Epson Stylus PHOTO 950 Service Manual page 52

EPSON Stylus PHOTO 950
The functions and operating principles for each of the sensors are described blow.
PE sensor
This sensor uses photo interrupter method and detects the following status.
The photo interrupt component and detection levers consists of this sensor.
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.
PG sensor
This sensor is located underneath the adjust lever, and it detects whether the platen
gap (PG) is large or normal. The sensing method used by the PG sensor is a
mechanical contact. When the PG is normal, a Low signal is output to the CPU.
When the PG is large, a High signal is output to the CPU.
Release sensor
This sensor is located underneath the adjust lever, and it detects whether the paper
guide is open or not. The sensing method used by the release sensor is a
mechanical contact. When the paper guide is open, a Low signal is output to the
CPU. When the paper guide is not open, a High signal is output to the CPU.
Ink cartridge sensor (CSIC connector on head circuit board)
This detects whether the ink cartridges are installed or not. Sensing is carried out
by detecting whether the CSIC is connected or not. If an ink cartridge is installed,
a Low signal is output to the ASIC. If no ink cartridge is installed, a High signal is
output to the ASIC.
Head thermistor
The thermistor is attached directly on the parenthood driver board. It monitors the
temperature around the parenthood 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. This circuit is different from head inside
temperature detection circuit.
PF rotary encoder
To make the paper feed pitch precisely. PF encoder always monitors the bar-code
on the rotary scale during PF motor drivers.
OPERATING PRINCIPLES
CR linear encoder
To make the current CR position manage, CR encoder always monitors the bar-
code on the linear scale during CR motor drivers. Also this model has no HP
sensor and judges the home position when the CR goes out of step at right side.
Paper width sensor
The paper width sensor is mounted on the head FFC. It is used in the control of the
home positioning operation when paper is fed manually from the front of the
printer, and also in detecting the leading edge of paper in rolls. When the sensor
detects the edge of the paper, it outputs a High signal to the CPU. When it does not
detect any paper, it outputs a Low signal.
Electrical Circuit Operating Principles
Revision A
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