Bipolar Stepper Motor Control

The subject of stepper motors is clearly very popular, with many reader responses to every published article. A design for a unipolar controller appeared in the May 1999 issue, and now we present a bipolar version. First, we want to explain how such a controller works and what’s involved. A bipolar motor has two windings, and thus four leads. Each winding can carry a positive current, a negative current or no current. This is indicated in Table 1 by a ‘+’, a ‘–‘ or a blank.