Stepper Motor

A stepper motor is a brushless DC electric motor that divides a full rotation into a number of equal steps. It rotates a specific incremental distance per each step. The number of steps that are executed controls the degree of rotation of the motor’s shaft.

Stepper motors have some inherent ability to control position, as they have built-in output steps. It can very accurately control how far and how fast the stepper motor will rotate. The number of steps the motor executes is equal to the number of pulse commands given by the controller. A stepper will rotate a distance and at a rate that is proportional to the number and frequency of its pulse commands.

A stepper motor controller can be either open loop or closed loop. The difference between the two is that an open loop system sends a consistent rate of power to the motor, assuming that the rotating field that the rotor follows is consistent. A closed loop system uses feedback to adjust power based on the kind of load the motor is bearing. Most motor applications work with an open loop system, because it is simpler and less expensive.

Stepper motors have several advantages over other types of motors. One of the most impressive is their ability to position very accurately. It can achieve the same target position, revolution after revolution. Standard stepper motors have a step angle accuracy of +/-5%. The error does not accumulate from step to step.

Return to main Motor Control page