Just to be thorough I thought it would be good to document the current setup I’m working with.
- one Arduino Duemilanove
- one Motor shield from adafruit
- two DC motors
- one 12V power supply from an old switch
The motor shield is stacked on top of the Arduino. The motors are connected to M1 and M2 on the motor shield. The motor shield draws power from the 12V PSU, for testing purposes it is configured not to share power with the Arduino. The Arduino draws power from the USB cable which connects it to my laptop.