Method of Controlling a Motorized Window Treatment

A system for controlling a motorized window treatment for adjusting the amount of sunlight entering a space of a building through a window to control a sunlight penetration distance in the space, comprising:

• a sensor for measuring a total light intensity at the window;
• and
• a processor configured to:
• calculate a solar elevation angle;
• calculate a cloudy-day threshold as a function of the calculated solar elevation angle;
• determine if the total light intensity exceeds the cloudy-day threshold;
• enable a sunlight penetration limiting mode when the total light intensity is greater than the cloudy-day threshold;
• operate in the sunlight penetration limiting mode to control the motorized window treatment to thus control the sunlight penetration distance in the space;
• and
• disable the sunlight penetration limiting mode when the total lighting intensity is less than the cloudy-day threshold.

An apparatus comprising:

• at least one processor;
• and
• a computer readable medium communicatively coupled to the at least one processor and having instructions stored thereon that when executed by the at least one processor direct the at least one processor to:
• determine from a sensor a total light intensity at a window of a building;
• calculate a solar elevation angle;
• calculate a cloudy-day threshold as a function of the calculated solar elevation angle;
• determine if the total light intensity exceeds the cloudy-day threshold;
• enable a sunlight penetration limiting mode when the total light intensity is greater than the cloudy-day threshold;
• operate in the sunlight penetration limiting mode to control a motorized window treatment to thus control a sunlight penetration distance of sunlight entering a space of the building through the window;
• and
• disable the sunlight penetration limiting mode when the total lighting intensity is less than the cloudy-day threshold.