Sky sensor device

1. A processing device comprising:

a first interface coupled to a camera sensor;

a second interface coupled to an illuminance sensor; and

a processor core coupled to the first interface and the second interface, wherein the processor core is to:

control the camera sensor to capture a series of exposure-bracketed images having a first dynamic range and generate an image from the series of exposure-bracketed images, the image having a second dynamic range higher than the first dynamic range;

control the illuminance sensor to measure a global illuminance value;

determine a global horizontal diffuse value based on at least the image; and

determine a direct normal illuminance (DNE) value using the global illuminance value and the global horizontal diffuse value.

2. The processing device of claim 1 , wherein the processor core is further to send the DNE value to an electrochromic window system for controlling a tint level of one or more electrochromic windows of the electrochromic window system.

3. The processing device of claim 1 , wherein the processor core is further to:

determine a first location of the sky's zenith in the image;

determine a second location in the image representing an expected location of the sun using solar altitude and azimuth values;

create a region of interest (ROI) mask in the image at a predetermined radius from the second location;

determine a centroid location of a set of pixels within the ROI mask having brighter pixel values than other pixels in the ROI mask;

determine an angle, relative to the sky's zenith, between the second location and the centroid location; and

rotate the image by the angle to obtain a rotated image.

4. The processing device of claim 3 , wherein the processor core is further to:

determine that the angle satisfies a threshold condition representing a misaligned camera sensor; and

send, to a user, a notification of the misaligned camera sensor responsive to the angle satisfying the threshold condition.

5. The processing device of claim 1 , wherein the DNE value is an amount of illuminance in the visible spectrum and is indicative of a sky condition in a field of view of the camera sensor, the sky condition relating to glare from the sun on a window near the camera sensor.

6. The processing device of claim 5 , wherein the processor core is to report the sky condition to an electrochromic window system for controlling a tint level of one or more electrochromic windows of the electrochromic window system based on the sky condition.

7. The processing device of claim 1 , wherein the processor core is further to:

control the illuminance sensor to measure multiple global illuminance values;

average the multiple global illuminance values to determine an average global illuminance value; and

determine the direct normal illuminance (DNE) value using the average global illuminance value and the global horizontal diffuse value.

8. A method comprising:

controlling a camera sensor to capture a series of exposure-bracketed images having a first dynamic range and generate an image from the series of exposure-bracketed images, the image having a second dynamic range higher than the first dynamic range;

controlling an illuminance sensor to measure a global illuminance value;

determining a global horizontal diffuse value based on at least the image; and

determining a direct normal illuminance (DNE) value using the global illuminance value and the global horizontal diffuse value.

9. The method of claim 8 , further comprising sending the DNE value to an electrochromic window system for controlling a tint level of one or more electrochromic windows of the electrochromic window system.

10. The method of claim 8 , further comprising:

determining a first location of the sky's zenith in the image;

determining a second location in the image representing an expected location of the sun using solar altitude and azimuth values;

creating a region of interest (ROI) mask in the image at a predetermined radius from the second location;

determining a centroid location of a set of pixels within the ROI mask having brighter pixel values than other pixels in the ROI mask;

determining an angle, relative to the sky's zenith, between the second location and the centroid location; and

rotating the image by the angle to obtain a rotated image.

11. The method of claim 10 , further comprising:

determining that the angle satisfies a threshold condition representing a misaligned camera sensor; and

sending a notification to a user of the misaligned camera sensor responsive to the angle satisfying the threshold condition.

12. The method of claim 8 , wherein the DNE value is an amount of illuminance in the visible spectrum and is indicative of a sky condition in a field of view of the camera sensor, the sky condition relating to glare from the sun on a window near the camera sensor.

13. The method of claim 12 , further comprising reporting the sky condition to an electrochromic window system for controlling a tint level of one or more electrochromic windows of the electrochromic window system based on the sky condition.

14. The method of claim 8 , further comprising:

controlling the illuminance sensor to measure multiple global illuminance values;

averaging the multiple global illuminance values to determine an average global illuminance value; and

determining the direct normal illuminance (DNE) value using the average global illuminance value and the global horizontal diffuse value.

15. A computing system comprising:

a memory; and

a processing device operatively coupled to the memory, wherein the processing device is to:

control a camera sensor to capture a series of exposure-bracketed images having a first dynamic range and generate an image from the series of exposure-bracketed images, the image having a second dynamic range higher than the first dynamic range;

control an illuminance sensor to measure a global illuminance value;

determine a global horizontal diffuse value based on at least the image; and

determine a direct normal illuminance (DNE) value using the global illuminance value and the global horizontal diffuse value.

16. The computing system of claim 15 , wherein the processing device is further to send the DNE value to an electrochromic window system for controlling a tint level of one or more electrochromic windows of the electrochromic window system.

17. The computing system of claim 15 , wherein the processing device is further to:

determine a first location of the sky's zenith in the image;

determine a second location in the image representing an expected location of the sun using solar altitude and azimuth values;

create a region of interest (ROI) mask in the image at a predetermined radius from the second location;

determine a centroid location of a set of pixels within the ROI mask having brighter pixel values than other pixels in the ROI mask;

determine an angle, relative to the sky's zenith, between the second location and the centroid location; and

rotate the image by the angle to obtain a rotated image.

18. The computing system of claim 17 , wherein the processing device is further to:

determine that the angle satisfies a threshold condition representing a misaligned camera sensor; and

send, to a user, a notification of the misaligned camera sensor responsive to the angle satisfying the threshold condition.

19. The computing system of claim 15 , wherein the DNE value is an amount of illuminance in the visible spectrum and is indicative of a sky condition in a field of view of the camera sensor, the sky condition relating to glare from the sun on a window near the camera sensor, wherein the processing device is to report the sky condition to an electrochromic window system for controlling a tint level of one or more electrochromic windows of the electrochromic window system based on the sky condition.

20. The computing system of claim 15 , wherein the processing device is further to:

control the illuminance sensor to measure multiple global illuminance values;

average the multiple global illuminance values to determine an average global illuminance value; and

determine the direct normal illuminance (DNE) value using the average global illuminance value and the global horizontal diffuse value.