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Door Locked
This indicates that the door lock is fully turned to the locked position. The
sensor is located on the Door Lock Sensor PCBA and feeds back to the
Sensor Master PCBA.
•
Carousel on Face
This indicates that the carousel is aligned on a face. The sensor is located
on the Carousel PCBA and it feeds back directly to the Executive PCBA.
•
Drive Locked1 and 2
Located on the Drive Bay PCBA, it is used to sense that a drive is in-
stalled. These devices do not have Schmidt triggers as the others do, but
rather they have a phototransistor output.
Hall Effect Sensors
These are simple three-lead devices, which indicate the presence or direction of a local
magnetic field.
•
Carousel Home
This sensor gives a once-around indication for the carousel, and is used to
find the home face of the carousel. It is located on the carousel PCBA, and
feeds back to the Executive PCBA. It looks for a magnet buried in the car-
ousel platform.
•
X Motor Phase A, B & C
These sensors are integral to the Brushless DC motors, and provide the
Executive PCBA with feedback for both commutation and position. They
route through the Carriage PCBA, the Interconnect PCBA, and finally to
the Executive PCBA. These sensors provide continuous incremental posi-
tion feedback so the library always knows where its carriage is.
•
Z Motor Phase A, B & C
These sensors are integral to the Brushless DC motors, and provide the
Executive PCBA with feedback for both commutation and position. They
route through the Carriage PCBA, the Interconnect PCBA, and finally to
the Executive PCBA.
•
Storage Array Index Sensor
This sensor is located on the Storage Array PCBA and senses a magnet
embedded in a cam to provide phasing information for the control system.
•
Storage Array Home Sensor
These two sensors are located on the Storage Array PCBA and sense a
magnet on the bottom of car "A", so the control system can identify which
car is the first one.
Modulated Optoelectronic Sensors
These are used where the range is greater that allowed by simple optoelectronic sen-
sor pairs. These sensors consist of an LED emitter, which is modulated, and a detec-
tor, which was designed for remote control of consumer products. The detector looks
for a particular carrier frequency, which is modulated by a sub-carrier that would
normally carry data. In our application, we use it to detect the presence of the modu-
lated signal, but impose no data on it. The part features an infrared filter, carrier and
2-8
Description and Theory of Operation
501510 Rev. S
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