Electronic cycle timer for a household appliance

Abstract

An electrical timer for a household appliance typically has an integrated circuit including an internal presettable clock registering the time of day, an internal register storing a presettable activation time, and a gate generating an activation signal when an activation enable signal is present and the clock registers the activation time. To prevent an activation signal from being generated on a daily basis without manual intervention, a bistable circuit is provided to generate the activation enable signal in response to a cycle enable signal received from the appliance operator. The bistable circuit is set to activate the activation enable signal upon receipt of the cycle enable signal, and is reset by the activation enable signal to disable the activation enable signal. For a coffee maker, the bistable circuit is preferably reset by the activation signal at the active-to-inactive transition signalling the end of brewing. To reject electrical noise pulses, the bistable circuit preferably has a response time of at least approximately five milliseconds. Preferably the cycle enable signal is generated by a three position switch having 'on' and 'off' positions which activate and deactivate the activation signal regardless of the time of day, and a middle 'automatic' position. In this case the bistable circuit is set when the switch is moved from the automatic position to the off position. Alternatively a separate push-button switch generates the cycle enable signal.