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BJC-6000
5.1.4 Ink sensor
Consists of an LED and photosensor to optically check for ink in the ink chamber part
of the ink tank. At the ink chamber bottom is a protrusion that acts as a prism. If
ink is present in the chamber, the refraction rates of ink and the prism resin are
nearly equal, producing less reflection. If there little ink left, the difference in
refraction rate between the ink and the resin increases so that more incident light to
the sensor will be reflected, thus increasing the intensity of reflected light. The printer
decides whether there is any ink in the ink chamber or not based on the difference in
the amount of reflection. The MPU, then, detects the voltage varying with reflection,
and the the A/D converter converts this analog voltage to a digital value. When the
printer decides that there is no ink left in the ink chamber, it generates a message on
the status monitor telling that ink is running low in the relevant ink chamber. After
the printer has decided that no ink is left, it starts counting the number of dots
equivalent to the amount of ink absorbed in the sponge (20% of the ink) to detect
"ink-out."
This detection takes place when the power is on, the front cover is closed, after
pumping operations are completed, or after a specified number of dots have been
printed. Do not open the front cover while measurement is going on, as external light
can make accurate measurement impossible. Note that ink tank presence cannot be
detected. If no ink tank is installed, the printer will determine that ink is present.
Refracted Light
Incident Light
Photo-transistor
5.1.5 Cover sensor
Detects whether the front cover is open or closed. If the printer detects the cover is
open, the carriage is moved to the replacement position.
5.1.6 Pump sensor
Switch-type sensor that detects the rotational position of the tube type pump. The
printer controls the pumping operation based on the detected rotational position of
the pump.
5.1.7 Printer temperature sensor (TH201)
Located on the control board, this sensor detects the temperature inside the printer to
control the print head drive. The thermistor resistance varying with the temperature
inside the printer is detected by the MPU as a varying voltage, so the incoming analog
values are converted into digital values by the built-in A/D converter.
Ink
Incident
Reflected
Light
Light
Photo-transistor
Ink Sensor
Ink Present
Figure 4-36 Ink Sensor
Ink Chamber
Air
Reflected Light
Ink Sensor
(Full Reflection)
No Ink
4-43
Part 4: Technical Reference
Prism
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