Keyboard pedals--the two cent version

Adding pedals to your keyboard depends on the kind of keyboard you are using. Most (probably 99% or more) keyboards today are the membrane style, which consists of two mylar sheets with silver-ink lines printed on them, and a spacer with holes between the sheets. [Older "quality" keyboards, like those on the original IBMs and Apples had a switch-per-key...they feel soooo nice but they are expensive. Kinesis Professional QD keyboards, for example, still use a switch-per-key design and cost around $300.]

Anyways, these mylar sheets in a membrane keyboard bond to a circuit board with a microcontroller that is the brains of the keyboard. The silver inked wires on the mylar sheets are equivalent to an x-y matrix (it doesn't look like it from the sheets, but one sheet has the "X" wires and the other has the "Y" wires). The microcontroller detects if a key is pressed when an X wire is mashed onto a Y wire by a finger depressing the flexible plastic membrane through a thin spacer.

If you want to add a pedal that acts like a particular key, all you need to do is trace the silver ink wires for the X,Y pair that defines the key back to the corresponding pin on the main circuit board. You can make this job easier by using a marker and drawing out the path on the back side of the mylar sheet (doing it on the printed side may render your keyboard non-functional). Then, solder a pair of wires to the connections on the main circuit board that connect the pedal in parallel with the keyboard switch. The pedal should, of course, be a normally open switch of some kind. Music stores sell all kinds of good footpedals for musical keyboards. They usually terminate at quarter inch jacks, so you can just drill a hole in your keyboard and mount a quarter inch jack on the side of your keyboard and run the wires to the main circuit board internally--it'll look like it was always meant to be there. It will also be robust and easy to take apart when you want to move the keyboard.

Don't try soldering to the mylar sheets themselves, they will melt. Solder to the main circuit board instead! Also, don't get your finger oils on the silver ink, as the ink will corrode with time. It's a subtle thing, so you don't have to do this work with gloves and tweezers, but at the same time eating pizza and smearing grease all over the traces is No Good (TM).

Finally, don't lose any screws to the metal sheets that are used to press the membranes together (most keyboards I've taken part use some sort of backing mechanism consisting of a metal sheet with a bazillion screws in them). The quality of the keyboard and ease of activating a key depends on the backing being solidly in there so the membranes deform in the right way. Also, be careful when flipping the half of your keyboard with the keycaps...some designs have the keycaps loose and you'll end up scattering keycaps everywhere!

Good luck -- bunnie (c) 2/18/2002

As usual, I am not responsible for any damages incurred to your keyboard if you try this and it doesn't work...caveat hacker!