Sensor Circuit - Epson Stylus COLOR 760 Service Manual

EPSON Stylus COLOR 760

2.2.2.6 Sensor Circuit

The Stylus COLOR 760 is equipped with the following five sensors to detect
the status of the printer.
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I/C detection sensor
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Head Thermistor sensor
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PE sensor
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ASF home position sensor
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PF motor encoder sensor
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CR unit encoder sensor
The block diagram for the sensor circuit is as shown below:
Figure 2-26. Sensor Circuit Diagram
Operating Principles
Function and detection method of each sensor is as described below.
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I/C detection sensor (for black I/C and color I/C)
The I/C detection sensor included in the CR unit determines whether a
black or color ink cartridge is installed. When an I/C is installed, this sensor
detects a mechanical contact with the cartridge and outputs a LOW signal
to the ASIC. If no cartridge is installed, it outputs a HIGH signal to the
ASIC.
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Head thermistor
The head thermistor is attached directly 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.
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PE sensor
The PE sensor is located at the bottom right edge of the top frame in the
printer mechanism. This sensor detects paper on the rear paper guide,
using a photo sensor and PE sensor lever that are included in the sensor.
When paper passes, the PE sensor does not interrupt the photo sensor
terminals. So a LOW signal is output to the ASIC. If there is no paper, on
the other hand, the lever cuts in between the photo sensor terminals, which
outputs a HIGH signal to the ASIC.
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ASF HP sensor
The ASF HP sensor, located at the left edge of the ASF, detects the ASF
home position. This sensor consists of the ASF HP detector wheel and a
photo sensor. A small portion of the ASF HP sensor has a cut out, and
when the cutout comes into position between the photo diode terminals,
ASF home position is detected. In this status, the photo diode terminals are
not blocked, and a LOW signal is output to the ASIC. Referring to the ASF
home position detected by this sensor, the printer drives the PF motor to
set the LD roller and paper return lever ready for paper loading.
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PF motor encoder sensor
The PF motor encoder sensor includes the loop scale attached to the left
end of the PF roller and the linear encoder. This encoder sensor outputs 2
kinds of the output pulse A-phase and B-phase and the minimum
resolution of the sensor is 1/5760 inch, and 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.
Electrical Circuit Operating Principles
Revision C
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