Abstract: A control system for controlling a stepper motor which uses six power transistors in a single, interconnected configuration with two stepper motor field coils. Two transistors are common to both field coils of the stepper motor with two stepper motor field coils. Control circuitry for switching the six transistors allows full and half step motor positioning to be performed. Transition phases are used between steady state phases to provide accurate motor operation. The transition phases are controlled entirely within the control circuitry without a requirement for input from outside the controller.

Abstract: A method for starting a polyphase motor of the type having a plurality of stator coils and a rotor includes the steps of measuring the rise time of current on each of the stator coils, determining from the rise time measurement the position of the rotor, and determining a coil to apply a voltage to produce maximum startup torque of the motor. Any position ambiguities are resolved by determining the direction of rotation of the motor by applying a voltage to the determined coil sufficient to produce at least a slight rotation of the rotor, remeasuring of the rise time of current on at least a plurality of the rotor coils, and determining a difference between the rise time measurement and remeasurement. The difference indicates the direction which the rotor was rotated.