A Stepper Motor is one of the most common motors used to control mechanical machines such as printers, scanners and CNC Machines.
See also Servo Motor.
Bipolar Stepper Motor
A Bipolar motor requires a little more complicated electrical configuration than a Unipolar motor since the coils must be capable of sending current through both sides of the current. The most common method for driving a bipolar motor is through an H-Bridge or a Chopper circuit.
Bipolar motors typically come in a 4 wire configuration only, though a 5, 6 or 8 wire motor can also be wired as a Bipolar motor by leaving the inner coil lines unconnected.
Because Bipolar motors use the full coil compared to Unipolar motors, they are more efficient and have more power compared to a similar size and weight unipolar motor.
Unipolar Stepper Motor
A Unipolar motor is often the simplest type of motor to drive electrically as the common wire in the center of the coil allows for the direction to be reversed by simply powering the opposite ends of the coil. Typically the common wires are connected directly to a high voltage DC power supply, and the ends of the A and B coils are alternatively connected to ground.
Unipolar motors typically come in 5, 6 or 8 wire configurations, in all cases the inner wires of the coil are all wired to a common point. A Unipolar Motor can be wired as a Bipolar Motor by leaving the common lines unconnected.
While the most common stepper motors have 0.9 - 1.8 degree rotation per step, it is possible to sub divide the available positioning resolution by utilizing half stepping and microstepping.