Battery-free power for wireless switches

Troy Davis is Sales Director at EnOcean Inc. In his job, he sees intelligent lighting control expanding rapidly. It is also a boon for app developers and battery-powered control devices, but in his article, Troy explains why there is a better way.

The abilities of wireless connectivity mean you can control almost all communicating devices via your smartphone. The most popular application is lighting control. Just reach into your pocket, type in your passcode, open an app, connect to, wait, reconnect to, finally connect to the system, find the lights you’d like to activate and BAAM – within 30 seconds, you have a light turned on!

So cool to be able to change the light with my phone, but this is approximately 29.5 seconds slower than the original light switch developed in 1889. That might be a bit of an exaggeration, but the truth is, not everyone wants to use a smartphone just to turn on a light. Of course, the world has made battery-powered switches and still continues to today, but as we implement millions (or even billions?) of connected luminaires, we can’t feel good about adding millions more light switch batteries to local landfills and recycling centers.

Burden of dead batteries

In the consumer market, batteries are annoying, and we grumble a bit and change the battery with something from the junk drawer. In the commercial space (office, retail, warehouse, schools, etc.) these same batteries can become significant unplanned costs of time, money and frustration. An occupant of the space needs to report the dead switch, a technician then travels to the building and replaces the battery in the switch, fills out the invoice for the time, then the battery is (hopefully) recycled, which adds another cost and time. And what’s to say the switch two rooms down won’t die next week and the process repeats? We’re 1 or 2 years into all these 2-4 year battery lives that are out there and this issue will continue to grow and grow.

Battery-free way

Enter EnOcean, the pioneer and world leader in energy harvesting wireless technology. As a 17 year old company, EnOcean has enabled millions of wireless light switches that do not contain batteries and has now introduced the “Battery-free by EnOcean” seal to highlight the self-powered switches’ benefits at a glance.

What is a self-powered switch? That’s the million dollar question, we get asked 500 times at every demonstration event. It’s not magic; EnOcean deploys a miniature generator, the electromagnetic ECO 200 energy harvester, inside a seemingly typical light switch, which uses the kinetic energy of a finger tap as source to power wireless transmission. A magnetic flux is passed through two magnetically conductive laminations by a small but very strong magnet, and is enclosed in a U-shaped core. An induction coil is wrapped around this core. The magnetic parts are held in position by a plastic frame and a spring-loaded clamp.

The U-shaped core leading through the coil is movable – it can take up two positions, each of which touches the opposite magnetic poles – and in each end position the magnetic flux is reversed in the U-core. This design ensures maximum magnetic flux alteration through the coil with minimal movement of the core, and therefore high efficiency for the smallest amount of energy waste. With an energy output of 120 μWs and an accompanying wireless module, it is possible to transmit three radio telegrams per operation. At room temperature, the ECO 200 energy converter enables a typical completion of more than 1,000,000 switching cycles.

Brightness via open wireless standards

Battery-free switches can power several open wireless standards such as EnOcean, Bluetooth and Zigbee, which makes them suitable for numerous different applications and lighting solutions. You can change the lights from the space without wires or batteries, and without using your phone. This wondrous use and miniaturization of a tried and true energy source “Battery-free by EnOcean” can eliminate batteries in light switches, while still allowing full control of the space, color, brightness, etc. And not one app was involved to make that adjustment to the light.

About the author

Troy Davis has been involved in sustainable buildings and controls since almost 20 years. This continues through his key position as sales director of EnOcean North America, the leading energy harvesting wireless company in the world, working together with manufacturers in North America to create advancements in a large number of products, eliminating hundreds of thousands of batteries being consumed.

Troy has spoken on self powered sensing and controls at AIA, AHR expo, Hi-Tech, APMA, USGBC Greenbuild, Lightfair international, EnOcean Alliance events, speaking in Europe, and North America. Troy is an annual participant in wireless industry roundtable events with WiFi, Bluetooth, Zigbee and other wireless protocols.

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