Released Rev. C 2000-1252-01 Page 27
VersaPort 2200 Technical Manual
Chapter 2: Theory of Operation
VersaPort Components
a
Three sets of circuits control the operation of the elevator motor, Pod latch and Pod door
motors, and wafer seater motor. The air exhaust motor is powered directly from the INX
Control PCB at 24vdc.
NOTE . . .
OPTICAL LIMIT SWITCHES ASSOCIATED WITH THE ACTUATOR MOTORS AND
ELEVATOR MOTOR HAVE SOFTWARE GENERATED TIME LIMITS FOR ACTUATION.
F
AILURE TO ACTUATE IN A GIVEN PERIOD OF TIME WILL CAUSE THE DC-MOTOR
TO STOP MOTION.
Port Plate Elevator and Cassette Shuttle Motors
(DC Servo motor) The port plate and cassette shuttle are controlled by a servo loop
consisting of: servo-motion controller, amplifier-driver, dc-drive motor, digital encoder, and
position capture circuit. The controller is programmable by the CPU. The forward and
reverse drive information is provided to the amplifier/driver that provides pulse-width
modulated (PWM) voltage to the motor. The encoder produces the equivalent of 2000
counts per lead screw revolution for feed back to the servo-controller. This produces
control and position data for the CPU. Motor current is sensed through the driver circuit to
prevent motor or circuit burnout due to a stalled motor or shorted winding. The
over-current trip-point is set at 3.0 amps nominal. The overcurrent condition is resettable
via the software.
The port plate/elevator and cassette shuttle both use limit switches to confirm they are at
the Home position. The encoder is used to indicate an over-travel condition. The port
plate/elevator motor includes a brake, which engages when power is removed to prevent
back-travel of the port plate.
Pod Latch and Wafer Seater Motors
(DC stepper motors) The Pod latch and the wafer seater share common circuitry. Each
motor has its own stepper-motor driver, but they share a step sequencer, since these
motors will never be energized at the same time. A current limiter is provided should an
overcurrent or short circuit occur in the wiring of one of the motors.
Each motor has limit switches that will cause the motor to stop when the desired position
is reached.
Pod-Door Lock/Unlock Motor
(DC motor) The Pod-door lock/unlock motor is driven by an amplifier-driver. When the
motor runs the Pod-lock mechanism to its locked position, the lock-limit (switch) is
detected, thus turning off the motor. This is the same procedure for the motor and the
unlock-limit switch. Motor current is sensed through the driver circuit. If the motor were to
stall, current would be limited until the condition was cleared. If a shorted motor winding
or some other type of short circuit were to occur, the over-current would be tripped. The
trip condition can be reset by powering down the VersaPort and then reapplying power.
The Pod-lock motor has the Pod-open and Pod-closed limit switches that ensure that the
motor is de-energized when it has reached the desired position.
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