To make your robot mobile, you will need motors, wheels, casters or tracks. There are a plethora of motors to choose from: tiny pager motors, servo motors, linear motors, stepper motors and DC geared motors. Tiny pager motors have an off-centre weight attached to the drive shaft, so when the motor spins, the motor vibrates. These type of motors are used in pagers and mobile phones to vibrate alerting the owner of a call or message.
Servo motors are DC motors with built in gearing and feedback control loop circuitry. They are used for RC planes and boats. Servos rotate about 90 to 180 degrees making them ideal for robot arms, legs and sensor panning. For wheel rotation you will need a continuous rotation servomotor, either by modifying a standard servo yourself or purchase the available ready “factory modified” servo. Linear actuators in contrast to conventional motors, create motion in a straight line. DC motors are rated at the most efficient running voltage. Apply power to both terminals and the motor will spin. Reverse the voltage wires and it will spin in the opposite direction. Small motors require a switch, but larger motors require a motor controller to perform more complex tasks.