Ricoh FW830 Service Manual page 40

31 December 1992
4.4.1 Image Density Sensor
5.0
4.0
3.0
Voltage
(V)
2.0
1.0
0.5
Weak
Toner density is detected by develop-
ing the sensor pattern and by check-
ing its reflectivity with the image
density sensor (photosensor). Light
from the sensor's LED reflects from
the drum and activates the phototran-
sistor. The output of the phototransis-
tor goes to CN102-12 of the main
board.
An average reference voltage (Vsg) is
calculated from eight samples of bare
drum reflectivity. After that, an aver-
age voltage is calculated from eight
samples of sensor pattern reflectivity.
These two values are then compared
to determine whether toner should be
added or not as follows.
No toner supply condition:
Toner supply condition:
The ID sensor checks toner density every 1220 mm. If Vsp/Vsg becomes
greater than 0.125 (1/8), then it starts checking toner density every 610 mm.
LED Light Intensity
VSG
4.0 + _ 0.2V
Thres-
hold
Level
0
Standard Intensity
Strong
ID Sensor [S2]
Vsp/Vsg < 0.125
Vsp/Vsg > 0.125
2-21
DEVELOPMENT
VSP
Main PCB [PCB1]
+5V
CN102
2 -14
CPU
3 -12
5
1 -15
Toner is
supplied
No toner
is supplied.
+24 V
CN104
-B10
SOL 1