How Does a Stepper Motor Work?

Stepper motors are electromagnetic actuators that convert input pulses to output motion. They are different from ordinary direct current (DC) motors in that, when energized by a voltage or current pulse train, the step motor moves an incremental amount for each pulse it reads.

Stepper motors are commonly used in computer peripheral equipment such as printers, tape drives, and disk drives. Additionally, they are used in machine tool controls, process control systems, robots, and other industrial applications.

The chief disadvantages of stepper motors include their limited size -- which limit their power capabilities -- and the resolution of movement. Since they move a certain amount for a single step, the smallest amount they can move is determined by this step size.

In the Proprinter one of two stepper motors is connected to the helix drive. Sending a pulse to the motor turns the helix drive by a small step angle. This in turn moves the printwheel, which is mounted on the helix drive, by a fixed increment. This increment is equal to the distance between two adjacent lateral print positions on the paper.

There are many types of stepper motors. The stepper motor pictured is a variable reluctance stepper motor which has 24 steps per revolution. As the wires to each of the positions (labelled 1,2,3) are energized, it creates a flux and the rotor moves one step.

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Last Updated: October 26, 1998, NEEDS Staff
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