- Should there be any diodes in the circuit? I am wondering if the magnet is moved near the coil if it will create an EMF that could blow out any of the components in the circuit. Possibly put it between the coil and the transistor.
Absolutely a diode is needed - the EMF will come when the transistor switches off - dI/dt = V/L. Moving a magnet near the coil won't be nearly as fast as transistor turn-off.
The diode needs to be parallel to the coil, see http://www.arduino.cc/playground/Learning/SolenoidTutorial