Electrical System (Electric Stretcher)
Chapter 3: Theory of Operation
The resistors, R22 - R25, R32 divide the regulated DC supply voltage to set the
trip points of the comparators. The trip points of the comparators are set to get
the desired electrical limits of the bed functions.
LED Outputs
The function power LEDs are on when patient and caregiver controls are
active.
When the controls are active, the regulated DC supply voltage is supplied to
the current limiting resistors, R10 and R11, by the patient control switches and
approximately 2.1 V DC is dropped across the LEDs to supply the desired
illumination.
Relay Outputs
Under the correct input conditions the relays K2 - K6 switch the AC supply
voltage to the motors to articulate the stretcher sections.
When the back section of the stretcher articulates, the relay K1 switches the
AC supply voltage to release the brake on the back section motor. When the
head function up or down control or switch is released, the relay opens, and
back section motion stops.
The spark quenchers, SQ1 - SQ4, protect the relay contacts from excessive
damage by arcing when they are opened and closed.
Potentiometer Calibration Board
The potentiometer calibration board tunes the output voltage of the position
sensor. This permits the comparator circuit on the control board to accurately
set the articulation limits of the stretcher independent of the position sensor’s
tolerance.
The calibration procedure for the board is completed at the factory. The output
voltage, which can be monitored on pin 2 of P1 on the control board, should be
approximately 10.8 V DC at the head down limit, 5.25 V DC at the patient
head up limit, and 3.15 V DC at the caregiver head up limit.
If it is necessary to replace the potentiometer calibration board, the entire
potentiometer cable assembly must be replaced.
3
Hill-Rom® Transport, Procedural, and Specialty Stretchers
Page 3 - 3
Service Manual (144386 REV 2)
Summary of Contents for P8000
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Page 441: ...Schematic Wiring Diagram Control Board P N 49603 ...
Page 442: ...Schematic Wiring Diagram Electric Stretcher P N 60389 ...
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