Kodak 700, 630, 500 service manual Theory of Operation

NovaJet 500/630/700 Series Service Manual

Each circuit contains four main functions (see Figure 2-7):

1.Reference waveform generator

The microprocessor uses a D/A (digital to analog) converter to set the desired level for the current in the stepper motor winding. The output of the D/A converter varies in time to create a reference waveform. This reference waveform is centered around 10V.

2.Motor current sense

The voltage across a series current sense resistor is measured and level shifted so that it is centered around 5V.

3.Comparator

This portion divides the output of the reference waveform generator by two and compares it to the output of the motor current sensor. Logic inside the gate array generates the control signals for the power driver that applies voltage across the motor winding in order to make the actual current match the reference waveform.

4.Power driver

An H-bridge allows the supply voltage to be applied across the winding in either polarity used to drive the current level to the desired value.

THEORY OF OPERATION

Theory of Operation 2-11