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IR sensor with LM324

Discussion in 'Electronic Basics' started by Manimozhi Baskaran, Feb 7, 2006.

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  1. I built the circuit below with the IR sensor on the bread board
    A large bowl of snow was brought inside the house to the sense the snow
    Varied the 50 K pot (20 turns on the pot)
    No buzz output from sensor

    Any suggestions on what is going wrong?

    Thanks
     
  2. Chris

    Chris Guest

    Hi, Manimozhi. To start with:

    1) Try just attaching the 9V supply to the piezo element. This won't
    kill it. But usually, beepers that have a specified DC voltage have
    the oscillator/driver built-in, and all you have to do is apply
    voltage. You might find your piezo element starts beeping when you
    apply DC voltage. If that's the case, the second op amp is doing
    exactly the wrong thing. But if you _do_ have a bare piezo element,
    you should be able to get much better results by bridging the drive
    with another 1/4 of the LM324.

    2) According to your diagram, you have "IR in" as the inverting input
    of the first op amp. I'm assuming you've actually got a
    phototransistor or something like that. I'd like to know what it is,
    and also how you've got it hooked up. Many IR sensors require a pullup
    resistor to show a voltage. If you've got a meter, you can test this
    by just measuring the input to the op amp with the sensor in what
    should be the "on" and "off" states. It should change. If it's not
    changing, either something let the smoke out, you've hooked it up
    wrong, or some combination.

    I'll tell you what. Answer those questions, and we can cobble together
    something that works for you, and put it in ASCII format for your
    safety and convenience.

    What about the beeper -- does it beep with DC applied? What are you
    using for an IR sensor, and how do you have it hooked up?

    Chris
     
  3. Bob Masta

    Bob Masta Guest

    OK, I'll bite: Why would an IR sensor respond to a bowl
    of snow? Am I missing something here?




    Bob Masta
    dqatechATdaqartaDOTcom

    D A Q A R T A
    Data AcQuisition And Real-Time Analysis
    www.daqarta.com
    Home of DaqGen, the FREEWARE signal generator
     
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