Qualstar RLS-8350 Technical & Service Manual page 19

Hall Effect Sensors
These are devices that indicate the presence or direction of a local magnetic field.
They are used in the following applications in the library:
The "Home" position sensor for the Theta axis. The control circuit boards
•
have a sensor that senses a moving magnet, indicating when the moving
part is at the "Home" end of travel.
The magazine locks. The locking mechanism moves a magnet in proximity
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to a Hall effect sensor on the Control Panel circuit board when the key
lock is in the locked position.
The I/O port latches. The IO port mechanism moves a magnet in proximity
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to a Hall effect sensor on the Control Panel circuit board when the I/O
port is securely latched closed.
An additional sensor on the Control Panel circuit board is used in combi-
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nation with the magazine lock sensor and the I/O port latch sensor to de-
termine which type of magazine or magazine filler is installed.
Detecting the tape drive carriers or drive filler panels. Hall effect sensors
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on the backplane board detect magnets mounted on the tape drive carri-
ers, or the filler panels, to determine what hardware is installed.
Rotor position sensing for the motors. Each motor is equipped internally
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with three Hall effect sensors that are used to commutate the motor wind-
ings, and determine the speed and position of the motor rotor. This is
used to control the position and speed of the axis of the robot that it oper-
ates.
Modulated Optoelectronic Sensors
These are used where the distance between the emitter and detector is greater than
allowed by simple optoelectronic sensor pairs. These sensors consist of an LED emit-
ter, which is modulated, and a detector, which senses the modulated light. One of
these sensor pairs is used to detect the presence of cartridges in the storage slots. A
beam of light is reflected off a reflective surface on the back of the storage slots, and a
detector senses the beam if it is not interrupted. If the beam is interrupted then the
storage slot is determined to be occupied. In addition, there are seven sensor pairs
that are located around the perimeter of the moving carriage. These are used to
sense obstructions to the motion of the carriage, and to aid in judging the success of
cartridge handling. The LED emitter for each pair is located on the sensor boards lo-
cated at the bottom of the carriage, and the detectors are located on the sensor boards
located at the top of the carriage. Any object protruding into the path of the moving
carriage will be detected, and if appropriate, the carriage will stop to prevent a dam-
aging collision. This may result in a fault condition, and a message explaining the
possible causes will be displayed on the control panel. The intensity of the emitters
for these sensor pairs is adjusted during the calibration process to optimize reliabil-
ity.
Drive
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Located at the on the drive side of the carriage, towards the left side.
Left Back
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Located on the left side of the carriage, in the corner closest to the drives.
511010 Rev. 07-01-19
Description and Theory of Operation 2-5