Constant current step motor system

Claim 1

A constant current drive system for a step motor having a rotor and a plurality of windings which, when energized in a specific sequence, will cause said motor to rotate in one direction an incremental step at a time, comprising: a power supply, including an AC power supply together with rectifier and smoothing means for producing direct current, gate controlled switch means between the AC power supply and the smoothing means, normally stopping flow from the AC power supply, the gate of said switch means being responsive to a pulse signal to allow the voltage to pass said switch means, sequence switching means for connecting said power supply selectively and in a predetermined sequence to each of said windings, motor control responsive to drive pulses and acting upon the sequencing switching means to cause said sequence switching meaNs to connect said power supply to said windings in proper sequence to produce successive incremental movements of said rotor, sensing means for sensing the amount of current passing through the windings, and feedback means responsive to the current sensed by the sensing means including comparison means providing a standard of desired current level and producing an error signal in the form of a pulse chain, the repetition rate of which is directly proportional to the amount of deviation from said standard, said pulse chain being synchronized with said AC power supply and acting upon the trigger of said gate controlled switch means to eliminate a forward portion of the rectified AC wave for a time corresponding to the period of the first pulse after the wave is in order to adjust the current passing through the windings so that uniform current is provided at all times.