Triggered wave generator

[Harry Bissell]

Piezos will only go to 20V with very light loading... put a 10K on them and
you're lucky to get 5V.

This reminds me of my first "drum trigger" circuit... I put a piezo double
sticky taped to the inside of a practice pad drum head... I tested it and
it worked... so I got my (then) drummer, Steve... to test it.

I said "go ahead - break it!"   He did with exactly one hit.  Never
underestimate the force of a Drummer !!!

I spent the next several years trying designs that would survive such
abuse. The best was with a piece of piezoelectric film that was intended as
a demo... it had a piezo bender about 2" long, hooked up to the leads of a
neon bulb. The piezo generated ENOUGH VOLTAGE (in this mode) to light the
neon at each extreme as you wiggle it back and forth...  My Bass player
broke that... now it lives (for years) in a Kick Drum pedal.

:^) Harry

KA4HJH wrote:

> >Usually piezo elements give up to 20V transients if you hit them hard.
> >Ie. you may even need some protection network/clamp.
> >Depends on mechanical application.
>
> I'd say clamp it. It's not worth taking the risk of zapping your
> circuit. If you smack a bare transducer directly with a drum stick
> you could get hundreds of volts--briefly. Sort-of a loose cannon in
> the circuit there.
>
> Anybody done any tests? Let's have a voltage peak contest...
> (breaking the transducer means instant disqualification)
>
> Terry Bowman, KA4HJH
> "The Mac Doctor"
>
> ICQ: 45652354