The Colour Sensor for Regulation of Tunable White Luminaires

Abstract

The quality of light is very important factor for human well-being. Except of the light intensity also the correlated colour temperature (CCT) of light is important parameter that influences the mood of people and their performance. The possibility of changing CCT of white light has gradually become a standard part of higher-class lighting installation. The manufacturers have developed various methods of Tunable white control – manual, remote-controlled or controlled via standard wired protocols such as DALI. The more complex control devices even offer possibility of dynamic CCT changing throughout the day according to the circadian cycle (according to the changes in CCT of sunlight). Nevertheless how complex the algorithm of CCT setting is, it can never dynamically react to the changes of ambient light condition unless there is a sensor for feedback measurement. The advantages of automated light intensity control using ambient light sensor are well-known. The aim of this paper is to describe an application of general purpose colour sensor as the feedback element for the regulation of Tunable white luminaires. Firstly, the theoretical basis of CCT measurement is described. Subsequently the paper presents the results of several measurements and case studies. Finally, the last part of the paper is dedicated to the concept of colour sensor that is powered directly from the light it is measuring using energy harvesting methods.