Triggered wave generator/piezo questions

[Harry Bissell]

I like to leave the Piezo in the plastic case... It mechanically protects it
and it is already supported at the nodal point (if you open pne you know what
I mean. I enlarge the sound hole (carefully) and glue a .177 caliber
wadcutter pellet (pellet gun ammo with a dead flat nose, so it makes good
mechanical contact) right to the center of the brass disk. This lowers the
resonant frequency a lot, and acts like an accelerometer more than a
microphone. I then glue this assy to whatever.... metal disk as below (I
prefer nylon).. or I use a length of radiator hose about 6" long by 2"
diameter. This makes a good cymbal style trigger... I call it a "HOSE HEAD"
tm.

:^) Harry

Matthew Helt wrote:

> Piezo's are really fragile, trying to get them to withstand the abuse of
> drummer is tricky, but there's an easy (and low-tech) way to do it.
>
> Take a coffee can and cut out the bottom. glue the piezo to the bottom
> of the metal disc (i've found hot glue works best). add a little glue
> around the wire joints to ensure the connection wont come lose. you can
> then mount this directly under a drum head (with a little foam it's the
> perfect trigger) or stuff it in a practice pad.
>
> I've also tried things like adding multiple peizos to pads to trigger
> differnt sources with the same pad, but this doesnt work very well as
> they are hard to isolate. using more then one pizeo also helps to make
> sure that the pad triggers even if you hit off center. This helped a lot
> when i couldnt get a finicky alesis dm4 to trigger correctly.
>
> For live performance situations (with a noisecore band i was in) i have
> my drums triggered (multi outputs, each piezo sends output to a drum
> machine, which barely works, some weird moog-like synth and a amplifier
> that i can control using an effects box with my foot), then mic'd and
> amplified, also affected. This all works to create a brutal and absurdly
> loud drum sound that will assure audience hearing loss. On that note,
> filling a drum with foam and a piezo wired disc also allows me to
> practice late nights without irate neighbors...
>
> -matt
>
> Q-Bot Eye wrote:
> >
> > 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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> > Bid and sell for free at http://auctions.yahoo.com
>
> --
> Matthew Helt (mhelt at truelink.com)
> Development
> http://www.truelink.com