Arduino and DC Motor with Transistor and Diode

Component List:
1. A DC Motor (not servo)
2. BC547 Transistor
3. 1N4007 Diode
4. 10k ohm potentiometer
5. 1k ohm resistor
6. 9V Battery for the external powering of motor

Wiring Diagram:

Notes:

1. The diode is like a valve and used in order to avoid the flow from the motor to arduino
2. This is a NPN transistor. The left and right pins are connected to ground. Middle pin is connected to  port ~11 of arduino
3. The motor can be 9V, 24V or more. By using transistor family components we can control them with our 5VDC controller.