whistle key finder project (or audio response) 2

Discussion in 'The Projects Forum' started by den421, Sep 29, 2011.

  1. den421

    Thread Starter New Member

    Sep 29, 2011
    with out mic how to get input for buzzer ?
  2. DerStrom8

    Well-Known Member

    Feb 20, 2011
    I believe BZ1 doubles as the mic.

    What exactly IS BZ1, though, mozikluv?

    I once built a circuit similar to that one that used a piezo transducer, but that required an input frequency of 40kHz, which is far higher than your average whistle. Someone didn't know what they were doing when they designed the circuit I tried....
  3. bertus


    Apr 5, 2008
  4. Audioguru


    Dec 20, 2007
    It is not a buzzer. A piezo buzzer (actually it is a beeper) has an oscillator inside. this project uses a piezo transducer.

    A similar circuit is at Red Circuits: http://www.redcircuits.com/Page29.htm except it uses a real microphone.
    The similar circuit was also at Electronics Lab (but not anymore) where I helped a student get it to work. It worked very poorly because the piezo transducer was not loud enough so we constructed a push-pull Cmos driver to double its driving signal level.

    I think this project will also have the beep not loud enough. The piezo transducer is most sensitive to 5kHz but nobody can whistle that high so it might not hear a whistle.

    My daughter bought a cheap Chinese Keys finder. It beeped whenever she talked and when the TV was turned on. I couldn't fix it because all of its circuit was inside a black blob.
  5. chino00007

    New Member

    Nov 16, 2011
    Thanks Audioguru,

    You help a lot with this Circuit! i was looking for something like this! thanks!