Tally Dascom 7010, Maintenance Manual

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2-2. Operation of Control Parts
2-24
Thus, the phototransistor conducts and the voltage corresponding to the amount of light
received is applied to the analog input (pin 6 (SENSMOVE)) of U1 (CPU) via OP amp. U20B.
The CPU senses this voltage and judges that the light is passing through media, namely, the
liner part without label is now passing through the sensors.
When the label part arrives at the sensors, the light is blocked by the label and does not reach
the phototransistor. So, the phototransistor turns OFF and pin 6 (SENSMOVE) of U1 (CPU)
goes from “High” to "Low". From this level change, the CPU can detect the leading edge
(arrival) of the label on the liner.
If media runs out, the light directly falls on the phototransistor and the phototransistor
continuously turns ON. From this, media end is detected.
The above principle applies when media with U-shaped notch is used. In this case, since the
light directly falls the phototransistor, the current flowing into the LED (the amount of light
emitted) is appropriately set for detecting the U-shaped notch.
Reflective sensor (used for detecting the black mark on tag):
The reflective sensor alone is used (media sensor menu: Reflect). In this case, pin 100
(LEDMOVE_R) goes “High”, Q27 and Q8 turn ON and the LED of the reflective sensor turns
ON. The current flowing into the LED (the light amount to be emitted) for detecting black mark
is determined by U4 (D/A converter), U5B and Q10 under the control of the U1 (CPU) and U14
(Custom IC).
When tag with black marks is used, light emitted from the LED is reflected by the tag and
reaches the phototransistor. At the place where no black mark exists, the phototransistor
receives the reflected light and conducts. So, the voltage corresponding to the amount of light
received is applied to the analog input (pin 6 (SENSMOVE)) of U1 (CPU) via U20B. When the
light falls on the black mark, no light is reflected, the phototransistor turns OFF, and pin 6 of U1
(CPU) goes “Low”.
When media runs out, the light is not reflected by media any more and the phototransistor
continuously turns OFF. From this, media end is detected.