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Need help amplifying Pulse Train to drive Pen Laser tia sal2

Discussion in 'Electronic Equipment' started by [email protected], Jul 23, 2006.

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  1. Guest

    Greetings All
    Need help amplifying Pulse Train to drive Pen Laser

    I would like to create a pulse train using my sound card and cooledit pro
    (creating square waves) but I don't think I have enough power to drive my
    ULN2003A Darlington Transistor Array
    (http://www.chipcatalog.com/TI/ULN2003A.htm) can anybody recommend a way
    to boost the voltage/current/power so I can drive my ULN2003A chip, I'm
    trying to make it very portable, is their a small chip that will allow me
    amplify my audio signal/pulse train?

    For those of you who are interested this is what I intend to do.
    1) Create various pulse trains by creating square waves in cool edit
    pro
    2) Saving audio file as wav or mp3 onto my iRiver iFP 799T mp3 player
    3) Using mp3 player with square wave audio pulse trains to drive my
    ULN2003A
    4) Have ULN2003a and 3V battery power/pulse a small pen laser less
    than 5mW

    I do have a bunch of 555/556 timers that could be made into voltage
    doublers http://www.reconnsworld.com/power_voltdoubler.html but my mp3
    player doesn't put out the required power to operate them.

    If anyone has any other recommendations or another way I should go about
    it I'm all ears.

    TIA
     
  2. Robert Baer

    Robert Baer Guest

    The output voltage is moer than enough; use a current limiting
    resistor from the output to the base of the darlington; 1K with 1V
    nominal output gives 1mA drive and that translates to way over an amp
    "saturated" (darlingtons *cannot* be saturated).
     
  3. Bob Masta

    Bob Masta Guest

    Perhaps you have already considered this in your plans, but all
    consumer audio devices that I have ever seen or heard of are
    AC coupled. So you will either need to keep the square wave
    frequencies high enough (at least in the low Hertz range) or
    you will need some sort of recovery circuit to convert switching
    spikes to flip-flop transitions. But sounds do-able, at least as
    WAV files.... I'd be really amazed if MP3s kept the waveform
    intact, though might be OK with the spike-to-flip-flop circuit.

    You might want to take a look at my DaqGen freeware
    sound card signal generator for your initial experiments.
    It generates everything in real-time, not to a file, but has
    extensive options for creating all sorts of waveforms,
    including pulses of various duty cycles, PWM, etc. (There
    is an extensive Help system, but let me know if you need any
    additional help with this.) This might help you optimize
    waveforms since you can tweak things while everything
    is running on the test bench.

    [SHAMELESS PLUG]
    DaqGen is the signal generator portion of the upcoming
    Daqarta system (couple more months), which *will* allow
    you to save waveforms to files. That's just a side benefit;
    it's main purpose is to create test signals and analyze the
    responses to those signals from a device or system under
    test. Lots of scope, signal averager, spectrum analyzer,
    and spectrogram options.

    Best regards,


    Bob Masta
    dqatechATdaqartaDOTcom

    D A Q A R T A
    Data AcQuisition And Real-Time Analysis
    www.daqarta.com
    Home of DaqGen, the FREEWARE signal generator
     
  4. Daniel

    Daniel Guest

    Big Call!!! "darlingtons *cannot* be saturated" Stick 1mA in the base
    of first, small signal Amp Transistor could easily become 50-100mA into
    base of second Transistor of the Darlington Pair could be 2.5-10 Amps,
    which could easily saturate some Darlington Pair Amplifiers.

    Daniel
     
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