Control system

A control system having means for changing an instantaneous temperature in an enclosed space to maintain it generally near a selected value comprising;

• means electrically energizable for enabling the temperature changing means;
• means for electrically indicating variations in the instantaneous temperature from the selected value including a regulated voltage source, a temperature sensitive impedance in thermal communication with the enclosed space, a plurality of temperature selecting impedances, and means for selecting at least one of the temperature selecting impedances and for connecting the selected impedance in series with the temperature sensitive impedance across the voltage source;
• and
• bistable means responsive to the voltage across one of the series connected impedances and coupled to the electrically energizable means to cause the temperature changing means to be enabled when the selected temperature exceeds the area temperature by a first predetermined amount and to be disabled when the area temperature exceeds the selected temperature by a second predetermined amount.

A control system having means for changing the temperature in an enclosed space to maintain it generally near a selected temperature comprising;

• means for electrically indicating variations in the temperature T.sub.2 in the enclosed space from the selected temperature T.sub.s ;
• bistable means responsive to the indicating means and coupled to the temperature changing means for enabling it when, for a preselected real number K.sub.1, [T.sub.2 - T.sub.2 ]>
• K.sub.1, and for subsequently disabling it when, for a preselected real number K.sub.2, [T.sub.a - T.sub.s ]>
• K.sub.2 ;
• and
• timing means effective upon the lapse of a selected time for selecting a new temperature for the enclosed space.

A control system for maintaining temperature in an enclosed space generally near a selected value comprising;

• a regulated voltage source;
• a voltage divider network including at least a temperature sensitive impedance in thermal communication with the enclosed space, and an impedance which may be varied;
• and
• a Schmitt trigger circuit having an output coupled to vary the temperature in the enclosed space and an input coupled to the voltage divider network, the Schmitt trigger circuit having output voltage versus input voltage hysteresis characteristics to provide a stable operating mode for the control system.