Sound Trigger

Discussion in 'The Projects Forum' started by bluebrakes, Apr 12, 2010.

  1. bluebrakes

    Thread Starter Active Member

    Oct 17, 2009
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    Anyone able to help with a reasonably sensitive sound trigger?

    Basically I need a sound activated trigger that would send a pulse to another circuit.

    It needs to be sensitive enough to pickup a small hand clap.

    Also, ideally relatively simple if possible.

    I've tried piezo transducer circuits with no luck, i'm thinking maybe electret microphones maybe the way forward...
     
  2. R!f@@

    AAC Fanatic!

    Apr 2, 2009
    8,754
    760
    Post the circuit you tried, then we can make it work
     
  3. bluebrakes

    Thread Starter Active Member

    Oct 17, 2009
    245
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    [​IMG]

    this off of the hiviz site but with a optocoupler (ILQ74) instead of an SCR.

    I don't think a piezo disc is sensitive enough, i hooked it up to an oscilloscope and clapped nearby it, no signal at all.

    0.05v/div
     
  4. R!f@@

    AAC Fanatic!

    Apr 2, 2009
    8,754
    760
    Ur circuit has errors, no matter what you do you won't get any thing across a diode.
     
    Last edited: Apr 13, 2010
  5. pilko

    Active Member

    Dec 8, 2008
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    Are you using Opto or SCR?

    What are you reading at collector?

    pilko
     
  6. rjenkins

    AAC Fanatic!

    Nov 6, 2005
    1,015
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    If you use another NPN transistor in place of the SCR (with base replacing gate, emitter to 0V/emiter of other transistor), then add the opto and a series resistor (470R or 1K) between the new transistors collector and V+, you should get a pulse out.

    The first transistor is biassed hard on, which normally clamps off the next device.
    A pulse from the piezo turns off the first transistor, allowing it's collector resistor to turn on the second device.

    You may be better off replacing the 68K with a 1M pot or preset, so you can adjust the bias accurately on the first transistor.

    It would definitely work with loud noises, but I have no idea how sensitive you could make it.

    Reversing the piezo wires may slightly affect sensitivity, once it's working to some level.
     
  7. retched

    AAC Fanatic!

    Dec 5, 2009
    5,201
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    I have seen many "clapper" circuits around before.. This also seems a color organ has the same functionality.
     
  8. BMorse

    Senior Member

    Sep 26, 2009
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    try this, see if it will work for what you need.... I used this for sound detection in one of my robots:
    [​IMG]

    or you can try his one, a little more elaborate than the first, this one I used in a sumo bot, in some sumo competitions, the robots are started with a whistle blow, or a loud beep from a piezo.... maybe you can alter it a bit to respond to the frequency of the clapping sound...

    [​IMG]

    B. Morse
     
  9. bluebrakes

    Thread Starter Active Member

    Oct 17, 2009
    245
    7
    thanks for your suggestions guys...

    It's all been very valuable input.

    Bmorse... I built your circuit tonight (top one) and on the breadboard, it seems to work a treat. I just need to amplify the circuit a bit more.

    Do you have any suggestions how best to approach?

    Thanks very much. :)
     
  10. BMorse

    Senior Member

    Sep 26, 2009
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    When I used the top circuit, I had taken the output of the circuit and fed it into an op amp to "amplify" the output more, I believe I had used a 741.... I will have to see if I can dig up the circuit.....

    B. Morse
     
  11. bluebrakes

    Thread Starter Active Member

    Oct 17, 2009
    245
    7
    that would be very helpful...

    I guess a LM358 would be a good replacement for the old 741?
     
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