I have a bunch of piezo buzzers that I salvaged from some older smoke detectors they have 3 wires:
red, black and white.
If I just use red and black it works but I was wondering what the white might actually be for?
I had always assumed it was ground but then why would you need something like this:
the extra wire in that schematic is labeled as "feedback"?
The “feedback” lead permits you to build oscillators that “automagically” run at the ideal frequency (and thus maximum volume) for a particular piezo element without having to have any timing elements in the circuit itself (other than the piezo itself, which is not dissimilar from a giant crystal.)
thanks for that knowledge nugget westfw,
that makes perfect sense for a smoke detector buzzer to play at the loudest possible volume.