AN001 - Directly Driving Stepper Motor

Schematic of stepper circuit

As can be seen in the schematic above, a unipolar stepper motor (3M3401) is driven directly from a TICkit 57 via 4 3055T transistors. The common side of the stepper motor windings connect to the positive motor supply. The ground side of the motor windings are switched. The stepper motor and the transistors can be obtained from Jameco Electronics.

The Program to control this circuit is below. Much of the code below deals with the LCD display and the buttons to create a wrist-watch type of interface for setting drilling depth and rate. The basic algorithm for generating the motor phases consists of using an array with 4 entries, one entry for each coil pattern of each phase. The index to this array is incremented or decremented depending on the direction of motor travel:



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