Sensors And Actuators - Brother MFC6800 Service Manual

3.2.3 Sensors and Actuators

This machine has ten sensors: seven photosensors, two thermistors and a mechanical switch as
described below.
Sensor name
Document front sensor
Document rear sensor
Document tray open sensor
Scanner open sensor
Registration sensor
Paper ejection sensor
CCD HP sensor
Toner sensor
Toner thermistor
Heater thermistor
• 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.
• Document tray open sensor which detects whether the document tray is closed.
• Scanner open sensor which detects whether the scanner unit is closed.
• Registration sensor which detects the leading and trailing edges of paper, which allows the
controller to determine the registration timing and check paper jam.
• Paper ejection sensor which detects whether the recording paper goes out of the machine.
• CCD HP sensor which detects whether the CCD unit is placed in the home position.
• Toner sensor which detects whether there is toner or a toner cartridge is loaded.
• Toner thermistor which allows the controller to monitor the ambient temperature of the toner
cartridge.
• Heater thermistor which allows the controller to monitor the temperature of the heater roller of
the fixing unit.
These photosensors are a photointerrupter
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.
Type
Photosensor
Photosensor
Mechanical switch
Photosensor
Photosensor
Photosensor
Photosensor
Photosensor
Thermistor
Thermistor
3 -1 0
Located on
Document sensor PCB in the
ADF
Document tray
Control panel PCB
Main-fan PCB
High-voltage power supply PCB
CCD PCB on the CCD unit
Toner sensor PCB
Heat-fixing unit