need help interfacing soundcard

Discussion in 'General Electronics Chat' started by lalalu, Sep 17, 2009.

  1. lalalu

    Thread Starter New Member

    Aug 16, 2009
    Hi I am planning to use my soundcard to drive a DC motor. As the motor needs more current and voltage than what my soundcard can supply, I am planning to use voltage amplifier and current.

    Can someone check my circuit and comment, before I fry my soundcard?:(

    Datasheets: power transistor, opamp
  2. blueroomelectronics

    AAC Fanatic!

    Jul 22, 2007
    Might be the worst way to drive a motor I've ever seen. Why use a soundcard? Use a printer or serial port.
  3. t06afre

    AAC Fanatic!

    May 11, 2009
    A sound card is in general a device for sound, hence the name sound card;) The frequency range is about 20-20KHz. So if you are going to use PWM, a sound card may not be optional. I do not know how it behave then you try to output DC either. The input of a sound card is in general AC coupled also. so it will block DC on the input (just FYI).
    In your circuit you will not fry the sound card. If you are afraid of frying your sound card, put a small resistor in series with with the pos input on the opamp. Sound card are in general capable of driving 32 ohms headphones, on the main output. But if you have several outputs on the sound card not all outputs are capable drive headphones
  4. russ_hensel

    AAC Fanatic!

    Jan 11, 2009
    If you have some good software to dirve the sound card for PWM or similar I would say go for it. A scope to look at the waveforms would be useful. Circuit should be more or less ok, but I would add a pot for attenuation and a way to set the dc offset. For more than experimentation this is a poor way to drive a motor, but to dink around it may be interesting.
  5. R!f@@

    AAC Fanatic!

    Apr 2, 2009
    What is every one talking about? :eek:
    Why the heck does any one need to drive a motor from sound :confused::confused:

    I say u have a few screw loose :D
    but if it helps..ur circuit might drive the motor with an analogue input, but it will definitely turn in one direction, and will be jumping in speed in accordance with the input frequency, still to drive the motor the frequency should be low enuf to fluctuate the DC component slowly enuf so tht the motor gives any RPM

  6. t06afre

    AAC Fanatic!

    May 11, 2009
    Amazing! Using so many words to produce so little useful information. Are you a politician
  7. R!f@@

    AAC Fanatic!

    Apr 2, 2009
    what ever do you mean? :confused:
  8. Audioguru


    Dec 20, 2007
    The sound card does not have a DC output.

    The output high voltage from a lousy old 741 opamp does not go as high as the supply (+9V?) but goes to only 1.5V less than the supply voltage (to +7.5V).
    The output high voltage of the darlington emitter-followers is 1.4V less than their input so the motor gets only 6.1V max.
  9. Wendy


    Mar 24, 2008
    I think the key question is, how are you trying to use your sound card? Are you generating a PWM signal? Or maybe a variable frequency? It can be done, but you will need more interfacing that what we're seeing to do it. All of the above comments are basically true, especially the one about the sound card only coming out with AC. A PWM signal could be pulled from an AC signal, but it does require signal processing, a fancy term for more circuitry.