Hill-Rom VersaCare P3200, Service Manual

Page: 126 / 379

Electrical System
Chapter 3: Theory of Operation
If the AC power is removed from the bed and the PPM system is armed a
priority and Nurse call are placed as well as a local alarm. If for any reason the
scale node goes away or cannot communicate the SideCom® Communication
System board monitors the scale nodes heartbeat and places the alarm if PPM
was armed. Under battery power neither the scale nor PPM systems work.
IntelliDrive® Transport System
Push Handles
The push handles incorporate strain gauge elements to sense the force applied
by a caregiver in either a forward or reverse direction. The strain gauges are
connected to the junction board. Each push handle also incorporates an enable
switch. The enable switches are connected to the junction board.
Junction Board
The junction board produces a regulated 12 VDC signal from the battery
voltage to excite the strain gauges in the push handles to produce a signal in
response to applied pressure. The strain gauge signals are then combined such
that the forces applied to each handle are added together. A net push causes a
positive signal, a net pull causes a negative signal. The junction board also
contains amplifier circuitry to convert these signals from the strain gauges into
a throttle signal for the drive motor controller. A positive signal results in a
forward throttle signal to the motor controller. A negative signal yields a
reverse throttle signal to the motor controller. The full scale forward throttle
signal is about 4.0 volts and the full scale reverse throttle signal is about 1.0
volt. A signal of 2.4 -2.6 V is neutral. These levels make sure that the throttle
signal to the motor controller is never out of range for a correctly connected
system.
The junction board has connectors for the enable switches in the handles,
paralleling the enable switches to produce one enable signal to the
IntelliDrive® Transport System box. There is also a connector on the junction
board for a steer switch.
Finally, the junction board contains a connector to receive bed power, both to
charge the battery and to raise the drive wheel if deployed, regardless of the
condition of the battery.
Power Assist Control Module
The Power Assist Control Module (PACM) consists of a printed circuit board
mounted to a heat-sink plate. The plate provides essential heat sinking for
Page 3 - 12 VersaCare™ Bed Service Manual (MAN333 REV 2)