Method of controlling a motorized window treatment
A method comprises measuring a light intensity at a window; determining if the light intensity exceeds a cloudy-day threshold; operating in a sunlight penetration limiting mode to control the motorized window treatment to control the sunlight penetration distance in the space; enabling the sunlight penetration limiting mode if the light intensity is greater than the cloudy-day threshold; and disabling the sunlight penetration limiting mode if the total lighting intensity is less than the cloudy-day threshold. The cloudy-day threshold is maintained at a constant threshold if a calculated solar elevation angle is greater than a predetermined solar elevation angle, and the cloudy-day threshold varies with time if the calculated solar elevation angle is less than the predetermined solar elevation angle. The cloudy-day threshold is a function of the calculated solar elevation angle if the calculated solar elevation angle is less than the predetermined solar elevation angle.
1. A method of controlling a motorized window treatment, the method comprising:
comparing a light level measured by at least one sensor to a stored light level value;
if a total light level measured by the at least one sensor differs from the stored light level value, then:
setting a cloudy-day threshold value to a first threshold value if a solar elevation angle is greater than a solar elevation cut-off value; and
determining the cloudy-day threshold value as a function of the solar elevation angle if the solar elevation angle is less than the solar elevation cut-off value; and
operating the motorized window treatment in a first mode if the light level measured by the at least one sensor is less than a second threshold value.
2. The method of claim 1 , further comprising:
operating the motorized window treatment in a second mode if the light level measured by the least one sensor is greater than the second threshold value.
3. The method of claim 2 , wherein operating the motorized window treatment in the second mode includes controlling movement of a window covering of the motorized window treatment according to a timeclock schedule to limit a sun penetration distance.
4. The method of claim 2 , wherein operating the motorized window treatment in the first mode includes moving a window covering of the motorized window treatment to a visor position.
5. The method of claim 2 , wherein the first mode is a cloudy-day mode and the second mode is a sunlight penetration limiting mode.
6. The method of claim 5 , wherein operating the motorized window treatment in the sunlight penetration limiting mode includes:
determining if a total intensity of light is greater than a third threshold value;
moving a window covering of the motorized window treatment to a first position if the total intensity of light is greater than the third threshold value; and
moving the window covering of the motorized window treatment to a second position if the total intensity of light is less than the third threshold value.
7. The method of claim 6 , wherein the covering covers more of a window when the window covering is disposed in the first position than when the window covering is disposed in the second position.
8. The method of claim 7 , wherein the window covering covers at least 75 percent of the window when the window covering is disposed in the first position.
9. The method of claim 7 , wherein the window covering covers less than 25 percent of the window when the window covering is disposed in the second position.
10. The method of claim 1 , wherein the stored light level value is a previous light level measured by the at least one sensor.
11. The method of claim 10 , further comprising:
calculating the solar elevation angle prior to determining the cloudy-day threshold value as a function of the solar elevation angle.
12. The method of claim 11 , wherein the solar elevation cut-off value is approximately 15 degrees.
13. The method of claim 1 , wherein the cloudy-day threshold value is a function of a constant threshold value, the solar elevation angle, and the solar elevation cut-off value.
14. A system, comprising:
a motorized window treatment adapted to be positioned adjacent to a window;
at least one sensor; and
a processor in signal communication with the at least one sensor and the motorized window treatment, the processor configured to:
compare a light level measured by the at least one sensor to a stored light level value;
if a total light level measured by the at least one sensor differs from the stored light level value, then processor is configured to:
set a cloudy-day threshold value to a first threshold value if a solar elevation angle is greater than a solar elevation cut-off value, and
determine the cloudy-day threshold value as a function of the solar elevation angle if the solar elevation angle is less than the solar elevation cut-off value.
15. The system of claim 14 , wherein the processor is configured to:
operate the motorized window treatment in a first mode if the light level measured by the at least one sensor is less than a second threshold value; and
operate the motorized window treatment in a second mode if the light level measured by the least one sensor is greater than the second threshold value.
16. The system of claim 15 , wherein the processor is configured to control movement of a window covering of the motorized window treatment according to a timeclock schedule to limit a sun penetration distance when operating the motorized window treatment in the second mode.
17. The system of claim 15 , wherein the processor is configured to control movement of a window covering of the motorized window treatment to a visor position when operating the motorized window treatment in the first mode.
18. The system of claim 15 , wherein the first mode is a cloudy-day mode and the second mode is a sunlight penetration limiting mode.
19. The system of claim 18 , wherein, when the processor operates the motorized window treatment in the sunlight penetration limiting mode, the processor is configured to:
determine if a total intensity of light is greater than a third threshold value;
control movement of a window covering of the motorized window treatment to a first position if the total intensity of light is greater than the third threshold value; and
control movement of the window covering of the motorized window treatment to a second position if the total intensity of light is less than the third threshold value.
20. The system of claim 19 , wherein the processor is configured to:
calculate the solar elevation angle prior to determining the cloudy-day threshold value as a function of the solar elevation angle.