Above is a schematic of the electrical system I used. I've colored the wires red and black out of convention. The solenoid actually has white wires as it does not matter which direction the current flows through it. You'll notice I used two push buttons (switch one and switch2). That was to allow one to act as a safety. The user must press both switches at the same time to get the air cannon to fire. As an additional safety measure, I always remove one of the batteries while loading, handling the air cannon off the game field.