Schematic view of a potentiometer, MOSFET, and lamp connected to an Arduino. The gate of a MOSFET transistor is connected to Digital Pin 9 of the Arduino. A 12V lamp connects to the drain of the transistor and a DC jack. The DC jack connects its positive wire to the first wire of the lamp. The negative wire of the DC jack connects to ground. The second wire of the lamp connects to the drain of the transistor. The source of the transistor connects to ground.