1. Post #241
    Gold Member
    Chryseus's Avatar
    February 2009
    2,470 Posts
    Finished hacking up a broken(ish) old Dell psu to use a desktop supply. Working nicely at the moment, hopefully it won't fail miserably under larger loads... Here it is hooked up to an atmega32 which I also just got working with a usbtinyISP.
    The job you've done on the case looks really nice, although you are missing the -12V which can be rather handy despite its low current.
    You should be aware that switch mode supplies tend to have rather high levels of noise so it would be no good for analog signal stuff like high gain amplifiers.

    You might also want to make a programming board for the atmega like I did some time ago with a proper IDC connector for the ISP, it makes life a lot easier.
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  2. Post #242
    Gold Member
    Little Green's Avatar
    March 2006
    188 Posts
    Sadly the power supply didn't have -12V to tap into (that I could find), just two different coloured +12V. The noise shouldn't be too bad for most of the things I can see myself using it for, so it should serve me well as a general purpose supply.

    And yes I definitely need to get around to making something with a proper connector, the clusterfuck of wires gets tiring. This is the first thing I've made not using the arduino, I have a whole bunch of components ready for a couple of projects - Now I just need to learn how to use them
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  3. Post #243
    amazer97's Avatar
    October 2009
    868 Posts
    So I found my Arduino recently, can anyone recommend anything short/fun to do with it?
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  4. Post #244
    Gold Member

    March 2005
    3,028 Posts
    You can make a -12V (actually more like -11V) source with a 555 timer and a few caps/diodes in a charge pump circuit. It'll only supply a little over a tenth of an amp (the 555 is rated for 200mA) and there might be some ripple, but having a negative supply really makes op-amp circuits (and just about anything that requires biasing) simpler.
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  5. Post #245
    Gold Member
    Chryseus's Avatar
    February 2009
    2,470 Posts
    You can make a -12V (actually more like -11V) source with a 555 timer and a few caps/diodes in a charge pump circuit. It'll only supply a little over a tenth of an amp (the 555 is rated for 200mA) and there might be some ripple, but having a negative supply really makes op-amp circuits (and just about anything that requires biasing) simpler.
    Good idea, he could also split the 12V rail into +-6V, which depending how it is split could still provide significant current.
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  6. Post #246
    Gold Member

    March 2005
    3,028 Posts
    Good idea, he could also split the 12V rail into +-6V, which depending how it is split could still provide significant current.
    That's a much better solution if need a lot of current without ripple, but it also means that your virtual ground won't be the same as earth ground which may or may not be a problem depending on your application (mostly for interconnected systems). Of course caps/transformers/opto-isolators solve that problem.
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  7. Post #247
    amazer97's Avatar
    October 2009
    868 Posts
    My father's friend was throwing out old stuff, and he gave me an old 80s Russian oscilloscope, analog. It's in pretty much mint condition, the manual that comes with it is still in shrink wrap. Shame I won't get to use it for another 2 weeks as I'm leaving for camp.
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  8. Post #248
    Gold Member
    Chryseus's Avatar
    February 2009
    2,470 Posts
    My father's friend was throwing out old stuff, and he gave me an old 80s Russian oscilloscope, analog. It's in pretty much mint condition, the manual that comes with it is still in shrink wrap. Shame I won't get to use it for another 2 weeks as I'm leaving for camp.
    Nice ! take some pictures of it when you can.
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  9. Post #249
    Gold Member
    Falcqn's Avatar
    July 2010
    3,016 Posts
    My father's friend was throwing out old stuff, and he gave me an old 80s Russian oscilloscope, analog. It's in pretty much mint condition, the manual that comes with it is still in shrink wrap. Shame I won't get to use it for another 2 weeks as I'm leaving for camp.
    Does it use vacuum tubes?
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  10. Post #250
    hOnK :o)
    i300's Avatar
    December 2009
    3,987 Posts
    I got an early birthday present from my brother :D
    (Or, well, I will be receiving it. It's coming in the mail)


    (this)

    Jackpot! I also was given a MintyBoost kit to make!
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  11. Post #251
    Gold Member
    Chryseus's Avatar
    February 2009
    2,470 Posts
    Rigol DS1052E just arrived, I'm very happy with it so far.
    Just built a small electret mic amplifier with an op-amp to test it:


    For those who can't read, blue = input, yellow = output.
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  12. Post #252
    Map in a box's Avatar
    July 2009
    7,420 Posts
    Rigol DS1052E just arrived, I'm very happy with it so far.
    Just built a small electret mic amplifier with an op-amp to test it:


    For those who can't read, blue = input, yellow = output.
    I would so abuse that
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  13. Post #253
    www.bff-hab.de
    Dennab
    February 2009
    7,832 Posts


    It was too late when I noticed that my voltage regulator was smoking off.
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  14. Post #254
    Gold Member
    Xera's Avatar
    November 2006
    3,097 Posts


    It was too late when I noticed that my voltage regulator was smoking off.
    Ouch. My breadboard has suffered orange juice and coffee, getting a little difficult to insert stuff into it.
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  15. Post #255
    Gold Member
    Lapsus's Avatar
    June 2006
    1,080 Posts
    Oh man, that photo reminds me of some of the breadboards from computer engineering in high school.

    Oh well, now your breadboard has a battlescar and a story to tell.

    Edited:

    Can someone help me out with a simple transistor amplifier? I pulled an electret mic off of my old FM transmitter from school, and I can't for the life of me get a signal out of it, though I'm fairly sure that's because it's too weak for me to measure.
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  16. Post #256
    Gold Member
    Zero-Point's Avatar
    March 2006
    7,687 Posts
    Oh man, that photo reminds me of some of the breadboards from computer engineering in high school.

    Oh well, now your breadboard has a battlescar and a story to tell.

    Edited:

    Can someone help me out with a simple transistor amplifier? I pulled an electret mic off of my old FM transmitter from school, and I can't for the life of me get a signal out of it, though I'm fairly sure that's because it's too weak for me to measure.
    http://en.wikipedia.org/wiki/Transis...s_an_amplifier
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  17. Post #257
    Gold Member

    March 2005
    3,028 Posts
    Can someone help me out with a simple transistor amplifier? I pulled an electret mic off of my old FM transmitter from school, and I can't for the life of me get a signal out of it, though I'm fairly sure that's because it's too weak for me to measure.
    You need to power it through a resistor. Those electret microphones generally have a JFET built-in to help amplify the signal. All you need to do is provide power and a load resistor, generally in the range of a few kOhms (2.2k is a good place to start). Higher resistor values produce more gain, as with all common-source amplifiers.

    Make sure you get the polarity right. You take the output from between the load resistor and the electret, generally coupled through a capacitor.

    Edited:

    Hopefully you didn't already hook it straight up to power or anything. Powering it without a load would probably cause permanent damage.
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  18. Post #258
    Gold Member
    Lapsus's Avatar
    June 2006
    1,080 Posts
    Thanks for the help, ROBO_DONUT. I don't exactly know how to do anything useful with the signal I'm getting out of the mic yet, but I am at least getting a signal.
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  19. Post #259
    www.bff-hab.de
    Dennab
    February 2009
    7,832 Posts
    Thanks for the help, ROBO_DONUT. I don't exactly know how to do anything useful with the signal I'm getting out of the mic yet, but I am at least getting a signal.
    You could build a class-D amplifier out of 3 op-amps and have a speaker outputting whatever the microphone picks up.

    The use of that is ???.
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  20. Post #260
    hOnK :o)
    i300's Avatar
    December 2009
    3,987 Posts
    Got a Wii Nunchuk working with my Arduino.


    That took for-fucking-ever.
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  21. Post #261
    Gold Member
    Zero-Point's Avatar
    March 2006
    7,687 Posts
    Got a Wii Nunchuk working with my Arduino.


    That took for-fucking-ever.
    Had a friend of mine do that once, except he managed to control two servos attached to each other for a 2-axis device. Never did anything else with it though, as much as he tinkers he's a lazy bastard.
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  22. Post #262
    Gold Member
    Jookia's Avatar
    July 2007
    6,768 Posts
    konami code is best code
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  23. Post #263
    www.bff-hab.de
    Dennab
    February 2009
    7,832 Posts
    Yeah I finished my accelerometer thingy

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  24. Post #264
    Gold Member
    Chryseus's Avatar
    February 2009
    2,470 Posts
    I had some fun building a simple 555 charge pump voltage inverter.
    Going to improve it to provide a positive and negative 2 x Vin and build my own RS232 level shifter.

    Schematic



    Results



    Yeah I finished my accelerometer thingy
    Send the data to a computer and write something to draw a nice graph.
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  25. Post #265
    quincy18's Avatar
    September 2007
    1,018 Posts
    After building 1 double h bridge I decided to just order 3 ic's from bitsbox. Have around a week until those arrive so in the meanwhile I am going to build a frame for the cnc machine, should I post pictures of the building process ?
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  26. Post #266
    Gold Member
    ddrl46's Avatar
    October 2007
    3,686 Posts
    After building 1 double h bridge I decided to just order 3 ic's from bitsbox. Have around a week until those arrive so in the meanwhile I am going to build a frame for the cnc machine, should I post pictures of the building process ?
    Yes, you should post pictures.
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  27. Post #267
    q3k
    Gold Member
    q3k's Avatar
    October 2009
    921 Posts
    Was working on amplifying the output of a PMA4601M IR receiver to 0V-5V, but accidentally made it emit magic blue smoke. Oh well, I'll buy a proper TTL-level IR detector tomorrow (this one was found in my junk box). vv

    el cheapo chinese Mastech multimeter owners represent!
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  28. Post #268
    Gold Member
    Mr.T's Avatar
    August 2010
    2,691 Posts
    I'm building a computer system for my large-scale UAV and I decided on Gumstix (Is there anything else?). So I'm wondering how to control the servos using a embedded system like Gumstix. Hope someone answers.
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  29. Post #269
    q3k
    Gold Member
    q3k's Avatar
    October 2009
    921 Posts
    I'm building a computer system for my large-scale UAV and I decided on Gumstix (Is there anything else?). So I'm wondering how to control the servos using a embedded system like Gumstix. Hope someone answers.
    PWM (pulse width modulation). Have a digital (TTL, 0-5V) output send out pulses every 20ms to the control wire of the servo (usually the middle one of the three, the other two being GND/0V and 5V). The pulse width is what sets the angle of the servo. A pulse width of 1ms will set the servo to 0 degrees, a pulse width of 2ms will set the servo to 180 degrees. Any other angle you want to obtain is proportional to the max time values I cited. So, for example, a 1.5ms pulse will set the angle to 90 degrees. It's that easy. Usually you don't even have to drive the outputs with transistors, as the current consumed by a servo on the control wire is very small.

    Now, how to implement that on a Gumstix system is something I have no idea about - I guess there are some GPIO ports that you can use?
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  30. Post #270
    Gold Member
    Mr.T's Avatar
    August 2010
    2,691 Posts
    Also, how do I connect Arduino with Gumstix?
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  31. Post #271
    Follow me on github!
    benjojo's Avatar
    January 2009
    2,622 Posts
    Does Gumtix have UART? If so use that?
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  32. Post #272
    Gold Member
    Mr.T's Avatar
    August 2010
    2,691 Posts
    Does Gumtix have UART? If so use that?
    Thanks, I also found out that gumstix uses i2c.
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  33. Post #273
    kill yourself
    Protocol7's Avatar
    June 2006
    26,086 Posts
    I have an old broken harddrive stripped apart. Time to fuck with the motor .
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  34. Post #274
    Gold Member

    March 2005
    3,028 Posts
    I have an old broken harddrive stripped apart. Time to fuck with the motor .
    Good luck. I got nowhere with my back-emf sensing BLDC motor driver.
    Funny thing is, each of the individual parts seemed to work fine. Zero-crossing detector worked fine, the constant acceleration spin-up routine seemed OK (after a little debugging), etc. But when I put it all together it just sat there like a lump of spaghetti.

    Probably doesn't help that I don't have any of the proper tools...
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  35. Post #275
    Gold Member
    Chryseus's Avatar
    February 2009
    2,470 Posts


    I was not expecting this when I lifted the mystery SOIC part, has to be one of the more
    unusual things I've found.
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  36. Post #276
    Gold Member

    March 2005
    3,028 Posts
    wat.
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  37. Post #277
    Gold Member
    bobthe2lol's Avatar
    July 2007
    1,370 Posts
    I think I may have fried my arduino. Yesterday, I had it working nicely, powering my 10 meters of a total of 600 RGB Leds. Then, today I plug it in and the program that's in there is acting VERY strangely (really slow responce time, not doing correct colors, etc.) and I haven't touched it since yesterday. The power was unplugged (when I wasn't using it). So I think that maybe the program got corrupted.
    So I go to re-upload it and here's exactly what happens (Arduino Uno): Click upload. Wait 1/2/3 seconds. L flashes. RX flashes 3 times in succession (100-300 ms apart).

    Then the IDE says,
    "avrdude: stk500_getsync(): not in sync: resp=0x00
    avrdude: stk500_disable(): protocol error, expect=0x14, resp=0x51"

    Any ideas?
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  38. Post #278
    Gold Member
    Chryseus's Avatar
    February 2009
    2,470 Posts
    I think I may have fried my arduino. Yesterday, I had it working nicely, powering my 10 meters of a total of 600 RGB Leds. Then, today I plug it in and the program that's in there is acting VERY strangely (really slow responce time, not doing correct colors, etc.) and I haven't touched it since yesterday. The power was unplugged (when I wasn't using it). So I think that maybe the program got corrupted.
    So I go to re-upload it and here's exactly what happens (Arduino Uno): Click upload. Wait 1/2/3 seconds. L flashes. RX flashes 3 times in succession (100-300 ms apart).

    Then the IDE says,
    "avrdude: stk500_getsync(): not in sync: resp=0x00
    avrdude: stk500_disable(): protocol error, expect=0x14, resp=0x51"

    Any ideas?
    Make sure you are programming it correctly.
    But it sounds to me like you've damaged it, powering 600 LEDs directly will almost certainly exceed the maximum pin current.
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  39. Post #279
    Gold Member
    bobthe2lol's Avatar
    July 2007
    1,370 Posts
    Make sure you are programming it correctly.
    But it sounds to me like you've damaged it, powering 600 LEDs directly will almost certainly exceed the maximum pin current.
    So... How should I power them? I got the 12v 5a power supply from adafruit, and it has a connector that I don't think I should just wrap a wire around and stick in the led strip. And doesn't the board have overcurrent protection?
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  40. Post #280
    Gold Member

    March 2005
    3,028 Posts
    Maximum pin current is 40mA. Small LEDs can draw 20mA each.
    600*20 = 12000mA.
    12000 > 40

    Hope you had a nice big FET driving those LEDs.
    And doesn't the board have overcurrent protection?
    No, because you shouldn't be powering anything through an I/O pin. They're strictly for signalling.
    You need a power transistor to switch larger loads.
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