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Attenuating piezo sounder for testing purposes

sjb741

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I have a commercial smoke detector which I'd like to use for experimental purposes. It uses a soic-16 chip by "SEMIC": CS2105AGQ-S1Z, TGAY2VU401L.

The piezo sounder is the type with 2 terminals (ground, brass and silver <--> ground, drive, feedback ?).

If the piezo has a resonant driver circuit (I can't tell, but it does use 3 wires) then I think brass is 'drive' and silver is 'feedback'. Or maybe it is simply driven by an H-bridge.


The piezo volume can be somewhat attenuated simply by squeezing between thumb and finger.

Ideally though I would like to be able to smoothly vary the volume. I was wondering whether a simple 'rheostat' in series with ground would work and if so what a sensible value would be?
 

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If the piezo sounder is a passive transducer (two terminals), a variable series resistor should work. For a transducer with feedback electrode (three terminals) or built-in oscillator (DC supplied), it doesn't.
 

sjb741

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It has 3 wires. I snipped the ground wire, and now I hear a muted 'buzz' which is acceptable.

Physic
Piezo Photo S,B, F.jpg
 

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