Apparatus and method for control of a thermostat

• US 8,190,296 B2
• Filed: 11/11/2008
• Issued: 05/29/2012
• Est. Priority Date: 11/11/2008
• Status: Active Grant

• Current Assignee: Copeland Comfort Control LP (Emerson Electric Company)
• Original Assignee: Emerson Electric Company
• Inventors: Alhilo, Esan A.
• Primary Examiner(s): Chaki, Kakali
• Assistant Examiner(s): Hanchak, Walter
• Application Number:
  US12/268,898
• Publication Number:
  US 20090062965A1
• Time in Patent Office: 1,295 Days
• Field of Search: None
• US Class Current: 700/278
• CPC Class Codes: G05B 11/28 using pulse-height modulation; using pulse-width modulation
• CPC Class Codes: G05B 13/021 in which a variable is automatically adjusted to optimise the performance
• CPC Class Codes: G05B 5/01 electric
• CPC Class Codes: G05D 23/1951 with control of the working time of a temperature controlling device

Abstract

A thermostat is provided that includes a temperature sensor for sensing ambient temperature, and a switching device that is configured to apply electrical power to a heating element when the switching device is activated. The thermostat further includes a processor that is configured to periodically determine for a finite switching time period a temperature delta value indicative of the difference between the sensed temperature and a desired set point temperature. The processor is further configured to calculate a duty cycle ratio of the switch activation time relative to the total switching time period. The calculated duty cycle ratio for determining the switch activation time is determined as a function of the temperature delta value, a duty cycle offset and a heat dissipation offset. The duty cycle offset and the heat dissipation offset are based on an average of a predetermined number of prior duty cycle ratios.

Claims

1. A thermostat for controlling the application of electrical power to a heating element for controlling the ambient temperature within a space, the thermostat comprising:

a housing having an interior space;

a temperature sensor disposed within the interior space of the housing and configured to sense an ambient temperature;

a switch disposed within the interior space of the housing and configured to apply electrical power to a heating element when the switch is activated;

a heat sink associated with the switch and disposed within the interior space of the housing, the heat sink configured to dissipate heat generated by the switch; and

a processor configured to determine a temperature delta value indicative of the difference between the sensed ambient temperature and a desired set point temperature, to calculate a heat dissipation offset based on an average of a predetermined number of prior calculated percentages of a finite switching time period, the heat dissipation offset associated with heat generated by the switch, and to calculate a percentage of the finite switching time period for activating the switch based on the temperature delta value and the heat dissipation offset;

wherein the processor is configured to activate the switch for the calculated percentage of the finite switching time period, to thereby control the extent of electrical power applied to the heating element.

2. The thermostat of claim 1 wherein the switch is configured to switch a line voltage source to the heating element, said switch being disposed within the interior space of the housing such that heat generated by said switch is dissipated within the interior space and affects the temperature sensor disposed within the housing.

3. The thermostat of claim 1 wherein the processor is further configured to calculate a duty cycle offset based on the average of the predetermined number of prior calculated percentages, said processor being configured to calculate the percentage of the finite switching time period based on the temperature delta value, the heat dissipation offset, and the duty cycle offset.

4. The thermostat of claim 1 wherein the heat sink associated with said switch is disposed within the interior space of the housing at a location distanced from the temperature sensor, such that heat generated by said switch is dissipated away from the temperature sensor within the housing.

5. The thermostat of claim 1 wherein the housing defines at least one lower vent opening and at least one upper vent opening, and wherein the heat sink is disposed within the housing such that heat dissipated by the heat sink causes an updraft airflow between the at least one lower vent opening and the at least one upper vent opening.

6. The thermostat of claim 1 wherein the processor is configured to determine the heat dissipation offset based on a default value where there is less than the predetermined number of prior calculated percentages of the finite switching time period.

18. The thermostat of claim 1 wherein the temperature delta value is determined periodically, and the heat dissipation offset is calculated periodically.

19. The thermostat of claim 1 wherein the processor is further configured to calculate a duty cycle offset based on multiple prior calculated percentages of the finite switching time period, and wherein the processor is configured to calculate the percentage of the finite switching time period based on the temperature delta value, the heat dissipation offset, and the duty cycle offset.

7. A thermostat for controlling the application of electrical power to a heating element for controlling the ambient temperature within a space, the thermostat comprising:

a housing defining an interior space;

a temperature sensor disposed within the interior space of the housing and configured to sense an ambient temperature of the interior space;

a switch disposed within the interior space of the housing, configured to apply electrical power to a heating element when the switch is activated;

a heat sink associated with the switch and disposed within the interior space of the housing and the heat sink configured to dissipate heat generated by the switch; and

a processor configured to determine, for a finite switching time period, a temperature delta value indicative of the difference between the sensed ambient temperature and a desired set point temperature, to calculate a heat dissipation offset as a function of an average of a predetermined number of prior percentages of the finite switching time period, the heat dissipation indicative of the heat dissipated by the heat sink within the housing, and to determine a percentage of the switching time period that the switch is activated, based on the temperature delta value and the heat dissipation offset, said processor configured to activate the switch for the determined percentage of the switching time period, to thereby control the extent of electrical power applied to the heating element, wherein the heat dissipation offset value varies proportionally with respect to the averaged of the prior switching percentages.

8. The thermostat of claim 7 wherein the switch is configured to switch a line voltage source to the heating element, said switch being disposed within the interior space of the housing such that heat generated by said switch is dissipated within the interior space of the housing and affects the temperature sensor disposed within the housing.

9. The thermostat of claim 7 wherein the processor is further configured to calculate a duty cycle offset that is determined based on an average of a predetermined number of prior switching percentages, said processor being configured to calculate the switching percentage based on the temperature delta value, the heat dissipation offset, and the duty cycle offset.

10. The thermostat of claim 7 wherein the heat sink is spaced apart from the temperature sensor.

11. The thermostat of claim 7 wherein the housing defines at least one lower vent opening and at least one upper vent opening, and wherein the heat sink is disposed within the housing such that heat dissipated by the heat sink causes an updraft airflow between the at least one lower vent opening and the at least one upper vent opening.

12. The thermostat of claim 7 wherein the processor is configured to determine a heat dissipation offset based on a default value where there is less than the predetermined number of prior calculated percentages of the finite switching time period.

13. A thermostat for controlling the application of electrical power to a heating element for controlling the ambient temperature within a space, the thermostat comprising:

a housing defining an interior space;

a temperature sensor disposed within the interior space of the housing and configured to sense an ambient temperature;

a switch disposed within the interior space of the housing and configured to apply electrical power to a heating element when the switch is activated;

a heat sink associated with the switch and disposed within the interior space of the housing, which is configured to dissipate heat generated by the switch; and

a processor, configured to periodically determine, for a finite switching time period, a temperature delta value indicative of the difference between the sensed ambient temperature and a desired set point temperature, the processor configured to determine a duty cycle offset based on an average of a predetermined number of prior switching ratios, and to determine a heat dissipation offset based on the average of the predetermined number of prior switching ratios, the heat dissipation offset being associated with heat generated by activation of the switch,

wherein said processor is configured to calculate a ratio of a switch activation time to the finite switching time period as a function of;

the temperature delta value, the duty cycle offset, and the heat dissipation offset;

wherein said processor is configured to activate the switch for the calculated ratio, to thereby control the extent of electrical power applied to the heating element.

14. The thermostat of claim 13 wherein the switch is configured to switch a line voltage source to a heating element, said switch being disposed within the interior space of the housing such that heat generated by said switch is dissipated within the interior space and affects the ambient temperature sensed by the temperature sensor disposed within the housing.

15. The thermostat of claim 14 wherein the heat sink associated with said switch is disposed within the interior space of the housing at a location distanced from the temperature sensor.

16. The thermostat of claim 15 wherein the housing defines at least one lower vent and at least one upper vent opening, wherein the heat sink is disposed within the housing such that heat dissipated by the heat sink causes an updraft airflow between the at least one lower vent opening and the at least one upper vent opening, thereby exhausting heat from the interior space of the housing.

17. The thermostat of claim 13 wherein the processor is configured to determine the heat dissipation offset and the duty cycle offset based on a default value where there is less than the predetermined number of prior switching ratios.