Brother 1920CN - Color Inkjet - Fax, Service Manual

Page: 41 / 286

III
- 10
2.3 Sensors and Actuators
This machine has ten sensors: eight photosensors and two thermistors as described below.
Sensor name Type Located on
Document front sensor Photosensor Document sensor PCB
Document rear sensor Photosensor Document sensor PCB
Manual insertion sensor Photosensor Engine PCB
Registration sensor Photosensor Engine PCB
Cassette sensor Photosensor Engine PCB
Paper ejection sensor Photosensor Paper ejection sensor PCB
Toner sensor Photosensor Toner sensor (LED) PCB and toner
sensor (light-receiver) PCB
Cover sensor Photosensor Toner sensor (LED) PCB
Heater thermistor Thermistor Heat-fixing unit
In-casing temperature sensor Thermistor Left-hand plate of the main chassis
• Document front sensor which detects the presence of documents.
• Document rear sensor which detects the leading and trailing edges of pages to tell the control
circuitry when the leading edge of a new page has reached the starting position and when the
scan for that page is over.
• Manual insertion sensor which detects whether paper is inserted manually through the paper
slot or whether paper fed through the paper cassette has jammed.
• Registration sensor which detects the leading and trailing edges of recording paper, which
allows the controller to determine the registration timing and check paper jam.
• Cassette sensor which detects whether the paper cassette is loaded.
• Paper ejection sensor which detects whether the recording paper goes out of the machine.
• Toner sensor which detects whether there is toner or a toner cartridge is loaded.
• Cover sensor which detects whether the front cover is closed.
• Heater thermistor which allows the controller to monitor the temperature of the heater roller of
the fixing unit.
• In-casing temperature sensor which allows the controller to monitor the temperature inside the
machine.
The above photosensors are a photo-
interrupter consisting of a light-emitting
diode and a light-sensitive transistor. Each
of them has an actuator separately arranged
as shown on the next page.