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Peel-and-stick electronics

A radio-powered light switch might not sound interesting at first, but EnOcean hopes to make the device ubiquitous.

Someday, installing a thermostat or remote volume knob for a home audio system might be as little effort as putting up a new air freshener.

Germany's EnOcean has come up with a series of sensors and switches that can extract energy from the environment and then transmit information via radio signals to a computer, which can then take the requested action. Because the sensors don't need to be linked to the building's electrical wiring, they can be installed without retrofitting. A dimmer switch, in other words, can be plunked on the wall without the need for cutting holes.

"One of the hot markets we are seeing is home automation," said Jim O'Callahan, vice president of EnOcean's U.S. operations. "You could have an 'all off' switch in your garage or your car that would turn off all the lights in your house. It could turn off the outlets with the coffee pot and things like that. There are systems that do this today, but you have to run Cat 5 (Category 5) wiring through the house."

EnOcean sensor
Credit: EnOcean
EnOcean light sensor
and solar cell.

Category 5 wiring is the unshielded, twisted-pair cabling normally used for computer networks and communications.

The system could also be employed to create microclimates (cool in the kitchen, warmer in the breakfast nook) or mood lighting in different rooms.

EnOcean, which spun out of Siemens and landed investments from 3i Group and BayTech Venture Capital, is one of several companies trying to eliminate one of the primary barriers to what could become a multibillion-dollar market for sensors--namely, power. If you scatter thousands of conventional sensors around a campus or industrial park, you'll have to hire an army of individuals to drive around and change the batteries all the time.

Rather than build long-life batteries, EnOcean is tinkering with ways to eliminate the need for them. It has been selling solar-powered sensors and is experimenting with sensors that can harvest electricity from vibrations and temperature differentials. As long as one surface is three degrees Celsius higher or lower than the immediate environment, EnOcean's prototype thermal sensor can harvest power.

"You could put it on a hot-water pipe. Typically, that will be warmer than the ambient air," O'Callahan said. "There are a lot of little spaces in buildings where the temperature differs by three degrees."

Wake-ups and power thresholds
Vibration sensors, unless hooked up to a machine with fairly precise oscillations, are a little tougher to create.

None of these energy sources, however, can provide the electric wallop of a battery, so the company curbs power consumption by keeping the sensor dormant as much as possible.

A temperature sensor that works with a thermostat, for instance, might wake up to take a reading only every 15 seconds. If the temperature hasn't changed, it won't send a signal to the unit that actually adjusts the thermostat. The signal goes out only if the temperature exceeds a certain threshold.

"We also use a frequency without a high probability of interference" to prevent misfires in communication, O'Callahan said. "They are designed to continually harvest miniscule amounts of energy and store it. The real key comes in minimizing the power consumption."

How low can they go? Typically, the company's sensors--which include a sensing device, a microprocessor and a radio--can operate on 50 milliwatts.

The solar panel on the light-powered units measure 1 by 1.5 inches. A similar setup based on the ZigBee wireless sensor would require a solar panel 10 times larger, O'Callahan claimed. ZigBee chips also operate in the milliwatt range.

Despite the low energy requirements, the signal carries. In an environment like a warehouse, with few physical barriers, a signal from a sensor can travel 300 meters. If walls are present, the signal goes about 30 meters. Signals can also be relayed via other sensors.

EnOcean sells its products to building automation and other manufacturers, which use them to create devices. So far, the company has landed deals mostly in Europe. Building sensor specialist Thermokon has incorporated EnOcean's technology into solar-powered thermostats, while Denmark's Servodan has created a portable light sensor that sends a signal to a building control unit that then automatically raises or lowers window blinds.

About 100,000 EnOcean sensors have been put into use, the company says.