Stepper Motor Controller - ENCAD 60e Service Manual

Novajet PROe Series Service Manual
Serial EEPROM
Serial EEPROM is an Electrically Erasable, Programmable, Read
Only Memory which provides storage for calibration constants and
user configuration data entered from the host computer.
An 8K bit serial non-volatile EEPROM stores calibration and con-
figuration information. It retains data while the unit is off.

Stepper Motor Controller

The media is driven by a Stepper Motor, which drives the media in a
direction perpendicular to the width of the printer. The media in the
printer can advance forward and backward, depending upon the
commands which the Stepper Motor receives from the microproces-
sor.
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.
A waveform generator receives digital data from the CPU and
generates a sine wave output. This signal is fed into a comparator
circuit that is measuring the current through the winding of the
stepper motor. If the current is too low, a pulse of 24V is generated.
When the current goes above the output of the waveform generator,
the pulse turns off. Every time the output of the waveform genera-
tor is changed by the microprocessor, the motor moves 1 "micro-
step".
34 Theory of Operation
Figure 2-7. Stepper Motor Controller.