Epson DFX-8500 Service Manual page 82

The printer has three deceleration control modes. The degree of deceleration is determined by which
carriage motor transistors are on. Table 2-8 describes how the transistors determine the mode.
Carriage Transfer Direction
Left -> Right
Right -> Left


Carriage Motor Pulse Control:
Carriage motor pulse control keeps the carriage motor speed constant using the encoder pulses ENCA and
ENCB with the gate array. The gate array generates the PWM (pulse width modulation) signal according to
the carriage motor speed, then sends the signal to the PWM port of the gate array and determines the duty
of the carriage drive timing. Carriage ports I0, I1, and I2 output the drive signal for the carriage motor.


Acceleration control :
Until the carriage speed reaches a constant speed (set by carriage motor pulse control), acceleration control
determines the speed of the carriage. The printer can print during acceleration. The carriage accelerates
smoothly to prevent the carriage motor from exceeding the constant control speed. The gate array controls
the motor driver (STK681-050), which performs current chopping. Figure 2-21 shows the acceleration
control curve.
Speed 0 - SP1
1. Control circuits cause the carriage to accelerate.
2. The control circuit measures time periods with the encoder signal; when the carriage speed reaches SP1,
the next sequence (SP1 - SP2) begins.
Table 2-8. Carriage Motor Drive Sequence
Driving Mode
Acceleration
Deceleration 1
Deceleration 2
Deceleration 3
Acceleration
Deceleration 1
Deceleration 2
Deceleration 3
OPERATING PRINCIPLES
Motor Transistors
(See Figure 2-19.)
Q1 Q2 Q3
ON
ON
ON ON
ON ON
ON
ON
Q4
ON
ON
ON
ON
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