Cocoon CWS 4000 - Control Board

Care Essentials CWS4000 Cocoon Warming System Service Manual
e LED display drivers.
e Run hour meter display.
e Filter life hour counter reset switch.
e Buzzer.
e Power supplies.
The CWS4000 Sensor Board implements the following functions:
» Digital temperature sensor.
e Temperature limit thermostats.
The more important of these functions are elaborated below.
6.1. Control Board
Microcontroller
The microcontroller (U1) integrates a number of functions:
e CPU.
e Program ROM.
e RAM.
e EEPROM.
ο Interrupt controller.
e External interrupts.
e Counter/Timers.
e Watchdog timer.
e Digital Input/Output ports.
The microcontroller performs the following functions:
e Monitors the exhaust air temperature through the digital temperature sensor.
Monitors the push-button switches.
Controls the display and buzzer drivers.
Controls the heater and fan.
The microcontroller ROM is factory programmed with the application software program. The
software program contained in the microcontroller ROM is subject to copyright. In the event of a
microcontroller fault, Care Essentials must fit a replacement part.
Reset Circuit
When the microcontroller is reset either by power-on or by the watchdog timer:
e Digital Input/Output ports 0 — 3 go high.
e Signal /FAN goes low switching on the fan relay.
The fan blower is switched on.
e Signal /HEAT goes high switching off the heater triac.
The heater is switched off.
Thus the reset process implements a safety strategy to prevent the fan biower being turned off
with the heater being turned on.
Revision | 13 June 2006 Page 14