Laika’s ears have never worked when we arrived at a convention. So we’ve decided to redo her hat as a standalone item — complete with a soft circuit stitched in.
What’s a soft circuit, you ask? Basically, like a regular circuit, but with conductive thread in place of wires. Instead of pins, there’s pads, which I can stitch around with the conductive thread, to both hold the items in place and connect them. It’s actually pretty cool.
We bought an Adafruit Gemma, the smaller of their two wearable microcontroller platforms, and devised a circuit:
Unfortunately, the battery pack — a neat little job that holds two d-cell batteries — could provide enough voltage, but not nearly enough amps to power the Gemma and two servos. After doing some research, we purchased a rechargeable battery pack that could do plenty of amps — but not enough volts. So we also had to get a booster that would up-step the voltage to 5V, which would be enough for the servos.
That got us almost all the way to where we wanted to go, but that’s when we discovered another problem: one of the two servos was misbehaving. Instead of going from 0 to 90 and back, it was rotating slightly backward, then rotating 180 degrees. Clearly that wasn’t going to work for the ears; however, we spent ages hunting down potential shorts, taking measurements with our multimeter, editing the servo library, and generally trying to figure out what was wrong before we finally figured it out: we needed a capacitor. The power draw from both servos together was just too much for the circuit.
But we finally got it working!