Sensor Circuit - Epson Stylus Photo 895 Service Manual

EPSON Stylus PHOTO 895/785EPX
+5V line reset circuit
The 5V line is monitored at the VDD port of IC6. It outputs the reset signal from
the RST port to the CPU ASIC if the irregular voltage (4.2V or less) is detected.
+42V line reset circuit
The 42V line is monitored at the VEX port of IC6. It outputs the reset signal
from the EXO port to the CPU, ASIC if the irregular voltage (36.0V or less) is
detected.
NOTE: IC6 also contains the RTC (Real Time Clock) function and performs the
timer control function by the BAT1 power supply while the power is
turned OFF.
EEPROM Control Circuit
Since EEPROM is nonvolatile memory, it keeps written information if the printer
power is turned off. Various adjustment values, factory shipment data and printer
condition values are written and stored in EEPROM. (Figure 2-24. "Reset
EEPROM Circuit Diagram")
EEPROM is connected to CPU with 4 lines and each line has the following function.
CE: Chip selection signal
CLK: Data synchronism clock pulse
DI: Data writing line (serial data) at power off.
DO: Data reading line (serial data) at power on.

2.2.2.7 Sensor Circuit

C408 MAIN is equipped with the following three sensors to detect the status of the
printer. Unlike the previous product, ASF HP sensor is not equipped on the ASF and
the ASF HP is determined with the clutch mechanism (2.1.5 "Paper Loading
Mechanism (ASF Unit)").
HP Sensor
This sensor uses the photoelectric conversion method and detects the CR home
position at the right end of CR shaft by the HP sensor when the power is turned on.
This sensor outputs the HIGH signal to the CPU as it detects the CR home position
when the power is turned on. If the LOW signal is outputted at the detection
position, the CR unit is not at the home position.
PE sensor
This sensor uses the photoelectric conversion method and detects if there is paper
in the ASF unit or not. This sensor outputs the HIGH signal when there is paper in
Operating Principles
the paper path. This sensor outputs the LOW signal when there is no paper in the
paper path. This condition is always monitored with this sensor while the printer
power is turned on.
Thermistor (THM)
The thermistor is attached directly on the printhead driver board. It monitors the
temperature around the printhead 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.
The block diagram for the sensor circuit is shown below
Electrical Circuit Operating Principles
IC2
HPV
E01A22CA
GND
145
C_P15
PEV
GND
144
C_P17
THM
Figure 2-25. Sensor Circuit Diagram
Revision A
3
CH4 HP Sensor
2
HP
1
3
CH5 PE Sensor
2
PE
1
CN9 Head FFC
13
52