Sensor Circuit - Epson FX-980 Service Manual

FX-980

2.3.7 Sensor Circuit

The CPU detects conditions of the following sensors: home position
(HP) sensor, release sensors 1 and 2, platen gap (PG) sensors 1 and 2,
rear and front paper end (PE) sensors, paper width (PW) sensor, and
cover open sensor.
Two types of sensors are used in this printer. Release sensors 1 and 2,
the PG sensors 1 and 2, the front PE sensor, and the cover open
sensor are momentary switches.
The other type of sensor is used for the HP sensor, rear PE sensor, and
PW sensor, which are photo diode switches. The HP sensor detects CR
home position when the photo diode rays are cut off by the printhead.
Operating Principles
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, as mentioned on the page 2-24 (LQ-2070 Service Manual),
the +35 V line and head temperatures are monitored to set the pulse
length of the head driver signal.
Figure 2-9. Sensor Circuit
Control Circuit
Revision A
36