Sensor Input Circuit - Dell 1600n - Multifunction Laser Printer B/W Service Manual

4.3.4 Sensor input circuit

1) Paper Empty Sensor
The Paper empty sensor (Photo Interrupter) on the engine board informs the CPU as to whether
the cassette is empty or not with operation of the actuator.
When the cassette is empty, it detects the fact by reading the D0 Bit of CPU. It highlights this by
selecting the second LED(yellow) among the panel LEDs.
2) MP Sensing
The MP Sensor (Photo Interrupter) on the engine board informs the CPU as to whether the MP is
empty or not. It reads the D0 Bit of CPU to recognize paper in MP, and the paper is fed from MP if
present.
3) Paper Feeding
When paper passes the actuator (feed sensor part), it detects the signal of Photo interrupter,
informs the paper feeding state to the CPU, and then sends the image data after a certain time. If it
doesn't detect the feed sensor within 1 sec. after paper is fed, paper Jam0 occurs (Red and Yellow
will be turned on among the OP panel LEDs), and whether the developer is inserted or not is
detected with the same principle. After the developer is mounted, the actuator is operated. The sig-
nal from the photo interrupter is detected when it is passing the actuator of the sensor part. That
process is called developer ID sensing.
4) Paper Exit Sensing
The system detects the paper going out of the set with the exit sensor assembled to the actuator
attached to the frame. Paper detects the on/off time of exit sensor, and the normal operation or jam
information is passed to the CPU.
The paper JAM2 is informed.
5) Cover Open Sensing
The Cover open sensor is located on the front cover. After the front cover is opened, +24V (DC fan,
solenoid, main motor, polygon motor part of LSU, HVPS), which is supplied to the each unit, is cut off.
The cover-open sensing is operated by the D0 bit of CPU, and the developer ID sensing is operated.
6) DC FAN / SOLENOID Driving
It is driven by transistor and controlled by D6 bit of CPU.
When it is high, the fan is driven by turning on the TR, and it is off when the sleep mode is select-
ed. There are two solenoids, and they are driven by the paper pick-up and MP signal. Its drive time
is 300ms. The diode protects the driving TR from the noise pulse, which is emitted when the sole-
noid is de-energizing.
7) Motor Driving
The motor driving circuit is formed when the Driver IC is selected. The 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.
Summary of Product
Service Manual
4-13