The circuit drives four outputs in the sequence required for driving a stepper motor. It can be driven from any computer that provides two digital output bits or simply by a low frequency oscillator. The SD-001 is based on the SAA1027 integrated circuit. The count rate and direction inputs are double buffered from the stepper IC by inverters and opto-isolators. Each output line has a parallel LED that turns on as the output is pulsed, giving a visual indication of the sequence of windings being pulsed on the stepper motor.
All user wiring to the circuit board is made via screw terminal blocks.
The motor voltage supplied can be between 9.5v and 18v and the outputs can source 350 ma to the stepper motor windings. Larger motors can be driven with the addition of a power output stage.