Of 99-2 Transmissive Sensor - Xerox DocuColor 2240 Service Manual

OF 99-2 Transmissive Sensor

Sensors consist of a light-emitting diode and a photo transistor. When energized, the light from
the LED causes the photo transistor to conduct, drawing current through a pull-up resistor. The
voltage drop across the resistor causes the input signal to the control logic to change from a
high to a low.
Transmissive sensors have a flag or actuator that is pushed into the space between the LED
and transistor, blocking the light beam and causing the output of the sensor to go to the high
(H) state. This actuation may be caused by a sheet of paper striking a pivoting flag, or a rotat-
ing actuator on a shaft or roll.
Some sensors have built-in inverters and the outputs will go to the low (L) state when the sen-
sors are blocked. In other situations, the processing of the signal in control logic may cause the
logic level displayed on the UI or the PWS to be the opposite of the actual voltage output by the
sensor. The specific RAP and/or Circuit Diagram will indicate if this is the case.
example of a typical sensor circuit for this machine
Procedure
Enter the component control code indicated in the specific RAP and/or Circuit Diagram. Block
and unblock the sensor. The display changes with each actuation.
Y N
Clean the sensor and then block and unblock it. The display changes with each actua-
tion.
Y N
Access to some sensors in this machine is difficult. Follow the Y leg if you can
access the sensor connector. Follow the N leg if access is not possible. The sensor
connector is accessible.
Y N
Check for +5VDC at the output of the PWB or power supply. Refer to the Circuit
Diagram. In the example for this generic procedure
vided from J533 on the I/F PWB. Check for pull-up voltage for the output signal.
This voltage will be either +5 VDC or +3.3 VDC, depending on the circuit. Refer
to the circuit diagram for the correct voltage.
Y N
Check for short circuit(s) that may be loading down the line. Check the
power input to the PWB(s). If this does not resolve the problem, replace
the PWB.
Refer to the Circuit Diagram. Check the wires from the PWB to the sensor for
opens, shorts, or loose contacts. If the wires are OK, replace the sensor. If this
does not resolve the problem, replace the PWB
The display indicates a constant L
Y N
Check for +5VDC to the sensor (typically pins 1 and 3 on a 3 pin connec-
tor). +5 VDC is present.
Y N
Use the circuit diagram and /or the wirenets in Section 7 to trace the prob-
lem.
A B C D
Status Indicator RAPs
OF 99-2
A B C
Disconnect the sensor. The display indicates H.
Y
Figure 1 is an
The sensor is shorted. Replace the sensor.
Look for unusual sources of contamination.
The sensor and the circuit appear to operate normally. Check the adjustment of the sensor.
Clean the sensor. Check the sensor actuator/flag for proper operation. Check for intermittent
connections, shorted, or open wires. If the problem continues, replace the sensor.
(Figure 1), voltage is pro-
Figure 1 OF 99-2 RAP Circuit Diagram - Typical Transmissive Sensor
02/03
2-516
D
Disconnect the sensor. Use a jumper wire to connect the output wire from the
sensor (typically pin 2 on a 3 pin connector) to DC COM or GND. The display
changes from H to L.
Y N
There is either an open circuit or a failed PWB. Use the Circuit Diagram to
trace the output wire to the PWB. If the wire is OK, replace the PWB.
Replace the sensor.
N
When sensors are unplugged, the input at the PWB should always be high if
there is no harness short or PWB failure. Check the output wire from the sensor
(typically pin 2 on a 3 pin connector) to the PWB for a short circuit. If the wire is
good, replace the PWB. Figure 1 represents a typical sensor for this machine
Initial issue
DC 3535/2240/1632