Paper Detection Circuit; Cover Open Detection; Paper Empty Detection; Paper Feeding - Ricoh B174 Service Documentation

ENGINE CONTROLLER

6.5.2 PAPER DETECTION CIRCUIT

1) Cover Open Detection

The cover open sensor is on the right rear side of the printer. If the right cover is
open, it stops the +5V (LSU laser unit) and +24V (main motor, polygon motor, fixer
LSU and HVPS) that are supplied to each unit. When the CPU detects that the
cover is open, the red LED on the operation panel will turn on.

2) Paper Empty Detection

The paper empty sensor (photo interrupter), at the bottom of the cassette detects
paper with the actuator connected to it and tells the CPU if there is paper. When
there is no paper in the cassette, the red LED on the operation panel will turn on to
tell the user to fill the cassette with paper.

3) Paper Feeding

When the paper is fed into the unit and goes past the actuator of the feed sensor
unit, the transistor inside the photo interrupter will turn on, the 'nFEED' signal will
turn low and tell the CPU that paper is fed into the machine. The CPU detects this
signal and writes video data to the OPC after a set time (related to the paper size
setting). If the paper does not get to the feed sensor within a set time, the CPU
detects this as "Paper Jam0" (the red LED on the operation panel will turn on).

4) Paper Exit Detection

The system detects paper going out of the unit with the exit sensor and the
actuator attached to the frame. If the CPU input does not turn back high a set time
after the paper hits the exit sensor, the CPU detects this as "Paper Jam2" (the red
LED on the operation panel will turn on).
B174 6-6 SM