Brother DCP375CW Service Manual page 127

• The carriage motor (CR) encoder sensor monitors the current position and speed of the head/
carriage unit. If the controller detects a head's travel speed error, it interprets the error state as
a paper jam or any foreign material getting into the carriage travel path and stops the
operation.
• The paper feed motor (PF) encoder sensor monitors the PF roller rotation angle and speed for
use in optimizing paper feed amount and speed.
• The Auto Sheet Feeder motor (ASF) encoder sensor monitors the rotation angle and speed of
the ASF motor shaft for use in optimizing paper pull-in amount and speed.
• The purge cam switch detects the drive positions of the purge cam.
• The cap lift cam switch detects the drive positions of the cap lift cam.
• The casing internal temperature thermistor monitors the temperature inside the machine. With
this thermistor signal, the controller determines the periodical automatic purge interval since
the casing internal temperature is almost equal to the ambient temperature of ink inside the
ink cartridges.
• There are four ink empty sensors, one for each color. The sensor actuator inside the ink
cartridge usually blocks the light path to indicate the presence of ink. When ink runs low
(near-empty state), the arm moves out of the beam, activating the sensor. The "Ink low"
message appears.
• There are four ink cartridge detection sensors, one for each color. The sensor detects whether
an ink cartridge is loaded.
• The hook switch* detects whether the handset is on the handset mount.
handset)
Most sensors are photointerrupters consisting of a light-emitting diode and a light-sensitive
transistor as shown below. The only exception is the paper width sensor, which uses reflective
type. The illustration on the next page gives the sensor and actuator locations.
The scanner cover sensor and the ink cartridge cover sensor use a carbon switch that consists of
a carbon on the rubber keypad and a carbon contact printed on the control panel PCB. Opening
the scanner cover or the ink cartridge cover releases the corresponding sensor actuator so that
the actuator is pressed against the rubber keypad by the spring force. Accordingly, the carbon
on the rubber keypad comes into contact with the carbon contact on the control panel PCB. The
conduction results in a voltage level change of the IC port, signaling the cover open.
Actuator's end
Light-emitting Light-sensitive
diode transistor
3-42
(*For models with
Confidential