Sensors And Actuators - Brother MFC4820C Service Manual

4.2.4 Sensors and Actuators

This machine has the following sensors and thermistors.
Scanner/ink slot cover open
sensor
Registration sensor
ASF switch
Paper width sensor (Media
sensor)
Purge cam HP switch
Ink cartridge sensors (x 4)
Hook switch (on the MFC4820C)
Air pump motor encoder sensor
Carriage motor (CR) encoder
sensor
Paper feed motor (PF) encoder
sensor
Casing internal temperature
thermistor
Head thermistor
• The scanner/ink slot cover open sensor detects whether the scanner unit and/or the ink slot
cover are closed.
• The registration sensor detects the leading and trailing edges of the paper, which allows the
controller to determine the registration timing and to check for paper jams.
• The ASF switch detects the switching timing of the forward/reverse direction of the ASF motor
rotation. If the ASF motor rotates in the forward direction, the paper stoppers lower to guide the
paper to the paper slot. If it rotates in the reverse direction, the ASF roller rotates to pull in
paper.
• The paper width sensor detects whether the paper width is "A4-size or wider" or "narrower than
A4-size."
• The purge cam HP switch detects whether the purge cam is in the home position or not.
• There are four ink cartridge sensors for four colors, each of which detects whether the
corresponding ink cartridge is ink-empty. When the optical path of the sensor is interrupted by
the sensor actuator built in the ink cartridge, the controller interprets it as ink present. As ink
remaining in the cartridge decreases, the sensor actuator comes out of the optical path and the
controller interprets it as ink empty. These sensors detect also whether ink cartridges are
loaded.
• The hook switch detects whether the handset is on the hook.
• The air pump motor encoder sensor monitors the rpm of the air pump motor (DC motor),
allowing the controller to accelerate or decelerate the motor using PWM control to produce
optimal positive pressure.
Sensor name Type
Photosensor
Photosensor
Mechanical switch
Photosensor
Mechanical switch
Photosensor
Mechanical switch
Photosensor
Photosensor
Photosensor
Thermistor
Thermistor
4 -3 1
Location
Control panel PCB
ASF
Head flat cable of the
needle tube ASSY (set in
the print head unit)
Purge unit
Ink cartridge sensor PCB
Hook switch PCB in the
handset
Air pump & motor module
Head flat cable of the
needle tube ASSY (set in
the carriage)
PF encoder PCB on the left
side of the engine unit
Print head unit