EPSON Stylus CX3500/CX3600/CX3650/CX4500/CX4600 Revision A
OPERATING PRINCIPLES Electrical Circuit Operating Principles 77
2.4.2.5 Sensor Circuit
CPU (IC8) 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 “2.2.4
Paper Loading/Feeding Mechanism” (p.58).)
V PE Sensor
This sensor is mounted at the right side center of the Printer Mechanism, and it
detects the presence/absence of paper when the paper passes through the Paper
Guide Rear. The PE Sensor is constructed of a transmissive photosensor and the
PE Sensor Lever.
T Paper Absent : Because the PE Sensor Lever does not interfere between
the photosensor terminals, a low signal is output to the
CPU.
T Paper Present : The PE Sensor Lever interferes between the photosensor
terminals, and a high signal is output to the CPU.
V PG Sensor
This sensor is mounted at the left end lower section of the Printer Mechanism, and
it detects the condition of PG (Platen Gap). The detection method used by the PG
Sensor is mechanical contact points.
T PG Normal : A low signal is output to the CPU.
T PG Large : A high signal is output to the CPU.
V PW Sensor
The sensor is mounted to the bottom of the Carriage Unit. It detects the top and
bottom, left and right edges of the paper being fed.
T Paper absent : A low signal is output to the CPU.
T Paper present : A high signal output to the CPU.
V CR Encoder Sensor
The sensor is composed of a transmissive photosensor mounted to the back of the
carriage and a linear scale mounted in the CR scan direction. Minimum resolution
of 1/180 inch is provided, and output to the CPU is a high signal for the black slits
on the linear scale and a low signal for transparent slits. Control of the CR Motor is
based on the output signal. The home position of the Carriage Unit is detected by
this sensor.
V PF Encoder Sensor
The sensor is composed of a transmissive photosensors mounted to the loop scale
of the PF Roller Unit left side and to the Main Board. Minimum resolution of 1/
180 inch is provided, and output to the CPU is a high signal for the black slits on
the loop scale and a low signal for the transparent slits on the loop scale. Control of
the PF Motor is based on the output signal.
V Thermistor (THM)
The thermistor is directly mounted on the Print Head driver board. It monitors the
temperature around the Print Head and determines the proper head drive voltage to
uniform the weight of the ink fired from the Print Head. 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.
V Scanner HP Sensor
Mounted in the Scanner Unit, this sensor detects whether the CIS Unit is inside or
outside the home position
T Inside HP : A high signal output to the CPU.
T Outside HP : A low signal is output to the CPU.
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