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Alarm Buzzer Driver? Answered

So I have removed a buzzer from an out of date smoke for fun use, but it doesn't work as expected.  I set up a driver circuit with a 555 and some resistors/capacitors.  I don't deal much with IC's or the 555 and haven't really bothered to learn to use them properly, but I took an LED flash circuit and vastly decreased the capacitance, upping the frequency drastically.  I have included an image of the circuit.  The 555 runs on 6 volts, the buzzer runs on 9 (the blue wires).  The volume was ok, but nowhere near expected levels and I wondered if it had to do with the higher than normal frequency.  I attached it to an arduino and ran the tone function from below audible to above it (whole frequency range) and the sound was very quiet, even using an npn transistor and 9 volts right off the battery hitting the buzzer.  As you can see, the buzzer has 3 leads, i only used two, but as with most 3 poll buzzers I assumed one was just for some form of feedback.  Any voltage in any direction across the three produces sound, so should I use all three, and if so how should I do so.  How would you recommend driving this buzzer?



Best Answer 4 years ago

3 terminal piezos are self oscillating and not meant to run off of a fixed frequency.

This one is can change due to subtle temperature and sonic loading.

3t piezzo.gif

what is RES1, I have seen these diagrams, but I don't understand them quite entirely and have found no documentation on that particular part.

RES1 is the outside metallic ring in you picture.

go see this page JJ for more details.


Thank you for your help with this, I plan on getting this work as soon as I get home today!

These buzzers are quiet on there own. Once they are in the correct housing things get much loader. You'll want to mount the buzzer to a PCB so the sound can resonate through the plastic houseing as it was designed to do.

I didn't remove it from the original mount (in a smoke alarm, on a pcb) until I had already tested it. It had no notable effect removing it.