Drum triggering circuit...

[Dr.EM]

I hear you can make drum trigger pads using piezo transducers stuck on mouse pad. Well, I assume that when you strike it, the piezo produces a voltage. So, I was wondering if there is a (preferably really simple) circuit that will convert this small, brief voltage into a switching output, like a relay. or if thats not possible, just a controlled voltage output (ie, any voltage above 1v from piezo triggers output voltage of 4v).

I think that its fairly simple, it could be done with op-amps, but theyare tricky to power, so and suggestion that uses discrete components would be welcome.

Ultimately, i'd like it to convert to MIDI, but I don't really care for the hassle, as I don't need velocity and multiple channels etc. Just something fun.

Actually, just thought. You know those little chips that record a couple of seconds audio? Perhaps I could load these up with different drum sounds. If anyone knows anything about that, let me know...

 

[jbeng]

Well, I assume that when you strike it, the piezo produces a voltage.

That's correct.

I think that its fairly simple, it could be done with op-amps, but they are tricky to power ...

I have used an LM311 voltage comparator to condition the signal from piezo transducers before. All you need is a couple of resistors on the input (a pot?) for sensitivity and a pull-up resistor on the output. It can be powered from +5v, so it's logic level compatible. In the attached image, connect pin 4 to gnd and pin 8 to +5v (both not shown). If you want the circuit to output a pulse of a specific width, just feed the LM311 output to the input of a 555 one-shot. Actually, not so difficult.

Here's a link to the LM111/211/311 datasheet: **broken link removed**

FYI, my application was a counter. I had a huge bag of fuses (like AGC2) and wanted to know the precise number. I fed the fuses thru a funnel and the fuses bounced off the piezo disk. The output of the circuit was fed to a digital counter. The fuses bouncing off the disk produced a pulse which I conditioned and sent to the counter. Worked quite well. 8)

JB

**edit** Added schematic image

 

[Dr.EM]

That looks ideal, and nice idea with th counter, btw!

If I begin this project, it will be a big one, so it may be some time before I get too far.