SpudFiles

The crystal last forever, piezo's never "run out". When they fail it is either because of the crystal breaking, or more commonly, a failure in the hammer mechanism.

Piezo's are used as the "tweeter" speaker in some stereo speakers. They last forever (or until a 3 year old pokes their finger through'm ). Put an AC voltage into a piezo and it vibrates. Vibrate a piezo and it makes an AC voltage.

pretty cool, but wouldnt i need two wires to run a current through the piezo?

jimmy101 wrote:Put an AC voltage into a piezo and it vibrates. Vibrate a piezo and it makes an AC voltage.

FWIW, a standard voice coil speaker will do the same thing. I've actually built an enclosure for and used a 6" car speaker to perform as a Kick Drum microphone! Yes, the sound is huge out of this "mic" but only at low frequencies. Sounds like crap above 400 hz or so. You would usually use this in conjunction with a standard mic inside the drum picking up the beater and this on the outside picking up the boom.

john bunsenburner wrote:pretty cool, but wouldnt i need two wires to run a current through the piezo?

All piezos have two wires (or other types of electrical contacts). Sometimes though the second contact is just a piece of metal somewhere on the piezo. On common configuration for BBQ igniter piezos is a single wire and a metal cap. Take a look at the photo of the Piezoelectric Igniter at the SciToys page: http://www.scitoyscatalog.com/Merchant2 ... y_Code=FCC

Yup thats like mine just mine has a singe wire not a bundel, its geat to ignite things seeign i dont have a lighter any more(guess where the piezo cam from). I always need to earth the mtal object the fuel is on to light it, i do so with my fingers, is that correct or is it just a wierd thign i came up with and not a fact?