Startup Offering Light-Powered Sensor For Wireless Security

The amount of light typically available in homes or offices can both operate the RF sensor continuously and store energy for up to six days use in total darkness, according to the company.
SAN FRANCISCO — Startup EnOcean GmbH, a provider of energy-harvesting wireless technologies, introduced a solar-powered radio frequency (RF) magnet-contact sensor Tuesday (Nov. 1) that the company claims can eliminate the dependence upon batteries for wireless security systems.

According to EnOcean (Oberhaching, Germany), by doing away with the burdens of battery monitoring and replacement, the STM250 can operate virtually forever without maintenance.

"The security industry has long had a need for simplified magnet-contact sensor installation and operation," said Jim O'Callaghan, EnOcean vice president, in a statement. "Wireless seemed to provide the answer, yet the cost and consistency of battery power has been a recurring concern. By combining solar power with robust RF technology, EnOcean has effectively merged all the benefits of wire — affordability, stability and reliability —with the convenience of wireless."

EnOcean, which spun off from Siemens AG in 2001, announced earlier this year that it raised $13 million for expansion of its U.S. business and to support integration of its technology within ASICs and MEMS. In June, the company introduced the STM 100 solar-powered wireless sensor module, which includes three analog and four digital sensor connections, but not the sensors themselves.

Whereas a typical wireless security system achieves long life through the use of expensive high quality lithium ion batteries, STM250 requires only ambient indoor or outdoor light, EnOcean said. The amount of light typically available in homes or offices is sufficient to both operate STM250 continuously and in addition to store energy for up to six days use in total darkness, according to the company.

The unit's embedded EnOcean RF transmitter will send a signal across 300 meters outdoors and 30 meters indoors through walls, the company said, adding that the entire transmission is initiated, undertaken and completed in approximately 1/1000 of a second.

The STM250 is designed to automatically transmit a signal, using sophisticated RF protocols, when the contact is opened/closed. A periodic presence signal is sent on the quarter-hour to indicate that the node is operating properly, using stored energy, EnOcean said.

In a package that is described as being smaller than a standard doorbell (109 x 17 x 16 mm), the STM250 consists of a solar cell energy generator, an energy reservoir, a reed contact switch, a microprocessor for sensor control and a radio transmitter/antenna.

EnOcean said its proprietary radio technology is approved for use in Europe, the U.S. and Canada. The STM250 sensors are available in OEM quantities for less than $30 each, the company said.

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