Raining? Wireless Sensors Tell You Which Windows to Shut
Wireless contacts make it possible to monitor all the windows in a house. They can tell whether a window is wide open, tilted open, or closed.
CREDIT: Fraunhofer IMS
Early raindrops from a summer thunderstorm can lead to frenzied activity indoors as people run around to check whether all the windows are closed. Now that ritual may go extinct thanks to a new wireless system that could let homeowners and others simply check their smartphones to see what windows are open.
Today's sensors can already detect whether a window is in an open or closed position, but must rely upon clunky or intermittent power sources such as batteries, power cords and solar cells . By contrast, the new system's sensors get power from wireless radio signals sent out by controllers in each room.
"Our wireless window contacts draw all their energy from ambient radio signals," said Gerd vom Bogel, a scientist at the Fraunhofer Institute for Microelectronic Circuits and Systems in Germany and lead researcher on the project.
Room controllers not only provide power to the window contacts, but also collect data from them and transmit the status of each room's windows to a central device. The central device could then use a wireless Internet connection to transmit the information to a homeowner's laptop or smartphone.
Such a wireless solution has proved tricky in the past because of the power issues. Batteries need constant replacement; solar cells don't work without sunlight. Most existing window contact systems simply run on power cables connected to the building's electricity supply a system tough to install in older buildings.
"Room controllers, too, have to comply with certain limits on the strength of their radio output," vom Bögel said. "This makes it particularly tricky to get enough energy to all the window contacts in bigger rooms. But we have made sure all the sensor modules, antennas and components are so finely tuned to each other that the system works reliably even over considerable distances."
The project marks a first step toward a broader "smart home " system capable of giving homeowners information about all parts of their house or apartment, researchers said. Such a system might also include data from scattered temperature sensors capable of better detecting a home's average temperature.
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