Light discriminator for a thermostat

A light discriminator for a thermostat for a heating, ventilation and air conditioning (HVAC) system to maintain the temperature of an occupancy space at a desired temperature, the thermostat including means for measuring the ambient temperature of the occupancy space and means for generating a control signal to the HVAC system for adjusting the temperature of the occupancy space in response to the ambient temperature of the occupancy space and a temperature set point;

• the light discriminator comprising:
• light sensing means for providing a detection signal representative of the intensity of the ambient light of the occupancy space;
• filtering means for generating a light signal representative of the intensity of artificial light present in the occupancy space in response to the detection signal, the filtering means including a full wave rectifier for rectifying an AC power source signal, a bandpass filter centered at about twice the power source frequency and coupled to an output of the full wave rectifier for generating a bandpassed signal having a frequency at about twice the AC power source signal, and a multiplier circuit for multiplying the detection signal and the bandpassed signal for generating a multiplied signal having a DC component having a magnitude indicative of the intensity of artificial light received by the light sensing means;
• and
• adjusting means for changing the temperature set point in response to the light signal.

A thermostat for a heating, ventilation and air conditioning (HVAC) system to maintain the temperature of an occupancy space at a desired temperature in accordance with a temperature set point;

• the thermostat comprising:
• light sensing means for providing a detection signal representative of the intensity of the ambient light of the occupancy space;
• filtering means for generating a light signal representative of the intensity of artificial light present in the occupancy space in response to the detection signal, the filtering means including a band pass filter for filtering the detection signal to pass only the frequency components within a predetermined frequency range, the frequency range being representative of the frequency of the intensity of the artificial light in the occupancy space, and a detector for measuring the frequency of the filtered detection signal and generating the light signal;
• adjusting means for changing the temperature set point in response to the light signal;
• temperature sensing means for providing a temperature signal indicative of the ambient temperature of the occupancy space;
• and
• actuating means for generating a control signal to actuate the HVAC system to adjust the temperature of the occupancy space in response to the temperature signal and the temperature set point.

A thermostat for a heating, ventilation and air conditioning (HVAC) system to maintain the temperature of an occupancy space at a desired temperature in accordance with a temperature set point;

• the thermostat comprising:
• light sensing means for providing a detection signal representative of the intensity of the ambient light of the occupancy space;
• filtering means for generating a light signal representative of the intensity of artificial light present in the occupancy space in response to the detection signal, the filtering means including a full wave rectifier for rectifying an AC power source signal, a bandpass filter coupled to an output of the full wave rectifier and centered at about twice the power source frequency for generating a bandpassed signal having a frequency at about twice the AC power source signal, and a multiplier circuit for multiplying the detection signal and the bandpassed signal for generating a multiplied signal having a DC component having a magnitude indicative of the intensity of artificial light received by the light sensing means;
• adjusting means for changing the temperature set point in response to the light signal;
• temperature sensing means for providing a temperature signal indicative of the ambient temperature of the occupancy space;
• and
• actuating means for generating a control signal to actuate the HVAC system to adjust the temperature of the occupancy space in response to the temperature signal and the temperature set point.

A method of adjusting the temperature of an occupancy space in accordance with the presence of artificial light;

• the method comprising the steps of:
• (a) generating a detection signal representative of the intensity of the ambient light of the occupancy space;
• (b) filtering the detection signal to eliminate the frequency components of light outside of a predetermined frequency range, the frequency range being representative of artificial light in the occupancy space;
• and
• (c) adjusting a temperature set point of a thermostat in response to the filtered detection signal, including determining the frequency of the filtered detection signal, and adjusting a temperature set point of a thermostat in response to the frequency of the filtered signal.

A method of adjusting the temperature of an occupancy space in accordance with the presence of artificial light;

• the method comprising the steps of:
• (a) generating a detection signal representative of the intensity of the ambient light of the occupancy space;
• (b) canceling low frequency components of the detection signal;
• (c) filtering the detection signal to eliminate the frequency components of light outside of a predetermined frequency range, the frequency range being representative of artificial light in the occupancy space;
• and
• (d) adjusting a temperature set point of a thermostat in response to the filtered detection signal.

A method of adjusting the temperature of an occupancy space in accordance with the presence of artificial light;

• the method comprising the steps of:
• (a) generating a detection signal representative of the intensity of the ambient light of the occupancy space;
• (b) filtering the detection signal to eliminate the frequency components of light outside of a predetermined frequency range, the frequency range being representative of artificial light in the occupancy space;
• and
• (c) adjusting a temperature set point of a thermostat in response to the filtered detection signal, including full wave rectifying an AC power source signal to produce a full wave rectified signal, filtering the full wave rectified signal over a range of frequencies centered at about twice the power source frequency for generating a bandpassed signal having a frequency at about twice the AC power source signal, and multiplying the detection signal and the bandpassed signal for generating a multiplied signal having a DC component having a magnitude indicative of the intensity of the ambient light of the occupancy space.