Electrical System (B Model and Newer Beds)
Chapter 3: Theory of Operation
Page 3 - 18 CareAssist® and CareAssist® ES Bed Service Manual (MAN330 REV 4)
sends CAN messages to the scale P.C. board to start activation of the switches
in the user interface.
All of the scale functions are done by microcontrollers on the scale P.C. board.
These include:
•Weigh
• Zero scale
• Add/Delete items
• Select LB/KG display mode
The Bed Exit System functions are shared between the scale P.C. board and the
scale display P.C. board. These include:
• Arm/Disarm bed exit
• Alarm tone select
• Alarm volume select
•Alarm
If the Bed Exit System is armed, AC power removed, and the bed equipped
with the SideCom® Communication System, the display P.C. board will cause
the SideCom® Communication System to send a nurse call. If the Bed Exit
System is armed and the display P.C. board loses communication with the scale
P.C. board, the display P.C. board will cause the SideCom® Communication
System to send a nurse call.
When the bed is unplugged from AC power, neither scale nor the Bed Exit
System will function.
Scale and Bed Exit Alarm System—C Model and Newer Beds
Power is supplied to the Scale/Bed Exit Alarm System system by the central
power supply. The power supply provides a pre-regulated 8-9 V DC reference
to signal GND at 400mA max, 200mA typical. The GND is common among
all nodes in the bed. This is important to the network transceiver explained
later.
The analog circuitry is a single chip solution specially designed for scale
transducers. It is located in the frame of the bed as close to the load beams as
possible. The load beams are resistive bridge sensors excited by a regulated
DC voltage. This regulated voltage is supplied to the beams and to the A/D
converter reference input to minimize the effects of variations.
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