The Clamshell Stompbox: Part 1

This is a DIY variable resistor I designed as an interface for live performance-- like a stompbox.

Resistance ranges from 0 to about 20k ohms. It's very sensitive to slight changes in pressure. If you want subtle manipulation, I'd recommend using your hands. But with an Arduino, you can use big jumps in resistance as an on/off switch-- perfect for foot-powered control! The important thing is that it can take a beating, as long as the solder points are protected.
Two holes punched on the same side of the case provide an exit for the wire leads (and prevent the case from crushing the wires).They're soldered to two identical flag-shaped pieces of copper foil glued to the insides of the case. When the case is closed, the "tails" of foil extend up opposite sides, not touching (very important).
One of the foils has a backing of craft foam between the foil and the plastic, which fills the air gap inside the case, so the rectangles of foil touch once the case is closed.

To create the variable resistance, I've taped a rectangle of velostat over each foil piece. The tape acts as a hinge-- I can fold it back if I want to decrease the resistance.

With the case closed, the clamshell can take a fair amount of stomping, just stay off the wire and solder points.

Next step: fixing it to a board to protect the wires.

[edit: I've posted the entire how-to on Instructables. Please find it here. ]