Place the battery holder in the box and close the lid.

Poke the power wires through the holes in the side of the box.

Tack the RGB power LED array to the center of the box. I used this as an opportunity to use a sample of Laird double sided sticky copper tape. The idea is to transfer some heat to the box, but this application doesn’t generate enough heat for it to really matter.

Tape a strip of copper tape down below the led array.

Cut three segments of piezoresistive fabric. I used a low resistance woven fabric from Eeonyx.

Cut three thinner but longer strips of Laird conductive fabric tape. The top of the tape connects to the RGB led pads. Stick the rest of the tape over the fabric. Make sure there are no conductive paths from the Laird tape to the copper tape.

Attach each power wire to the copper tape and a bus wire for the cathodes (or anodes if you prefer) of the LEDs. Remember arrows in schematics point to ground. The Sparkfun array has diode symbols on the silkscreen.

Install batteries (3volts suffices. I use cheap Carbon Zinc batteries). The array should now work. Notice that it flickers when you don’t touch it as there is no on/off switch.

Place an oversized strip of Zoflex switch rubber between the fabric and copper tape. No power will flow in the circuit when you don’t use the synthesizer and there is no confusion with the state of the device that would be caused by a separate switch.

You will need to add a diffuser to get a satisfying color mix. Ping pong balls or frosted plastics work well.

Another extension to explore and ONLY if you use the Zoflex rubber is to run the Laird tape all the way around and underneath the resistive fabric. The bottom of the interaction surface will now pump the led to a very high current. Don’t stare directly at the led, use a diffuser and limit the current by using a cheap carbon Zinc battery instead of an alkaline.