Toner Density And Toner Empty Circuits - Printronix L5535 Maintenance Manual

Toner Density And Toner Empty Circuits

The toner density control circuit regulates the supply of toner to the printer. A
separate toner empty detection circuit signals the operator when the toner
level becomes too low.
Toner Density Control Circuit
The following items together form a feedback control system that monitors
and adjusts the amount of toner in the hopper:
•
The toner in the hopper
•
The toner density sensor
•
The toner supply clutch and roller
•
The associated control electronics (MC board and controller)
When the toner density in the vicinity of the toner density sensor drops below
11%, the output signal (TDSD) from the toner density sensor goes low, and
the MC board gate array asserts the toner supply clutch drive signal (TSMO),
causing the toner supply clutch to engage for 1 second.
The controller can also engage the toner supply clutch independent of the
toner density sensor. When the printer is offline, if the controller issues a
command to supply toner, then the gate array asserts the toner supply clutch
drive signal (TSMO), causing the toner supply clutch to engage for 1 second.
Further, the controller can adjust the toner monitoring cycle by issuing a
command to the MC board to set the toner density monitoring cycle. This
command contains a full dot count value, which is a number from 0 through
250 that represents the number of LEDs illuminated from one density
sampling to the next. (If the dot count value does not reach the set value after
9 seconds, monitoring begins at 9 second intervals.)
Toner Empty Detection Circuit
The toner empty sensor generates an AC signal (TESI) which it sends to the
MC board. The amplitude of this signal is inversely proportional to the amount
of toner remaining in the hopper: more toner makes the signal weaker; less
makes it stronger. On the MC board, this signal is rectified, then converted to
a digital signal, before being sent to the gate array. When the numeric value
of this signal rises above a predetermined threshold, corresponding to a low
toner level, the MC board reports a "toner empty" condition to the controller.
Toner Density And Toner Empty Circuits
II–183