Help me with this keyboard hack!

[GekigangarV]

Hey all, if there is anyone out there that knows about the circuits in keyboard, any help would be appreciated.

What I'm trying to do is build a generic drumset to use with DTXMania (a drum simulator for the PC). I've already taken apart an old keyboard and mapped the points that I want to use and which characters they correspond to. Here comes the hard part. I plan to use piezo elements to pick up the drum strikes, and somehow make it trigger the character. I have no idea if this would work, but I've tried to hook it up different way but none of them worked. If I try to connect it directly, it just keeps going as though the button was continually held down.

[Joachim]

I'm not sure if I read this correctly:
You have connected the peizo elements, and the reaction is as if the key is continually held down? Or does it simply start triggering as soon as the connection is completed?
In any case, it seems to me that you might want to try isolating the peizo through a multivibrator circuit.
It's been a while since I messed around with component hardware, but as I recall the principle of these things, they generate a voltage in response to mechanical input. I would say that the keyboard encoder is simply seeing the element as a resistor whose value is lower than that required to register as open contacts. Bearing this in mind, what you need is a buffer circuit which registers voltage signal from the peizo element and then sends a keypress signal to the encoder. Hence the multivibrator.

[GekigangarV]

I'll have to look into that.

The keys keep going as though it was continually pressed down. After reading some forums where people were making their own arcade cabinets, I saw some mention of them using diodes to prevent "ghosting" on old keyboards and thought I'd give that a try. I had a 2.6V LED lying around so I hooked it up, and it worked... sorta. The trigger isn't as sensitive as I'd like it to be. I'll try to read up on the multivibrator. Thanks for the tip.

[Captain Slug]

A keyboard is basically a set of switches that trigger the output of certain codes. Peizo elements (unless made as a normally-open device) don't function as switches and therefore are simply feed off a continual current.