3–33OPERATIONS AND TIMINGCOPYRIGHT © 1998 CANON INC. CANON NP6621 REV.0 FEB. 1998 PRINTED IN JAPAN (IMPRIME AU JAPON)4. Driving the Scanner Motora. OutlineThe scanner motor is a 4-phase control step-ping motor. It is turned ON/OFF and its directionand the speed of its rotation are chanceged bycontrolling the output timing of pulse signals SCA/A* and SCB/B*.b. OperationsThe microprocessor (Q301) on the DC control-ler PCB receives such information as on the se-lected copying mode and reproduction ratio fromthe control panel circuit. In response, it issues drivepulses to the scanner motor (M2) by way of themotor drive circuit.The scanner motor is a 4-phase control step-ping motor and controls the scanning direction andspeed by changing the frequency and the sequenceof drive pulses (SCA through SCB*).The motor drive voltage ON/OFF switching cir-cuit controls whether to apply power to drive themotor or to remove power to keep the motor at rest.The current switching control circuit determinesthe current flowing into the motor according to therevolution of the motor, and the motor driver circuitcontrols the constant current according to the valuedetermined by the circuit.Figure 3-207(Q301)(Q324)J302SCASCA*SCBSCB* M25VA,A*,B,B*MicroprocessorDC controller PCBCurrentvalueswitching Current valueswitching controlcircuitMotor drivercircuit
