Rings every time an angel gets his wings (or First Opinion account).

Basically, the circuit we build triggers the solenoids to rapidly move the nail down onto the xylophone, then get pulled back up by the rubber band.

Each of the solenoids is hooked up to its indiviual pin on the Raspberry Pi.

These pins are controlled by the Pi's own build-in GPIO/RPi api. The pins are initialized by this code:

pins = [12,16,18,22,32,36,38,40] #the numbers are the id's of the pins that were available for GPIO output (some are reserved for grounding, etc.)
GPIO.setmode(GPIO.BOARD)
for x in pins:
   GPIO.setup(x,GPIO.OUT)

Then the pin is triggered by the following command:

GPIO.output(pins[pinid],GPIO.HIGH)  #turn pin on
GPIO.output(pins[pini],GPIO.LOW)    #turn pin off

The two commands are separated by about a 0.05 second interval.