Panasonic KX-FL513RU Service Manual page 183

7.11.10. TONER SENSOR.... "TONER EMPTY", "TONER LOW", "CHANGE DRUM"
The Sensor detects whether or not the Drum unit and the toner are present.
When there is not Drum unit, Hall IC (IC60) turns off, and the input signal of IC605-7 pin (Digital P.C.B) becomes a High level
over 9s. When the Developer unit is set, Hall IC (IC60) turns ON/OFF. If the time of IC605-7 pin´s Low level is under 600ms,
there is enough toner in Developer unit, if not, toner is near empty.
Toner Sensor
The rest of toner is detected by the move speed of the magnet put on the pendulum of Mixing Paddle. The pendulum is pushed
up by the Mixing Paddle, then it falls down by its own weight. The rotation speed of paddle is set slower than the one of
pendulum which falls down by its own weight. When the toner is still left, the pendulum falls and stops on the toner, then pushed
by the paddle, it starts to rotate. When no toner is left, the pendulum falls to the bottom. Consequently the contact time between
the magnet and steel becomes short when toner is left and long with no toner.
Toner Set (full)
Near Empty Toner
Mixing Paddle does not rotate
("CHANGE DRUM")
State
CHANGE DRUM
Display
-
TONER LOW
High level fix or Low level fix
183
Signal (IC605-7pin)
Low level = about 0.3s
Low level>0.6s
KX-FL513RU