Epson Stylus PHOTO 890 Service Manual page 59

EPSON Stylus Photo 890/1280/1290
Each sensor's functions and operating principles are as described below:
o
PE sensor
The PE sensor is located at the bottom right edge of the top frame in the printer
mechanism. It detects paper on the rear paper guide using a photo sensor and PE
sensor lever that are included in the sensor. When paper is present, the PE sensor
lever does not cut in between the photo sensor terminals. So it outputs a LOW
signal to the ASIC. If there is no paper, on the other hand, the lever cuts in between
the photo sensor terminals. So it outputs a HIGH signal to the ASIC.
o
ASF sensor
The ASF sensor, located at the left edge of the ASF, detects ASF home position.
This sensor consists of the ASF HP detector wheel and a transmission photo
sensor. A small portion of the ASF HP sensor has a cutout, and when the cutout
comes into position between the photo diode terminals, that condition is detected
as ASF home position. In this status, since the photo diode terminals are not
blocked by the wheel, a LOW signal is output to ASIC. Otherwise, a HIGH signal
is output. Referring to the ASF home position detected by this sensor, the printer
drives the ASF/Pump motor to set the LD roller and paper return lever ready to the
paper loading position.
o
Ink cartridge sensor (CSIC connector on the head board)
Ink cartridge sensor detects whether a black or color ink cartridge is installed.
Installation condition is determined depending on the CSIC's connection. When a
cartridge is installed, a LOW signal to ASIC is output. On the other hand, a HIGH
signal is output when a cartridge is out.
o
Head thermistor
The head thermistor is directly attached on the head driver board. It monitors the
temperature around the printhead and feeds back the temperature to the CPU
analog port. The printer refers to this information to control head driver voltage
based on the ink viscosity.
o
PF motor encoder
The PF motor encoder includes the loop scale attached to the left end of the PF
roller shaft and the transmission photo sensor. The minimum resolution of the
sensor is 1/180 inches. The sensor outputs HIGH signals for the black lines and
LOW signals for the transparent parts to the ASIC. The printer controls the PF
motor based on the signals output from this sensor.
o
CR motor encoder
CR motor encoder consists of the transmission photo sensor assembled in the CR
unit and the linear scale attached along the CR scanning line. The minimum
OPERATING PRINCIPLES
resolution of the sensor is 1/180 inch. It outputs HIGH signals for the black bands
and LOW signals for the transparent parts of the linear scale to the ASIC. The
printer controls the CR motor based on the signals output from this sensor. CR
home position is also detected based on the signals from this sensor.
Electrical Circuit Operating Principles
Revision C
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