GB1519401A - Electronic thermostat - Google Patents

Abstract

1519401 Temperature control J M PALMIERI and A M ESPOSITO 7 Jan 1976 00506/76 Heading G3R A digital electronic thermostat compares binarycoded decimal representations of an actual and a desired temperature and furnishes an 'operate' signal when the temperature error has a given sense. A thermistor 20 controlling an oscillator 18 feeds a temperature-dependent frequency to two counters 24, 28 which respectively register the tens and units digits of the number of cycles of oscillation occurring in a time interval determined by a clock 34. The tens and units are compared, by devices 72 and 70, with values set by devices 62 and 54. With the switches 86 and 94 set as shown, an output is obtained at 110 of the sensed temperature is too low. By reversing these switches, the output may be given if the sensed temperature is too high. Thus either heating or cooling may be controlled. Modifications, Figs. 2 and 3 (not shown), provide for a "dead zone" (errors of the relevant sense but less than a predetermined magnitude ignored) and for switching of the input from one to another of several temperature sensors (e.g. from a living-room to a bed-room at night).