Wireless battery-powered daylight sensor

A wireless battery-powered daylight sensor for measuring a total light intensity, the sensor comprising:

• a photosensitive circuit operable to generate a light intensity control signal in response to the total light intensity;
• a wireless transmitter for transmitting wireless signals;
• a controller coupled to the photosensitive circuit and the wireless transmitter, the controller operable to periodically sample the light intensity control signal and transmit wireless signals in response to the light intensity control signal, the controller operable to store sampled light intensity values in a memory and to analyze the sampled light intensity values to determine an amount of change of the total light intensity;
• and
• a battery for powering the photosensitive circuit, the wireless transmitter, and the controller;
• wherein the controller is operable to transmit the wireless signals using a variable transmission rate that is dependent upon the amount of change of the total light intensity, the controller operable to determine at least one predicted light intensity value, calculate an error between the total light intensity and the at least one predicted light intensity value, and transmit a digital message if the error is too great.

A method of transmitting a digital message in response to a total light intensity, the method comprising:

• generating a light intensity control signal in response to the total light intensity;
• periodically sampling the light intensity control signal;
• storing sampled light intensity values in memory;
• analyzing the sampled light intensity values stored in the memory to determine an amount of change of the total light intensity;
• transmitting wireless signals by a controller using a variable transmission rate wherein the variable transmission rate is dependent upon the amount of change of the total light intensity, the wireless signals comprising digital messages, each digital message including a value representative of the total light intensity;
• determining at least one predicted light intensity value;
• and
• calculating an error between the sampled light intensity values and the at least one predicted light intensity value;
• wherein the controller is operable to transmit a digital message if the error is too great.

A method of transmitting a digital message in response to a total light intensity, the method comprising:

• measuring the total light intensity;
• storing sampled light intensity values in response to the step of measuring;
• analyzing the sampled light intensity values to determine an amount of change of the total lighting intensity and a rate of change of the total light intensity;
• determining if the rate of change of the total light intensity is within predetermined limits;
• and
• transmitting wireless signals using a variable transmission rate that is dependent upon the amount of change of the total light intensity and the rate of change of the total light intensity, the wireless signals comprising digital messages including a value representative of the total light intensity;
• wherein the step of transmitting wireless signals further comprises transmitting a digital message if the amount of change of the total light intensity exceeds a predetermined amount and the rate of change of the total light intensity is within predetermined limits.