On Sat, 12 Oct 1996 03:43 Pedro Drummond wrote:

>>
>>Piezos are made from the same kind of stuff ceramic capacitors are.
>>In fact some ceramic caps actually can be used as beepers.

>Sounds interesting. You mean in a useful manner ? What types ?

I have actually heard sounds coming from ceramic capacitors in a
power supply circuit. A quick test using some parts in my junk box
attached to a signal generator revealed no obvious beeper candidates.

Barium Titanate also known as X7R is used in both piezoelectric
devices and capacitors. Any sound you hear would probably be from the
radial resonant mode where the crystal vibrates like a ripple in a
pond from the center outward to the edges and back. The frequency
depends mostly on the diameter.

In the thickness mode you are more likely to generate ultrasonic
energy because the resonant frequency For a 2mm thick capacitor
would be roughly 700kHz.

Eric

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| Eric Strauts                          |
| TEEM Electronics                      |
| Park Ridge, IL 60068                  |
| Email: estrauts@ix.netcom.com         |
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