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Digital thermostat

  • US 4,337,822 A
  • Filed: 11/13/1980
  • Issued: 07/06/1982
  • Est. Priority Date: 08/16/1979
  • Status: Expired due to Term
First Claim
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1. In an automatic thermostat of the type having a programmable switch circuit for cycling heat transfer apparatus on and off, the improvement comprising:

  • a system mode interrogator for generating a signal representative of the selected system mode;

    a temperature comparator circuit for performing the comparative relation operations (TA -TSET) or (TSET -TA) and for generating a turn-on command signal when either one of the following comparative relations is satisfied;

    TA -TSET

    K1 in response to a mode signal indicating the cooling mode,TSET -TA

    K2 in response to a mode signal indicating the heating mode;

    a timing circuit responsively coupled to the programmable switch and to the temperature comparator for enabling the transmission of the turn-on command signal after the elapse of a predetermined minimum-off interval following the generation of the turn-on command signal; and

    ,a temperature differential control unit coupled to the temperature comparator to carry out the following operations in response to the presence of the turn-on command signal and to the enabling condition of the minimum-off timer;

    TA -TSET

    Δ

    T1, in response to a mode signal indicating the heating mode, andTSET -TA

    Δ

    T2, in response to a mode signal indicating the cooling mode,the turn-on command signal being terminated when either of the latter comparative relations are satisfied,wherein K1, K2, Δ

    T1, and Δ

    T2 are arbitrary temperature bias values, and TA =ambient temperature, TSET =set point temperature.

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