Oil End Sensor - Ricoh FT7770 Service Manual

30
April, '89

Oil End Sensor

4.
- Basic Operation -
The oil end sensor's operation is based on the difference between the refrac-
tive index of air and that of silicone oil. When the sensor is immersed in
oil, the light from the LED bends only slightly at the interface of the oil
and the sensor casing, and almost no light is reflected to the phototransis-
tor. When oil runs out, the light bends more, and most of the light is
reflected to the phototransistor.
- circuit -
The oil end sensor circuit is powered by +15
activates the phototransistor, Tr1 turns on. Then, Tr2 turns off and Tr3 turns
on. The main board then receives a LOW signal at CN201-B7. Upon receiv-
ing this signal the CPU lights the Add Oil indicator, turns the Start key red,
and stops the copier.
volts, when light
2-84
from the LED