Electrical System
Chapter 3: Theory of Operation
remaining charge in the battery, each successive LED representing
approximately 20 percent of the battery capacity.
The battery capacity indicator also includes a shutdown switch to signal the
PACM logic to disconnect the battery.
Pneumatic
The air system contains the following components: air mattress, pneumatic
system, control board, scale system, left and right force sensing resistors, and
the air board software, which manages the entire operation of the above items.
The air mattress contains five air bladders: head, seat, heel, left turn assist and
right turn assist. The head, seat, and heel bladders are used to support the
patient. The left and right turn assist bladders are used to aid the caregiver in
rotating a patient in order to change linens or reposition the patient.
The pneumatic system consists of the pneumatic valves, air compressor, and
mattress connector. The control board and software currently support two
different valve types. The SMC pneumatic valves are a pilot pressure operated
valve. They pull very little current due to their pilot operation; however, the
pilot pressure must be maintained in order for the valves to work correctly. The
second type is the MAC valve which has a standard solenoid construction. The
MAC valves draw much more current than the SMCs and therefore; the MAC
valves are pulse width modulated after the valve has been actuated to reduce
the amount of current draw. The power supply board controls the air
compressor. The air system commands the power supply to turn on the
compressor by the CAN network. The mattress connector has a hall effect
sensor so as to detect the presence of the air mattress.
The air control board has the hardware to activate the valves, read pressures
from the air bladders, read the patient head section force sensing resistors,
detect the presence of the air mattress, give an audible alarm to the caregiver,
store operating variables in non-volatile memory, measure valve currents and
supply voltages, and measure head angle.
The scale system supplies load beam and PPM sensor data by the CAN
network. This data, along with the measurements of the head section FSRs, are
used to determine patient weight, detect the presence of a patient, and detect if
a patient is sitting up.
Page 3 - 16 VersaCare™ Bed Service Manual (MAN333 REV 2)
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