Feed-Motor Drive Circuit - Star Micronics TSP400 Series Technical Manual

THEORY OF OPERATION

2-3. Feed-Motor Drive Circuit

The printer employs a 4-phase step motor (phase 1-2 excitation) to implement paper feed. The motor rotates through a
certain angle each time it receives a pulse from the drive circuit. The following diagram illustrates the phase 1-2 excitation
method. Diagram 2-8 shows the feed-motor drive circuit.
1
2
3
4
Step
1
IC5
CPU
PA4
PA0
PA2
PA3
PA1
Voltage to the motor is controlled to produced the required action, as follows.
Voltage is controlled by PA4 of the CPU, which goes HIGH or LOW to switch transistors DQ2 and Q2 ON or OFF. When
Q2 is ON, the motor receives +24V (VM). When Q2 is OFF, +5V is supplied to the motor via diode D1.
ON
ON
2 3 4 5
Reverse Feed
Fig. 2-8 Motor Control by Phase 1-2 Excitation
DQ2
Fig. 2-9 Feed-Motor Drive Circuit
Mode
Operating VM (+24V)
VL (+5V)
Idle VL (+5V)
ON
ON
6 7 8
Forward Feed
+24V +5V CN4
D1
1
2
Q2
B
TA1 3
4
5
6
E
M-GND
Voltage Action
Drives the motor
Holds the motor
– 26 –
ON
Paper-feed motor
1
M
3
2 4