Microprocessor based control circuit for washing appliances

DETAILED DESCRIPTION The foregoing and other objects and advantages are accomplished by providing a microprocessor based control circuit for appliances such as dishwashers which employ a microprocessor programmed to respond to user selected options to determine the operating sequence of the appliance.
The control circuit includes a drain feedback system which permits the microprocessor to detect and identify a plurality of drain fault conditions including failure to drain, slow drain and plugged drain.
If the microprocessor identifies the occurrence of any one of these plurality of fault conditions it initiates a protective response.
The user is advised of the specific fault mode via an alpha-numeric digital display on the machine control panel.
In the event a rapid drain occurs, the feedback system immediately terminates pump-out and transfers the time saved to a subsequent time-insensitive cycle thereby eliminating undesirable operation of pump and motor while maintaining the total cycle time as originally programmed.
The drain feedback system includes an electrical feedback switch positioned to detect operation of the solenoid-actuated drain valve, thereby providing an input to the microprocessor.
The condition of the switch is periodically monitored by the microprocessor and based upon the state of the switch and the time elapsed from the beginning of the drain cycle, the microprocessor is programmed to detect drain system failures of the type previously indicated and, if necessary, to abort cycle operation to prevent flooding.