Thermostat with efficient wireless data transmission

1. A thermostat for transmitting data wirelessly to a controller in a building, the thermostat comprising:

a temperature sensor configured to measure a current temperature value of the building;

a wireless radio configured to transmit data from the thermostat to the controller; and

a processing circuit configured to:

receive a current measured temperature value of the building from the temperature sensor;

determine a current temperature error based on the current measured temperature value and a setpoint temperature;

transmit the current measured temperature value to the controller via the wireless radio in response to determining that both:

a difference between the current temperature error and a previous temperature error is greater than an error threshold; and

a length of time since the thermostat transmitted a temperature value to the controller is greater than a time threshold.

2. The thermostat of claim 1 , wherein the processing circuit is configured to:

determine whether a maximum amount of time has passed since transmitting the temperature value to the controller; and

transmit the current measured temperature value to the controller via the wireless radio in response to determining that the maximum amount of time has passed.

3. The thermostat of claim 1 , wherein the temperature value transmitted by the wireless radio is a filtered temperature value that is a filtered version of the current measured temperature value, wherein the processing circuit is configured to:

determine the filtered temperature value by providing the current measured temperature value as an input to a deadband filter and calculating the filtered temperature value as a function of the current measured temperature value using one or more equations of the deadband filter; and

transmit the filtered temperature value to the controller via the wireless radio.

4. The thermostat of claim 3 , wherein the processing circuit is configured to determine the filtered temperature value based on the current measured temperature value and the deadband filter by:

setting the filtered temperature value equal to the setpoint temperature in response to determining that the current measured temperature value is within a temperature band, wherein the temperature band comprises temperature values between the setpoint temperature plus half a deadband threshold and the setpoint temperature minus half the deadband threshold; and

setting the filtered temperature value equal to a shifted temperature value in response to determining that the current measured temperature value is not within the temperature band.

5. The thermostat of claim 4 , wherein the processing circuit is configured to determine the shifted temperature value by:

subtracting half the deadband threshold from the current measured temperature value if the current measured temperature value is greater than a maximum of the temperature band; or

adding half the deadband threshold to the current measured temperature value if the current measured temperature value is less than a minimum of the temperature band.

6. The thermostat of claim 1 , wherein the processing circuit is configured to:

cause the wireless radio to operate in an operating power mode in response to determining that the current measured temperature value should be sent to the controller; and

cause the wireless radio to operate in a low power mode after transmitting the current measured temperature value to the controller.

7. The thermostat of claim 1 , wherein the processing circuit is configured to:

filter the current measured temperature value with a deadband filter by providing the current measured temperature value as an input to the deadband filter and calculating a filtered current measured temperature value as a function of the current measured temperature value using one or more equations of the deadband filter;

use the filtered current measured temperature value to:

determine a filtered current temperature error based on the filtered current measured temperature value and the setpoint temperature; and

determine whether a difference between the filtered current temperature error and a previous filtered temperature error is greater than the error threshold; and

transmit the filtered current measured temperature value to the controller via the wireless radio in response to determining that both:

the difference between the filtered current temperature error and the previous filtered temperature error is greater than the error threshold; and

the length of time since the thermostat transmitted the temperature value to the controller.

8. A method for efficiently transmitting data wirelessly to a controller in a building, the method comprising:

receiving, by a thermostat, a current measured temperature value of the building from a temperature sensor;

determining, by the thermostat, a current temperature error based on the current measured temperature value and a setpoint temperature; and

transmitting, by the thermostat, the current measured temperature value to the controller via a wireless radio in response to determining, by the thermostat, that both:

a difference between the current temperature error and a previous temperature error is greater than an error threshold; and

a length of time since the thermostat transmitted a temperature value to the controller is greater than a time threshold.

9. The method of claim 8 , the method further comprising:

determining, by the thermostat, whether a maximum amount of time has passed since transmitting the temperature value to the controller; and

transmitting the current measured temperature value to the controller via the wireless radio in response to determining that the maximum amount of time has passed.

10. The method of claim 8 , the method further comprising:

determining, by the thermostat, a filtered temperature value by providing the current measured temperature value as an input to a deadband filter and calculating the filtered temperature value as a function of the current measured temperature value using one or more equations of the deadband filter, wherein the temperature value transmitted by the wireless radio is the filtered temperature value that is a filtered version of the current measured temperature value; and

transmitting, by the thermostat, the filtered temperature value to the controller via the wireless radio.

11. The method of claim 10 , wherein determining, by the thermostat, the filtered temperature value based on the current measured temperature value and the deadband filter comprises:

setting, by the thermostat, the filtered temperature value equal to the setpoint temperature in response to determining that the current measured temperature value is within a temperature band, wherein the temperature band comprises temperature values between the setpoint temperature plus half a deadband threshold and the setpoint temperature minus half the deadband threshold; and

setting, by the thermostat, the filtered temperature value equal to a shifted temperature value in response to determining that the current measured temperature value is not within the temperature band.

12. The method of claim 11 , wherein determining, by the thermostat, the shifted temperature value by:

subtracting, by the thermostat, half the deadband threshold from the current measured temperature value if the current measured temperature value is greater than a maximum of the temperature band; or

adding, by the thermostat, half the deadband threshold to the current measured temperature value if the current measured temperature value is less than a minimum of the temperature band.

13. The method of claim 8 , the method further comprising:

causing, by the thermostat, the wireless radio to operate in an operating power mode in response to determining that the current measured temperature value should be sent to the controller; and

causing, by the thermostat, the wireless radio to operate in a low power mode after transmitting the current measured temperature value to the controller.

14. The method of claim 8 , wherein the method further comprises:

filtering, by the thermostat, the current measured temperature value with a deadband filter by providing the current measured temperature value as an input to the deadband filter and calculating a filtered current measured temperature value as a function of the current measured temperature value using one or more equations of the deadband filter;

using, by the thermostat, the filtered current measured temperature value to:

determine a filtered current temperature error based on the filtered current measured temperature value and the setpoint temperature;

determine whether a difference between the filtered current temperature error and a previous filtered temperature error is greater than the error threshold; and

transmitting, by the thermostat, the filtered current measured temperature value to the controller via the wireless radio in response to determining, by the thermostat, that both:

the difference between the filtered current temperature error and the previous temperature error is greater than the error threshold; and

a minimum amount of time has passed since transmitting the temperature value to the controller.

15. The method of claim 8 , wherein the transmitted current measured temperature value is an unfiltered temperature value and the method further comprises:

filtering, by the controller, the unfiltered temperature value with a deadband filter by providing the unfiltered temperature value as an input to the deadband filter and calculating a filtered temperature value as a function of the unfiltered temperature value using one or more equations of the deadband filter; and

controlling, by the controller, an HVAC device to affect a change in temperature of the building based on the filtered temperature value and a control method, wherein an execution time of the control method is longer than a rate at which a processing circuit of the thermostat receives a measured temperature of the building from the temperature sensor.

16. A system for transmitting data wirelessly in a building, the system comprising a thermostat and a controller, the thermostat comprising:

a temperature sensor configured to measure a current temperature value of the building;

a wireless radio configured to transmit data from the thermostat to the controller; and

a processing circuit configured to:

receive a current measured temperature value of the building from the temperature sensor; and

transmit the current temperature value to the controller via the wireless radio in response to determining that both:

a difference between a current temperature error and a previous temperature error is greater than a threshold;

a length of time since the thermostat transmitted a temperature value to the controller.

17. The system of claim 16 , wherein the temperature value transmitted by the wireless radio is a filtered temperature value that is a filtered version of the current measured temperature value, wherein the processing circuit of the thermostat is configured to:

determine the filtered temperature value by providing the current measured temperature value as an input to a deadband filter and calculating the filtered temperature value as a function of the current measured temperature value using one or more equations of the deadband filter by:

setting the filtered temperature value equal to a setpoint temperature in response to determining that the current measured temperature value is within a temperature band, wherein the temperature band comprises temperature values between the setpoint temperature plus half a deadband threshold and the setpoint temperature minus half the deadband threshold; and

setting the filtered temperature value equal to a shifted temperature value in response to determining that the current measured temperature value is not within the temperature band; and

transmit the filtered temperature value to the controller via the wireless radio.

18. The system of claim 17 , wherein the processing circuit of the thermostat is configured to determine the shifted temperature value by:

subtracting half the deadband threshold from the current measured temperature value if the current measured temperature value is greater than a maximum of the temperature band; or

adding half the deadband threshold to the current measured temperature value if the current measured temperature value is less than a minimum of the temperature band.

19. The system of claim 16 , wherein the processing circuit of the thermostat is configured to:

cause the wireless radio to operate in an operating power mode in response to determining that the current measured temperature value should be sent to the controller; and

cause the wireless radio to operate in a low power mode after transmitting the current measured temperature value to the controller.

20. The thermostat of claim 16 , wherein the transmitted current measured temperature value is an unfiltered temperature value and the controller comprises a processing circuit configured to:

filter the unfiltered temperature value with a deadband filter by providing the unfiltered temperature value as an input to the deadband filter and calculating a filtered temperature value as a function of the unfiltered temperature value using one or more equations of the deadband filter; and

control an HVAC device to affect a change in temperature of the building based on the filtered temperature value and a control method, wherein a rate at which the control method executes is longer than a rate at which the processing circuit of the thermostat receives a measured temperature of the building from the temperature sensor.

21. A thermostat for transmitting data wirelessly to a controller in a building, the thermostat comprising:

a temperature sensor configured to measure a current temperature value of the building;

a wireless radio configured to transmit data from the thermostat to the controller; and

a processing circuit configured to:

receive a current measured temperature value of the building from the temperature sensor;

determine a current temperature error based on the current measured temperature value and a setpoint temperature;

determine whether a difference between the current temperature error and a previous temperature error is greater than an error threshold;

determine whether a length of time since the thermostat transmitted a previous measured temperature value to the controller is greater than a time threshold;

determine a filtered measured temperature value based on the current measured temperature value and a deadband filter; and

transmit the filtered measured temperature value to the controller via the wireless radio.