Mechanical Control Block; Head Control Block; Ic-Tag Control Block - Sony UP-55MD Service Manual

5-2-5. Mechanical Control Block

*
The drive circuit (MEC-24 board) of a motor that drives a
mechanism is connected to the DC motor and stepping
motor control ports of a printer-dedicated circuit (IC301),
and mechanical sensors (sensor boards) are connected to
the A/D and general-purpose I/O ports of a printer-
dedicated circuit, using connectors (CN802 and CN803) on
the MEC-24 board, respectively. Mechanical control is
done when SOC (IC103) controls these ports. A stepping
motor is controlled (ON/OFF) by changing the reference
voltage of a motor drive circuit. A voltage is changed by
switching transistor Q701 from the general-purpose port of
a printer-dedicated circuit (IC301) and switching the
voltage that is voltage-divided using R736 to R738.
A level conversion of 3.3 V and 5 V is required because a
mechanical drive circuit including a sensor circuit uses 5
V. For the output of a motor control port, a pull-up resistor
is connected to 5 V because of its open drain, and the
sensor signal connected to a general-purpose port is sent
through a buffer (IC803). The dynamic range of an A/D
port is 2.5 V. The sensor connected to this A/D port is the
open collector of the phototransistor combined with a
photodiode. A pull-up resistor is connected to 2.5 V by A/
D input. Refer to the outline of the MEC-24 board and
sensor boards (5-5. Mechanical Control Block) for the
operation of each motor and sensor.
(*) Reference No. of motor driver circuit
Stepping motor: IC207
DC motor (ribbon): IC202, IC203
DC motor (head): IC204, IC206

5-2-6. Head Control Block

The thermal head control port of a printer-dedicated circuit
(IC301) can output data (20 ports), a clock signal, a latch
signal, and a strobe signal. A 2560-element head (20 ports
x 128 elements) is controlled by these control signals. To
correctly reproduce print density, a temperature is detected
from two types of thermisters for the calculation of print
data correction.
Thermal head temperature detection
The voltage that was voltage-divided by the thermister and
fixed resistors (R705, R706, and R707) installed in a
thermal head is input to the A/D pin of a printer-dedicated
circuit so as to detect a temperature.
5-8
In-printer temperature detection
Similarly, the voltage that was voltage-divided by
thermister TH131 and fixed resistors (R720, R721, and
R722) on the SE-754 board is input to the A/D pin of a
printer-dedicated circuit so as to detect a temperature.
The voltage supplied to a thermal head can be changed
according to the mean resistance value of the thermal head.
The head voltage control terminal (CN201, 3-pin) of a
switching regulator is controlled from the D/A pin (pin 90)
of a printer-dedicated circuit. A head voltage can be
changed from 24 V to 37 V corresponding to 1 V to 3 V of
a voltage control terminal. When this terminal is set to 0
V, the head voltage output is turned off and set to 0 V. For
an abnormal temperature (high or low temperatures), the
head voltage is controlled (turned off) by software.
However, the head voltage is also controlled (turned off)
by hardware for an abnormal temperature at which the
detection voltage (temperature) of the thermister described
above is input to a comparator (IC702).

5-2-7. IC-TAG Control Block

IC-tag is an IC chip installed in print media. It stores the
information on the remaining amount of an ink ribbon.
This information is sent to this unit via the CCM-53 board
when print media is set to a printer. The presence of an ink
ribbon is judged by whether information is obtained during
communication with IC-tag. An IC-tag control circuit
(IC401) is mounted on the CCM-53 board. The control
signal line of this circuit is connected to the general-
purpose I/O port of a printer-dedicated circuit (IC301)
through the connector (CN301) on the MA-142 board.
UP-55MD