Xerox Phaser 3600

Phaser 3600 Printer Service Manual 2-13
Theory of Operation
Sensor Functions
Sensor Types
The types of sensors used vary with function. In general, there are three types
in use:
Photo Sensors
Two types of photo sensors are used, photo-reflective and photo-receptive.
Photo-reflective sensors use light reflected back from an object to detect its
presence. Photo-receptive sensors use an actuator or the object itself to block
the light path to detect an object or condition.
Photo-reflective sensors have the light emitter and light receiver aligned on a
si
ng
le surface. Output of the photo-receptor is High (> +4.5 V) when light is
being reflected back and Low (< +.3 V) when it isn’t.
Photo-receptive sensors consist of a LED in one arm of a U-shaped holder,
and a p
hoto-transistor in the other arm. When the sensing area is vacant,
nothing is between the arms of the sensor, light falls on the photo-receptor
sending the signal High. If the light is interrupted, the photo-transistor goes
Low.
Actuator
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