Sensor Circuits; Figure 2-23. Sensor Circuit Block Diagram - Epson Stylus 820 Service Manual

Operating Principles

2.3.2.2 Sensor Circuits

The following sensor circuits enable the C162 MAIN Board to monitor printer mechanism status:
HP sensor The photocoupler-type home position (HP) sensor is attached to the surface of the printer
mechanism to detect the carriage home position. A LOW level signal indicates the carriage
is in home position.
PE sensor A mechanical switch-type paper end (PE) sensor is built into the printer mechanism to
determine whether there is paper in the printer or not. A LOW level signal indicates no
paper is loaded.
CO sensor, The cartridge out (CO) sensor is mechnical switch attached to the head unit.
Thermistor A thermistor is attached to the black or CMY printhead unit to monitor its temperature using
the thermistor's resistance value (at 25° C or 77° F, approximately 10K Ω). The CPU
changes the printhead drive signal's pulse width (PWM control) based on the temperature
level.
M/C sensor The circuit pattern is decided as follows:
q
q
When the printhead is installed in the carriage unit, the control board recognizes the current
head automatically.
ID sensor There are four ID ports in the head unit. When the printer is turned on, the control circuit
decodes this ID data and outputs it automatically with the correct voltage. (During servicing,
it is not necessary to install a resistor array onto the control board as with previous printers.)
ASF sensor If the user changes the paper select lever to manual feed mode, the ASF sensor monitors this
and changes the paper feed sequence.
M/C
TH
Common Drive
Circuit

Figure 2-23. Sensor Circuit Block Diagram

2-22
Black head: LOW
CMY head: HIGH
IC2 (CPU: M3772)
CN4 19-pin
76
CN4 18-pin
AN PORT
99
98
81
Stylus Color IIs / Stylus 820
CN4 5-pin
96
CN4 6-pin
95
CN4 7-pin
94
97
CN4 10-pin
75 74
ID1
ID2
ID3
ID4
Rev. A