inexpensive.</p> <p>What are the electrical challenges in designing high-quality circuits for sampling DC-frequency analog signals? I'm trying to understand why there is this huge difference in cost.</p>

What's the difference (electrically) between AC- and DC-coupled sampling circuits?

2009-12-11T17:50:36.977

994

|pic|c|compiler|

<p>SDCC works fine for the 18F4550. The code it produces is maybe not as compact as the expensive compilers. But recent builds of SDCC seem to be doing a pretty good job.</p> <p><a href="http://vivara.net/blog/?p=55" rel="nofollow">Here's a project</a> I did with SDCC and the 18f2550. </p>

<p>I'm a long time AVR user. I really like that AVR-GCC works on the two main OSes I use (Mac OS X and Linux), is open-source, and is supported by Atmel. I'd like to get back into PIC programming (used them in the 90s) since there are some pretty good PICs out there, like the PIC18F4550-class of chips.</p> <p>Unfortunately, most all the compilers for PIC18s seem to be Windows-only and for-pay. And they almost always have an IDE that I do not need. I prefer command-line compilers and Makefiles so I can tell by glancing at a single file how code gets built. (and not wade through a twisty maze of dialog boxes) </p> <p>I poked around at <a href="http://sdcc.sourceforge.net/">SDCC</a> but it doesn't appear to have PIC18F4550 support and even if it did, grumblings on the net make it sound like its PIC18 support is weak, or at best very confusing to use.</p> <p>So, what's a good cross-platform command-line C-compiler with PIC18F4550 support out there?</p> <p>Failing that, what's the best-of-breed C-compiler for PIC18F4550 and how does one use it with Makefiles?</p>

PIC18F4550 C-compiler that's open-source & cross-platform?

2009-12-11T20:02:13.650

997

|arduino|avr|voltage-measurement|

<p>If your Arduino doesn't support measuring the internal bandgap reference, just use an external reference.</p> <ul> <li><a href="http://www.national.com/mpf/LM/LM431.html" rel="nofollow">http://www.national.com/mpf/LM/LM431.html</a></li> <li><a href="http://www.national.com/mpf/LM/LM4040.html" rel="nofollow">http://www.national.com/mpf/LM/LM4040.html</a></li> <li><a href="http://www.linear.com/pc/productDetail.jsp?navId=H0,C1,C1154,C1002,C1223,P1209" rel="nofollow">http://www.linear.com/pc/productDetail.jsp?navId=H0,C1,C1154,C1002,C1223,P1209</a></li> <li>Or just a Zener or two regular diodes in series</li> </ul> <p>The voltage at the input pin will be held constant by the reference diode, but the value you read will vary depending on the supply, since the ADCs are referenced to the supply. If your reference is 1.0 V, for instance, and your ADC reads 512 out of 1024, then you know the voltage rails are at 2 V.</p>

<p>I'm working on a little sensor platform that runs off of batteries. I'd love to be able to trigger an alert when the voltage gets too low. The problem is that anything I use to measure that voltage will be powered by that same voltage source. For what it's worth, I'm running Arduino Pro-mini clones (3.3 V) off of 4xAA rechargeables (4.8 V to start with, but the system seems to work right down to 2 V or so, including the XBee transmitter).</p> <p>Does anyone have any clever ideas for how to work this? It seems like anything using the analog inputs of the ATmega chip will just be comparing the input voltage with itself. Maybe checking the difference between what comes from the regulator and what comes from the batteries themselves?</p>

Monitoring voltage without a known reference

2009-12-12T16:16:19.007

1030

|fpga|xilinx|vhdl|

<p>What I'm doing is making a bit CPU. It's a nice rounded out way to cover all the basics.</p> <p>You'll cover all the basics of a large project in VHDL and be exposed to all of the core topics in VHDL design (clocks, inputs, outputs, logic, buses, and sequential design most prominently) as well as many core electronic and computer design and architecture concepts like registers, data operations, memory, and computer arithmetic. </p> <p>You can start with just addition and subtraction and then add more functionality as you learn, working your way up to a fully functional (albeit simple...or as I prefer to call it "retro") computer. At least, that's my plan.</p> <p>Plus, having your own custom-designed computer on a chip is just plain cool :) Like a 16 bit Raspberry Pi :P</p> <p>Other common FPGA projects:</p> <p>-Music synthesizer</p> <p>-DSP effect generator</p> <p>-MIDI controller/interrupter</p> <p>-Bitcoin miner</p> <p>-Video game console emulators</p> <p>-Custom Arduino shields</p> <p>-Parallel processors (very useful for certain mathematical problems that conventional computers aren't great at)</p> <p>-Robotics/control systems</p> <p>-Data acquisition (fair few oscilloscope designs out there for FPGAs if you know how to work with op amps)</p> <p>VHDL on its own isn't horribly complicated. The most important thing to remember is that you're designing a physical electronic digital circuit, not writing a program for a microcontroller. Your simulation is not a program that is going to run line by line, basically, so don't let the superficial similarity to C fool you, VHDL is a very different paradigm. </p>

<p>I am an EE student and can write [at least simple] programs in more languages than I have fingers. I have just started learning VHDL and I was wondering what a good project would be to really get to know the language and the relevant tools? I am having trouble coming up with one because it is a really different style of programming for me.</p> <p>I have made simple things like adders, but I am looking for a more long term (ie a month or so) project.</p> <p>In case it is relevent, I have Xilinx Webpack and a Digilent Spartan3 board.</p>

Project to learn VHDL

2009-12-15T08:03:03.230

1039

|wire|components|sourcing|

<p>So that you understand why test lead wire meets your needs where general purpose wires don't:</p> <p>Wire flexibility is determined by two things:</p> <ul> <li>The wire</li> <li>The insulation</li> </ul> <p>The insulation aspect is pretty easy to understand - the stiffer the insulation, the stiffer the wire. Test lead wire uses a tough, but very pliable rubber for insulation, so not only is it flexible, it's also heavy so it drapes on the workbench rather than standing up stiffly where it's stressed.</p> <p>The wire is a little bit more interesting.</p> <p>Notice that the test lead wire has the property:</p> <pre>Stranding Gauge Strands/Gauge 18 65/36</pre> <p>If you look at a comparable standard stranded hookup wire you'll find this parameter as:</p> <pre>Stranding Gauge Strands/Gauge 18 16/30</pre> <p>This means that the test lead wire is composed of 65 individual 36 awg wires, while the appliance wire (which is still pretty flexible, just not limp noodle flexible) only has 16 wires of 30 awg each.</p> <p>With AWG gauges when you drop the gauge by 3 (ie, from 30 to 33 gauge) the area of a slice of the wire (thin disc) drops by a factor of 2 (which, among other things, means the current carrying capacity drops by 2). This area affects the stiffness similarly, so from 30 gauge to 36 gauge, the wire's flexibility increases by almost 4 times, while the current carrying capacity decreases by 4 times.</p> <p>Of course, that also means you need over 4 times the number of wires (more than 4x since it's not solid copper) to attain the same 'awg' gauge.</p> <p>But the flexibility increase is worth the extra cost for many applications.</p> <p>So when you're looking for wire, keep in mind that this parameter (strands/awg per strand) is important.</p>

<p>Can someone suggest a source and part number for insulated, stranded small-gauge wire (around 22AWG) that is flexible and doesn't hold its shape? Something along the lines of the wire found on multimeter probes. I want something to connect to my bench power supply that will lay flat on the workbench; standard stranded hookup wire is too stiff and retains the shape of the spool. When <a href="http://mouser.com/Wire-Cable/Wire-Single-Conductor/_/N-5ggs?P=1z0wxmeZ1z0wxmfZ1yzvwzvZ1z0wxluZ1z0wxjo" rel="noreferrer">searching Mouser</a>, there are multiple choices for stranding, jacket material, and wire type, but I don't know how to correlate those to my needs.</p> <p>Thanks! Brian</p>

Source for flexible, stranded wire

2009-12-15T13:47:21.890

1043

|arduino|control|triac|solid-state-relay|

<p>I would stick with the SSR's too. It will be less parts and the opto-isolation is already built-in.</p>

<p>I want to control lava lamps using Arduino. I think it shouldn't be hard project, but I have no experience with hardware projects so I'm not sure witch design will feet best for me.</p> <p>I consider using S202T01 Series Solid State Relays (I already have two of them). I think it's the easiest way to do it (Am I right?, Are my SSR good for that?). Probably I could use LED blinking example and use SSR instead of LEDs. I think there are some other advantages of this approach. It's safety because of optoisolation, and it can switch very fast. Unfortunately SSR are quiet expensive and I need control ten devices. </p> <p>I'm looking for cheaper solution (but not much harder to use, and also safety). Me by I should use TRIACs (if yes what models)?</p> <p>And one more question: how about cooling? Should I use radiator on Solid State Relays or TRIACs?</p>

Controlling High Voltage device with Arduino

2009-12-15T18:33:11.030

1060

|fpga|

<p>To save money and risk vs. an ASIC. Unless you</p> <ol> <li>Deeply care about power or</li> <li>Are building a bunch of them (say >10k units)</li> </ol> <p>the fixed (NRE) costs of doing an ASIC make it cost prohibitive.</p> <p>Since you can change a FPGA easily, you can simulate the design less and get into lab quicker. Also you can do a partial design and build on it, as in software.</p>

<p>I've seen a lot of people talking about FPGA's before and I know that it stands for field-programmable gate array but how does it work and what is the purpose of using an FPGA?</p>

What is an FPGA?

2009-12-16T01:11:45.480

1065

|conductive|thread|

<p>I believe that the thread sold by Sparkfun is made by <a href="http://www.shieldextrading.net">ShieldEx</a>. According to the <a href="http://www.shieldextrading.net/images/pdfs/STATEX%5F%5F%5FMATERIAL%5FSAFETY%5FDATA%5FAg.pdf">material safety data sheet</a> for the silver-coated thread:</p> <blockquote> <p>Eye Protection: SHIELDEX® silver coated non-woven/or/woven nylon fabric and yarns does not cause significant eye irritation or eye toxicity requiring special protection. Use good industrial practice to avoid eye contact.</p> <p>Skin Protection: SHIELDEX® silver-coated non-woven/or/woven nylon fabric and yarns does not present a significant skin concern requiring special protection.</p> </blockquote> <p>Comprehensive <a href="http://www.fashioningtech.com/page/conductive-thread">review</a> of other conductive threads</p>

<p>Is the <a href="http://www.sparkfun.com/commerce/product%5Finfo.php?products%5Fid=8549">conductive thread</a> non toxic?</p> <p>Safe to wear up against your skin for extended periods of time?</p>

Conductive Thread - non toxic?

2009-12-16T02:52:37.580

1069

|clock|microcontroller|

<p>Yes, you can stop the clock completely and restart it at a later time without consequences. You could even replace the clock by a pushbutton and go through your program literally step by step (frequency: about 0.1 Hz).</p> <p>Power is almost linear with frequency: at 10 MHz the microcontroller will consume 10 times as much power as at 1 MHz. This does not mean that at 0 Hz the consumption is completely zero, though. There's always static dissipation, but that's very low, typically 1 uA or less. </p> <p>PS: notice that the ADC does have a minimum operating frequency. If the frequency is too low the capacitor over which the voltage is measured will discharge too much and your measurement will be wrong.</p>

<p>The datasheet for the ATTiny13A, for instance, lists Min frequency of 0 MHz. Does this mean the clock can be run at any arbitrarily low frequency with no ill effects? I'm assuming it draws lower current at lower clock speeds? Does 0 MHz mean you can stop the clock completely, and as long as power is still applied, it will remember its state indefinitely?</p>

Can microcontrollers be run at arbitrarily low clock frequencies?

2009-12-16T03:58:52.437

1092

|microcontroller|microprocessor|

<p><strong><em>Long answer short:</em></strong><br> <strong>MicroProcessor</strong> - Does the 'thinking', is basically is the chip itself which handles math.<br> <strong>Microcontroller</strong> - A system with a microprocessor included, readily capable of interfacing with electronic components for developing embedded system. (Think arduino, PI, PSOC4 etc.</p>

<p>What's the difference between a microcontroller and a microprocessor?</p>

What's the difference between a microcontroller and a microprocessor?

2009-12-17T21:18:22.430

1099

|arduino|gsm|

<p>I found a shield that uses a virtual serial port to communicate to the modem. I think the store is from Chile, here is the link <a href="http://www.olimex.cl/product_info.php?products_id=733" rel="nofollow noreferrer">Arduino GM862 Shield</a>.</p> <p><img src="https://i.stack.imgur.com/iH7bv.jpg" alt="enter image description here"></p>

<p>I know there are tons of projects that use WIFI or simple LAN shields to send sensor data from the Arduino as Twitter messages. How could this work with a mobile phone connection? Are there libraries or handware layers that enable TCP via GSM or GPRS? If not with Twitter, could I email the data or send to other APIs which would be HTTP requests?</p>

How to connect the Arduino with Twitter via GSM/GPRS?

2009-12-18T04:50:02.847

1113

|fpga|picoblaze|

<p>Look in the documentation for the cores. See how many LUTs (Look Up Tables) or registers they have. See if the requirements are less than the cheap board provides.</p> <p>The Picoblaze will fit on virtually anything.</p>

<p>I'm looking at a cheap board to start on and I'm wondering if I'll be able to fit a Picoblaze, LEON, S1, or OpenRISC core on there. Is there any way to tell?</p>

How do you tell if an FPGA is capable of running an ip core?

2009-12-18T18:44:08.030

1117

|arduino|

<p>Another option for a breadboard-based arduino compatible is the <a href="http://www.pjrc.com/teensy/" rel="nofollow">Teensy</a>. They have a mini-USB connector so you don't need the external USB to serial, and can be programmed as an Arduino using the free provided code to add to the Arduino IDE (or program as a straight AVR, your choice). They are available with and without the headers for breadboarding. I've used several of these on various projects.</p>

<p>Okay, here's some background info leading up to the [obvious] question with further elaboration: I have been using a 28 pin PICAXE for small projects here and there for the last couple of years and am ready to move up. My current project is the PICAXE as a data acquisition module. I have simply mounted the board inside an enclosure, and run the inputs and outputs to [a lot] of screw terminals on the outside for quick and painless component swapping. (And for further visualization, I also built in a 5V regulator and put in a DC jack so i can hook up a universal wall wart for power and wired the USB connection to a mini-usb that can be plugged into from the outside.) Well, interfacing with the computer is pretty much a pain with the PICAXE, and it can only be programmed with their official program. </p> <p>So, I am going to upgrade to Arduino. I was thinking <a href="http://amzn.com/w/2O8ZU4GC7X4C">the Arduino Mega Starter Kit</a> because it seems like the most versatile, and I know that whatever board I get will be the board I will be using for a good while. If I could do it over again, I would have started with the Arduino. </p> <p>The things I am most interested in is data acquisition and sending data back to my computer, as well automation, which I know will not be an issue. I have experience with C and BASIC but I prefer C; I am not sure if the there is a difference in language across Arduino's or not. So, what would you recommend as the most versatile Arduino that will accomplish my current goals and keep me fat and happy on capabilities for whatever strange things I desire doing next?</p> <p>As a secondary question: is it possible to interface any (or all) of the Arduino's with LabVIEW? </p>

Recommendation for Arduino

2009-12-19T05:47:15.027

1118

|robotics|

<p>It's certainly used in medical applications for expanding <a href="http://en.wikipedia.org/wiki/Stent" rel="nofollow noreferrer">stents</a> in the body. <img src="https://i.stack.imgur.com/vhZdw.jpg" alt="enter image description here"></p> <p>It's also used for coupling hydraulic tubes in military applications. However, it's not a lot of good for the use we normally, imagine, that of an actuator. For me, the killer is that I don't know of any applications that use Nitinol for repeated contractions under load. The problem is that it stretches over time, making it essentially useless.</p>

<p>I have been considering using Nitinol wire for some experimentation as a component in an autonomous system. My understanding is that it will return to its original, contracted state when it reaches ~70°C, which seems to be capable of some pretty neat applications by passing current across it. I assume that if I were to buy some, I should purchase the stuff with the thinnest diameter for maximum resistance in relatively short (&lt;20cm) lengths. </p> <p>So, for those of you who have been able to play with the stuff, is Nitinol the nerdy engineer-candy it appears to be? </p>

Nitinol: Useful stuff?

2009-12-19T06:07:42.927

1128

|legal|licensing|

<p><a href="http://www.tapr.org/ohl.html" rel="nofollow">TAPR Open Hardware License</a> is specifically aimed at hardware.</p>

<p>Can anyone give me a rundown of the various licenses that are well-suited to open hardware? I've designed a few circuit boards and would like to make them available for others to use, so I need to choose a license for them.</p> <p>Things I'm concerned about:</p> <ol> <li><p>Attribution. Are others required to credit me? If so, how? I know this turned out to be a big issue with some BSD licenses for software.</p></li> <li><p>Commercial use. Can folks copies of my work, or not? I don't really care if they do, but I'd like some credit if so :)</p></li> <li><p>Can others take my work and make "closed" derivatives of it? Similar to #2, but for when people start changing things.</p></li> <li><p>How "strong" is this license? 2 lines made up by a random hacker can constitute a license, but I'd prefer someone with legal training to have looked at it.</p></li> </ol>

Best licenses for Open Hardware

2009-12-19T19:00:55.147

1140

|pic|programmer|isp|microcontroller|

<p>I don't have much experience across multiple programmers, but I have the Pickit 2 and it seems pretty cool, I bought the signal analysis daughter board with the hopes of using it somewhat as a o-scope, but havn't gotten a chance to really play with it yet, I've managed to program the 16F913, and 16F684 I believe using the 100 microcontroller projects for the evil genius as a reference and it's been really helpful.</p> <p>I would recommend that one, but until I've used others I won't know if it's the best.</p> <p>EDIT: (I thought I fixed this already....arghhh), I've had pretty good experience with Pickit 1, I don't actually have the pickit 2, I'm sorry, I got confused.</p>

<p>I would like to start using PICs in my projects and was wondering which programmer I should get. I have plenty of experience using micro-controllers (68k, avr), I also have lots of experience with electronics (so building a programmer is possible).</p> <p>I would like to be able to use MPLAB, icsp, and the in-circuit debugging feature seems pretty neat. USB would also be convenient, but is not necessary. In your answer, I would appreciate a comparison of the pros and cons of your recommendation.</p>

Best PIC programmer?

2009-12-20T16:10:32.043

1151

|pcb|pcb-fabrication|

<p>The best way? A bench notcher, it can cut through sheet metal a few mm thick and does great on PCBs leaving nice straight lines. I would use these to shear off PCBs and it could cut straight enough to not short adjacent layers</p> <p><a href="https://i.stack.imgur.com/kI4Em.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/kI4Em.png" alt="enter image description here" /></a></p> <p><a href="https://jettools.com/metalworking/forming/plate-notchers/" rel="nofollow noreferrer">https://jettools.com/metalworking/forming/plate-notchers/</a></p>

<p>I just spent about 20 minutes trying to cut through a PCB with a hacksaw. These things are really tough.</p> <p>What is the correct tool to cut PCB material, and get a nice straight line?</p> <p>I saw something about a guillotine, but can't find a vendor.</p>

How do you cut PCB?

2009-12-21T07:19:30.943

1154

|motor|dc|

<p>Has anyone tried to control speed of low voltage DC motors using a pulse width modulator (PWM) circuit? Instead of controlling speed by reducing voltage (which kills the motor's torque), the PWM simply controls the duty cycle of the DC voltage used. In other words, the full DC voltage is applied to the motor, but it is switched on and off many times a second. The key point is that everytime the voltage is applied to the motor, it affords full torque. As a result, there is no vibration or noise which is typical of motors trying to overcome inertia.</p> <p>Small PWM circuits are available for around $20.00 that will handle up to 1.0 amps at 12 VDC. I use it to control HO gage model railroad engines. It allow them to creep without making a sound. </p>

<p>A customer has asked:</p> <blockquote> <p>I want to slow down a small hobby sized DC motor to a user variable range that runs from slow to zero RPM. I would simply use a wall wart for a power supply and a potentiometer to set the speed but the load on the motor might change slightly. Although the drag on the motor will be very low, if that drag does change, I would like the speed of the motor to stay fairly steady in spite of this.</p> <p>A couple of people told me to use a PWM controller for this purpose because a PWM has a range of 0 to 100%. Of course this in not in RPM. One other person said that the motor might not slow down properly because the hertz rating on the PWM could be to high to allow this or because the pulses might not have an adequate amount of strength to excite motor enough to move it at all when the motor speed is set near zero.</p> <p>I thought about using a steper motor so I looked a an Adafruit Motor/Stepper/Servo Shield for Arduino kit - v1.0 but I know almost nothing about this stuff so I don't know if this would be just the right thing either.</p> <p>I want to turn a knob to vary the speed of a motor form a few parts of an RPM up to a "slow" speed ...say 60 RPM? ...maybe?</p> <p>Oh ...comparatively inexpensive and simple to set up would be great as well !</p> </blockquote> <p>Any thoughts? </p>

Very Slow Electric Motor

2009-12-21T07:22:04.530

1175

|vhdl|verilog|

<p>At Intel's career center (i.e., jobs.intel) I have found two positions that could help answering this question. According to their website, it is expected from a <strong>Logic Design Engineer</strong> [<a href="https://jobs.intel.com/ShowJob/Id/1616913/Logic-Design-Engineer/]" rel="nofollow noreferrer">1</a>] to:</p> <blockquote> <p>Performs logic design, Register Transfer Level RTL coding, and simulation to generate cell libraries, functional units, and subsystems for inclusion in full chip designs. Participates in the development of Architecture and Microarchitecture specifications for the Logic components. Provides IP integration support to SoC customers and represents RTL team.</p> </blockquote> <p>I have also found a Logic Design Engineer position at ARM [<a href="https://careers.peopleclick.com/careerscp/client_arm/external/jobDetails.do?functionName=getJobDetail&amp;jobPostId=36498&amp;localeCode=en-us" rel="nofollow noreferrer">2</a>] which agrees with Intel's definition. Therefore, in a very short summary, a <strong>Logic Design Engineer</strong> seems to design, simulate and debug RTL logic.</p> <p>On the other hand, Intel expects from an <strong>Engineer for digital circuit design</strong> [<a href="https://jobs.intel.com/ShowJob/Id/1432312/Engineer-for-digital-circuit-design-CDG-Haifa/" rel="nofollow noreferrer">3</a>] to:</p> <blockquote> <p>Conducts or participates in multidisciplinary research in the design, development, testing and utilization of information processing hardware and/or electrical components, mechanisms, materials, and/or circuitry, processes, packaging, and cabinetry for central processing units CPUs and/or peripheral equipment. Prepares specifications, evaluates vendors, and analyzes test reports. Ensures products conform to standards and specifications. Develops plans and cost estimates and assesses projects to analyze risk. Develops procedures, analysis and design for computer components, products, and systems. Initiates, guides, and coordinates overall design and development of new ideas and products. Responds to customer/client requests or events as they occur. Develops solutions to problems utilizing formal education and judgement.</p> </blockquote> <p>Those tasks, in my opinion, seem to be more related to "project management" and "decision making" than to the actual implemention (not that this engineer doesn't get its "hands dirty"). Additionally, the <strong>Digital Circuit Engineer</strong> position seems to comprehend chip fabrication tasks, while the other position doesn't. Accordingly, it seems that for Intel there is a difference between the two job positions. However, I could not found a <strong>Digital Circuit Designer</strong> position at ARM. This could either mean ARM does not use this definition, or that there is simply no positions open at the moment.</p> <p>Overall, I would advice looking into which positions each company offers and what they expect from each of them as presented definitions could easily vary for other companies.</p> <p><strong>Note</strong>: References will eventually expire as they are job positions. Therefore, I have inserted all relevant content from them in this answer.</p>

<p>I'm aware that different companies have different definitions for job titles, but in general, is "logic design" the same thing as "digital circuit design"?</p>

"Logic Design" vs. "Digital Circuit Design"

2009-12-21T15:21:08.913

1184

|soldering|surface-mount|

<p>I use a small toaster oven modded with temperature (profile) control. Seems to work nice so far. Smallest parts on these boards are FT232RL chips. A typical run is 10 boards. Doing it by hand would be perfectly possible, but would take much more time. A simple (plastic) solder paste sheat saves a lot of time compared to hand-applying solder paste.</p>

<p>I've read quite a few write ups on converting toaster ovens or skillets for reflowing SMT components. The important parts appeared to be:</p> <ul> <li>Attempting to match a reflow profile (temperature pattern to ramp up and then down that gets hot enough to reflow but not hot enough to damage components/PCB)</li> <li>To make applying paste easier to specific areas: use a template (laser cut appears to be popular)</li> </ul> <p>SparkFun even <a href="http://www.sparkfun.com/products/81" rel="noreferrer">offers a kit</a> to control an oven or skillet but apparently due to liability concerns, the kit uses a 12v relay instead of a 110/120v or 220v relay (adapting it to full voltage is left up to the DIYer).</p> <p>What is your personal experience with this? It would be great to hear actual experience on what works and what to avoid.</p>

DIY SMT Reflow: Toaster Oven, Skillet or?

2009-12-21T16:40:39.010

1231

|dc|

<p>I had a look at the 551 timers and I don't think they will be that loud when hooked up to a regular piezo buzzer. So I've decided to try and boost the voltage, I couldn't find most of the ICs available locally at short notice, but I did manage to find some NCP1403s that can be delivered tomorrow. So I'll try them out with the trusty 555 timer and I'll let y'all know if it works well. The only thing I'm worried about is the lack of current!</p>

<p>Anyone got any super simple circuit designs for converting 1.5 V DC to 9 V DC? Maybe something that uses a couple of transistors would be good?</p>

Simple circuits 1.5 V DC to 9 V DC

2009-12-22T13:43:11.987

1234

|led|driver|

<p>As was suggested twice already you do not want to power this directly from the line. You should have an isolated low voltage supply. </p> <p>I would use a current-sink to provide a regulated current. An easy way to make a current-sink is to use an op-amp, resistor and FET. I have been working on a prototype that is four channels at 20A per channel. For an LED application the practical limits would be around 2A per channel (due to cooling). A picture of my prototype that is powering 5 1W LEDs is at <a href="http://tinyurl.com/yzg9kd7" rel="nofollow">http://tinyurl.com/yzg9kd7</a> </p> <p>I have mounted the LEDs on a heatsink. I use thermal grease between the LEDs and heatsink. I have a schematic of a current-sink (a.k.a. load cell) at <a href="http://tinyurl.com/6cbn6h" rel="nofollow">http://tinyurl.com/6cbn6h</a> (scroll down to the "Electronic Load" section.</p>

<p>Looking to play around with the <a href="http://www.cree.com/products/xlamp%5Fxpg.asp" rel="nofollow">CREE Xlamp series LED</a> and was wondering what would I need to drive them off 110V household power?</p> <p>Output current needs to be in the range of 800-900mA. </p> <p>EDIT: I am looking to do this for creating lighting for a NanoReef tank. I would be combining several of these in series. </p>

Current source for CREE XLamp XP-G

2009-12-22T18:47:50.420

1245

|led|colour|

<p>Sadly, not all LEDs are well made, and some will deteriorate over time even without mishandling. How long have you had this LED running? If it's just a few hundred hours, it probably was damaged by something, but if it has been in use for thousands of hours, it may just be aging. </p>

<p>Can a LED change colour over time?</p> <p>I've had a blue LED set up for some time and it use to be a much brighter (ultramarine blue) now it's heading to a more greenish dull colour. How is this happening?</p>

LED changing colour over time

2009-12-23T01:01:58.163

1246

|led|voltage|

<p>As the others have said before, plotting and IV curve would give you all the answers.</p> <p>What I could add to the discussion is that 3V is a bit too large for a green LED. Since the plastic is green (for light dispersion and... marketing reasons) and even at 3V they're rather dim as you mentioned, I think these might be 12V LEDs for automotive purposes. I've seen these at some resellers. They have a build in resistor, which allows them to operate at 12-15V as found in a car when running. They are usually used as dashboard lights and such.</p>

<p>I have a bunch of green LEDs (not super bright), the plastic around the actual LED is physically green, but they did not come with a turn on voltage. 3V seems to work but they're not too bright, is there any way I can figure it out? What's the standard turn-on voltage for non super bright green LEDs?</p>

Turn-on voltage for LED

2009-12-23T01:20:08.820

1251

|power-supply|equipment|

<p>I recently picked up a kenwood bench psu for a very low price on ebay as new old stock, it's only 1A 60V but that's quite enough for 99% of things I will ever do and it cost about 10% of it's list price. So ebay might be worth a look.</p>

<p>For my projects I have always used hacky power supplies: wall plug + 7805, a USB port or an ATX PSU. I am looking at getting into 3.3 V circuits and I am having trouble getting hold of the necessary regulators in Australia. Can anyone recommend a good lab/bench-top power supply or alternatively a cheap way of getting 3.3 V?</p>

Investing in a bench-top power supply

2009-12-23T04:47:38.953

1253

|sensor|capsense|

<p>There's a relatively new material with the fancy name of "Quantum Tunnelling Composite"</p> <p><a href="http://en.wikipedia.org/wiki/Quantum_tunnelling_composite" rel="nofollow">http://en.wikipedia.org/wiki/Quantum_tunnelling_composite</a></p> <p>It acts as resistor by default, but when pressure is applied, it transitions to a conductor. You can buy them in the form of even more strangely named "QTC Pills".</p> <p>They're basically solid(y) state touch buttons.</p>

<p>How can I sense the touch of a hand through a thick surface? I'm working on a device that has to be completely enclosed in a 1-2" thick wooden casing (or 1-3mm thick metal) due to design requirements, so no chance of pushbuttons.</p> <p>I thought we could use capacitance touch sensing, but I don't know what will work.</p> <p>Any ideas?</p>

Sensing touch through a thick surface?

2009-12-23T05:26:28.077

1262

|avr|atmel|fuse-bits|

<p>I see blalor already has an excellent answer for the purpose of Atmel fuses.</p> <p>To answer the follow-on question of "are they physical fuses or are they software programmable", the answer is neither. All modern Atmel and Microchip microcontrollers store the "fuse bits" in nonvolatile memory cells -- physically the same as SLC flash cells.</p> <p>When you use a chip programmer to download a new program into the microcontroller program Flash memory, it also erases and re-programs those fuse bit memory cells.</p> <p>However, the software running on a microcontroller cannot change the fuse bits -- not even if you are using a "self-programming" microcontroller -- i.e., a microcontroller that allows bootloader software running on it to re-program its own program flash memory.</p> <p>Some Atmel processors (especially the low-power ones) allow software running on them to change the clock source on-the-fly by writing to some configuration register -- but whenever they are reset (or the power goes away and then comes back), they go back to using the clock source specified in the fuse bits. The only way to change those fuse bits is with a chip programmer.</p> <p>Decades ago, those configuration bits (and the program memory as well) were actually stored in fuses -- a bunch of thin strands of metal; appropriate ones were selectively "blown" by applying 12 V until the metal melted and disconnected and the bit became non-conductive. As you have probably figured out, that make the microprocessor one-time programmable (OTP) -- the only way to un-blow a fuse was to throw the entire microprocessor away, pull out a fresh new one, and start all over.</p> <p>We still call those configuration bits "fuse bits" for historical reason -- much like we often call the program memory "ROM" (even though it's not really "read-only" on a self-programming microcontroller), and we have "solid-state relays" that have no moving parts, and "telephone companies" that spend only a small fraction of their time actually dealing with sound, and "computers" that spend most of their time displaying pictures and playing music rather than, you know, computing numbers.</p>

<p>What are Fuses in Atmel microprocessors and when I should or need to change the default settings?</p>

What are Atmel Fuses?

2009-12-23T10:42:19.433

1287

|microcontroller|heat|

<p>Another good choice is an old 2 gallon type coffee pot. it's temperature setting works off of a thermo-switch at about 180 degrees F. They can be had for pennies at your local thrift store. I have used them from such sources my entire life and they seem to last decades in hard use. If you do build your own, consider using a solid-state type relay from your local electronics supplier. if you get one which is slightly overkill it should last forever and it can be switched on and off using low voltage sources.</p>

<p>I have a project where I want to be able to cook food (very similar to a crock pot). What would anybody here recommend to use to convert AC to useable DC and what should I use to heat the food? Should I use cartridge heaters? How many watts would be OK? Also, I would need to turn on/off the heating element so what should I watch out for?</p>

Electronics used for cooking

2009-12-26T19:40:52.050

1291

|avr|avrdude|linux|development|

<p>ECLIPSE is working fine on an EeePC with the AVR patch... But it is a little slow.</p>

<p>I am looking for some input into getting a good integrated development environment set up for AVR programming under Linux (Assembly and C).</p> <p>My studies gave me some limited practical experience with AVRs but I fear I am getting a bit rusty so want to get busy with some projects but also want to persist in performing all development under Linux.</p> <p>I use Ladyada's USBtinyISP and have been programming my chips using AVRdude but have yet to find an IDE that works as I like under Linux so have been compiling and building via my Windows lappie and AVRstudio. (This is why I love Arduino, good IDE &amp; works straight away!)</p> <p>So, does anyone have any first hand experience using an IDE with Linux that they have successfully developed their AVR projects with start to finish?</p>

Firsthand experience with Linux AVR IDE

2009-12-26T23:05:29.577

1299

|avr|spi|i2c|digital-communications|

<p>One advantage not yet mentioned of SPI over I2C is that all SPI wires are unidirectional and are always driven high or low. This allows much faster communication than is possible with I2C, reduces susceptibility to noise, and allows simple gates to be used as repeaters. Another useful option is simple async communication (one wire each direction). The only downside I can see to async communication is that it generally requires both sides to be "awake", with a stable clock, to exchange data.</p> <p>For a project of my own, I used a 3-wire slightly-modified SPI protocol and have found the results satisfactory. I send display bitmap data (where occasional data corruption would be no big deal) at 10mbps and other data at 2.5mbps without difficulty.</p>

<p>I'm contemplating a project that would require several AVRs talking to each other over a bus. They'd be separated by as much as 6 feet.</p> <p>It seems like both I2C and SPI can let a series of micros communicate over a bus, but I haven't seen anything talking about how long that would be. Has anyone tried connecting these protocols over distances of several feet?</p>

SPI or I2C: which to use for a longish bus

2009-12-27T16:46:46.567

1308

|arduino|12v|

<p>How much current do you require? For specs you want a FET with a breakdown voltage (BVDSS) above 12V and a current rating that exceeds your load. A logic-level FET can sometimes be better but it probably will not matter if your current requirement is only a few amps. N-channel is usually what you want.</p> <p>I use the On-Semi NTP65N02 with a 3.3V gate drive level for a current-sink. TO-220 package and a fairly low Rds(on) at that level.</p>

<p>I am working on an Arduino project where I would like to use an output pin to control a 12v load with a mosfet. I think it should be an n-fet, but am not sure. I have been looking at specs, and don't know how to pic a fet that will do what I want. Can anyone point me at a part I could use?</p>

picking a FET for 12v use with Arduino

2009-12-28T02:04:18.800

1313

|connector|

<p>While you're probably way after your holidays, for anyone who stumbles upon this question - a fairly creative solution for dealing with 2mm rasters is to use a 2,5-to-3,5-inch HDD converter:</p> <p><img src="https://i.stack.imgur.com/PKCDQ.jpg" alt="enter image description here"></p> <p>Note that this will only work on exposed pins, not with the shrouded connectors (unless it happens to be a 40-pin one).</p>

<p>I recently got hold of an LED matrix that I would really like to use in a project. The problem I have is that it uses a 2mm (not 2.54mm) pitch pin header connection for which I can find no standard sockets close by. Making a pcb would be the next best option but by the time it gets fabbed and shipped my holidays will be over. Are there any secret tricks around that would allow me to solder this matrix onto veroboard? </p>

Dealing with weird connectors

2009-12-28T07:04:54.887

1315

|soldering|protoboard|

<p>I found this page to be a useful starting point on techniques for prototyping with perfboards:<br> <a href="http://elm-chan.org/docs/wire/wiring_e.html" rel="nofollow">http://elm-chan.org/docs/wire/wiring_e.html</a></p> <p>The techniques used are shown in a video as well:<br> <a href="https://www.youtube.com/watch?v=i5MNLTc7YhY" rel="nofollow">https://www.youtube.com/watch?v=i5MNLTc7YhY</a></p> <p>There is also a company selling some tools, although none of these a strickly necessary and they are a bit pricey:<br> <a href="http://www.roadrunnerelectronics.com/" rel="nofollow">http://www.roadrunnerelectronics.com/</a></p> <p>For instance, this Instructable shows how to create a wiring pen:<br> <a href="http://www.instructables.com/id/Wiring-Pen/" rel="nofollow">http://www.instructables.com/id/Wiring-Pen/</a></p>

<p>What's the proper way to solder with bus wire on perfboard.</p> <p>I used perfboard for the first time on a project recently. I designed a great layout and started soldering the components to the copper pads; the joints were perfect and beautiful. Then I realized I still needed to add the connections. So I put the bus wire down and was successful in getting the device working, but it was pretty ugly underneath.</p>

Soldering with bus wire on perfboard

2009-12-28T11:29:51.047

1324

|sensor|

<p>Futurlec has a few barometric sensor in the $5-10 range. These use I2C interface though, so a bit more involved in the MCU side than a simple analog voltage.</p> <p><a href="http://www.futurlec.com/Pressure_Sensors.shtml" rel="nofollow">http://www.futurlec.com/Pressure_Sensors.shtml</a></p> <p>If you're in Australia, you can buy from their Australian website as well.</p>

<p>I'm looking for a very low cost barometric pressure sensor. The SCP1000-D01 available at Sparkfun and elsewhere is around $25 but I was hoping to find something in the $5-10 range. I am only interested in rough relative pressure change, so it does not have to have high precision or be calibrated. Basically something like the thermistor equivalent for pressure...</p>

Low cost barometric pressure sensor

2009-12-28T16:32:44.733

1332

|arduino|led|driver|avr|

<p>I wrote a library for Arduino to do this with shift registers, it's called ShiftPWM.</p> <p>You can find detailed documentation here: <a href="http://www.elcojacobs.com/shiftpwm" rel="nofollow">http://www.elcojacobs.com/shiftpwm</a></p> <p>And a schematic for regular LED's here: <a href="http://www.elcojacobs.com/using-shiftpwm-to-control-20ma-rgb-leds/" rel="nofollow">http://www.elcojacobs.com/using-shiftpwm-to-control-20ma-rgb-leds/</a></p> <p>I recommend using a TLC5916 over a 74HC595, which is a shift register with constant current sink outputs. You would not need resistors with this driver.</p>

<p>I need to control 25 groups of 3 LEDs or 25 RGB LEDs. Each group will be dismissed from the uC by up to 20 cm (about 8 inches). 20 cm is very safe assumption but I think it will be 10 cm or less. </p> <p>However, I think If it be even 5 cm, it will be hard to create in matrix way, so I think using MAX7219 likie IC (<a href="http://www.arduino.cc/playground/Main/MAX72XXHardware" rel="noreferrer">http://www.arduino.cc/playground/Main/MAX72XXHardware</a>) is not best idea.</p> <p>I will probably use shift registers (<a href="http://www.arduino.cc/en/Tutorial/ShiftOut" rel="noreferrer">http://www.arduino.cc/en/Tutorial/ShiftOut</a>). I can connect multiple 74HC595 or use something like STP16C596.</p> <p>I prefer STP16C596 but they are obsolete. I found SCT2026 (<a href="http://zefiryn.tme.pl/dok/a04/sct2026.pdf" rel="noreferrer">http://zefiryn.tme.pl/dok/a04/sct2026.pdf</a>) but I'm not sure is It right choice.</p> <p>One more note. My current project requires only "2 bit control" over each group (3 LEDs off, or selected and turned on only one of them), but I don't think it make my project easier or cheaper, also controlling each LED separately will give much more flexibility in case of changes. </p> <p>What solution will be fit best for my requirements. </p> <p>It will be nice if parts will be available in this shop - <a href="http://www.tme.eu/en/katalog/?&amp;page=1,20#main" rel="noreferrer">http://www.tme.eu/en/katalog/?&amp;page=1,20#main</a> or <a href="http://eu.mouser.com/" rel="noreferrer">http://eu.mouser.com/</a> (but i prefer first one).</p>

Best way to control 75 LEDs with Arduino

2009-12-29T01:48:12.750

1342

|atmel|led|current|

<p>They did not build a current limiting function into the chip, however they are CMOS drivers, and by their nature increase their resistance the warmer they get, so they will generally safely self-limit on a per-port basis (although you could end up driving more than 20mA through a given LED, which might exceed the LED's rating) as long as you keep the voltage low (ie, each port doesn't have to drop more than a volt or two above the diode). </p> <p>But the supply lines internal to the chip cannot handle all 8 lines being maxed out.</p> <p>It's not ideal to do this, as you are stressing the part, but if you really want to drive an LED without the resistor, as long as you don't exceed the aggregate current, you are ok.</p> <p>However, you can get around this by running the LEDs in a PWM manner. Only drive one LED at a time, but sequence through them quickly enough that they appear constantly on to humans, even though you're actually blinking them at 30+ times per second individually.</p> <p>Still, resistors are cheap, so unless you have a great reason to drive them directly with no current limiting, it's best to design the circuit so that both the microcontroller and the LEDs are operating within their design limits.</p>

<p>From the <a href="http://www.atmel.com/dyn/resources/prod%5Fdocuments/doc0838.pdf" rel="noreferrer">datasheet</a>, I though the AT90S1200 had current-limited pins and when running at 5V would sink the proper amount of current through a green LED attached to + (0 turns on the LED, 1 turns it off) without any external resistors. Unfortunately when I attached 8 of them the IC burned out after a few minutes. I also have a dodgy solderless breadboard and may have otherwise shorted out the part.</p> <p>What did I misunderstand about that <a href="http://www.atmel.com/dyn/resources/prod%5Fdocuments/doc0838.pdf" rel="noreferrer">datasheet</a>?</p>

Is it OK to attach an LED directly to a 5V Attiny?

2009-12-30T15:33:39.847

1347

|avr|motor|driver|

<p>Microchip makes devices specifically for that sort of application:</p> <p><a href="http://www.microchip.com/stellent/idcplg?IdcService=SS%5FGET%5FPAGE&amp;nodeId=2125&amp;param=en542235" rel="nofollow">Microchip BLDC control</a></p>

<p>I want to run/control a BLDC motor from a DVD/CD-rom player and found a schematic how to do this, the so called three phase inverter (see right schematic on this page: <a href="http://en.wikipedia.org/wiki/Inverter_%28electrical%29#Three_phase_inverters" rel="noreferrer">http://en.wikipedia.org/wiki/Inverter_%28electrical%29#Three_phase_inverters</a>).</p> <p>I already made it with some some different types of transistors and an ATtiny2313 for the signal/timing and opening of the transistors, but I don't get the BLDC running. I can get LED's burning correctly, but not enough power for BLDC, I think. There are no 'anti-parallel diodes' in this set-up of my.</p> <p>Now my question, do you think I can make the NPN's in the schematic with BC639 's? I can get 50 for 3,50 euro, so I can use them also for other stuff. What about the 'anti-parallel diodes' for back EMF, do I need those? The motor doesn't need to turn very fast, easy speed is enough. And what about timings, how long should the open/pulse take (how many ms)? Or do I need to use other stuff/different transistors/schematics?</p> <p>Thanks for the help.</p>

BLDC and three phase inverter

2009-12-30T22:20:52.347

1356

|microcontroller|relay|solid-state-relay|heat|

<p>I think triacs are the normal semi conductor, maybe the one in the solid state relay. In any case inductance is not much of an issue. If the current rating of the ssr is ok and so is the isolation voltage ( 200 volts would be good ) I think you can go ahead.</p>

<p>I'm using Nichrome wire for a heating application and just using some scavenged parts from a slow cooker. What would be the easiest way to turn on/off the Nichrome? I'm thinking of just having a microcontroller switch 120VAC via a solid state relay (SSR) which would feed the Nichrome wire directly.</p> <p>Is there any inductance issues I need to worry about? The nichrome is just one long strip and not coiled in any way.</p>

Interfacing with Nichrome heater

2010-01-02T19:50:46.403

1358

|sensor|analog|temperature|lm335|

<p>I know this is an old thread, but just wanted to supply my findings for using LM335 at 3.3v using Arduino Pro Mini.</p> <p>This article <a href="http://www.learningaboutelectronics.com/Articles/LM335-temperature-sensor-circuit.php" rel="nofollow">here</a> suggests using a 2kΩ resistor at 5v, so using the R = V/I formula we can change to 1.3kΩ resistor. I had a 1.2kΩ one handy and this worked.</p>

<p>The answer to this question is probably staring me in the face, but I just can't see it. I'm attempting to interface with an LM335AZ temperature sensor (<a href="http://www.st.com/stonline/books/pdf/docs/2158.pdf" rel="nofollow">datasheet</a>) at 3.3V. The datasheet clearly states that the output voltage is 10mV/K, and that at 25°C and 1mV it should output between 2.92V and 3.04V. What I do <b>not</b> see specified is the minimum voltage it will operate at, and the sensor I have in hand doesn't appear to work correctly at 3.3V.</p> <p>With a 3.3KΩ resistor the current to the LM335 should be 1mA at 3.3V. If I directly measure the output voltage when supplying 3.3V, I get 2.46V, which correlates to −27°C; if I supply 5V I get 2.93V, or about 20°C. Suffice it to say that I'm not performing these tests outside at the North Pole. :-)</p> <p>Does the LM335AZ only work on 5V, or 5V and up?</p>

What is the minimum supply voltage for an LM335?

2010-01-02T22:57:49.723

1369

|arduino|sensor|voltage|

<p>Just use a voltage divider. You can measure thousands of volts that way. <a href="http://www.rossengineeringcorp.com/hv_dividers.htm" rel="nofollow">http://www.rossengineeringcorp.com/hv_dividers.htm</a></p> <p>And yes, dividers work for AC, too. :D They just make the signal smaller. You'll want a capacitor coupling the piezo to your input to block DC and bias it to the Arduino's reference voltage.</p> <p>I doubt it will do any damage, because the arduino input already has clamping diodes, and the current will be very low (piezos are high impedance sources, plus your divider provides a large impedance), but you can always add an extra clamping diode to protect the input.</p> <p>Actually, depending on what you're doing, you might want a high-impedance amplifier right at the piezo to prevent it from being loaded down or picking up interference. What specifically are you trying to do?</p>

<p>I found a sensor recently that emits ±90V (AC) on stimulus. How would I go about reading this from an arduino?</p> <p><strong>Update</strong></p> <p>I didn't think there were so many options. :) The kind of thing I'm looking at is a <a href="http://www.sparkfun.com/commerce/product%5Finfo.php?products%5Fid=9196">piezo vibration sensor</a>.</p> <p>The current is small, but 90V sounds like a lot (and I'm kind of new to electronics, so I don't really understand what high voltage/low current means in terms of damaging stuff).</p> <p>If it were just 90V DC then I'd get the voltage divider idea, but reversing polarity sounds like it could be a bad thing. Perhaps voltage divider + a diode or two (or a rectifier) would work?</p>

How do I read analog devices that produce relatively high voltage?

2010-01-05T05:56:59.953

1378

|arduino|

<p>As a teacher for 17 years (Maths not Technology or ICT) in the UK, if I wanted schools to focus on using Arduinos to teach basic electronics then I would need to do one of two things (or both):</p> <ol> <li><p>Convince the School Improvement Officer/Advisor who deals with Technology teaching for a particular Local Authority that the Arduino was the best match for his Schools' Electronics needs, in fact I would probably need to convince a number of them which means getting to them at a conference. The people who would need to be doing this convincing would themselves probably need to be experienced Technology Teachers who may or may not have used Arduinos in a classroom situation and are able to provide practical demonstrations as well as field what-if questions. Unfortunately if there weren't experienced people demonstrating to me, I would just assume that the demonstrators were salesmen and that at most 50% (and that's being generous) of what they were telling me was doable. The Advisors/School Improvement Officers are the people who in England at least organise much of the In Service Training so getting them on board would be a first step. If you manage to sell them on the idea of Arduinos then they would need to organise more demonstrations/training at a more regional level to disseminate ideas/techniques/suggested course content to the teachers themselves. It might be worth showing people how to build there own Arduino clones too so that they can get started with little monetary cost.</p></li> <li><p>Another route would be to persuade either the Government's Key Stage 3 Technology people or one or more of the Major Exam boards that Arduinos are the thing that has been missing from Electronics teaching all these years. Again this would involve demonstrations to relevant people first, which would then need to result in training for the actual teachers "at the chalk face" (I haven't had a blackboard in my room in 7 years but it's still know as being at the chalk face). </p></li> </ol> <p>In practical terms at the school where I work each Key Stage 3 pupil will get about 12-18 weeks of electronics education, which revolves around basic circuits, basic soldering, and designing an electronic game which uses a PCB designed by each pupil (a technician handles the actual etching). That's it for the first 3 years of secondary school technology, there might be some work on circuits in science too, there are no microcontrollers involved. If they want to pupils who choose to take Technology at GCSE can create a more complex version of this electronic game for their GCSE coursework, but that's it. In ICT the focus is on using various software packages to solve common problems, with a brief whistle stop tour of flow charts and simple programming. If they do anything more complicated than LOGO I'd be surprised.</p> <p>Other schools may do more electronics but I'm not actually sure how far they take it, much of the Technology curriculum seems to be focused on Design techniques and using skills which are taught to solve specific problems rather than saying lets equip people to use these specific tools or pieces of technology.</p>

<p>So I have this friend with a problem...I swear...it's not me! I like Arduino. I wasn't sold on the concept at first but I'm firmly in the "it's awesome" camp.</p> <p>Anyway, what I'm really looking for is a pitch to some (tech) friends about the benefits of Arduino over going out and rolling a different solution from scratch (or ordering a eval kit from a uC vendor). I'm also trying to convince a school that Arduino is a great way to teach kids programming over other starter kits and such. They also want to do some robotics eventually, so I figured I could sell them on that.</p> <p>I have some ideas on what to tell them, but I really want to hear what others have to say. And before anyone says it, I understand the best way would be to show them. But some things need to be explained before that and that's what I hope to hear from everyone. Thanks!</p>

How do you convince people to use Arduino

2010-01-06T13:44:58.180

1383

|arduino|os|avr|

<p>Here is a good run-down of four different OS for the Arduino <a href="http://antipastohw.blogspot.com/2009/11/4-operating-systems-for-arduino.html" rel="noreferrer">http://antipastohw.blogspot.com/2009/11/4-operating-systems-for-arduino.html</a></p>

<p><a href="https://electronics.stackexchange.com/questions/1374/what-is-the-best-arduino-operating-system">This question</a> seems to suggest that people are developing Operating Systems for the Arduino platform.</p> <ul> <li>What Arduino OS projects are you aware of?</li> </ul> <p><strong><em>Please list only one project or OS per answer</strong>, and give a short list of goals or features of that OS.</em></p> <p>For the purposes of this question software frameworks, task handling utilities, and similar projects are considered Operating Systems. While there are many AVR frameworks and OS projects that work on Arduino hardware, please only list those that work within the Arduino software development tools and platform without modification.</p>

What Operating Systems are available for Arduino?

2010-01-06T15:34:47.760

1388

|soldering|

<p>More tips, </p> <p>Use a damp sponge to keep the tip clean. When soldering normal components (not SMD) use a powerful hot iron (I use an Antex 25w for general work). When wiring up a big job I'll often use a 40w iron with a fine tip. It stays hot and I can get a good rhythm going. The quicker you get the joint done the less chance of damage/excess heat transfer to other parts etc.</p>

<p>Is there a tutorial that shows different techniques and the dos/don't of soldering?</p> <p>I was doing a kit last night that just said heat up both components for 5 seconds then put the solder close and let it oose into the join -> they all worked nicely....but as instructions go they are a bit basic, and from past experience there are certain components that you shouldn't heat up too much.</p> <ul> <li>I was doing Through-hole soldering but Surface Mount would also be great to learn about.</li> </ul>

What are the best Electronics Soldering Techniques?

2010-01-06T22:55:40.560

1393

|soldering|tools|

<p><a href="https://web.archive.org/web/20100410075942/http://www.sterntech.com/soldering.php" rel="nofollow noreferrer">Mini-wave tip</a></p> <p>My two cents worth. I recently had to solder on of our prototype boards, which had only SMD components. I agree with most of the comments above for general SMD parts. The toughest part I found (only when I did this for the first time), was to solder the microcontroller on the board.</p> <p>It is extremely critical to get this part aligned on the pads. There are a few tricks that make this the easiest part to solder in the end:</p> <ol> <li>Lots of FLUX on the pads where the part will be placed!</li> <li>And then this magical tip called the mini-wave tip. After tacking on the corner pins to ensure proper alignment, you fill the tip with solder and just slightly drag it along the pins of the microcontroller. Once all the pins are tacked on, you can use this tip to drag/suck away the excess solder off the pins! Works much better than tacking each pin on and using wick to dab away the excess solder.</li> </ol>

<p>This is a pretty open-ended question intentionally. :-)</p> <p>All of the soldering I've done to this point has been with through-hole components. I hope to move up to some smaller surface-mount parts at some point in the future. I've got a Weller WES51 soldering station that came with a "screwdriver" tip (ETA, I think) that's starting to feel a bit like working with a sausage as my skills (incrementally) improve. There is a <a href="http://www.cooperhandtools.com/brands/weller/index.cfm?model_list=1&amp;att_id=WEL007%20%20%20%20%20%20%20%20%20%20%20%20&amp;att1=Tips%20and%20Nozzles%20%20%20%20%20%20%20%20%20%20%20%20%20%20&amp;att2=ET%20Series%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20">large number of ET series tips available</a>. How do I choose the right tip for the components I'll be working with? </p>

Which soldering iron tip should I use?

2010-01-07T00:20:42.440

1402

|arduino|atmega|

<p>I ran into the same issue with a regular atmega168. I was able to initially communicate with it using avrdude, then I plugged it into the arduino board and tried to flash it using the IDE. The error I got was:</p> <p>avrdude: initialization failed, rc=-1</p> <p>I was using the wiring scheme from a Sparkfun tutorial which does not contain an external oscillator. I rewired everything multiple times with no luck. I finally decided to try this circuit with an external 16Mhz oscillator and it worked:</p> <p><a href="http://upvector.com/atmega/" rel="nofollow">http://upvector.com/atmega/</a></p>

<p><img src="https://farm5.static.flickr.com/4066/4252490413_f480929c6e.jpg" alt="alt text"></p> <p>I bought about 10 ATMEGA168V's (which I thought were P's) and tried to flash with TinyISP via the Arduino IDE with the arduino mini pro board selected. Well this fails for the obvious reason that the mini does not use the ATMEGA168V. The lilypad actually uses the V.</p> <p>Now when I try to:</p> <p>avrdude -c tinypisp -p m168 </p> <p>I get an error that tells me to recheck the connections. However I know the connections are fine since I was able to get the fuses set msg with this very same command BEFORE I tried to flash it with the Arduino IDE.</p> <p>I applaud you for getting this far into my rambling back story. The question is are these chips now dead? Is there something I can do to get these guys talking to avrdude again?</p> <p>Thanks,</p> <p>Ril3y</p>

ATMEGA168 (P/V/ 10/20 AU?) + Arduino Booloader Flashing via AVRDUDE?

2010-01-07T14:47:19.407

1404

|bluetooth|

<p>My vote goes for these: <a href="http://www.ebay.com/itm/190433073764" rel="nofollow">http://www.ebay.com/itm/190433073764</a> and their kind. (many more on dx.com) Very easy to interface.</p>

<p>What is the lowest cost way to add a Bluetooth integrated radio to an embedded system?</p> <p>I am using a BlueGiga WT12 which works well. IIRC these are in the $20-$25 range. Are there comparable modules that are less expensive?</p> <p>For example, I've also considered the Zigbee integrated radios (e.g. XBee). However, everything seems to be in the $20-$25 range.</p>

Low Cost Bluetooth

2010-01-07T15:53:53.797

1408

|motor|speed|

<p>Decreasing the voltage going into the motor will cause it to go slower. As Jim said putting a resistor just before going into the motor is an excellent way but you will need to switch resistors each time you want to speed back up. Better then using just a regular resistor you may try a potentiometer which is a variable resistor. You use it the same way but you can turn the potentiometers up or down to give more speed or less</p>

<p>I put together the a Herbie the <a href="http://www.solarbotics.com/products/k%5Fhm/" rel="noreferrer">Mousebot</a> the other day and he is FAST! Too fast to demonstrate in a small area.</p> <p>Have a look a this <a href="http://www.youtube.com/watch?v=KVaVRlmiQUs&amp;feature=player%5Fembedded" rel="noreferrer">video</a> to see just how he zips around.</p> <p>Documentation: <a href="http://www.solarbotics.com/assets/documentation/khm%5Fherbie%5Fthe%5Fmousebot%5Fmanual.pdf" rel="noreferrer">Mousebot</a></p> <p>So my question is - how should i go about slowing him down a bit - so i can demonstrate it in a 1m x 1m area.</p> <p>Cheers,</p> <p>Mad_z</p>

Slowing down a motor - Mousebot

2010-01-08T00:18:54.537

1409

|pcb|soldering|

<p>Clean the traces with steel wool and tin them. Then solder <strong>0.2mm</strong> (32 AWG) <strong>tinned wire</strong> onto them. This diameter lets itself bend easily to follow the traces' turns. The small diameter also means that during soldering only little heat is transported over the wire to points you soldered earlier; a thicker wire may come loose again.<br> I find <strong>Erem 102ACA</strong> precision tweezers handy to place the wire, </p> <p><img src="https://i.stack.imgur.com/stCTi.jpg" alt="Erem 102ACA tweezers"></p> <p>and a pointy knife like <strong>X-Acto</strong> to cut the wire after soldering. </p> <p><img src="https://i.stack.imgur.com/YTZyS.png" alt="X-Acto knife"> </p>

<p>I've made a couple of PCBs which need the odd few 10 mil tracks, but are mostly 20/30 mil. Unfortunately the etching process isn't fantastic and there are numerous breaks in the traces, most of them small.</p> <p>I've managed to convince solder lumps to go over the top of the smaller gaps, and have used components legs to bridge some of the larger ones. The solder lumps don't feel particularly reliable though, and there are some gaps which are too small and awkward to get a piece of wire across but too big to be bridged with just the iron.</p> <p>Are there any standard ways to reliably fix up broken traces?</p> <p><b>Update:</b> Thanks for the suggestions everyone!</p> <p>I found and tried out a silver conductive pen. As a first time user I found it difficult to dispense, and obviously I didn't use enough of it or mix it properly because it didn't even end up being conductive.</p> <p>It seems like the main problem was that I was trying to use pieces of wire which are too short. I found some small gauge tinned wire and used longer lengths, running it over significant lengths of good track on either side of the fault. That makes it much easier to position, and you can tack them down one end at a time.</p>

Best methods to fix broken tracks

2010-01-08T02:38:44.183

1420

|linux|microcontroller|

<p>I just got started with EZ430 Chronos hacking, but it seems that on a contemporary Debian, all the tools you need are easily available:</p> <pre><code>apt-get install mspdebug gcc-msp430 git clone git@gitorious.org:openchronos/openchronos.git OpenChronos cd OpenChronos make config &amp;&amp; make mspdebug rf2500 prog\ build/eZChronos.txt </code></pre>

<p>So I just got my <strong>TI eZ430-Chronos</strong> Dev kit (a runners watch &amp; eZ430 micro dev combined), and I am chomping at the bit to start playing around with my new toy. I have just a few issues the recommended tools from TI are Windows based, and I am lacking a valid windows OS right now. Also I brought the watch back to work, but left the programmer and AP at home. So I am left reading articles and links to wiki's, but unable to try anything out for myself. </p> <p>Stuff I have read so far:<br> <a href="http://www.linuxjournal.com/article/8682">http://www.linuxjournal.com/article/8682</a><br> <a href="http://wiki.msp430.com/index.php/EZ430-Chronos">http://wiki.msp430.com/index.php/EZ430-Chronos</a><br> <a href="http://sourceforge.net/projects/mspgcc4">http://sourceforge.net/projects/mspgcc4</a><br> <a href="http://blog.makezine.com/archive/2010/01/ti_ez430_-_chronos_development_kit.html">http://blog.makezine.com/archive/2010/01/ti_ez430_-_chronos_development_kit.html</a><br></p> <p>I also searched the mspgcc sf mailing-list, it had no mention of the chronos.</p> <p>Has anyone been able to get mspgcc or mspgcc4 to work with the Chronos. I have searched for information about this on the various sites, but found no answers. It should be very straight forward, but I will give it a shot later and report back if I don't hear back.<br></p>

eZ430-Chronos Development on *nix?

2010-01-08T23:34:19.600

1435

|blinkm|i2c|

<p>You mentioned you are in Australia; try searching Jaycar for "IDC Line Socket" and "IDC Cable". The smallest connector they sell is <a href="http://jaycar.com.au/productView.asp?ID=PS0984&amp;keywords=idc&amp;form=KEYWORD" rel="nofollow">2x5</a> and the smallest ribbon cable is <a href="http://jaycar.com.au/productView.asp?ID=WM4502&amp;keywords=IDC+ribbon&amp;form=KEYWORD" rel="nofollow">16 wires</a> but you can easily tear that cable apart. You just get some connectors, run the ribbon through and put them in a vice; simple!</p>

<p>I came across this post on the todbot blog about controlling BlinkMs over an I2C bus: <a href="http://todbot.com/blog/2008/06/17/get-on-the-blinkm-bus-with-a-blinkm-cylon/" rel="nofollow">http://todbot.com/blog/2008/06/17/get-on-the-blinkm-bus-with-a-blinkm-cylon/</a></p> <p>I LOVE his connectors, but cannot find a good source for the ribbon cable/push through connectors...</p> <p>Has anyone seen where I can get these easily? Its such an elegant solution.</p>

Source for parts to make a BlinkM I2C bus cable? (from todbot blog)

2010-01-12T00:49:35.933

1437

|atmega|avr|linux|osx|

<p>Hey dude you can still use avrstudio in ubuntu. Thinking how can you do that .....</p> <p>Answer is just install wine application and run those windows softwares with wine.</p> <p>Avr studio, proteus ... even games of windows can be run in ubuntu with wine.</p> <p>You dont have to even mess with the makefiles blah blah.(just install with wine and get started).</p> <p>There are many sites to get started with avr MCU's like extremeelectronics , AVR tutorials etc. Just give a google search.</p> <p>I will tell in detail how to install avrstudio 4 in wine since avrstudio 5 and 6 doesn't work with it but you can use virtual box in linux to run even avr stud 5 and 6 with windows on virtual box.</p> <ol> <li><p>Open Ubuntu software center and type wine in the search and then install it.</p></li> <li><p>Then get the setup for avrstudio4 and also you need to install win avr</p> <p>try these links for </p></li> </ol> <p>a. avr studio 4 <a href="http://mycomsats.com/blogs/download-atmel-avr-studio-4-free/" rel="nofollow">http://mycomsats.com/blogs/download-atmel-avr-studio-4-free/</a> </p> <p>b. win avr <a href="http://sourceforge.net/projects/winavr/files/WinAVR/20100110/WinAVR-20100110-install.exe/download?use_mirror=kaz&amp;r=http%3A%2F%2Fsourceforge.net%2Fprojects%2Fwinavr%2Ffiles%2F&amp;use_mirror=kaz" rel="nofollow">http://sourceforge.net/projects/winavr/files/WinAVR/20100110/WinAVR-20100110-install.exe/download?use_mirror=kaz&amp;r=http%3A%2F%2Fsourceforge.net%2Fprojects%2Fwinavr%2Ffiles%2F&amp;use_mirror=kaz</a></p> <p>3.Open the folder where the setup for AS(avr studio 4) is and then right click and then open it with "windows wine program loader" or "a wine application".</p> <p>4.Then you need to click on the next buttons as you would do it in windows.</p> <p>5.Then again install win avr similarly with wine(go into the win avr setup ....).</p> <p>6.Download the classic menu indicator from ubuntu software center. You will get to know about it in just five minutes.</p> <p>7.From the classic menu -> wine -> Programs -> avr tools</p> <p>the sixth step is an extra step so that you dont have to mess with where the avrstudio4 executable option is in the wine folder.</p>

<p>I have been coding and using Arduinos for quite some time now. However I am ready to move up to using straight AVR chips without the arduino bootloader. My question is what are resources to do this? </p> <p>I want to use linux / mac so winavr is out of the picture as is avrstudio. If there is no such thing as what I am after I will settle for a windows virtual machine. But until I know for sure. What I want is some type of IDE that uses avr-gcc.</p> <p>As a bonus to this question does anyone have any good resources on learning C for avr? Specifically how to configure Makefiles etc for the various different chips?</p>

Linux / Mac AVR Programming Suite?

2010-01-12T01:28:57.977

1450

|arm|microprocessor|development|board|ethernet|

<p>Another option is a <a href="http://www.friendlyarm.net/" rel="nofollow">mini2440 or a micro2440</a>. I bought mine (including an LCD touch screen) for 85$ on Ebay.</p> <p>Support is very extensive, it includes what you need/wanted (ethernet adapter)</p>

<p>I am looking for a cheap but powerful dev board for an ARM9 processor. It needs to be able to run linux. I am unsure about the exact specifications for RAM and such(thats partly why I'm posting this question). I would however like it to have SD, Ethernet(or WIFI) and USB. Any suggestions?</p>

Best development board for ARM9?

2010-01-13T05:12:38.853

1460

|analog|

<ul> <li>a log-amplifier (output voltage increases by V0 volts every time input voltage doubles)</li> <li>an optical interrupter (put two LEDs on either end of a tube with a slot cut through it; put current into the transmit LED, amplify the current produced by the receive LED)</li> <li>a thermocouple temperature reader (amplifier + cold-junction compensation + ADC) </li> </ul>

<p>My college undergraduate electronics classes covered some analog design, and I'd like to further my knowledge and experience. What would be a good project that would require significant effort as far as research and learning new material? Ideally, the project, when finished, would also serve as evidence that I have analog design skills.</p>

Good analog design learning project

2010-01-13T21:20:36.990

1465

|power-supply|arduino|

<p>It might be a good idea to use two power supplies, otherwise transients from the solenoids will affect the Arduino's operation. A single power supply could be used, but you need to design it carefully.</p>

<p>I'm trying to find an off the shelf plug in ac/dc power supply unit to work with my project. I want to power an Arduino Duemilanove and six 12v 1A solenoids. Here's the solenoids -> <a href="http://www.rapidonline.com/productinfo.aspx?&amp;tier1=Electronic+Components&amp;tier2=Relays+%26+Solenoids&amp;tier3=Solenoids&amp;tier4=PCB+miniature+solenoids&amp;moduleno=29536&amp;catref=60-3210" rel="nofollow">http://www.rapidonline.com/productinfo.aspx?&amp;tier1=Electronic+Components&amp;tier2=Relays+%26+Solenoids&amp;tier3=Solenoids&amp;tier4=PCB+miniature+solenoids&amp;moduleno=29536&amp;catref=60-3210</a></p> <p>I'd like to buy one of the power supply units from this page -> <a href="http://www.rapidonline.com/Electrical-Power/Power-Supplies/Plug-In-PSUs" rel="nofollow">http://www.rapidonline.com/Electrical-Power/Power-Supplies/Plug-In-PSUs</a> </p> <p>But I don't know how to work out the right one. Cheers </p>

power supply unit for Arduino/solenoid project

2010-01-14T16:27:47.420

1475

|lcd|driver|atmel|

<p>You can hook up the LCD as described in that article, and start testing pins by hooking the common up to one pin, and the drive up to another pin. Map out the whole LCD this way and you should soon see which segments go to which pins. </p> <p>A static LCD will have one pin, common, that will drive all other segments (should be easy to find) and another pin for each segment on the display.</p> <p>A multiplexed display will have 2 or more common pins that each drive a number of segments, an each other pin will drive a few segments.</p>

<p>I got some static LCD's from an old cheap clock, calculator and the like and now I would like to use them for displaying simple things like temperature. They are connected with those pink with grey connector bars, if you know what I mean.</p> <p>I found this article: <a href="http://www.ubasics.com/driving%5Fstatic%5Flcds" rel="noreferrer">http://www.ubasics.com/driving_static_lcds</a> but he talks about non-multiplexed LCD's. How can I see/test/check what for static LCD I have?</p> <p>It would be great if I could use these static LCD's, do you guys got more info on how to use these things (multiplexed or not)? Can I use it with an ATtiny2313?</p> <p>Thanks.</p>

How to test if it is a non-multiplexed (static) LCD?

2010-01-15T11:47:25.130

1478

|power|batteries|

<p>The output current required from the 3.3V regulator is </p> <p>\$1 \mu A \times 0.999 + 50mA \times 0.001 + 25uA = 75.999uA \$</p> <p>The output power is</p> <p>\$ 3.3V \times 75.999 \mu A = 250.8\mu W\$</p> <p>The input power to the regulator is</p> <p>\$ \frac{250.8\mu W}{0.8} = 313.5\mu W \$</p> <p>When the batteries are fully charged the input current to the regulator is</p> <p>\$ \frac{313.5 \mu W}{3V} = 104 \mu A \$</p> <p>If the batteries have a flat discharge curve then you will get a life of</p> <p>\$ \frac{2700mAh}{104 \mu A} \$ = 25837 hours = 2.95 years</p> <p>Since your batteries are 2700mAh 1.5V AA I am guessing that the discharge curve is not flat. You will need to draw higher currents as the voltage drops.</p> <p>Also your regulator efficiency probably drops at lower voltages. Again I am guessing since I have not seen the design. </p> <p>Be careful when calculating using currents. You may be inadvertently assuming that the input and output voltage of the regulator is the same. With an input of 3V and an output of 3.3V it is not a big error. If you do a more accurate estimate of the battery discharge curve it will matter.</p>

<p>How do I calculate how long a battery operated product will run?</p> <p>Here's what I've got:</p> <ol> <li>2 AA, 1.5V, 2700mAH batteries</li> <li>Voltage Regulator with a Iq of 25 uA</li> <li>Voltage Regulator Eff = 80%</li> <li>Active Current = 50mA </li> <li>Sleep Current = 1uA </li> <li>Duty Cycle = 99.9% (only active 0.1% of the time) </li> <li>Active Voltage is 3.3V</li> </ol> <p>I've gone the current route and got an answer. I went the power route and got a TOTALLY different answer (days vs years different).</p> <p>How do you do this?</p>

How to calculate battery life

2010-01-15T21:10:20.187

1487

|light|

<p>Your question stirred some cobwebs deep in the recesses of my dusty brain. I seem to remember building such a thing myself way back when. I don't remember the specifics, but if I recall correctly, we used RC filters to segment the incoming audio signal and SCRs to trigger short strings of 110V AC Christmas lights. Probably a transistor to drive the SCR. These things were all the rage, along with strobe lights, back in the late 70's.</p>

<p>When I was a teen, I joined an electronics club and built a disco board. I had 5 light bulbs, I painted them different colors. Then I built a board which was connected to these light bulbs. I'd connect my stereo to the board and the each light bulb would flash when a specific instrument would play (e.g. green for drums, etc...).</p> <p>I want to build something similar with my son now, but I totally and utterly forgot how to do this. Can someone point me in the right direction? </p>

How to build disco lights?

2010-01-17T23:01:52.430

1494

|microcontroller|adc|

<p>Use a serial ADC (preferably SPI-based). There are many good 14 or 16 bit ADCs (I like the 14-bit <a href="http://focus.ti.com/docs/prod/folders/print/tlc3541.html">TLC3541</a> -- you can substitute with the TLC4541 for 16bits, or TLV2541 for 12bits) that are very easy to use with a microcontroller that you are already familiar with.</p> <p>Many microcontrollers have SPI master peripherals, and even if yours doesn't, SPI is really easy to control via bitbanging. </p>

<p>I'm trying to find a powerful MCU that has multiple analogue to digital converters. I want around a 14 bit resolution to do some serious audio sampling. Any suggestions or comments would be great, cheers. </p>

What MCU, need hi res ADCs?

2010-01-18T15:20:12.047

1497

|avr|

<p>The menu you are currently in is for selecting which emulator/simulator/debugger. AVRISP MKII doesn't support that, it's "only" a programmer. So simply pick whatever option in that menu, then later, pick the programmer in a different menu.</p>

<p><img src="https://farm3.static.flickr.com/2794/4277616111_1e8e96c5cf.jpg" alt="AVRISP MKII Custom Enclosure"></p> <p>I have a AVRISP MKII that I wish to program avr chips with through avrstudio 4 with. However on the "select platform" the only think that resembles MKII is JTAGICE MKII which is not what I have? Am I missing something here? When I plug in the AVRISP MKII the drivers are all working and says it "sees" the device at least in windows.</p> <p>Thanks,</p> <p>Ril3y</p>

AVRISP MKII does not appear in AVRStudio 4 (latest build 4.18 SP1)

2010-01-18T18:47:37.800

1508

|sound|sensor|

<p>I agree that the piezo sensor that PPVI suggested is a very cost effective way to go at less than $3 ea. However I would suspect it would not be discrete enough to distinguish between a ball being struck on the laces versus the toe or instep. I am a long time soccer coach as well and understand the precision you are looking for. Although it would be a much more expensive alternative I think you could use a softpot membrane potentiometer. Sparkfun has them for about $13ea. <a href="http://www.sparkfun.com/commerce/product%5Finfo.php?products%5Fid=8680" rel="nofollow">Check them out Here</a></p> <p>However for the price difference you may want to try the piezo first.</p> <p>Good luck and let us know how it works.</p>

<p>I'm thinking about putting together something simple for my young son's soccer team. I'd like to build a simple circuit that could be placed on/underneath the laces of their shoes and plays a sound when the kids kick the ball on the laces.</p> <p>Any ideas on what would be the simplest route to do something like this? I'm wondering what kind of contact sensor would work best and how bulky I'd have to make things to produce a sound loud enough for the kids to hear. </p>

Simple (?) pressure activated sound

2010-01-22T07:14:10.690