Principles of Operation

Carriage Motor Drive Circuit

The carriage motor drive circuit controls the CR motor. An open loop, constant-current drive arrangement runs the CRmotor. 2-2 and 1-2 phases are used to excite the motor. A 2-2 phase step is equivalent to a 1-2 phase step doubled. Table 6-6 describes the motor drive modes.

The CR motor drive circuit of the SLA7024M (IC6) detects and regulates the amount of current flowing in the carriage motor coil. The current flowing through the coil varies, depending on the speed of the CR motor. The CPU sets the amount of current via the I/O port of the gate array. Signals are sent to the ports (L, M, HOLD) on the SLA7024M. The SLA7024M sets the coil current depending on the CR motor speed.

The printer may stop printing to protect the CR motor from overheating if a continuous printing of short columns (less than 10 columns) is repeated. The printer uses CPU ports P60 to P63 exclusively to control the CR motor.

CPU(IC2Cl)SLA7024M (IC6)

CR MOTOR

 

 

A S S E M B L Y

P60

P61

P62

P63

4-phase, 200-p, HB-type pulse motor

5.4 fi 2 10% (per phase) (at 77” F, 25°C)

Figure 6-27. Carriage Motor Drive Circuit

 

Table 6-6. Carriage Motor Drive Modes

 

 

 

 

 

 

 

 

Speed ModePPSExcitation Phase

 

Characters Printed

 

 

 

 

 

 

 

413

4468

 

 

2-2

 

Super draft

910

3840

 

2-2

 

Super draft copy

1

3357

 

 

2-2

 

Draft 10 cpi

516

2800

 

 

2-2

 

 

2l3

2240

 

 

2-2

 

4/3 high duty

l/2

1680

 

1-2

 

NLQ

5/l 2

1400

 

l-2

 

 

l/4

840

 

l-2

 

 

5124

700

 

l-2

 

5/12 high duty

ua

420

 

I -2

 

l/4 high duty

 

 

 

 

 

 

 

EpsonFX-870/1170

6-27