Epson 2080 - LQ B/W Dot-matrix Printer, Service Manual

Page: 30 / 55

LQ-2080 Revision A
Operating Principles Control Circuit 30
2.3.6 Sensor Circuits
The CPU detects conditions of the following sensors: home position
(HP) sensor, release sensors 1 and 2, platen gap (PG) sensor, rear and
front paper end (PE) sensors, paper width (PW) sensor.
Figure 2-9. Sensor Circuit
Two types of sensors are used in this printer. Release sensors 1 and 2,
the PG sensors, and the front PE sensor are momentary switches.
The HP sensor, rear PE sensor, and PW sensor are photo diode
switches. The HP sensor detects CR home position when the photo
diode rays are cut off by the printhead. The rear PE sensor detects that
paper has been loaded when the photo diode rays are cut off by the
sensor plate, which is included in the rear PE sensor. The PW sensor,
used for paper width measurement and paper loading positioning,
detects the paper edge by comparing the measured voltage with
standard voltage, which was measured during the power on sequence.
Additionally, the +35 V line and head temperatures are monitored to set
the pulse length of the head driver signal.
C P U ( I C 4 )
P 3 6
P 4 0
A N 2
P 5 3
P G S e n s o r
R e l e a s e
S e n s o r 1
R e l e a s e
S e n s o r 2
+ 5 V
+ 5 V
H P S e n s o r
+ 5 V
+ 5 V
R e a r P E
S e n s o r
+ 5 V
F r o n t P E
S e n s o r
+ 5 V
+ 5 V
P W , T O P
S e n s o r
7 6
7 5
6 8
7 0
G A ( I C 3 )
R e l e a s e 1
R e l e a s e 2
1 1 6
1 1 7
6 1
P 2 7