Step Motors - Methods For Controlling Them

Full Step control is achieved by turning on the completeexiting each winding in a pattern on one winding on,
winding of the motor. This is the simplest and thereforetwo windings on, and then repeating this over and
lowest cost method for controlling the stepper motor.over. The control is similar to that of the full step in that
Most step motors are four phase which requires eachtransistors such as mosfets can be used to
phase to be turned on individually. The most commoninexpensively control the motor. The motor will run
method of achieving this is to use a transistor toslightly smoother and have minimized resonance issues
switch the phases on and off. There are chips that arewhen run in halfstep.
available off the shelf that contain internal transistorsMicrostepping control for step motors was developed
and they can control external mosfets as well. Whenin the 1980's and was popularized by Compumotor.
full step is utilized, the motor shaft will rotate 1.8This drive technique is the most desirable, but is much
degrees mechanically. The motor will require 200 stepsmore costly than the half step or full step control. The
to make one revolution.drive for the motor must vary two sine-waves to
The term Half Step refers to the fact that the motorproduce small incremental mechanical steps, thus the
rotates only one half of a step at a times, comparedname microstepping for the small steps they are
to taking a full step each time that was mentionedtaking. Many ICs have been developed over the years
previously. Instead of moving 1.8 degrees per step, theto help reduce the cost of microstepping versus half
motor will rotate half of that or 0.9 degrees per step.stepping. Most step motor drivers on the market today
The way this motor drive topology is achieved is byare microsteppers.