Triggered wave generator/piezo questions

[Q-Bot Eye]

This reminds me of the drum trigger I was trying to make the other day.
And leads me to a question I was pondering.

I was using some piezo speakers that were encased in a little metal
jacket (disk inside jacket). I had put the speaker under the head of
the practice pad ($1 at goodwill!). I had it right in the middle, right
under the head, and was hitting the pad, and it was firing the seq on
my sh-101 with the wires from the disk running directly into the ext.
clock in-jack (no other componants inbetween). After a little abuse
(the only time I would get a good trigger was when I would hit the head
right where the disk was), one of the wires ripped out from the disk,
so I ripped the metal jacket off of the disk with my teeth :), and
soldered the wire back onto the disk. I left the jacket off, because I
sort of had to destroy it to get it off, but now it will not work as a
trigger. Anyone know why? It may just be something very simple, but to
be honest, I have no idea how a piezo works, or if the metal jacket
serves a purpose. I hooked the wires up to a jack and pluged it into an
amplifier, and it still acted as a mic, so what is up? Could it be that
If I had hooked up the wires from the jack backwards this time (which I
may have, now that I think of it), would that make a difference? Would
that send -volts?

Also, with what you guys have been saying, is it a bad idea to run the
trigger directly into the sh-101? Could I damage it?

Thanks for putting up with my noviceness <---word?

-Andy!

--- Harry Bissell <harrybissell at prodigy.net> wrote:
> 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
> 
> 

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