Sensor Circuit - Epson Stylus PHOTO 820 Service Manual

EPSON Stylus PHOTO 810/820

2.2.2.7 Sensor Circuit

CPU (IC1) on the Main board monitors the status of the printer by several sensors.
However, unlike the previous product, ASF unit on this printer does not have ASF
sensor. Instead of ASF sensor, Change lever and the Clutch mechanism is used to
detect ASF home position. (As for the ASF home position detection, refer to 2.1.4.)
HP/PE sensor
HP/PE sensor uses photo interrupter method and always monitors the two status
during the printer is in the power on status.
The photo interrupt component and two detection levers consists of this sensor.
CR home position
The CR home position is detected on the right edge of the CR shaft with the
HP/PE sensor during the variety sequence. In case that the CR home position
is detected, this sensor outputs HIGH signal to the CPU (IC1).
If CR home position is not detected in the detection position correctly, this
sensor outputs LOW signal to CPU and the printer indicates the error (As for
the error indication, refer to 1.4.3.)
Paper top & end position
When the Paper is in the paper path during the paper loading/feeding
sequence, HP/PE sensor outputs the HIGH signal.
When the Paper is not in the paper path, this sensor outputs the LOW signal
and the printer indicates the error (As for the error indication, refer to 1.4.3.)
Thermistor (THM)
The thermistor is directly mounted on the printhead driver board. It monitors the
temperature around the printhead and determines the proper head drive voltage to
uniform the weight of the ink fired from printhead. 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.
Operating Principles
:
Electrical Circuit Operating Principles
IC1
E01A24CA
+5V
+5
C-P15
29
13
6
C-P40
Figure 2-23. Sensor circuit diagram
Revision A
HPPV
3
GND
CN4
2 HP/PE Sensor
HPPE
1
GND
CN8
Head FFC
THM
50