Canon NP6012 Service Manual page 118

C. Detecting an Original
1. Outline
The ADF's original detection mechanism
has the following two functions:
1. Detecting the Presence/Absence of an
Original
Checks whether there is an original on
the original tray.
2. Sdentifying the Length of the Original
'Checks the length of the original placed
on the original tray.
2. Detecting the Presence/Absence of an
Original
The original placement sensor (PI3) is
used to check the presence/absence of an
original.
When an original is placed on the origi-
nal tray, the original placement sensor (PI3)
sends the original detection signal (PDP3) to
the ADF controller PCB in response to the
movement of the detecting lever away from
the sensor.
y_ Original tray
Detecting lever
PI3
Original detection signal (PDP3)
ADF controller PCB
Figure 3-706
3. Identifying the Length of the Original
The registration paper sensor (PI2) is
used to identify the length of the original, if
any.
The ADF controller computes the length
of the original based on the time it takes for
the original to move past the registration
paper sensor (P12).
Using the result of the computation, the
ADF controller determines whether the size
of the original is A4/LTR or smaller or LGL,
thereby switching to the appropriate ADF
operation.
Table 3-701 shows the lengths of origi-
COPYRIGHT © 1995 CANONINC.
CANON NP8O12/NP6O12 / NP6212 REV.1 SEPT. 1995 PRINTED IN JAPAN (IMPRIME AU JAPON)
OPERATIONS AND TIMING i
nals that determines ADF operation
sequence.
ml Original
PIS riginal tray
ADF controiler PCB
Figure 3-707
Original Lengths and Operation Sequences
Sequence
For A4/LTR originals
For LGL originals
Table 3-701
3-73