For my final project in my Physical Computing class, I chose to build a small robotic piano-like instrument. Building upon the ideas I had for my previous project (a sort of robotic lap steel), I decided to add dampers and ditch the string bending to try to keep things simpler. Besides the dampers, I wanted to figure out how to control many more digital outputs than are available in the arduino.

I decided on using the 74HC595 shift registger to expand my outputs. Since I wasn't too worried about having PWM to control solenoids, I figured this would work fine. There's also a good tutorial about using them with an arduino, so it was pretty easy to get going.