Piezo switch to trigger drum lights

[jman 31]

I am trying to design a simple circuit that would work with the piezo transducers on a set of electronic drums to trigger an LED when the drum head is struck. I am using a simple MOSFET switching transistor, with a 9v battery and an LED. The led has a built in resistor to handle the voltage although that is not shown on the schematic.

Can someone take a look at this and see if I have it set up properly, and if there is anything that would work better?

Thanks
Jeremy

[jman 31]

I went ahead an built this circuit to test it, but now I've hit a slight snag. I will have to rely on some of you electronics experts on this one. When I use a piezo in the shell to trigger the light, it generates about 1 volt before the light will trigger. When i use a drum trigger, even when I hit it fairly hard, I am only generating about .3v.

I need the transistor to switch at around .25v.. I couldn't find the one that was specified (ZVN2106) on the schematic, so I used this one. This has a much higher voltage threshold and I was wondering if the one that is specked out will switch at a lower voltage from the piezo?

Any help would be greatly appreciated!

Jman

[jman 31]

It occurred to me also that the diode is interfering with my voltage. Is there another way to protect this circuit and not lose the precious voltage? And is my reasoning sound on this? I can't have the voltage from the battery getting back to the piezo. Also can the current even go that way through the transistor? Oh my head is starting to ache!

[BenLucid]

So did your LED trigger work?

[jman 31]

Originally Posted by BenLucid

So did your LED trigger work?

Not as shown above. Have a look here to see the progress.

I am now in the process of building a midi trigger for drum lights. You can read about it HERE and HERE.

You may have to register to see the pictures. Sorry to send you to another site, but I can't begin to reproduce all of the info here.