Triggered wave generator

[Martin Czech]

:::Hello, I am an electronics student and I hope you don't mind me asking a few 
:::questions about a progect I am doing at the moment.
:::
:::I am building a wave generator which is to be triggered by a piezo 
:::transducer. I see it should be easy enough but I need to know a few things. 
:::Do I need to amplify the signal from the transducer to trigger the WG? I 
:::want the sound to be close to that of a snare drum, (so I can use it to 
:::practice), any suggestions on oscillator circuits to use? I was thinking a 
:::wein-bridge with gated white noise?.
:::

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.

Why do all people say Wein-Bridge if it is Mr. Wien who invented it?
I like a glass of wine, though. Oscillateur a la vienese ?

;->

Seriously, many circuits I've seen for that purpose use the simple
common emmiter transistor with tripple RC lowpass feedback oscillator.
You can find this in National semiconductor applications, oor allmost
anywhere else.

Simple to use, you can tune the resonance and apply your piezo trigger
as input. Should give a nice ringing response.

Wien Bridge is also ok, and you can tune that, but I think a bit
overdesigned for that purpose, exept you want very high Q, ie. very
long ringing.  But this may be very difficult to be stable
over long time/sessions anyway.

Wien Brigde oscillators are usually designed deep into the instable
region, then a servo loop keeps the thing from clipping.
This is not what you might want.

m.c.