•
The I/O port slot extends to receive or deliver a cartridge and then re-
tracts. The I/O port slot's leadscrew is driven by a DC stepper motor.
•
A large gear at the bottom of the Carousel Assembly is turned by a pinion
gear on a DC stepper motor.
The drive circuitry for all motion systems is located on the Executive Printed Circuit
Board Assembly (PCBA). Each of the brushless DC motors has three internal Hall-
Effect sensors. The Hall-Effect sensors are used to commutate the motors and deter-
mine their relative positions. The brushless DC motors are driven by a three-phase
MOSFET bridge, using a 12 volt supply. Each stepper motor is driven by four discrete
MOSFET devices from the regulated 12 volt supply.
Each motion system has an opto-switch (infrared, opto-interrupter-type detector),
which is used to determine the reference position of the corresponding motion system.
2.2.2 Sensors
TLS models have two types of infrared optical sensors: analog and digital. Each opti-
cal sensor has two parts: an emitter and a corresponding detector.
Analog Sensor Operation
Analog sensors are used over longer distances than the digital sensors, which have a
range of about only one inch.
All analog infrared optical sensors produce a DC voltage proportional to the strength
of the infrared signal at the sensor. This signal is measured by the Analog to Digital
(A/D) Converter on the Executive PCBAs.
Analog Sensors
•
I/O Port Clear Sensor
This sensor detects the presence of a tape cartridge in the I/O port slot.
•
Y-Clear Sensor
This sensor is referred to in the Installation and Operation manual as the
Inventory Sentry Beam. A sensor consists of an infrared emitter mounted
on the bottom pan and a detector mounted on the I/O port PCBA. The in-
frared beam is modulated at a high frequency. The sensor circuitry is AC–
coupled to eliminate its sensitivity to ambient light. The Y–Clear sensor
serves three purposes:
1. When the front door is closed, the Y–Clear sensor verifies that the vertical path
traveled by the handler is unobstructed and that, therefore, it is safe for the car-
riage to move vertically.
2. When the front door is open, the Y–Clear sensor determines whether or not the
inventory has been violated, by someone reaching inside the cabinet and removing
or inserting a cartridge. Just the presence of someone's hand between the Y–Clear
sensor’s emitter and detector is sufficient to interrupt the sensor’s infrared beam
and trigger an audible alarm.
501380 Rev. B
Description and Theory of Operation
2-3