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LED powered by parellel port?

Discussion in 'General Electronics' started by Paul, Mar 3, 2004.

  1. Paul

    Paul Guest

    Just wanted to know if I could safely connect a 12 volt LED to the voltage
    out of the parellel port on my PC? I need to place a constant load on the
    parellel port so my PC will think that something is plugged into it. The
    parellel port device that I have plugged in stops working after a few
    minutes. It's USB powered and not by the parellel port so I think the PC
    shuts the parellel port off thinking nothing is plugged in. Thanks in
    advance.
     
  2. JRW68

    JRW68 Guest

    I am by no far an expert at parallel ports but I have been researching
    it and trying to learn about them. From what I have read the
    parallel port only outputs 5Vs at 6mA..... my point is .. maybe a
    smaller LED with an inline resistor (4.7kohm)? Ive read that you can
    overload the parallel port circuit easily by overloading it.

    I dont know if that helps at all, most of that information pertains to
    the outputs of the parallel port. I am not familar with a 12v supply
    coming out of the P.P. unless the 12v diode will work at alot less
    voltage.

    I bet you already knew that.... just thought I would throw it out
    there.

    Seems like your quite abit more knowledgable than me with respect to
    P.P. and USB uses.... any suggestions on where I might find some
    info, good book, one miracle site that ive missed?
     
  3. Paul

    Paul Guest

    I would try forums instead of news groups. Forums seemed to attract more
    folks with knowlege than news groups do. I posted here because I was too
    lazy to do a google search for a decent electronics forum. I'm not sure
    what the voltage is from a PP but I know that a USB is 5V. I thought that
    the PP was 12 but I could be wrong.
     
  4. scada

    scada Guest

    The input/output (IO)of the parallel port is 5V logic. If the PC program is
    actually polling the port for activity, it probably won't be in the form of
    a load. It would likely send some information, then expect a reply back! The
    possibilities are many. Your best bet would be to get a port monitor program
    (do a google search, you will find free ones!) and monitor what your device
    is seeing! Or buy a port monitor, which is a device that plugs between the
    parallel port and the hardware. It has LEDs on each pin, to monitor the
    status.
     
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