2.3.7 Sensor Circuits
TheCPU dete ctsconditions of the followingsensors: homeposition (HP) sensor,release sensors 1 and 2,
platen gap(PG) sensors 1 and 2,rear and frontpaper end(PE) sensors, paper width(PW) sensor, andcover
open sensor.
Two typesof sensors are used inthis printer. Release sensors 1 and2 , PG sensors1 and 2, thefront PE
sensor, andcover open sensorare momentary switches.Pages 2-3 and 2-4describe therelationship between
release and PG sensor operation andactual printoperation.
Theother type of sensor isused for the HP sensor, rearPE sensor, and PWsensor, which are photodiode
switches.The HP sensor detects CR homeposition when thephoto diode rays arecut off bythe printhead.
Therear PE sensor detects that paperhas been loaded whenthe photo dioderays are cutoff by the sensor
plate, which is included inthe rear PE sensor.The PW sensor, used for paperwidth measurement andpape r
loading positioning, detects the paperedge bycomparing the measured voltage withstandard voltage, which
was measured during thepower onsequence.
Additionally, as mentionedon the page2-24, the+35 V line andhead temperature are monitored toset the
pulselength of the head drivesignal.
CPU
P36
P40
AN2
P53
P32
P33
P34
P35
+5V
+5V
PG Sensor 2
PG Sensor 1
Release
Sensor 1
Release
Sensor 2
+5V
+5V
+5V
+5V
HP Sensor
+5V
+5V
Rear PE
Sensor
+5V
Front PE
Sensor
+5V
+5V
PW Sensor
INT7
+5V
Cover Open
Sensor
18
67
66
65
64
76
75
68
70
Figure 2-38 Sensor Circuits
FX-2170 ServiceManual Operating Principles
Rev.A 2-27