But how do you actually control and run a stepper motor? There are two modes that can be used to operate a stepper motor: unipolar and bipolar mode. Unipolar mode only operates in the positive voltage range. Normally, this would mean that current could only be driven in one direction through the electromagnetic coils, producing a magnetic field in only one direction, implying that the central shaft would only be able to tilt back and forth between the two electromagnets.
This potential issue is overcome by the fact that unipolar hybrid stepper motors actually have an additional wire attached to the middle of the two coils. This allows current to flow in two different directions, from the middle to one side of the coil or to the other side of the coil. These two directions produce magnetic fields in the “opposite” directions, allowing the teeth of the magnetized central shaft rotate a full 360 degrees.
Bipolar stepper motors also have current flow in two different directions through the coils. Instead of using a central tap, they use both positive and negative (bipolar) voltage to induce the current flow in both ways through the coil. Because current is able to flow through the entire coil, instead of just half of the coil in unipolar mode, bipolar stepper motors have more torque to rotate and hold the central shaft in place.
How do you know if your stepper motor is a unipolar or a bipolar stepper motor for sale just by looking at it? In most cases, the motor you are looking at is both. Unipolar and bipolar are just modes that you can use to run the stepper motor. The only time a stepper motor is not able to be run in either mode is when there are only four wires coming out of the stepper motor, corresponding to the both ends of the two coils and no central tap wire.