Browse Prior Art Database

Original Publication Date: 1994-Feb-28
Included in the Prior Art Database: 2004-Apr-06

Publishing Venue

Xerox Disclosure Journal


A method for controlling multiple unipolar stepper motors (full or half step) using a limited number of control signals is disclosed. One example of a unipolar stepper motor is a four phase, six lead motor, that is used, for example, to drive a raster output scanner (ROS) in an electronic printing machine. A unipolar stepper motor of this type rotates using the four phases shown in Figure 1A that are provided by a CPU control unit. To reverse the direction of rotation, two of the phase signals shown in Figure 1A are inverted as shown in Figure 1B. Some raster output scanners (ROS) require a total of six unipolar stepper motors to position the laser beams of the ROS. The disclosed method of controlling multiple (e.g. six) stepper motors requires fewer than normal (e.g. four) CPU signals to pass phase information to the motor windings. The method reduces the required number of control signals by sharing the phase information among the multiple stepper motors. Traditional motor control requires six signals from a control source, such as a microprocessor, for each motor (e.g. thirty-six signals to control six motors). The disclosed method on the other hand requires the total of sixteen control signals to control six motors, as shown in Figure 3: six enable signals, six directional signals and four phase signals.