Epson Stylus Color 880, Service Manual

Page: 51 / 179

EPSON Stylus COLOR 880 Revision A
Operating Principles Electrical Circuit Operating Principles 51
2.2.2.4 PF Motor Driver Circuit
TheStylus COLOR 880 is equipped with a DC motor for the PF motor. The
block diagram for the PF motor driver circuit is as shown below:
Figure 2-22. PF Motor Driver Circuit Block Diagram
IC15 CPU controls paper feeding amount by referring to the encoder pulses
sent from IC25 ASIC. It also sets a proper drive current value according to the
paper feeding amount and direction. So it outputs specified control signal to the
motor driver. The motor driver IC19 outputs PF motor drive current to the PF
motor according to the control signals from the IC15 CPU.
Unlike a stepping motor, the DC motor that drives the PF motor can not detect
a paper feeding amount by referring to the pulses given. For this reason, a loop
scale is attached on the Gear 57 to mechanically detect a paper feeding
amount.
The loop scale encoder sensor outputs two kinds of TTL level pulses Phase A
and Phase B to IC25 ASIC.
Figure 2-23. Loop Scale Encoder Pulse
Rotational direction of the PF motor is determined by the phase between the
output waveforms of Phase A and Phase B. Refer to Figure 2-23 for different
phase for each direction.
NOTE: If the drive voltage for the PF motor reaches 1A, a fatal error occurs.
A
A
B
B
+
-
+
-
P h o t o
D i o d e s
C o m p a r a t o r s
L E N S
L E D
P h a s e A
P h a s e B
P h a s e A
P h a s e B
P h a s e A
P h a s e B
1/1440 inches
1/5760 inches
PF motor CW rotation
PF motor CCW rotation