Epson STYLUS PHOTO 925 Service Manual page 46

EPSON Stylus Photo 925
PF MOTOR DRIVER CIRCUIT
Figure below shows the outline of the PF motor drive circuit.
ENA
PF Encoder
ENB
(CN12)
CPU (IC11)
E01A27CA
Figure 2-22. PF Motor Driver Circuit
The CPU (IC11) controls the paper feed length by referring to the encoder pulse. The
CPU sends a specific control signal to the motor driver so that the drive current is
output to the PF Motor.
Unlike the stepping motor used with the conventional printer models, the DC motor
does not detect paper feed length by the given control pulse. Therefore, a loop scale is
mounted on the spur gear 73.6 to detect the paper feed length. The loop scale encoder
outputs two types of TTL level pulses (phase A and phase B).
The rotational direction of the rotor of the PF Motor is determined by the phase
between the phase A and phase B waveforms. Figure 2-23 shows the output waveforms
from the loop scale encoder.
Operating Principles
+42V
PF-A
Motor Driver
IC (IC14) PF
PF-B Motor
Electrical Circuit Operating Principles
Phase A
Phase B
Phase A
Phase B
Figure 2-23. Output Waveforms from the Loop Cable Encoder
Revision A
PF Motor runs forward
(Rotor rotates clockwise)
PF Motor runs backward
(Rotor rotates
counterclockwise)
Phase A
Phase B
46