Epson PH890 Service Manual page 57

EPSON Stylus Photo 890/1290
Figure 2-25. PF Motor Driver Circuit Block Diagram (C393MAIN-C)
ASIC(IC19)controls paper feeding amount by referring to the encoder pulses. ASIC
sends a proper drive current value to the motor driver. Based on the control signal from
ASIC, the motor driver (IC9or IC1) outputs drive current to the PF motor.
Unlike a stepping motor, this DC motor can not detect paper feeding amount by
referring to the pulses given. For this reason, a loop scale is attached on the Gear 76 to
detect paper feed amount.
The loop scale encoder sensor outputs two kinds of TTL level pulses Phase A and
Phase B to ASIC (IC19). Direction of the PF motor rotation is determined by the phase
between the output waveforms from Phase A and the waveforms form Phase B
OPERATING PRINCIPLES Electrical Circuit Operating Principles
1/1440"
1/5760"
Phase A
Phase B
Phase A
Phase B
Lens
Photo Photo
Diodes Diodes
LED
Figure 2-26. Loop Scale Encoder Pulse
Revision B
Forward Rotation
(Clockwise)
Backward Rotation
(Counterclockwise)
Comparators Comparators
A
+
A Phase A
-
B
+
B
Phase B
-
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