Adjustable Sensor - Citizen CL-S400DT Technical Manual

Chapter 2 Operating Principles
2-2. Operation of Control Parts

(2) Adjustable sensor

The upper sensor (SA Adjust Sensor U) is a phototransistor and the lower sensor (SA Adjust
Sensor L) is a reflective type photointerrupter, and media passes between upper and lower
sensors.
To use the adjustable sensor as a transparent sensor, both phototransistor of the upper sensor
and the light emitter of the lower sensor are used. Meanwhile, when the adjustable sensor is
used as a reflective sensor, the lower sensor is used.
Transparent sensor (for label detection and U-shape notch detection of tag):
When label media is used, in the liner area where no label is stuck, the light emitted from the
light emitter of the lower sensor passes through the liner and reaches the phototransistor of the
upper sensor. Thus, the phototransistor conducts and the voltage corresponding to the amount
of light received is input to pin 5 (TRAMON) of CPU (U1A).
In the label area (consisting of both liner and label), the amount of light that can pass through
the label area becomes relatively small.
Since the voltage input at pin 5 (TRAMON) of CPU (U1A) varies according to the position (liner
area or label area), CPU (U1A) can detect the leading edge (arrival) of the label that is stuck
on liner. When media runs out, as the light directly falls on the phototransistor, media end can
be detected. In this case, pin 5 (TRAMON) of CPU (U1A) will go "High" level.
The voltage input at pin 5 (TRAMON) can vary with the characteristics of a phototransistor to
be used and with other factors. To solve this problem, FPGA (U11) outputs TSNSCTL0 (pin
R13) and TSNSCTL1 (pin R14) signals to turn ON/OFF (connect/disconnect) R85 and R86
(voltage dividing resistors) to minimize the difference in level at pin 5 (TRAMON).
The current flowing into the light emitter is determined by the data sent from the CPU to the
digital-to-analog converter (U4). The digital-to-analog converter (U4) converts the data
received from the CPU and outputs resultant level at pin 2. Since the base current of transistor
Q7 is determined by this level, the current flowing into the light emitter is also determined by
this level. In the actual control, the CPU changes data (current flowing into the light emitter) to
keep the level at pin 5 (TRAMON) of the CPU constant.
The same principle applies to detecting the U-shape notches of tag. However, in this case,
since the light emitted from the light emitter is blocked by the tag or passes through the
U-shaped notch, the voltage at pin 5 (TRAMON) will be "Low" or "High".
Reflective sensor (for black mark detection of tag):
When tag with black marks is used, in a place where no black mark is there, the light emitted
from the light emitter of the lower sensor is reflected and reaches the photodetector of the
lower sensor. Then, the photodetector conducts and the voltage corresponding to the amount
of light is input to pin 6 (REFMON1) of CPU (U1A).
When the light falls on the black mark, no light is reflected by the black mark, the photodetector
turns OFF, and pin 6 (REFMON1) of CPU (U1A) goes "Low".
When media runs out, the light is not also reflected and pin 6 (REFMON1) of CPU goes "Low".
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CL-S400DT