Star Micronics TSP400 Feed-Motor Drive Circuit, Motor Control by Phase 1-2 Excitation

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

ON

ON

2

ON

3

ON

4

ON

Step

1 2 3 4 5 6 7 8

Forward Feed

Reverse Feed

Fig. 2-8 Motor Control by Phase 1-2 Excitation

IC5

CPU

PA4

	+24V	+5V CN4
DQ2		D1
		1
		2
B		Q2
	TA1	3

Paper-feed motor

PA0

PA2

4

1

3

M

PA3

PA1

5

6

E

M-GND

2 4

Fig. 2-9 Feed-Motor Drive Circuit

Voltage to the motor is controlled to produced the required action, as follows.

Mode	Voltage	Action
Operating	VM (+24V)	Drives the motor
	VL (+5V)
Idle	VL (+5V)	Holds the motor

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.

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