Epson STYLUS COLOR 480, Service Manual

Page: 50 / 149

EPSON Stylus COLOR 480 Revision B
Operating Principles Electrical Circuit Operating Principles 50
2.2.2.7 Sensor Circuit
C367MAIN-B is equipped with the following two sensors to detect the status of the
printer. Unlike the previous product, ASF HP sensor is not equipped on the ASF and
the ASF HP is determined with the clutch mechanism (2.1.4 Paper Feeding
Mechanism).
o
HP/PE/IC Sensor
This sensor uses photo interrupter method and detects the following three status.
The photo interrupt component and two detection levers consists of this sensor.
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CR home position
The CR home position is detected on the right edge of the CR shaft with the HP/
PE/IC sensor during the power on sequence. In case the CR home position is
detected in the power on sequence, this sensor outputs HIGH signal to the CPU.
When the LOW signal is output to the CPU in the detection position, the CR unit
is out of home position.
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.Ink cartridge installation condition.
When the printer is powered on, the CR unit moves to the left side with the
specific steps. And in case the plate molded on the Ink cartridge cover push the
sensor detection lever, the sensor detects that the ink cartridge is not installed in
the CR unit and outputs HIGH signal.
When the ink cartridge is installed in the CR unit, the plate molded on the ink
cartridge cover dose not contacts with the sensor detection lever and the LOW
signal is outputs to the CPU. The Ink cartridge installation condition is monitored
in the ink cartridge replacement sequence also.
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Paper Top & End position
When the Paper is in the paper path, this sensor outputs the HIGH signal.
When the Paper is not in the paper path, this sensor outputs the LOW signal.
This status is always monitored during the printer is in the power on status with
this sensor.
o
Thermistor (THM)
The thermistor is attached directly on the printhead driver board. It monitors the
temperature around the printhead and determines the proper head drive voltage
according to the ink viscosity that varies by the temperature. This information is
fed back to the CPU analog port. When the temperature rises, the head drive
circuit lowers the drive voltage: When the temperature lowers, the head drive
circuit rises the drive voltage.
The block diagram for the sensor circuit is shown below
:
Figure 2-24. Sensor Circuit Diagram
G N D
H P P V
+ 5 V
+ 5 V
+ 5 V
3 2
S W H P P E
G N D
T H M
C N 1
H P / P E / I C S e n s o r
C N 4
H e a d F F C
I C 1
E 0 1 A 1 4 N A
H P P E
1
A N 0
2 2
2
1
3