whistle key finder project (or audio response) 2


Joined Feb 20, 2011
with out mic how to get input for buzzer ?
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....


Joined 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.