The first step in connecting a DC motor to Arduino is to actually obtain a DC motor. The motors that you will be dealing with here are simple, small DC motors. The motors must not require much current because Arduinos cannot supply more than 40 mA of current directly. For this example, you can use a small 6 V DC motor available at most electronics or hobby stores. The following figure shows one such motor:

In order to connect this motor to your Arduino, you'll need some additional parts. You'll need two male-to-male solderless jumper cables and two alligator clip jumper cables. You'll also need a transistor, a TIP120 to be specific. In this case, the transistor will act like an electronic switch; when you send a control signal to it, the power will flow from the battery. You'll also need a diode, the 1N4004 diode. The diode is a device that protects from reverse power flow. You'll need a 1000 ohm resistor; this will translate the control signal out...