Sensor Functions; Paper Empty Sensor; Tray 1 Paper Empty Sensor; Registration Sensor - Xerox Phaser 3500 Service Manual

Theory of Operation

Sensor Functions

Paper Empty Sensor

Media supply is monitored by the Paper Empty Sensor. When a tray runs out of paper, the
sensor will send a signal to the Main Board, the control panel LED will blink orange, and the
"No Paper in Tray {2|3}" message will display on the control panel.

Tray 1 Paper Empty Sensor

The Tray 1 paper empty sensors monitors paper from Tray 1. If Tray 1 is selected and there is
not paper, a message appears on the control panel. If there is no paper in Tray 2 or Tray 3 and
the printer is in auto-select mode, the printer will look for paper in all the trays and report "No
Paper in Tray 1".

Registration Sensor

The Registration Sensor has two purposes. First, it is used to monitor paper movement. If the
paper takes too long getting to the sensor, or it stays at the sensor location too long, the Main
Board will shut down the machine, the control panel LED will blink orange, and a "Jam" error
message will display on the control panel.
Second, the signal generated by the sensor tells the Main Board that the paper is almost at the
transfer area and it is time to start the xerographic process. It is important that the leading edge
of the paper enters the transfer area at the same time as the leading edge of the developed
image on the drum.

Fuser Exit Sensor

The Exit Sensor monitors paper exit and detects the "Jam at Exit" error if the paper takes too
long getting to the sensor, or it stays at the sensor too long. At this point the Main Board will
shut down the printer, the Control Panel LED will blink red, and a "Jam at Exit" error message
will display on the Control Panel. The signal from the Exit Sensor is also used to control paper
feed to the Duplex Unit for duplex print jobs.

Cover Open Sensor

The cover open sensor detects whether the top cover is open or closed. When the top cover is
open the "Close Top Cover" message is displayed on the Control Panel.

Duplex Unit Sensor

The Duplex Unit slides into the rear of the printer above Tray 2. As paper leaves the Fuser
Assembly and is picked up by the Exit Rollers, the drive direction is reversed to send the paper
down to the Duplex Unit. As the paper leaves the Duplex Unit, it activates the Duplex Sensor.
This activates the feed roller to position the paper for printing on the front side of the paper.
Phaser® 3500 Laser Printer Service Manual
8-8