Motor Driver Circuit; 1 ] Stepping Motor Driver Circuit - Brother PT-530 Service Manual

3.2.7

Motor Driver Circuit

[ 1 ] Stepping motor driver circuit

Figure 3.2-9 shows a driver circuit of the stepping motor which feeds tapes and ink ribbon. This
circuit drives the motor with a bipolar 2-2 phase excitation. The motor is a 30-mm in diameter and
has 24 poles with the exciting coils whose internal resistance is 108Ω each.
The CPU controls the motor rotation direction with the signals on P74 (pin 26) and P75 (pin 25)
and turns on/off the motor with an activation signal of transistor array (TA7774F, #7) on P104 (pin
92). When P104 is High, the motor rotates in the direction defined by the signals on P74 and P75.
(1) Printing in a constant speed
For regular printing in a constant speed, the CPU drives the motor at the rate of 144 pps. To
provide buffered starting and stopping for the motor, the gradual acceleration and deceleration are
programmed to consume 8 and 3 pulses, respectively.
To rewind the tape of the color print cassette in color printing, the CPU drives the motor in the
reverse direction at the rate of 182 pps.
(2) Print halt for saving tapes or at print buffer full
After completion of the current printing, the CPU brakes the motor with 3-pulse gradual
deceleration and then counter-drives it by 20 pulses to stop the motor.
Figure 3.2-9 Stepping Motor Driver Circuit
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