US 7,608,807 B2 · Closed loop daylight harvesting light control system having auto-calibration

Abstract

An apparatus and method for enabling an automatic calibration sequence for a light control system having a daylight harvesting scheme is disclosed herein. An ambient light sensor connects to a detection circuit for detecting the amount of ambient light within a given zone. A microprocessor connects between the detection circuit and a dimming circuit for providing control to initiate dimming and to start the auto-calibration sequence. Responsive to the amount of ambient light detected, the dimming circuit controls the power supplied to a plurality of electrical loads. A storage unit connects to the microprocessor for storing minimum light levels assessed during the auto-calibration sequence wherein the ambient light levels are monitored for a predetermined amount of time to determine the lowest level of ambient light generated for the purpose of setting and storing a target voltage level associated with such.

Claims21

Dependent claims

A method of auto-calibration for setting the target voltage level of a light sensor included within a daylight harvesting controller, comprising the steps of:

a. forcing all attached electrical loads to full illumination for a defined period of time;
b. disabling all control device inputs to each electrical load during the defined time period;
c. monitoring the light sensor during the defined time period;
d. detecting the light level sensed by the light sensor;
e. comparing each detected light level with a previously stored light level;
f. determining which light level is the lowest light level;
g. generating a target voltage level based upon the lowest light level;
h. storing the lowest light level and the target voltage level;
and
i. repeating steps c through h.

7 more elements

A light control system for controlling the brightness of a plurality of electrical loads, comprising:

an ambient light sensor that outputs a first signal in response to being exposed to radiation for sensing the ambient light level;
a detection circuit coupled to the light sensor to generate a second signal from the first signal;
a storage unit coupled to receive the second signal;
a microprocessor, having an auto-calibration subroutine, the microprocessor coupled to receive the second signal from the detection circuit to control the plurality of electrical loads;
and
a dimming circuitry unit coupled between the microprocessor and the plurality of electrical loads for increasing and decreasing the illumination of the plurality of electrical loads;
wherein, during the activation of the auto-calibration subroutine for a predetermined period of time, the microprocessor generates a third signal and sends the third signal to the dimming circuitry to force the plurality of electrical loads to full illumination and disables control of the plurality of electrical loads, the microprocessor sets a target signal level equal to the second signal at the beginning of the predetermined period of time and stores the target signal level in the storage unit, the microprocessor monitors the second signal for the predetermined period of time and compares the second signal with the stored target signal level to determine which is a lower signal, the microprocessor sets the target signal level to equal the lower signal and stores the target signal level in the storage unit.

4 more elements

Dependencies are inferred from the claim text.

Closed loop daylight harvesting light control system having auto-calibration

Life of this patent

Closed loop daylight harvesting light control system having auto-calibration

Life of this patent

Abstract

Claims21