Abbott VP 2000 Service Manual page 61

Section 3
Abbott VP 2000™ Processor Service Manual
30-608308/R1—September 2008
Hardware-Software Interfaces
Stepper Motors (X-Direction and Rotation):
The stepper motors are controlled by a parallel output port
from the computer fed through some high-current drivers. To
make a stepper motor turn, its windings must be energized in
the correct order at the correct rate. This is all done in the
interrupt handler. The motors and direction to energize are
determined during the state and event part of the program.
AC Motor:
A 120 VAC reversible motor is used for the up/down direction
to get the required amount of torque and speed. This motor is
controlled by a parallel port from the computer fed to a 120
VAC triac.
Audible Feedback"
The "beeper" is a solid state device driven by a 5 VDC output
from the computer.
Dryer:
The dryer fan is controlled by another triac driven by an
output from the computer. The heater is controlled by varying
the frequency of a pulse generating IC which feeds a frequency
to voltage converter IC. The corresponding voltage is used as
part of a feedback loop, using the temperature sensor, to
control the duty cycle of the heater element.
Recirculation Pump:
The pump is turned ON by another triac fed from the
computer.
Theory of Operation
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