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Ports and voltages.....

Discussion in 'General Electronics Discussion' started by eptheta, Apr 27, 2010.

  1. eptheta

    eptheta

    188
    0
    Dec 20, 2009
    Is there any port on the computer that can take analog inputs so that i can check voltages ?
    I want a good voltmeter that can log data, but they are rather costly with USB interfaces.
    Is there any port that doesn't just take 1's and 0's, but accepts varied voltages ?

    Any other ideas for measuring voltage using a computer ?
    Thanks
     
  2. NickS

    NickS

    367
    0
    Apr 6, 2010
    Microphone or Aux audio inputs work for analog signals, but as I have said before you will likely ruin the audio card and or motherboard if you do not take care to properly limit and isolate the signals sent to the card for capture.

    You will also be frequency limited (and it may not pass DC depending on the specs of your hardware).
     
  3. eptheta

    eptheta

    188
    0
    Dec 20, 2009
    I already tried with my microphone input. I limited my voltage to 2V max and downloaded one of those PC-oscilloscope software and tried it out. It recognizes simple waveforms ( which i generated with 555 oscillators) like sine waves and square waves, but from what i know there's a capacitor on the sound card that only allows AC not DC.

    Is there any other port that can register DC ?
     
  4. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,214
    2,695
    Jan 21, 2010
    The only other analogue input I'm aware of is the old joystick port. However I believe that measured the period of an RC oscillator where the R was varied (the joystick was a pot).

    Aside from that, you can buy boards that provide all manner of interfaces, including analogue inputs.
     
    Last edited: Apr 29, 2010
  5. NickS

    NickS

    367
    0
    Apr 6, 2010
    So this is a bit more involved but you could use a VCO(voltage controlled oscillator) to transform your DC voltage to an AC frequency then you would have to interpret that frequency and in software to derive what the DC level was.

    Or you could do a similar alternative by modulating the duty cycle on a square wave. ie a large voltage = 85% duty cycle and small voltage =15% duty cycle. But this way may significantly reduce your resolution.

    But by the time you add hardware you may as well be buying a ADC with USB interface.
     
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