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Stepper Motors


Stepper Motors: Stepper motors are brushless electric motors that divide the full rotation into a large number of steps. When controlled electronically, the motors position can be precisely controlled without any feedback mechanism (unlike Servos which require constant monitoring). Stepper motors are generally identified by how many steps are required to make a complete rotation. For instance, a 200 step stepper motor makes two hundred 1.8 degree steps to make a full rotation.

The actual control of a stepper motors rotation is fairly complicated. It is an oversimplification but imagine that there are 200 electromagnets surrounding a rotating arm and these electro magnets can be activated one at a time. If each magnet was activated sequentially the arm would move in a circle.

Simple animation of a stepper motor operating.

Slightly more sophisticated animation of an operating stepper motor.

Video of a stepper motor speed and position controller

Because of the precise control that stepper motors allow they are often used in robotics. When controlled by a computer the stepper motor can be moved to very precise positions by controlling the number of steps that the motor is commanded to take.

An advantage of stepper motors is that they maintain the same torque (power) regardless of the speed that they are operating. (See the tutorial on DC Motor Control)

The stepper motor controller in the video above is a very complicated device. The lesson plans for the Basic Stamp II show a very simple circuit that can be used to control a stepper motor using an IC (Integrated Circuit) that is generally available for less than $1.

The best place to find inexpensive stepper motors is at surplus dealers either online or locally.

There are many types of stepper motors: unipolar, bipolar, etc. Teams will have to do their own research to understand each of these types of motors.