Energy-Harvesting RF Switches Can Replace Cabled, Powered Components in Industrial Applications

Switches, like those used to power lights and machines on and off, seem like such simple components. But there is a lot of cabling behind the scenes to make them communicate with other systems in both consumer and industrial applications, something that will become a bit cumbersome especially with the increased adoption of the Internet of Things (IoT).

That scenario is being addressed now with the introduction of energy-harvesting wireless switches from ZF Friedrichshafen AG’s CHERRY electronics business unit, which use the energy from the flip of the switch -- be it manual or automated -- to power the switch’s wireless transmission.

ZF Friedrichshafen, a multinational provider of electronics products and components, is offering two standard versions of the new switches -- a rocker switch for actuation by hand or a snap-action switch for mechanical actuation by machine as a limit switch or position switch. Both variants are available for European (868 MHz) or North-American (915 MHz) frequency bands with a radio range of 30 m (100 ft) inside buildings and a minimum life of 100,000 operations.

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“The use of energy-harvesting switches removes the cost of supplying and installing cables between the switch/sensor and system controller,” Michael Groom, director of CHERRY switches, told Design News in an interview. “They also eliminate any factory down time due to damaged cables in industrial applications.”

Groom used the example of an installation in a factory or an oil rig, in which there might be need for a connecting cable from a drill head back to a control room. “The cost of cable is expensive, cost of installation is expensive, and there is a chance of damage to the cable,” he said. “With this you have a wireless transmission, and the energy harvesting means you don’t have to put a battery in it.”

This wireless connectivity and battery-free combination make the switches ideal for IoT applications, Groom added. “It’s not just an energy-harvesting switch that needs no copper or battery to turn something on or off, but also it allows you to monitor the state of your installation or machine,” he said. “It’s a very small part of a very big thing, but the first step in doing this.”

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The compatible enclosed standard receiver module for 868 MHz and 915 MHz frequencies offers several output interface options, according to the company. It comes with a power supply and can be mounted to a wall. A flexible pairing function allows operation of several receivers with one switch or several switches with one receiver, while a “unique ID” feature prevents interference between different RF switches, the company said.

The switches cost about $50 for a single unit but normally are sold in bulk at volume pricing, Groom said. The CHERRY division also is offering an evaluation kit for prospective customers to test the technology before purchasing.

The switches come out of the box with a standard CHERRY proprietary wireless protocol but also will support standard industrial protocols for wireless communication, including KNX-RF, EnOcean, and ZigBee Greenpower, Groom said. To ensure worldwide wireless compatibility the system may be specified to operate at 868 MHz and 915 MHz, or 2.4 GHz for lighting applications, he said.

Elizabeth Montalbano is a freelance writer who has written about technology and culture for more than 15 years. She has lived and worked as a professional journalist in Phoenix, San Francisco and New York City. In her free time she enjoys surfing, traveling, music, yoga and cooking. She currently resides in a village on the southwest coast of Portugal.