Electrical System (A Model Beds)
Chapter 3: Theory of Operation
Page 3 - 8 CareAssist® and CareAssist® ES Bed Service Manual (MAN330 REV 4)
Patient Pendant
The patient pendant controls operate at 3.3 V DC supplied by the main bed
control and integrate three main principles:
• Filtering and amplification of inputs for electrostatic protection and signal
formatting
• Multiplexing for the management of the controls
• Demultiplexing for the control of the indicators
Data from the controls and indicators are transmitted in series (link type - SPI)
so as to reduce the number of wires. The clock signal that starts these
exchanges is controlled by the main bed control P.C board. All the data is sent
in tens of milliseconds. When the system is in stand-by mode, the power is cut
off and the clock signal is no longer controlled. The battery control is therefore
directly wired so as to have continuous operation.
Motor Characteristics
For motor characteristics, see table 3-4 on page 3-8.
Table 3-4. Motor Characteristics and Dimensions
Management of the Motors
The motors control signals are supplied by the main bed control P.C. board.
Their extreme positions are detected in series by upper and lower internal EOT
devices. These devices directly cut off the power supply for the head section,
knee section and foot section actuators. In addition, the head section and foot
section motors have intermediate internal microswitches to control the
automatic contour and Dining Chair® position.
Description
Hilow column
motor
Head motor Knee motor Foot motor
Power 96 W (x2) 120 W 84 W 84 W
Voltage 18 to 40 V DC 18 to 40 V DC 18 to 40 V DC 18 to 40 V DC
Intermittent
service
10%
3 min/30 min
10%
2 min/18 min
10%
6 min/60 min
10%
6 min/60 min
Actuator/
column travel
400 mm
± 5 mm (15.75")
239 mm
± 2 mm (9.4")
60 mm
± 2 mm (2.36")
45 mm
± 2 mm (1.77")
Retracted rod/
center distance
445 mm
± 2mm (17.5")
310 mm
± 2mm (12.2")
325 mm
± 2mm (12.8")
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