Integra CROMA24 service manual Stepper Motor Controller

Croma24 Service Manual

Stepper Motor Controller

Figure 2-6. Stepper Motor Controller.

The media is driven by a Stepper Motor, which drives the media in a direction perpendicular to the length of the printer. The media in the printer can advance forward and backward, depending upon the commands which the Stepper Motor receives from the micro- processor.

The Stepper Motor Controller contains two identical circuits, one for each winding of the stepper motor. The circuit is a combination of two simpler types of circuits and can be thought of as a variation of either one.

Adigital-to-analog (D/A) converter receives digital data from the CPU and generates a sine wave output. This signal is fed into a comparator circuit that measures the current through the winding of the stepper motor. If the current is too low, a pulse of 24 V is generated. When the current goes above the output of the wave- form generator, the pulse turns off. Every time the output of the waveform generator is changed by the microprocessor, the motor moves 1 “micro-step”.

Each circuit contains four main blocks (see Figure 2-6):

1. Reference waveform generator

THEORY OF OPERATION

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 10 V.

Theory of Operation 33