Light and light sensor

An LED-based light tube for use in a conventional fluorescent fixture comprising:

• a housing including a light transmitting portion;
• at least one electrical connector attached to the housing and configured for engagement with the conventional fluorescent fixture;
• at least one LED arranged to produce light in a direction toward the light transmitting portion to contribute to a brightness level in an area in combination with an ambient light source other than the at least one LED, such that the brightness level is responsive to the at least one LED and the ambient light source;
• a sensor operable to detect the brightness level and output a signal corresponding to the detected brightness level;
• a controller in electrical communication with the at least one electrical connector and operable to:
• compare the signal to a predetermined value corresponding to a desired brightness level,
• increase an amount of power provided to the at least one LED in response to the signal if the comparison shows that the brightness level is less than the desired brightness level to adjust the light produced by the at least one LED to achieve the desired brightness level,
• decrease an amount of power provided to the at least one LED in response to the signal if the comparison shows that the brightness level is more than the desired brightness level to adjust the light produced by the at least one LED to achieve the desired brightness level, and
• estimate an efficiency of the at least one LED at least partially based on a brightness level detected by the sensor while the at least one LED is operational, wherein the estimated efficiency is proportional to the brightness level detected by the sensor;
• and
• a transmitter operable to transmit at least one of the brightness level and the estimated efficiency of the at least one LED.