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infrared proximity sensor

Discussion in 'Electronic Design' started by inetquestion, Jun 25, 2006.

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  1. inetquestion

    inetquestion Guest

    I've been working on an ir proximity sensor, but am having problems
    with its sensitivty. With the emitter and detector side by side, the
    approaching object has to be about 3 inches away before any objects are
    detected. Is there a way to get more sensitivity out of these systems?


    One other question I have is about the emitter circuit. Right now the
    best output i've found is any tv remote. The ones i've build tend to
    burn out the emitter or are way to weak. Is there something really
    simple I'm missing?

    Regards,

    -Inet
     
  2. Luhan

    Luhan Guest

    How about the wavelength of your emitter - does it match the detector?

    How about the frequency of the modulation - does that match the
    detector?

    I'm assuming the emitter is normally off, and only pulses on for the
    modulation with a near 50% duty cycle.

    Luhan
     
  3. Jamie

    Jamie Guest

    maybe its the way your Tx and Rx it ?
    if your looking for a simple presents of
    IR in the Rx LED then you might have problems
    there since the levels will vary alot..
    using mulitple Tx leds also helps to spread
    the radiation patern around a bit.
    you should be using a pulsed IR tx output and
    on the RX end passing it through a bandpass filter
    to clean up other noise.
    if you use op-amp with the - input for the RX
    LED and then have a resistor from that input over to the
    + input with a series LC reasonator from the + input to
    common selected for the carrier frequency your using, you
    should be able to detect very weak to strong signals with no problem.
    i did such a project years ago.
    you can simply use a cap to common if you wish for only
    the high freq effects to the present but then you may
    run into problems of other IR devices tripping the signal
    unless you use a PLL chip like the old LM567 i think it was?
     
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