The brakeDrum is my attempt at making a drum pad system based on circuit bend toys. It consists of 4 drum pads with piezo elements in them and a box with 5 bend toys, 4 almost identical steering wheel toys and a small beat box toy. To make it all work i had to go through fire and water. First i tried to trigger the toys directly with the piezoes, but that didn't really work. Then i made a small preamp for the four piezos, that helped, but when i started to pitch the toys down, the piezoes wouldn't trigger them any more. After a lot of experimenting, trial and error, and hair pulling i realised that the pulses from the preamp was too short, so when the toys were pitched down the internal processor in the (black blob) toys would simply scan the "buttons" to slowly and miss the trigger pulse. So i build a pulse stretcher, after advice from Paul Perry, 4 monostable 555 circuits, and that solved the problem. I also had to build a "Power distribution unit" because the toys and the pulsestretchers and the built in mixer runs at different voltages, so in all, the thing consists of 5 recased toys, a 4 channel preamp, a 4 channel pulse stretcher and a 5 channel mixer, and the voltage regulator thingie. Everything is connected with a lot of wires, i lost count somewhere around 85. It makes a lot of cool noises, drum sounds from cars braking (hence the name), weird chirps and growls and also lots of long and not very percussive sounds.
I have documented the whole thing as good as possible, you can check schematics, block diagram, PCB layouts and see pictures of all the details, including close ups of the front panel, here.