In Your Future: Lightbulbs That Know When You Are in the Room

SAN DIEGO—In a few years, your light bulb will track you.

The declining cost of photo sensors (which detect light) and motion sensors will allow light manufacturers to ultimately include them inside of light bulbs, speculated Konstantinos Papamichael, a professor with the California Lighting Technology Center at UC Davis during a session at the Emerging Technologies Summit taking place in San Diego this week.

When you walk out of the room, the bulbs will know and thus crank down the light they produce or turn themselves off entirely. Right now, building owners install sensors to do this same job, but with sensors incorporated into every light, the bulbs will be able to do a better job of balancing the needs of the people who work in the buildings against the goals of energy efficiency. Achieving that balance is crucial, he said, adding that an hour of employee productivity lost is equal to the energy savings of a single light fixture for a year.

The bulbs will also be able to take more advantage of sunlight. If the photo sensor notes that it is fairly light in the room already (presumably from light coming in from the window) it can correspondingly turn down the bulb.

Getting lighting systems to take advantage of sunlight has actually turned out to be much more difficult than anticipated, he said. Objects in the room can easily throw off a photo sensor. If you move a white table into a room, for instance, the photo sensor begins to detect more light and cranks down the bulbs.

Wal-Mart had trouble in one store where the company installed a lighting system activated by photo sensors. The idea was that the lights would dim or turn off when sunlight was streaming through the skylight. The lights one day went off and wouldn’t go back on, which caused customers to complain about shopping in darkness. The problem? The store had held a celebration one day and released balloons inside the store. One of the balloons sailed to the roof and got lodged near the sensor. The shiny surface of the balloon reflected some of the sunlight and tricked the sensor into thinking it was bright inside.

Davis researchers first realized this would be a big problem when one day researcher Michael Siminovitch, a Davis professor and one of the leading experts in lighting walked underneath a photo sensor (see video of him and the California Lighting Technology Center here). Siminovitch typically only wears black clothes. The clothes absorbed the light and the signal going to the photo sensor dropped by 80 percent.