Quiet a Piezo Transducer

Put an additional R across it and make a divider.

Probably not, since they're basically capacitive.

Maybe a cotton ball?

Good Luck! Rich

Silicone sealant (or instant gasket) works quite well.

Aha! Add some damping! ...Jim Thompson

"Jim Thompson" wrote in message news: snipped-for-privacy@4ax.com...

A less permanent solution is cover the sound hole with sticky tape - try different types & thickness to adjust volume.

Actually, it does. On one of my fax machine I snipped the piezo because it annoyed me. Then the machine began to have sticky keys and I wanted to hear the little "bipp" after a key was pressed. But not *BIPP*, just bipp. So I hung a resistor in series. Worked.

That's more appealing to me than "sticky tape" ;-)

Any ballpark value? ...Jim Thompson

Don't remember, I think it was either 3.9k or 4.7k. Most piezos have an impedance between a few hundred ohms and 1k or so at resonance. Initially I had a tape over it but that kept falling off, on account of the summer temps.

However, this does not work with self drive versions (feedback comes off of the same disk, they have three pins) or ones with the electronics in there.

These ringers have an RA2418B chip plus a 2-terminal piezo disk. I think they were designed for warehouse use ;-) ...Jim Thompson

"Jim Thompson" schreef in bericht news: snipped-for-privacy@4ax.com...

Suppose so, when it's driven by some voltage source anyway. The energy dissipated by the resistor will not be transduced into noise.

petrus bitbyter

It couldn't generate any sound unless its input impedance has a resisitive component--it would violate conservation of energy. (And even a pure capacitor would see a decrease in voltage swing if a series resistance were added.)

Cheers

Phil Hobbs

I don't know that chip but 2-terminal sounds good.

I was thinking you meant a 'speaker' type piezo but if you mean a tone generating piezo, like a sonalert, they have built in oscillator circuitry. You can lower it some by reducing the drive voltage but it must have a minimum to operate and, depending on the unit, you might get a 6dB to 16dB change. You'd likely be better off getting one with the level you want as they have models ranging from 95dB down to 50dB, or so.

As for the 'speaker' type, they are relatively high impedance, when compared to an 8 ohm speaker anyway, on the order of a thousand ohms, or more, that varies with frequency but they're primarily capacitive so just putting a resistor in series doesn't work real well.

"Jim Thompson" wrote in message news: snipped-for-privacy@4ax.com...

If you're talking about the 2-terminal (externally excited) transducer, They're largely capacitive and putting a series R will make a low pass filter. The voltage across the piezo is proportional to the displacement. This should give a high frequency roll-off according to the RC value.

I've been working with piezo actuators that work in the 0-100V range. Capacitance is somewhere like 10uF on each piezo.

Oppie

This is a good source of information on piezo actuators/transducers

Yes. But you may not get the attenuation range you need. (I'm assuming by "noise maker" you are referring to the kind that have the oscillator built in, not the kind that are driven by an external oscillator.) The series R limits the current which reduces the volume, but it also might stop the internal circuitry from oscillating due to Vdrop. If you mean the other type where the oscillator is external, you can shunt attenuate with a parallel cap, or use a capacitor divider.

Ed

"Jim Thompson" wrote in message news: snipped-for-privacy@4ax.com...

Never heard of pre-set pots?!

IME it's often just a matter of time until the wiper contact to the track becomes iffy.

I usually use something in the series 1k to 10k ohm region to quiet the piezo noise makers.