Sensor Input Circuit - Samsung SCX-4720F Service Manual

Summary of Product

4.3.6 Sensor input circuit

1) Paper Empty Sensor
The Paper Empty sensor (Photo Interrupter) on the SMPS/HVPS PBA (CON2-2) is monitored by the
CPU on signal (nP_EMPTY). When the cassette is empty the printer displays a message on the LCD
panel.
2) MP Sensing
Presence of paper in the MP tray is detected by operation of the MP Sensor (Photo Interrupter) on the
SMPS/HVPS PBA (CON2-14). The CPU monitors signal(MP_EMPTY) to recognize paper in the MP, and
paper is fed from MP if there is paper present.
3) Paper Feed Sensor, (Toner Cartridge Sensor)
When paper passes the actuator on the feed sensor (CON2-1), it is detected by the Photo interrupter. sig-
nal(nP_FEED) monitored by the CPU and this signal starts the process of creating the image after certain
delay time If the feed sensor is not detected within 1 sec. after paper is fed, a paper Jam0 occurs.
(Displayed on the LCD panel).
When a toner cartridge is inserted it also operates the Paper Feed sensor. A message is displayed on the
LCD if no cartridge is detected.
4) Paper Exit Sensor
This detects that paper exits cleanly from the Machine using an exit sensor (CON2-24) on the engine
board and actuator on the frame. The monitors signal (P_EXIT) and detects the on/off time of the exit
sensor and if jam status is detected then JAM2 is displayed the on the LCD panel.
5) Cover Open Senser
The Cover open sensor actuator is located on the front cover and the senor is in the main frame. When the
front cover is opened the +24V supplies to the DC fan, solenoid, main motor, polygon motor part of LSU,
HVPS that are cut off. The CPU monitors signal (COVER_OPEN) to recognize when the cover is opened.
6) DC FAN / SOLENOID Driving
It is driven by a transistor and controlled by signal (FAN (SMPS, CON2-23)) bit of the CPU.
When it is high the fan is activated by turning on the TR, and it is off when the sleep mode is selected.
There are two solenoids and these are driven by the Paper Pick-up and MP signals. The drive time is
300ms. The diode protects the driving TR from the Back-EMF pulse which is generated when the sole-
noid is de-energized.
7) Motor Driving
The motor driving circuit is activated when the Driver IC is enabled. An A3977 (Motor driver IC) is used in
this case. The resistance Rs value of sensing and the voltage value of the V reference can be changed
by the motor driving voltage value.
Service Manual
4-14
Samsung Electronics