TAOS Ambient Light Sensor for Sophisticated Daylight Harvesting

The sensor family has been developed by TAOS, a global supplier of intelligent light sensors acquired by austriamicrosystems in 2011. It offers a wide sensitivity range from 3 lux to 220,000 lux, preventing saturation even in direct sunlight, while implementing a photonic response model that spectrally matches light perception in the human eye.

The TSL4531 ambient light sensor provides a simple direct lux output and a 16-bit digital interface. Sophisticated filters automatically reject the 50-60Hz ripple typically produced by a building's fluorescent lighting systems, enabling the sensed light levels to more accurately measure the daylight that is entering the building.

Daylight harvesting is regarded as major step in the development of integrated lighting systems, enabling luminaires to dim in response to the amount of outside light that is entering a building through windows or skylights. By supplementing the working space with only the amount of light needed to maintain a uniformly lit environment, energy savings of 30% or more can be realized when compared to existing installations which do not respond to changes in ambient light.

According to austriamicrosystems General Manager of Optical Sensors and Lighting Kirk Laney, ambient light sensors have already proven themselves in millions of mobile devices, displays, televisions, and automotive and medical applications across the globe. "Now we are bringing these same capabilities to general lighting", Laney said. "The coming wave of 'Cognitive Lighting' will demand independent smart sensors that are 'environmentally aware'".

Being aware of the lit environment allows optimization beyond energy savings. In integrated building management and control systems, the combination of proximity/motion and light sensing provides an abundance of data concerning the interior environment. Additionally, daylight sensing/harvesting combined with precise control mechanisms enable the lighting system to deliver not just the needed amount of light, but also offers the ability to tune the type of light to suit the activity and users in a particular space. Environmentally aware, decision-directed, multi-sensor networks and optimized light will enhance not only the productivity of the built space, but also worker and group productivity, as well as increasing the health and well-being of individuals.

The new TSL4531 features a spectral sensitivity that resembles the human eye. Three user selectable integration times of 100ms, 200ms, and 400ms along with a wide dynamic range from 3 to 220,000 lux translate into a very versatile system. In power-down mode, the device consumes only 2.2 µA, making it suited for battery operation.

The TSL4531 ambient light sensor IC is available now in volume production. For more information on the device, please visit www.austriamicrosystems.com and www.taosinc.com.