Xerox Phaser 6360, Service Manual

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2-18 Phaser 6300/6350/6360 Color Laser Printer Service Manual
Theory of Operation
Sensors
The printer contains sensors of various types that perform a variety of
functions. One group of sensors track the progress of the paper along the
paper path, and detects if a paper jam occurs. Other sensors detect the
presence of the Toner Cartridges, stop printer activity if a door is open
(interlock), detect the presence and size of media in the trays, and monitor the
fusing temperature.
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
single 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 photo-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.
Microswitches
Microswitches are used primarily as paper size sensors and cover interlocks.
They are in a normally open state, and close when actuated. A bank of
microswitches is used to detect paper size in the universal trays.
Microswitches also employ hooks or catches for retention in the bracket or
frame.
Thermistors
Thermistors have a known value of resistance whose value varies with
temperature. Used primarily in the Fuser for temperature sensing.