Scanner Motor - Canon 1000 Service Manual

3. OPERATION AND TIMING
C. Scanner Motor
1. Outline
Figure 3-205 shows the circuit used to control the scanner motor, and the circuit has the following
functions:
1 Controls the direction of rotation of the scanner motor.
2 Controls the speed of rotation of the scanner motor.
The scanner motor changes its direction of rotation between when the scanner moves forward and
when it moves in reverse, and its speed of rotation varies according to the selected reproduction ratio.
Its speed of rotation when the scanner is moved in reverse is the same regardless of the selected
reproduction ratio. It rotates about 10 times as fast as when the scanner is moved forward in Direct.
Reader controller PCB
2. Operation
The CPU (Q651) on the scanner motor driver PCB receives mode, distance, and reproduction data from
the image processor PCB. Then, in response to the start command, it sends drive pulses to the scanner
motor to suit these data units. The scanner motor is a 5-phase stepping motor; the direction and the speed of
scanning are varied by changing the order of the drive pulses (A through E) and the frequency.
To rotate the motor at a high speed when the scanner is moved in reverse, the drive voltage switching
circuit switches the power used to drive the motor from 8 V (forward) to 24 V (reverse).
The constant current control circuit controls the current flowing to the motor to a constant current to suit
the speed of rotation.
The circuit cuts the current to the motor by the HOLD-OFF signal while the motor remains at rest during
standby to prevent heating of the motor.
3-32
COPYRIGHT © 2001 CANON INC.
Q651
Voltage switching
HOLD-OFF
A~E
A~E
Current switching
4
Scanner motor driver PCB
Figure 3-205
CANON CLC1000/1000S/3100 REV.2 MAY 2001 PRINTED IN JAPAN (IMPRIME AU JAPON)
+24V +8V
Drive voltage
switching circuit
24Vor8V
Motor driver
circuit
Constant current
Current
control circuit
detection
A
B
C
D
E
Scanner motor (M29)