Breadboard view of an Arduino connected to a potentiometer, a transistor, a DC motor, and a DC jack, a protection diode, and a second diode across the motor
Breadboard view of a potentiometer connected to analog in 0 of the Arduino. A transistor is connected to Digital Pin 9. A DC motor connects to the transistor and a DC jack. The DC jack connects its red wire to the first wire of the DC motor. The other wire of the DC jack connects to ground. The second wire of the DC motor connects to the collector of the transistor. A Power Diode with the Cathode connected to the collector of the transistor and anode connected to ground. A second power diode connects to the leads of the DC motor with the Cathode connected to the lead also connects to + voltage of the DC jack. The anode connects simultaneously to the collector of the transistor and the other lead of the DC motor.