In this instructable we will be building a simple circuit that will allow us to control a solenoid using the popular physical computing platform arduino. I became interested in controlling solenoids for robotic music applications. A similar circuit can be used to control a motor or other devices that require more current than the arduino can provide directly from its output pins.
Since the solenoid requires higher current than the arduino can provide we will be using an alternative power source for the solenoid (a couple batteries) and will be "driving" it with a TIP120 transistor.
Build time was exactly one-beer. Excluding the arduino and computer you use to program it, we are using less than $10 in parts. Ok!