Method of Calibrating a Daylight Sensor

• US 20100244706A1
• Filed: 03/19/2010
• Published: 09/30/2010
• Est. Priority Date: 03/27/2009
• Status: Active Grant

• Current Assignee: Lutron Technology Company LLC
• Original Assignee: Lutron Electronics Company Incorporated (Lutron Electronics)
• Inventors: Sloan, Greg Edward, Steiner, James P.
• Granted Patent: US 8,410,706 B2
• Time in Patent Office: Days
• US Class Current: 315/149
• CPC Class Codes: G01J 1/02 Details
• CPC Class Codes: G01J 1/0219 Electrical interface; User interface
• CPC Class Codes: G01J 1/0233 Handheld
• CPC Class Codes: G01J 1/16 using electric radiation detectors G01J1/20 takes precedence
• CPC Class Codes: G01J 1/1626 Arrangements with two photodetectors, the signals of which are compared
• CPC Class Codes: G01J 1/32 adapted for automatic variation of the measured or reference value regulation of light intensity G05D25/00
• CPC Class Codes: G01J 1/4228 arrangements with two or more detectors, e.g. for sensitivity compensation
• CPC Class Codes: H05B 47/11 by determining the brightness or colour temperature of ambient light
• CPC Class Codes: Y02B 20/40 Control techniques providing energy savings, e.g. smart controller or presence detection

Abstract

A wireless lighting control system comprises a daylight sensor for measuring a light intensity in a space and a dimmer switch for controlling the amount of power delivered to a lighting load in response to the daylight sensor. For example, the daylight sensor may be able to transmit radio-frequency (RF) signals to the dimmer switch. The system provides methods of calibrating the daylight sensor that allow for automatically measuring and/or calculating one or more operational characteristics of the daylight sensor. One method of calibrating the daylight sensor comprises a “single-button-press” calibration procedure during which a user is only required to actuate a calibration button of the daylight sensor once. In addition, the daylight sensor is operable to automatically measure the total light intensity in the space at night to determine the light intensity of only the electrical light generated by the lighting load.

Claims

1. A method of calibrating a daylight sensor for measuring a light intensity in a space, the daylight sensor operating as part of a lighting control system that comprises a dimmer switch for controlling a present light intensity of a lighting load, so as to control a total light intensity on a task surface in the space, the method comprising the steps of:

installing the daylight sensor on a surface;

adjusting the present light intensity of the lighting load, such that the total light intensity on the task surface is at a target task surface light intensity;

actuating a button on the daylight sensor;

measuring the total light intensity at the daylight sensor in response to the actuation of the button on the daylight sensor;

the daylight sensor subsequently transmitting the total measured light intensity to the dimmer switch; and

the dimmer switch subsequently calculating a daylight gain in response to the total light intensity measured by the daylight sensor and the present light intensity of the lighting load.

2. The method of claim 1, comprising the step of:

the dimmer switch subsequently determining a new light intensity for the lighting load in response to the daylight gain and the total light intensity measured by the daylight sensor.

3. The method of claim 2, comprising the step of:

the dimmer switch calculating a measured light intensity from only the lighting load when the total light intensity on the task surface is at the target task surface light intensity using the present light intensity of the lighting load and a maximum light intensity possible on the task surface from only the lighting load.

4. The method of claim 3, comprising the step of:

the dimmer switch calculating a light intensity on the task surface from only daylight by subtracting the measured light intensity from only electric light from the target task surface light intensity.

5. The method of claim 4, wherein the dimmer switch calculates the daylight gain by dividing the light intensity on the task surface from only daylight by the total light intensity measured by the daylight sensor.

6. The method of claim 2, comprising the step of:

the dimmer switch loading a default value of the daylight gain when power is first applied to the dimmer switch.

7. The method of claim 6, wherein the default value of the daylight gain is approximately 1.5.

8. The method of claim 2, wherein the step of adjusting the present light intensity of the lighting load comprises actuating an intensity adjustment actuator on the dimmer switch.

9. The method of claim 2, wherein the step of adjusting the present light intensity of the lighting load comprises actuating an actuator on the daylight sensor.

10. The method of claim 2, further comprising the steps of:

placing the daylight sensor on the task surface; and

displaying on a visual display on the daylight sensor a representation of the total light intensity measured by the daylight sensor;

wherein adjusting the present light intensity of the lighting load comprises adjusting the present light intensity of the lighting load until the visual display on the daylight sensor displays a representation of the target task surface light intensity.

11. The method of claim 1, further comprising the steps of:

the dimmer switch turning the lighting load on to a maximum light intensity;

subsequently measuring the light intensity at the daylight to determine a total measured light intensity;

the daylight sensor subsequently transmitting the total measured light intensity to the dimmer switch;

the dimmer switch subsequently turning the lighting load off;

subsequently measuring the light intensity at the daylight sensor to determine a measured light intensity from only daylight;

the daylight sensor subsequently transmitting the measured light intensity from only daylight to the dimmer switch; and

the dimmer switch calculating an electric light gain in response to the total measured light intensity and the measured light intensity from only daylight.

12. The method of claim 11, further comprising the step of:

the dimmer switch calculating a measured light intensity from only electric light by subtracting the measured light intensity from only daylight from the total measured light intensity.

13. The method of claim 12, wherein the dimmer switch calculates the electric light gain by dividing a maximum light intensity possible on the task surface from only the lighting load by the measured light intensity from only electric light

14. The method of claim 11, comprising the step of:

the dimmer switch loading default values of the daylight gain and the electric light gain when power is first applied to the dimmer switch.

15. The method of claim 14, wherein the default value of the daylight gain is approximately 1.5.

16. The method of claim 1, further comprising the steps:

the load control device adjusting the intensity of the lighting load to a predetermined intensity when the total light intensity measured by the daylight sensor has dropped below a threshold;

the daylight sensor measuring the magnitude of the light intensity in the space when intensity of the lighting load is at the predetermined intensity to generate an electric-light-only measured light intensity value, the electric-light-only measured light intensity value being representative of the light intensity of only the lighting load;

the daylight sensor subsequently transmitting the electric-light-only measured light intensity value to the dimmer switch; and

the dimmer switch storing the electric-light-only measured light intensity value in a memory.

17. The method of claim 16, comprising the step of:

the dimmer switch loading a default value of the electric-light-only measured light intensity value when power is first applied to the dimmer switch.

18. The method of claim 1, further comprising the steps of:

placing a second daylight sensor on the task surface;

measuring the total light intensity at the second daylight sensor in response to the actuation of the button on the daylight sensor;

the second daylight sensor subsequently transmitting the total measured light intensity to the dimmer switch; and

the dimmer switch subsequently calculating the daylight gain in response to the total light intensities measured by both daylight sensors and the present light intensity of the lighting load.

19. A dimmer switch for controlling the amount of power delivered from an AC power source to a lighting load to control a present light intensity of the lighting load in response to a light intensity in a space, so as to control a total light intensity on a task surface in the space, the dimmer switch comprising:

a controllably conductive device adapted to be coupled in series electrical connection between the source and the load for controlling the amount of power delivered to the load;

a controller coupled to a control input of the controllably conductive device for controlling the controllably conductive device to adjust the present light intensity of the lighting load, such that the total light intensity on the task surface is at a target task surface light intensity; and

a communication circuit coupled to the controller and adapted to receive a digital message including a value representative of the light intensity in the space;

wherein the controller is operable to calculate a daylight gain in response to the value representative of the light intensity in the space and the present light intensity of the lighting load.

20. The dimmer switch of claim 19, wherein the controller is operable to adjust the present light intensity of the lighting load in response to digital messages received via the communication circuit.

21. The dimmer switch of claim 19, further comprising:

an intensity adjustment actuator operatively coupled to the controller;

wherein the controller is operable to adjust the present light intensity of the lighting load in response to actuations of the intensity adjustment actuator.

22. A method of calibrating a daylight sensor for measuring a light intensity in a space, the daylight sensor operating as part of a lighting control system that comprises a load control device for controlling the power delivered to a lighting load, the method comprising the steps of:

installing the daylight sensor on a surface;

the daylight sensor periodically measuring the light intensity in the space;

comparing the measured light intensity to a threshold;

the load control device adjusting the intensity of the lighting load to a predetermined intensity when the measured light intensity has dropped below the threshold;

the daylight sensor measuring the magnitude of the light intensity in the space when intensity of the lighting load is at the predetermined intensity to generate an electric-light-only measured light intensity value, the electric-light-only measured light intensity value being representative of the light intensity of only the lighting load; and

storing the electric-light-only measured light intensity value in a memory.

23. The method of claim 22, wherein the load control device comprises a dimmer circuit, the method further comprising the steps of:

the dimmer circuit adjusting the intensity of the lighting load to two predetermined intensities when the measured light intensity has dropped below the threshold;

the daylight sensor measuring the magnitude of the light intensity in the space when intensity of the lighting load is at each of the predetermined intensities to generate two electric-light-only measured light intensity values, each of the electric-light-only measured light intensity values representative of the light intensity of only the lighting load; and

storing the two measured light intensities from below the threshold in the memory.

24. The method of claim 23, further comprising the steps of:

using the two electric-light-only measured light intensity values in the memory to calculate a new intensity for the lighting load; and

the dimmer circuit subsequently adjusting the intensity of the lighting load to the new intensity.

25. The method of claim 24, further comprising the step of:

using the two electric-light-only measured light intensity values in the memory to calculate a value representative of the light intensity at the daylight sensor that results from only the light emitted by the lighting load;

wherein the new intensity is a function of the difference between a present measured light intensity and the value representative of the light intensity at the daylight sensor that results from only the light emitted by the lighting load.

26. The method of claim 23, wherein the two predetermined intensities comprise 100% and 50% of a maximum intensity of the lighting load.

27. The method of claim 22, further comprising the step of:

connecting the daylight sensor to a power source.

28. The method of claim 27, further comprising the steps of:

the daylight sensor starting a timeout timer when the daylight sensor is connected to the power source;

the daylight sensor storing each of the periodic measured light intensities and a respective time of day in the memory; and

determining the time of day of a lowest one of the measured light intensities in the memory if the timeout timer expires before the measured light intensity has drops below the threshold.

29. The method of claim 28, further comprising the steps of:

the dimmer circuit adjusting the intensity of the lighting load to the predetermined intensity at the time of day of the lowest one of the measured light intensities;

the daylight sensor measuring the magnitude of the light intensity in the space at the time of day of the lowest one of the measured light intensities to generate the electric-light-only measured light intensity value; and

storing the electric-light-only measured light intensity value at the time of day of the lowest one of the measured light intensities in a memory.

30. The method of claim 28, further comprising the steps of:

the daylight sensor determining an offset time from the present time and the time of day of the lowest one of the measured light;

the daylight sensor initializing a calibration timer with the offset time;

the daylight sensor subsequently starting the calibration timer decreasing in value with respect to time;

the dimmer circuit adjusting the intensity of the lighting load to the predetermined intensity when the calibration timer expires;

the daylight sensor measuring the magnitude of the light intensity in the space after the calibration timer expires to generate the electric-light-only measured light intensity value; and

storing the electric-light-only measured light intensity value in a memory.

31. The method of claim 27, further comprising the steps of:

storing a default light intensity value in the memory, the default light intensity value in the memory representative of the light intensity of only the lighting load;

using the default light intensity value in the memory to calculate a new intensity for the lighting load after the daylight sensor has been connected to the power source and before the measured light intensity has dropped below the threshold; and

the dimmer circuit subsequently adjusting the intensity of the lighting load to the new intensity.

32. The method of claim 27, wherein the step of connecting the daylight sensor to a power source further comprises installing a battery in the daylight sensor.

33. The method of claim 22, further comprising the steps of:

the daylight sensor starting a recalibration timer after the daylight sensor measures the magnitude of the light intensity in the space when the light intensity of the lighting load is at the predetermined intensity;

the load control device re-adjusting the intensity of the lighting load to the predetermined intensity when the recalibration timer expires;

the daylight sensor re-measuring the magnitude of the light intensity in the space after the recalibration timer expires; and

storing the re-measured light intensity in the memory.

34. The method of claim 33, further comprising the steps of:

determining an error between the previous measured light intensity from below the threshold and the re-measured light intensity from after the recalibration timer expires; and

the daylight sensor re-starting the recalibration timer if the error exceeds a maximum error.

35. The method of claim 33, wherein the recalibration timer expires after approximately two days.

36. The method of claim 22, further comprising the step of:

the daylight sensor transmitting a digital message to the load control device when the measured light intensity has dropped below the threshold;

wherein the load control device adjusts the intensity of the lighting load to the predetermined intensity in response to receiving the digital message.

37. The method of claim 22, wherein the load control device comprises an electronic switch and the predetermined intensity comprises approximately 100% of the maximum intensity of the lighting load.

38. A daylight sensor for measuring a light intensity in a space, the daylight sensor adapted to operate as part of a lighting control system that comprises a dimmer circuit for controlling the amount of power delivered to a lighting load, the daylight sensor comprising:

a photosensitive circuit operable to generate a light intensity control signal in response to the light intensity in the space;

a transmitter for transmitting signals; and

a controller coupled to the photosensitive circuit and the transmitter, the controller operable to transmit signals in response to the light intensity control signal, the controller further operable to periodically measure the light intensity in the space, compare the measured light intensity to a threshold, and transmit a command to adjust the intensity of the lighting load to a predetermined intensity when the measured light intensity has dropped below the threshold;

wherein the controller measures the magnitude of the light intensity in the space when the light intensity of the lighting load is at the predetermined intensity to generate a electric-light-only measured light intensity value, and stores the electric-light-only measured light intensity value in a memory, the electric-light-only measured light intensity value being representative of the light intensity of only the lighting load.

39. The sensor of claim 38, further comprising:

a battery for powering the photosensitive circuit, the wireless transmitter, and the controller; and

a memory coupled to the controller for storing measured light intensities;

wherein the controller starts a timeout timer when the controller becomes powered by the battery, the controller operable to store each of the periodic measured light intensities and a respective time of day in the memory, the controller further operable to determine the time of day of a lowest one of the measured light intensities in the memory if the timeout timer expires before the measured light intensity has dropped below the threshold.

40. The sensor of claim 39, wherein the controller transmits a command to adjust the light intensity of the lighting load to the predetermined intensity at the time of day of the lowest one of the measured light intensities, the controller further operable to measure the magnitude of the light intensity in the space at the time of day of the lowest one of the measured light intensities to generate the electric-light-only measured light intensity value, and to store the electric-light-only measured light intensity value in a memory.

41. The sensor of claim 40, wherein the controller determines an offset time from the present time and the time of day of the lowest one of the measured light, initializes a calibration timer with the offset time, subsequently starts the calibration timer decreasing in value with respect to time, and transmits a command to adjust the intensity of the lighting load to the predetermined intensity when the calibration timer expires, the controller further operable to measure the magnitude of the light intensity in the space after the calibration timer expires to generate the electric-light-only measured light intensity value, and store the electric-light-only measured light intensity value in a memory.

42. The sensor of claim 38, wherein the controller starts a recalibration timer after the photosensitive circuit measures the magnitude of the light intensity in the space when intensity of the lighting load is at the predetermined intensity, transmits a command to adjust the intensity of the lighting load to the predetermined intensity when the recalibration timer expires, re-measures the magnitude of the light intensity in the space after the recalibration timer expires to generate a re-measured electric-light-only light intensity value, and stores the re-measured electric-light-only light intensity in the memory.

43. The sensor of claim 42, wherein the controller determines an error between the previous measured light intensity from below the threshold and the re-measured electric-light-only light intensity from after the recalibration timer expires, and re-starts the recalibration timer if the error exceeds a maximum error.

44. The sensor of claim 38, wherein the transmitter comprises a wireless transmitter for transmitting wireless signals.

45. A method of controlling the amount of power delivered to a lighting load to a new light intensity in a system comprising a dimmer circuit and a daylight sensor for measuring a total light intensity in a space, the method comprising the steps of:

storing in a memory one or more light intensity values representative of the light intensity of only the lighting load;

calculating a light intensity value representative of the light intensity at the daylight sensor that results from only the light emitted by the lighting load at the new light intensity as a function of the light intensity values stored in the memory;

calculating the new intensity value as a function of the difference between a present measured light intensity and the value representative of the light intensity at the daylight sensor that results from only the light emitted by the lighting load; and

the dimmer circuit subsequently adjusting the intensity of the lighting load to the new intensity.

46. A daylight sensor for measuring a light intensity in a space, the daylight sensor adapted to operate as part of a lighting control system that comprises a dimmer circuit for controlling the amount of power delivered to a lighting load, the daylight sensor comprising:

a photosensitive circuit operable to generate a light intensity control signal in response to the light intensity in the space;

a transmitter for transmitting signals;

a controller coupled to the photosensitive circuit and the transmitter, the controller operable to transmit signals in response to the light intensity control signal; and

a memory for storing one or more light intensity values representative of the light intensity of only the lighting load;

wherein the controller is operable to calculate a present light intensity value representative of the light intensity at the daylight sensor that results from only the light emitted by the lighting load at a present light intensity of the lighting load as a function of the light intensity values stored in the memory, the controller further operable to calculate a new light intensity for the lighting load as a function of the difference between a present measured light intensity and the present light intensity value representative of the light intensity at the daylight sensor that results from only the light emitted by the lighting load, the controller further operable to transmit a command to adjust the intensity of the lighting load to the new light intensity.

47. A dimmer switch for controlling the amount of power delivered from an AC power source to a lighting load to control an present light intensity of the lighting load in response to a light intensity in a space, so as to control a total light intensity on a task surface in the space, the dimmer switch comprising:

a controllably conductive device adapted to be coupled in series electrical connection between the source and the lighting load for controlling the amount of power delivered to the lighting load;

a controller coupled to a control input of the controllably conductive device for controlling the controllably conductive device to adjust the present light intensity of the lighting load, such that the total light intensity on the task surface is at a target task surface light intensity;

a memory for storing at least one light intensity value representative of the light intensity of only the lighting load; and

a communication circuit coupled to the controller and adapted to receive a digital message including a value representative of a total light intensity in the space;

wherein the controller is operable to calculate a present light intensity value representative of total light intensity in the space that results from only the light emitted by the lighting load at a present light intensity of the lighting load as a function of the light intensity value stored in the memory, the controller further operable to calculate a new light intensity for the lighting load as a function of the difference between a present measured light intensity and the present light intensity value representative of the light intensity at the daylight sensor that results from only the light emitted by the lighting load, the controller further operable to adjust the intensity of the lighting load to the new light intensity.

48. A method of calibrating a daylight sensor for measuring a light intensity in a space, the daylight sensor operating as part of a lighting control system that comprises a dimmer switch for controlling a present light intensity of a lighting load, so as to control a total light intensity on a task surface in the space, the method comprising the steps of:

placing the daylight sensor on the task surface;

actuating a button on the daylight sensor to adjust the present light intensity of the lighting load, such that the total light intensity on the task surface is at a target task surface light intensity;

measuring the light intensity at the daylight sensor to generate a total-at-task-surface light intensity value;

turning off the lighting load;

measuring the light intensity at the daylight sensor to generate a daylight-at-task-surface light intensity value;

installing the daylight sensor on a ceiling surface;

adjusting the present light intensity of the lighting load, such that the total light intensity on the task surface is at the target task surface light intensity;

measuring the light intensity at the daylight sensor to generate a total-at-ceiling light intensity value;

turning off the lighting load;

measuring the light intensity at the daylight sensor to generate a daylight-at-ceiling light intensity value; and

calculating one or more gains using the total-at-task-surface light intensity value, the daylight-at-task-surface light intensity value, the total-at-ceiling light intensity value, and the daylight-at-ceiling light intensity value.

49. A method of calibrating a first daylight sensor for measuring a light intensity in a space, the first daylight sensor operating as part of a lighting control system that comprises a dimmer switch for controlling a present light intensity of a lighting load, so as to control a total light intensity on a task surface in the space, the method comprising the steps of:

installing the first daylight sensor on a ceiling surface;

placing a second daylight sensor on the task surface;

measuring the light intensity at the first daylight sensor to generate a total-at-ceiling light intensity value;

adjusting the present light intensity of the lighting load, such that the total light intensity on the task surface is at a target task surface light intensity;

measuring the light intensity at the second daylight sensor to generate a total-at-task-surface light intensity value;

turning off the lighting load;

measuring the light intensity at the first daylight sensor to generate a daylight-at-ceiling light intensity value;

measuring the light intensity at the second daylight sensor to generate a daylight-at-task-surface light intensity value;

and

calculating one or more gains using the total-at-task-surface light intensity value, the daylight-at-task-surface light intensity value, the total-at-ceiling light intensity value, and the daylight-at-ceiling light intensity value.

50. A method of calibrating a daylight sensor for measuring a light intensity in a space, the daylight sensor operating as part of a lighting control system that comprises a dimmer switch for controlling a present light intensity of a lighting load, so as to control a total light intensity on a task surface in the space, the method comprising the steps of:

placing the daylight sensor on the task surface;

measuring the light intensity at the daylight sensor;

displaying a representation of the total light intensity measured by the daylight sensor on a visual display of the daylight sensor;

adjusting the present light intensity of the lighting load until the visual display on the daylight sensor displays a representation of a target task surface light intensity, such that the total light intensity on the task surface is equal to the target task surface light intensity;

storing the present light intensity of the lighting load in a memory;

measuring the light intensity at the daylight sensor to generate a total-at-task-surface light intensity value;

turning off the lighting load;

measuring the light intensity at the daylight sensor to generate a daylight-at-task-surface light intensity value;

installing the daylight sensor on a ceiling surface;

adjusting the present light intensity of the lighting load to the stored light intensity in the memory;

measuring the light intensity at the daylight sensor to generate a total-at-ceiling light intensity value;

turning off the lighting load;

measuring the light intensity at the daylight sensor to generate a daylight-at-ceiling light intensity value; and

calculating one or more gains using the total-at-task-surface light intensity value, the daylight-at-task-surface light intensity value, the total-at-ceiling light intensity value, and the daylight-at-ceiling light intensity value.

51. A method of calibrating a daylight sensor for measuring a light intensity in a space, the daylight sensor operating as part of a lighting control system that comprises a dimmer switch for controlling a present light intensity of a lighting load, so as to control a total light intensity on a task surface in the space, the method comprising the steps of:

actuating a button on the daylight sensor until a visual display of the daylight sensor displays a representation of a target task surface light intensity;

automatically adjusting the present light intensity of the lighting load, such that the total light intensity on the task surface is equal to the target task surface light intensity;

placing the daylight sensor on the task surface;

measuring the light intensity at the daylight sensor to generate a total-at-task-surface light intensity value;

turning off the lighting load;

measuring the light intensity at the daylight sensor to generate a daylight-at-task-surface light intensity value;

installing the daylight sensor on a ceiling surface;

adjusting the present light intensity of the lighting load, such that the total light intensity on the task surface is at the target task surface light intensity;

measuring the light intensity at the daylight sensor to generate a total-at-ceiling light intensity value;

turning off the lighting load;

measuring the light intensity at the daylight sensor to generate a daylight-at-ceiling light intensity value; and

calculating one or more gains using the total-at-task-surface light intensity value, the daylight-at-task-surface light intensity value, the total-at-ceiling light intensity value, and the daylight-at-ceiling light intensity value.