Wireless Battery-Powered Daylight Sensor

• US 20100244709A1
• 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 8,451,116 B2
• Time in Patent Office: Days
• US Class Current: 315/158
• CPC Class Codes: G01J 1/02 Details
• CPC Class Codes: G01J 1/0219 Electrical interface; User interface
• CPC Class Codes: G01J 1/0228 Control of working procedures; Failure detection; Spectral bandwidth calculation
• CPC Class Codes: G01J 1/0247 using a charging unit
• CPC Class Codes: G01J 1/16 using electric radiation detectors G01J1/20 takes precedence
• 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 1/44 Electric circuits for command of an exposure part G03B7/02
• CPC Class Codes: H05B 47/10 Controlling the light source
• CPC Class Codes: H05B 47/11 by determining the brightness or colour temperature of ambient light
• CPC Class Codes: H05B 47/19 via wireless transmission
• CPC Class Codes: Y02B 20/40 Control techniques providing energy savings, e.g. smart controller or presence detection

Abstract

A wireless battery-powered daylight sensor for measuring a total light intensity in a space is operable to transmit wireless signals using a variable transmission rate that is dependent upon the total light intensity in the space. The sensor comprises a photosensitive circuit, a wireless transmitter for transmitting the wireless signals, a controller coupled to the photosensitive circuit and the wireless transmitter, and a battery for powering the photosensitive circuit, the wireless transmitter, and the controller. The photosensitive circuit is operable to generate a light intensity control signal in response to the total light intensity in the space. The controller transmits the wireless signals in response to the light intensity control signal using the variable transmission rate that is dependent upon the total light intensity in the space. The variable transmission rate may be dependent upon an amount of change of the total light intensity in the space. In addition, the variable transmission rate may be further dependent upon a rate of change of the total light intensity in the space.

Claims

1. A wireless battery-powered daylight sensor for measuring a total light intensity in a space, the sensor comprising:

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

a wireless transmitter for transmitting wireless signals;

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

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

wherein the controller is operable to transmit wireless signals using a variable transmission rate that is dependent upon the total light intensity in the space.

2. The daylight sensor of claim 1, wherein the wireless signals comprise digital messages, each digital message including a value representative of the total light intensity.

3. The daylight sensor of claim 2, wherein the variable transmission rate is dependent upon an amount of change of the total light intensity in the space.

4. The daylight sensor of claim 3, wherein the controller periodically samples the light intensity control signal, the daylight sensor further comprising a memory coupled to the controller for storing sampled light intensity values, the controller operable to analyze the sampled light intensity values stored in the memory to determine the amount of change of the total light intensity in the space.

5. The daylight sensor of claim 4, wherein the controller determines at least one predicted light intensity value and calculates an error between the sampled light intensity values and the at least one predicted light intensity value, the controller operable to transmit a digital message if the error is too great.

6. The daylight sensor of claim 5, wherein the controller collects a predetermined number of sampled light intensity values during consecutive non-overlapping time intervals, the controller operable to analyze the sampled light intensity values of each time interval to determine the amount of change of the total light intensity in the space.

7. The daylight sensor of claim 6, wherein the controller determines at least one estimator during a previous time interval, and uses the at least one estimator to determine the at least one predicted light intensity value during a present time interval.

8. The daylight sensor of claim 7, wherein the controller calculates multiple predicted light intensity values during the present time interval.

9. The daylight sensor of claim 8, wherein the controller uses a linear prediction model to calculate the multiple predicted light intensity values, the estimators comprising a slope and an offset of a line that best represents the change of the total light intensity in the space.

10. The daylight sensor of claim 9, wherein the controller transmits the slope and the offset of the line that best represents the change of the total light intensity in the space when the error between the sampled light intensity values and the predicted light intensity values is too great.

11. The daylight sensor of claim 9, wherein the controller performs a linear least-squares fit to determine the slope and the offset of the line that best represents the change of the total light intensity in the space.

12. The daylight sensor of claim 8, wherein the controller uses a parabolic prediction model to calculate the multiple predicted light intensity values, the estimators comprising coefficients of a parabola that best represents the change of the total light intensity in the space.

13. The daylight sensor of claim 8, wherein the controller calculates a mean-square error between the predicted light intensity values and the sampled light intensity values, the controller operable to transmit a digital message if the mean-square error exceeds a maximum error.

14. The daylight sensor of claim 7, wherein the estimator comprises a minimum sampled light intensity value from the previous time interval, the controller operable to transmit a digital message if the difference between the estimator and a minimum sampled light intensity value from the present time interval exceeds a maximum error.

15. The daylight sensor of claim 14, wherein the controller transmits the minimum sampled light intensity value from the present time interval when the difference between the estimator and a minimum sampled light intensity value from the present time interval exceeds the maximum error.

16. The daylight sensor of claim 7, wherein the estimator comprises an average value of the sampled light intensity values from the previous time interval, the controller operable to transmit a digital message if the difference between the estimator and an average value of the sampled light intensity values from the present time interval exceeds a maximum error.

17. The daylight sensor of claim 7, wherein the estimator comprises a median value of the sampled light intensity values from the previous time interval, the controller operable to transmit a digital message if the difference between the estimator and a median value of the sampled light intensity values from the present time interval exceeds a maximum error.

18. The daylight sensor of claim 6, wherein the controller is operable to analyze the samples stored in the memory to determine if the data is misbehaving.

19. The daylight sensor of claim 18, wherein the controller calculates a behavior metric and determines if the data behavior metric is outside of one or more data behavior metric limits.

20. The daylight sensor of claim 19, wherein the data behavior metric comprises a rate of change of the total light intensity in the space.

21. The daylight sensor of claim 20, wherein the controller is operable to transmit a digital message if the rate of change of the total light intensity in the space is within the one or more data behavior metric limits.

22. The daylight sensor of claim 21, wherein the controller uses a maximum sampled light intensity value and a minimum sampled light intensity value from the present time interval to determine if the rate of change of the total light intensity in the space is within the one or more data behavior metric limits.

23. The daylight sensor of claim 19, wherein the data behavior metric comprises a dynamic change in the total light intensity in the space.

24. The daylight sensor of claim 5, wherein the controller periodically samples the light intensity control signal and stores the samples in memory, the controller operable to analyze the samples stored in memory using a sliding window time interval to determine the amount of change of the total light intensity in the space.

25. The daylight sensor of claim 2, wherein the variable transmission rate is also dependent upon a rate of change of the total light intensity in the space.

26. The daylight sensor of claim 25, wherein the controller periodically samples the light intensity control signal, the daylight sensor further comprising a memory coupled to the controller for storing sampled light intensity values, the controller operable to analyze the samples stored in the memory to determine the rate of change of the total light intensity in the space.

27. The daylight sensor of claim 26, wherein the controller does not transmit a digital message if the rate of change of the total light intensity is outside of predetermined limits.

28. The daylight sensor of claim 2, wherein the variable transmission rate is also dependent upon a dynamic change in the total light intensity in the space.

29. The daylight sensor of claim 1, wherein the controller is operable to enable the photosensitive circuit and subsequently sample the light intensity control signal at a sampling period, the controller further operable to disable the photosensitive circuit after the light intensity control signal has been sampled, such that the photosensitive circuit only draws current from the battery for a small time period during each sampling period.

30. The daylight sensor of claim 29, wherein the controller is operable determine a new light intensity for the lighting load in response to the light intensity control signal, the controller operable to transmit a digital signal if the new light intensity differs from a present light intensity of the lighting load by a predetermined increment.

31. The daylight sensor of claim 1, wherein the controller is operable to disable the photosensitive circuit, such that the photosensitive circuit does not draw current from the battery when the wireless transmitter is not transmitting a wireless signal.

32. A wireless battery-powered daylight sensor for measuring a total light intensity in a space, the sensor comprising:

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

a wireless transmitter for transmitting digital messages;

a controller coupled to the photosensitive circuit and the wireless transmitter, the controller operable to transmit digital messages including values representative of the total light intensity in response to the light intensity control signal; and

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

wherein the controller is operable to transmit digital messages using a variable transmission rate that is dependent upon an amount of change of the total light intensity in the space, and a rate of change of the total light intensity in the space.

33. A wireless battery-powered daylight sensor for measuring a total light intensity in a space, the sensor comprising:

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

a wireless transmitter for transmitting wireless signals;

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

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

wherein the controller is operable to disable the photosensitive circuit, such that the photosensitive circuit does not draw current from the battery.

34. The sensor of claim 33, wherein the photosensitive circuit comprises a photosensitive diode for conducting a photosensitive diode current having a magnitude responsive to the light intensity in the space, the magnitude of the light intensity control signal responsive to the magnitude of the photosensitive diode current.

35. The sensor of claim 34, wherein the photosensitive circuit further comprises a controllable switch coupled in series with the photosensitive diode, the photosensitive diode operable to conduct the photosensitive diode current when the switch is closed, the controller coupled to the switch for opening the switch, such that the photosensitive diode does not conduct the photosensitive diode current and the photosensitive circuit is disabled.

36. The sensor of claim 35, wherein the light intensity control signal is sampled periodically at a sampling rate and the switch is only closed for a portion of the time between each sample.

37. The sensor of claim 36, wherein the controller is operable to determine when it is nighttime in response to the light intensity control signal, and to decrease the sampling rate during the nighttime.

38. The sensor of claim 35, wherein the photosensitive circuit further comprises a transimpedance amplifier coupled between the photosensitive diode and the controller, the transimpedance amplifier operable to generate the light intensity control signal in response to the photosensitive diode current.

39. The sensor of claim 33, wherein the daylight sensor operates as part of a lighting control system that comprises a dimmer switch for controlling the amount of power delivered to a lighting load, the controller operable determine a new light intensity of the lighting load in response to the light intensity control signal, the controller operable to enable the wireless transmitter and to transmit a wireless signal if the new light intensity differs from a present light intensity of the lighting load by a predetermined increment.

40. The sensor of claim 33, wherein the controller is operable to enable the wireless transmitter and to transmit a wireless signal if the total light intensity in the space changes by a predetermined amount.

41. The sensor of claim 33, further comprising:

a wireless receiver coupled to the controller and operable to receive a wireless signal, the wireless receiver powered by the battery; and

a laser pointer circuit adapted to be exposed to light from a laser pointer, the laser pointer circuit coupled to the controller;

wherein the controller is operable to enable the wireless receiver in response to light from a laser pointer shining on the laser pointer circuit, and to subsequently receive a wireless signal.

42. The sensor of claim 33, wherein the controller is operable to enable the photosensitive circuit and subsequently sample the light intensity control signal at a sampling period, the controller further operable to disable the photosensitive circuit after the light intensity control signal has been sampled, such that the photosensitive circuit only draws current from the battery for a small time period during each sampling period.

43. A wireless battery-powered daylight sensor for measuring a total light intensity in a space, the daylight sensor operates as part of a lighting control system that comprises a dimmer switch for controlling the amount of power delivered to a lighting load, the sensor comprising:

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

a wireless transmitter for transmitting wireless signals;

a controller coupled to the photosensitive circuit and the wireless transmitter, the controller operable to determine, in response to the light intensity control signal, a new light intensity to which the dimmer switch should control the intensity of the lighting load;

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

wherein the controller is operable to enable the wireless transmitter and to transmit to the dimmer switch a wireless signal including a command that includes the new light intensity for the lighting load if the new light intensity differs from a present light intensity of the lighting load by a predetermined increment.

44. A wireless battery-powered daylight sensor for measuring a total light intensity in a space, the sensor comprising:

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

a wireless transceiver for transmitting and receiving wireless signals;

a laser pointer circuit adapted to be exposed to light from a laser pointer;

a controller coupled to the photosensitive circuit, the wireless transceiver, and the laser pointer circuit, the controller operable to transmit a wireless signal in response to the light intensity control signal;

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

wherein the controller is operable to enable the wireless transceiver in response to light from a laser pointer shining on the laser pointer circuit, and to subsequently receive a wireless signal.

45. A load control system for controlling the power delivered from an AC power source to an electrical load located in a space of a building, the load control system comprising:

a load control device coupled in series electrical connection between the source and the load for controlling the power delivered to the load; and

a wireless battery-powered daylight sensor for measuring a light intensity in the space, the sensor operable to transmit wireless signals to the load control device in response to the light intensity control signal, such that the load control device controls the power delivered to the load in response to the light intensity in the space, the controller operable to transmit the wireless signals using a variable transmission rate that is dependent upon the light intensity in the space.

46. The system of claim 45, wherein the wireless signals comprise digital messages, each digital message including a value representative of the light intensity in the space.

47. The system of claim 46, wherein the variable transmission rate is dependent upon an amount of change of the light intensity in the space.

48. The system of claim 47, wherein the variable transmission rate is also dependent upon a rate of change of the light intensity in the space.

49. The system of claim 48, wherein the controller transmits a digital message if the rate of change of the total light intensity is within predetermined limits.

50. The system of claim 47, wherein the daylight sensor only transmits a digital message to the load control device if the light intensity in the space has changed by a predetermined amount.

51. The system of claim 47, wherein the controller does not transmit a digital message if the data is misbehaving.

52. The system of claim 47, wherein the variable transmission rate is also dependent upon a dynamic change in the light intensity in the space.

53. The system of claim 45, wherein the wireless signals comprise digital messages, each digital message including a command to control the electrical load in response to the light intensity in the space.

54. The system of claim 53, wherein the load comprises a lighting load, and the load control device comprises a dimmer switch.

55. The system of claim 54, wherein the daylight sensor is operable determine a new light intensity for the lighting load in response to the light intensity in the space, the daylight sensor operable to transmit a digital signal to the dimmer switch if the new light intensity differs from a present light intensity of the lighting load by a predetermined increment.

56. A method of transmitting a digital message in response to a total light intensity in a space, the method comprising:

measuring the total light intensity in the space; and

transmitting wireless signals using a variable transmission rate that is dependent upon the total light intensity in the space.

57. The method of claim 56, wherein the wireless signals comprise digital messages, each digital message including a value representative of the total light intensity.

58. The method of claim 57, wherein the variable transmission rate is dependent upon an amount of change of the total light intensity in the space.

59. The method of claim 58, further comprising:

generating a light intensity control signal in response to the total light intensity in the space;

periodically sampling the light intensity control signal;

storing sampled light intensity values in memory; and

analyzing the sampled light intensity values stored in the memory to determine the amount of change of the total light intensity in the space.

60. The method of claim 59, further comprising:

determining at least one predicted light intensity value; and

calculating an error between the sampled light intensity values and the at least one predicted light intensity value;

wherein the controller is operable to transmit a digital message if the error is too great.

61. The method of claim 60, further comprising:

collecting a predetermined number of sampled light intensity values during consecutive non-overlapping time intervals;

wherein the step of analyzing further comprises analyzing the sampled light intensity values of each time interval to determine the amount of change of the total light intensity in the space.

62. The method of claim 61, further comprising:

determining at least one estimator during a previous time interval;

wherein the step of determining at least one predicted light intensity value comprises using the at least one estimator to determine the at least one predicted light intensity value during a present time interval.

63. The method of claim 62, wherein the step of determining at least one predicted light intensity value comprises calculating multiple predicted light intensity values during the present time interval.

64. The method of claim 63, wherein the step of calculating multiple predicted light intensity values comprises using a linear least-squares prediction model, the estimators comprising a slope and an offset of a line that best represents the change of the total light intensity in the space.

65. The method of claim 64, wherein the step of transmitting wireless signals comprises transmitting the slope and the offset of the line that best represents the change of the total light intensity in the space when the error between the sampled light intensity values and the predicted light intensity values is too great.

66. The method of claim 64, wherein the step of determining at least one estimator during a previous time interval comprises performing a linear least-squares fit to determine the slope and the offset of the line that best represents the change of the total light intensity in the space.

67. The method of claim 63, wherein the step of calculating multiple predicted light intensity values comprises using a parabolic prediction model, the estimators comprising coefficients of a parabola that best represents the change of the total light intensity in the space.

68. The method of claim 63, wherein the step of calculating multiple predicted light intensity values comprises using a linear predictor to calculate the predicted light intensity values.

69. The method of claim 63, further comprising:

calculating a mean-square error between the predicted light intensity values and the sampled light intensity values;

wherein the step of transmitting wireless signals comprises transmitting a digital message if the mean-square error exceeds a maximum error.

70. The method of claim 62, wherein the estimator comprises a minimum sampled light intensity value from the previous time interval, and the step of transmitting wireless signals further comprises transmitting a digital message if the difference between the estimator and a minimum sampled light intensity value from the present time interval exceeds a maximum error.

71. The method of claim 70, wherein the step of transmitting wireless signals further comprises transmitting the minimum sampled light intensity value from the present time interval when the difference between the estimator and a minimum sampled light intensity value from the present time interval exceeds the maximum error.

72. The method of claim 62, wherein the estimator comprises an average value of the sampled light intensity values from the previous time interval, and the step of transmitting wireless signals further comprises transmitting a digital message if the difference between the estimator and an average value of the sampled light intensity values from the present time interval exceeds a maximum error.

73. The method of claim 62, wherein the estimator comprises a median value of the sampled light intensity values from the previous time interval, the step of transmitting wireless signals further comprises transmitting a digital message if the difference between the estimator and a median value of the sampled light intensity values from the present time interval exceeds a maximum error.

74. The method of claim 61, further comprising:

analyzing the samples stored in the memory to determine is the data is misbehaving.

75. The method of claim 74, wherein the step of analyzing the samples stored in the memory to determine if the data is misbehaving further comprises calculating a behavior metric, and determining if the data behavior metric is outside of one or more data behavior metric limits.

76. The method of claim 75, wherein the data behavior metric comprises a rate of change of the total light intensity in the space.

77. The method of claim 76, wherein the step of transmitting wireless signals comprises transmitting a digital message if the rate of change of the total light intensity in the space is within the one or more data behavior metric limits.

78. The method of claim 77, wherein the step of analyzing the samples stored in the memory to determine is the data is misbehaving further comprises using a maximum sampled light intensity value and a minimum sampled light intensity value from the present time interval to determine if the rate of change of the total light intensity in the space is within the one or more data behavior metric limits.

79. The method of claim 60, further comprising:

periodically sampling the light intensity control signal;

storing the samples in memory; and

analyzing the samples stored in memory using a sliding window time interval to determine the amount of change of the total light intensity in the space.

80. The method of claim 57, wherein the variable transmission rate is also dependent upon a rate of change of the total light intensity in the space.

81. The method of claim 80, wherein the controller periodically samples the light intensity control signal, the daylight sensor further comprising a memory coupled to the controller for storing sampled light intensity values, the controller operable to analyze the samples stored in the memory to determine the rate of change of the total light intensity in the space.

82. The method of claim 81, wherein the step of transmitting wireless signals further comprises transmitting a digital message if the rate of change of the total light intensity is within predetermined limits.

83. The method of claim 57, wherein the variable transmission rate is also dependent upon a dynamic change in the total light intensity in the space.

84. The method of claim 56, wherein the wireless signals comprise digital messages, each digital message including a command to control a lighting load in response to the total light intensity.

85. The method of claim 84, further comprising:

determining a new light intensity for the lighting load in response to the light intensity control signal;

wherein the step of transmitting wireless signals further comprises transmitting a digital signal if the new light intensity differs from a present light intensity of the lighting load by a predetermined increment.