Ambient light sensor auto-calibration in a lighting control system

• US 8,648,550 B2
• Filed: 03/13/2010
• Issued: 02/11/2014
• Est. Priority Date: 03/13/2010
• Status: Active Grant

• Current Assignee: ZiLOG Incorporated (Littelfuse Incorporated)
• Original Assignee: ZiLOG Incorporated (Littelfuse Incorporated)
• Inventors: Staab, David R.
• Primary Examiner(s): Owens, Douglas W
• Assistant Examiner(s): LUONG, HENRY T
• Application Number:
  US12/661,205
• Publication Number:
  US 20110221350A1
• Time in Patent Office: 1,431 Days
• Field of Search: 315/154, 315/158, 315/312, 315/295
• US Class Current: 315/312
• CPC Class Codes: H05B 47/11 by determining the brightness or colour temperature of ambient light
• CPC Class Codes: H05B 47/115 by determining the presence or movement of objects or living beings
• CPC Class Codes: H05B 47/19 via wireless transmission
• CPC Class Codes: H05B 47/195 the transmission using visible or infrared light
• CPC Class Codes: Y02B 20/40 Control techniques providing energy savings, e.g. smart controller or presence detection

Abstract

A lighting system includes a master that controls a plurality of light fixtures via wireless RF communications. An ambient light sensor in the master is used to monitor total ambient light and to prevent excessive illumination. In an auto-calibration process, the master makes ambient light measurements A, B and C when the light fixtures are illuminating an area at a minimum setting, at a maximum setting, and at an intermediate setting, respectively. A first threshold is set to be approximately (B−A). A second threshold is set to be slightly larger than (B−A)+(B−C). In normal system operation, total ambient light measurements are taken and compared to the two thresholds. In one example, if detected brightness is lower than the first threshold then the system is set at its maximum illumination setting, whereas if detected brightness is greater than the second threshold then the system is set at its intermediate illumination setting.

Claims

1. A method comprising:

(a) obtaining first measurement information A, wherein A is indicative of a brightness within a room when both a first group of lamps and a second group of lamps are off;

(b) obtaining second measurement information B, wherein B is indicative of a brightness within the room when both the first group of lamps and the second group of lamps are on;

(c) obtaining third measurement information C, wherein C is indicative of a brightness within the room when the first group of lamps is on and the second group of lamps is off;

(d) setting a first threshold value to be (B−

A);

(e) setting a second threshold value to be slightly larger than (B−

C)+(B−

A);

(f) obtaining fourth measurement information D, wherein D is indicative of a brightness within the room when the first group of lamps is on and the second group of lamps is off;

(g) determining that D is smaller than the first threshold value and in response to the determining of (g) causing the second group of lamps to be turned on;

(h) obtaining fifth measurement information E, wherein E is indicative of a brightness within the room when both the first group of lamps and the second group of lamps are on; and

(i) determining that E is larger than the second threshold value and in response to the determining of (i) causing the second group of lamps to be turned off, wherein the determining of (g) and the determining of (i) are performed by a device, wherein the device can cause the first group of lamps to be turned on and off, and wherein the device can cause the second group of lamps to be turned on and off.

2. The method of claim 1, wherein (a), (b), (c), (d), and (e) are all performed in a period of time of less than twenty minutes, and wherein (f), (g), (h) and (i) are performed after the period of time.

3. The method of claim 2, wherein the first threshold value is within plus or minus twenty percent of (B−

A), and wherein the second threshold value is within forty percent of (B−

C)+(B−

A).

4. The method of claim 3, wherein the first group of lamps is a first group of fluorescent lamps, and wherein the second group of lamps is a second group of fluorescent lamps.

5. The method of claim 1, wherein the setting of the first threshold value of (d) involves the device performing a mathematical operation involving B and A.

6. The method of claim 1, wherein the setting of the second threshold value of (e) involves the device performing a mathematical operation involving B and C.

7. The method of claim 1, wherein the device includes an ambient light sensor, and wherein A, B and C are obtained by making a measurement using the ambient light sensor.

8. The method of claim 1, wherein the obtaining of (a) involves receiving ambient light sensing information onto the device via a wireless communication.

9. The method of claim 1, wherein the device causes the second group of lamps to be turned on in (g) by transmitting at least one wireless command from the device.

10. The method of claim 1, wherein the obtaining of (b) is performed before the obtaining of (a).

11. A method comprising:

(a) obtaining first measurement information A, wherein A is indicative of a brightness within a room when a lighting system is set at a minimum illumination setting;

(b) obtaining second measurement information B, wherein B is indicative of a brightness within the room when the lighting system is set at a maximum illumination setting;

(c) obtaining third measurement information C, wherein C is indicative of a brightness within the room when the lighting system is set at an intermediate illumination setting;

(d) setting a first threshold value to be (B−

A);

(e) setting a second threshold value to be slightly larger than (B−

C)+(B−

A);

(f) obtaining fourth measurement information D, wherein D is indicative of a brightness within the room when the lighting system is set at the intermediate illumination setting;

(g) determining that D is smaller than the first threshold value and in response to the determining of (g) causing the lighting system to be set at the maximum illumination setting;

(h) obtaining fifth measurement information E, wherein E is indicative of a brightness within the room when the lighting system is set at the maximum illumination setting; and

(i) determining that E is larger than the second threshold value and in response to the determining of (i) causing the lighting system to be set at the intermediate illumination setting, wherein the determining of (g) and the determining of (i) are performed by a device, wherein the device can change an illumination setting of the lighting system.

12. The method of claim 11, wherein the lighting system includes a plurality of dimmable lamps, and wherein the device changes an illumination setting of the lighting system by changing how at least one of the dimmable lamps is dimmed.

13. The method of claim 11, wherein (a), (b), (c), (d), and (e) are all performed in a period of time of less than twenty minutes, and wherein (f), (g), (h) and (i) are performed after the period of time.

14. The method of claim 11, wherein the obtaining of (b) is performed before the obtaining of (a).

15. An apparatus comprising:

an ambient light sensor functionality;

a Radio Frequency (RF) transceiver; and

a processor that sets a threshold value to be (B−

A), wherein A is a first ambient light measurement value obtained when an area was illuminated by a lighting system when the lighting system was set at a minimum illumination setting, wherein B is a second ambient light measurement value obtained when the area was illuminated by the lighting system when the lighting system was set at a maximum illumination setting, wherein the processor causes a third ambient light measurement to be taken when the lighting system is illuminating the area at a setting other than the maximum illumination setting, wherein the third ambient light measurement results in a third ambient light measurement value, and wherein the processor determines that the third ambient light measurement value is smaller than the threshold value and in response to the determining the processor causes a wireless RF command to be sent from the RF transceiver thereby causing the setting of the lighting system to be changed to a higher illumination setting.

16. The apparatus of claim 15, wherein the first, second and third ambient light measurement values are obtained using the ambient light sensor functionality of the device, and wherein the first and second ambient light measurement values are obtained and the threshold value is set in a period of time of less than twenty minutes.

17. The apparatus of claim 16, wherein the processor causes the lighting system to illuminate the area using the minimum illumination setting when the first ambient light measurement value is obtained, and wherein the processor causes the lighting system to illuminate the area using the maximum illumination setting when the second ambient light measurement value is obtained.

18. The apparatus of claim 17, wherein the lighting system includes a plurality of light fixtures, wherein each of the light fixtures includes an RF transceiver, and wherein the processor causes the setting of the lighting system to be changed to the higher illumination setting by causing at least one wireless RF command to be sent out of the RF transceiver of the apparatus and to the RF transceivers of the plurality of light fixtures.

19. The apparatus of claim 15, wherein the threshold value is within plus or minus twenty percent of (B−

A).

20. The apparatus of claim 15, wherein the processor sets a second threshold value to be slightly larger than [(B−

A)+(B−

C)], wherein C is a fourth ambient light measurement value obtained when the area was illuminated by the lighting system when the lighting system was set at an intermediate illumination setting.

21. The apparatus of claim 20, wherein the processor causes a fifth ambient light measurement to be taken when the lighting system is illuminating the area set at the maximum illumination setting, wherein the fifth ambient light measurement results in a fifth ambient light measurement value, and wherein the processor determines that the fifth ambient light measurement value is greater than the second threshold value and in response to the determining the processor causes a wireless RF command to be sent from the RF transceiver thereby causing the setting of the lighting system to be changed to the intermediate illumination setting.

22. The apparatus of claim 15, wherein the apparatus further comprises:

an occupancy detector functionality that detects a lack of motion in the room throughout a period of time, and wherein the processor causes the setting of the lighting system to remain at the minimum illumination setting for substantially all of the period of time regardless of ambient lighting conditions in the room.

23. A method comprising:

(a) obtaining first measurement information A, wherein A is indicative of a brightness within a room when a lighting system is set at a first illumination setting;

(b) obtaining second measurement information B, wherein B is indicative of a brightness within the room when the lighting system is set at a second illumination setting, wherein the lighting system has a plurality of different dimming settings in addition to the first illumination setting and the second illumination setting;

(c) setting a first threshold value to be (B−

A);

(d) setting a second threshold value to be a value greater than the first threshold value;

(e) obtaining third measurement information C; and

(f) determining that C is larger than the second threshold value and in response to the determining of (f) causing the setting of the lighting system to be changed from the second illumination setting to one of the dimming settings.

24. The method of claim 23, wherein the obtaining of (b) is performed before the obtaining of (a).