Cr Motor Driver Circuit - Epson Stylus COLOR 880 Service Manual

EPSON Stylus COLOR 880

2.2.2.3 CR Motor Driver Circuit

The Stylus COLOR 880 is equipped with a DC motor for the CR motor.
CR motor driver circuit
The internal equivalent circuit of the CR motor driver IC (LB1947) is as
shown below.
Figure 2-19. Internal Equivalent Circuit of the CR Motor Driver IC
The IC 15 C P U controls the C R position by referring to the pulses sent from the
linear encoder via IC 25 A S IC . The C P U also sets an appropriate drive
current value for the C R position and the direction in w hich the C R m oves
based on the data transm itted from the A S IC . S o the slave C P U outputs
specified control signals to the m otor driver. The m otor driver IC 18 then
outputs the C R m otor drive current to the C R m otor based on the signals
sent from the IC 15 C PU .
Operating Principles
U nlike a stepping m otor, the D C m otor that drives the carriage can not detect
the current carriage position by referring to the pulses given. For this
reason, a linear scale is attached along the carriage operation range to
detect the carriage position. The linear encoder sensor outputs tw o kinds of
TTL level pulses Phase A and Phase B to IC 25 AS IC .
Direction for the current CR's movement is detected based on the waveforms
of the Phase A and Phase B that are out of phase, while carriage position is
controlled by using the waveforms output from Phase A on a cycle basis (1
cycle: 1/180 inches). Phase between the output waveforms A and B is as
shown in Figure 2-20. Note all edges in Phase A, Phase B output waveforms
(1/720-inch cycle) are used to control the CR position while it is in the home
position for ink system.
Electrical Circuit Operating Principles
1/180 inches
1/720 inches
Figure 2-20. CR Linear Scale Encoder Pulse
Revision A
1/360 inches
CR Motor CW rotation
CR motor CCW
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