Importance

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Abstract

An electronic digital programmable wall thermostat system for controlling heating and cooling systems supplying an indoor area or space. The thermostat includes a digital clock, a display for displaying desired parameters of time and temperature and a data entry keyboard for programming the thermostat to maintain desired temperatures during selected time intervals. The heart of the system is a digital processor with memory, which responds to signals from a temperature sensing means which includes an analog to digital converter for controlling the heating and cooling systems in accordance with the sequence programmed therein. An output from the processor gates a triac on and off which in turn activates or deactivates the heating and cooling systems. In a preferred embodiment, a single chip digital processor is used to control the operation of the thermostat system, the keyboard, display and temperature sensing means being selectively scanned from output terminals of the digital processor. The processor is also programmed such that the hysteresis of the thermostat is variable with time in discrete steps. For example, in the heat mode when the triac (heat) is turned on, the hysteresis may be 0.5.degree. F. above the set temperature for a predetermined time period (6 minutes) and then decreased to the set temperature until the triac is turned off. When the triac is turned off, the hysteresis is varied to be 0.5.degree. F. less than the set temperature for 6 minutes and then is increased to the set temperature until the triac is turned back on.

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First Claim