Step Motors – Methods For Controlling Them

You can achieve full step control by turning on all the windings of the motor. This is the most cost-effective and simple way to control the stepper motor. Each phase must be turned on separately as most step motors have four phases. To do this, a transistor is used to turn the phases on or off. There are many chips on the market that have internal transistors that can also control external mosfets. 

The step machine shaft rotates mechanically at 1.8 degrees when it is used to its maximum. To make one revolution, the motor requires 200 steps. Half Step is the term for the fact that the motor only rotates one-half of a step per time, as opposed to taking a full step each time. Instead of moving at 1.8 degrees per step the motor will move half that, or 0.9 degrees per stage. 

This motor drive topology can be achieved by exiting each winding one at a time, then two at a time, and then repeating the process over and over. This control can be done in a similar way to the full-step except that transistors, such as mosfets, can be used to cheaply control the motor. Halfstep will make the motor run smoother and reduce resonance.

Compumotor popularized microstepping control for stepmotors in the 1980's. Although this drive method is most popular, it is more expensive than half-step or full step controls. To produce small incremental mechanical steps, the drive for the motor must change two sine-waves. This is microstepping. 

Over the years, many ICs were developed to reduce the cost of microstepping compared to half stepping. Microsteppers are the majority of step motor drivers currently on the market.