Fig. 3-11 Developer Monitoring Circuitry - Canon NP-70 Service Manual

NP•70 3-47
3.4-6
DEVELOPER MONITORING CIRCUITRY (ALL COPIERS)
The monitoring of the developer is performed in two way. The first, developer density, is
performed by the A. T. R. circuit and the second, developer level, is performed by mechanical
means (float & microswitch operation).
Fig. 3-11 shows the circuitry associated with both modes of developer monitoring.
+24VDC O
CdS3
MSS
SL6
_~
COMP.
NET.
AMP
Q14
L2
O
+SVDC
A. T. R. CIRCUIT CARD
PL3
MS12
J
Fig. 3-11
Developer Monitoring Circuitry
O OVDC
1) OPERATION — A. T. R. CIRCUIT
The A. T. R. circuit, which constantly monitors the density of the developer liquid, operates
as shown in the flowchart in Fig. 3-12. When the density drops below the correct level due
to copy operations, the illumination of photocell CdS 1 is sufficient to cause the comparator
output (Q13
©)to
change to +24VDC. This change results in the gating of Q14 and, when
the next MSS pulse occurs, the feeding of toner into the Developer Assembly.
© CANON INC. Second PrintingJune, 1974