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Question about ultrasonic range finder

Discussion in 'Electronic Basics' started by Joe, Jan 15, 2007.

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  1. Joe

    Joe Guest

    Hello to the group,

    The only experience I have with ultrasonics is that I built a bat
    detector a few years ago which took in 40Khz and divided it down to
    where I could hear the clicks of some types of bats (mostly the little
    brown bats we have around here). Occasionally, I would also hear other
    things, like insects, and who knows what else. What I learned was that
    it may not be such a good rangefinder when run at just the 40 Khz
    frequency.

    Now I would like to design an ultrasonic range finder. I was wondering,
    since I will be sending out a pulse and waiting for the echo (actually
    the micro will be waiting for the echo). If the signal was modulated
    with, say a 1Khz square wave (or whatever), on the same idea as the TV
    remotes and receivers (say, tsop series receivers) used which have
    pretty high noise rejection, should this, in theory, give me more noise
    immunity? The receiver would be the standard 40Khz receiver, but then
    the signal would have to go thru a bandpass filter to get at the
    modulating frequency. No modulation, then the signal is ignored. If the
    modulating frequency comes thru, then 'echo received' .Does this make
    sense?

    Has anyone done this before, or heard of it being done? Any info, links
    (within a reasonable number). I did use google and got 19,800 hits, but
    only the first few were relevant, and the articles are only available
    for sale. As usual, this is a low budget deal for me. Most of the other
    links talked about PWM. I think that's different then what I am asking
    about here.

    Any questions on clarification (if I did not supply enough
    information), opinions, experiences, links, or advice are, as always,
    appreciated.

    TIA,
    Joe
     
  2. Joe

    Joe Guest

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