Kodak 630, 500, 700 service manual Servo Motor Controller

NovaJet 500/630/700 Series Service Manual

Servo Motor Controller

			MOTOR			SERVO	SERVO
	GATE		DRIVER	CONNECTOR			MOTOR
ARRAY
					CARRIAGE
				CONNECTOR
		MAIN PWA

ENCODER

CARRIAGE

Figure 2-8. Servo Motor Controller.

The Carriage Assembly is driven by the Servo Motor. The speed of the Carriage Assembly is controlled by varying the duty cycle of the signal applied to the controller. The microprocessor checks the position of the Carriage Assembly approximately 1,000 times per second (during the servo interrupt). It then updates the PWM (pulse width modulator) register in the gate array which sets the duty cycle to make adjust- ments to the Carriage Assembly speed. A linear optical encoder is used to monitor the Carriage Assembly position.

The optical encoder strip runs the length of the Stabilizer Bracket and contains 150 lines and spaces per inch. Thus there are 300 edges per inch. The detector circuit actually consists of two optical edge detectors. They are separated from each other by one half the width of one of the optical lines on the encoder strip. This allows 4 evenly spaced pulses to be developed for each line on the encoder strip. This is known as quadra- ture signals. It gives an effective resolution of 600 lines per inch. See figure 2-9 for a graphical representation of quadrature signals. For 300 dpi resolution, one of the detectors is not used.

2-12 Theory of Operation