Toner Empty Detect Circuit - Toshiba DP120F Service Manual

3.7 Toner Empty Detect Circuit

The toner empty detect circuit consists of the PTC GA (IC45), A/D converter (IC54), I/OP-2 GA
(IC48), and its peripheral devices. It detects the amount of toner according to the output signal
of the toner empty sensor installed on the developer assembly.
The I/OP-2 GA causes the TONEREN signal to be HIGH to turn on Q8. This allows a +5V
power supply to be delivered to the toner empty sensor to turn on the sensor which then starts
detection of the amount of toner.
The TES signal output from the toner empty sensor changes in voltage according to the amount
of toner. The voltage increases when the toner is large in amount, and decreases when it is
small in amount. The amount of toner is detected by observing the change in voltage. The
TES signal is amplified by the OP amplifier (IC55) and applied to the A/D converter as a TONERH
signal. The A/D converter converts the TONERH signal to a digital value and outputs it to the
PTC GA. The input digital value is compared with the reference value by the software process.
A digital value lower than the reference value will be judged to be a toner near empty. When the
count by which the toner near empty exceeds a fixed count after this detect operation is re-
peated several times, toner empty will be assumed.
Being a piezo-electric element, the toner empty sensor produces noise during operation. If
much noise is produced, the remaining amount of toner cannot be detected accurately. To
restrain the occurrence of noise, the I/OP-2 GA periodically causes the TONEREN signal to be
LOW to turn off the piezo-electric element.
Signal Name Type
TONEREN O
TES I
TONERH I
DP120F/DP125F Circuit Description
Fig. 7-3-7
Active
H Toner Empty Detect Start Signal
- Toner Empty Detect Signal
- Toner Empty Detect Amplify Signal
Description
7-40
07-03-07
Destination
Toner empty
sensor
IC55
A/D converter
March 2000 © TOSHIBA TEC