Citizen iDP3240, Service Manual

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iDP3240 SERVICE MANUAL
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1.3.2 Paper-near-end sensor
The paper-near-end sensor detects when the remaining amount of recording paper becomes
small. When the remaining amount of recording paper decreases (about 50 cm to 2 m for
specified recording paper), the outside diameter of the paper roll becomes small with its edge
surface getting out of the range of the sensor. This permits the paper-near-end sensor to detect
that the paper supply has become low. The amount of remaining paper differs with the thickness
of the recording paper and the material of the roll core. Remaining amount cannot be adjusted.
1.4 Print head mechanism
A thermal head is employed as the print head of this printer. The thermal head consists of a heat
generating unit and a head driver to drive and control the thermal head.
1.4.1 Outline of drive control
The serial print data which is input from DATA
IN (DI) is transferred to the shift register in
synchronism with CLOCK (CLK), and then
stored in the latch register by LATCH (LAT)
signal.
When the gates are turned ON by head electric
signals (print command STR1 to 6), power is
applied to the heating elements which
correspond to the print data stored, enabling the
data to be printed on thermal paper by the heat.
Platen roller
Paper-near-end sensor
Recording paper
Thermal head
Feed roller
Heating element
Gate
Latch register
Shift register
Thermistor
Equivalent circuit of thermal head
TH
TH
GND
Vcc
DATA OUT
CLOCK
DATA IN
/LATCH
dot 832 dot 1
STR 1
STR 3
COM
(Vp)