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Slot car timing circuit

Discussion in 'Electronic Basics' started by Ron Collins, May 1, 2004.

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  1. Ron Collins

    Ron Collins Guest

    I'm trying to put together a slot car timer for my son. I came upon a
    design using and IR led and IR detector set from Radio Shack and hooking
    up to the parallel port of a computer. I was able to get the computer to
    register the output from the IR led but only if it was about 1 1/2"
    away. Any farther and there was no response. The IR led is powered by
    12V through a 100 ohm resistor. The IR detector is connected directly to
    the parallel port. Am I doing something wrong?

    Thanks - Ron Collins
  2. the Wiz

    the Wiz Guest

    The IR detector may be designed for short distances. It may not be designed to
    connect to the parallel port (voltage levels, current capabilities).

    You may want to do a google search for
    slot car timer
    slot car timing
    pinewood derby timer
    pinewood derby timing

    There are a number of circuits available, both build-your-own and commercial.

    More about me:
    VB3/VB6/C/PowerBasic source code:
    Freeware for the Palm with NS Basic source code:
    Drivers for Pablo graphics tablet and JamCam cameras:
    johnecarter [email protected] mindspring com. Fix the obvious to reply by email.
  3. Ron Collins

    Ron Collins Guest

    Thanks for your response. I'll have a look.
  4. David Knaack

    David Knaack Guest

    If you haven't already, try shading the IR detector. A short paper tube
    can often help, coloring it black with a marker might help also.
    Experiment with the length of the tube.

    You can also do the same with the IR LED. Sometimes the IR from the LED
    can bounce off of the ground or other objects and continue to trip the
    receiver. If the LED is fairly wide angle this can increase with the
    distance from the receiver.

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