NXP and Cherry team up to make an energy-harvesting wireless light switch
Last week, at CES 2013 NXP Semiconductors and Cherry — yes, the same Cherry that makes switches for mechanical keyboards — showed off a light switch. It might not seem like something that could stand up against huge OLED televisions or Android-based mobile gaming platforms, but after surveying the best of CES, you might change your mind about just how impressive this switch is. After all, this switch is wireless, battery-less, energy-harvesting, and parting of the “Internet of Things,” making it one of the most high-tech — and on trend — gadgets at the show.
The light switch, which looks like any other and includes a dimmer, is simply a combination of Cherry’s energy-harvesting switch and a radio. That radio communicates with a receiver that is placed inside the base of an LED light bulb (in most cases a standard E27 base). This means that the switch isn’t designed to work with any old LED bulb, unless the receiver, NXP’s ultra-low-power JN5168 microcontroller, is moved to a fixture or some other component behind the bulb. The JN5168 is designed to support JenNet-IP, ZigBee, and RF4CE networking stacks so it can work with multiple home automation scenarios, not just lighting.
The JN516x parts — which were actually unveiled in November — are surprisingly powerful given their size and modest power requirements. The entry level model, the JN5161, packs in 64KB of flash, 8KB RAM, and 4KB EEPROM, while the top tier JN5168 moves up to 256KB of flash, 32KB RAM, and 4KB EEPROM. Each is powered by a 32-bit RISC CPU.
The wireless isn’t the interesting component here, it’s Cherry’s energy-harvesting switch. The device, which Cherry seems to have actually named the “Energy Harvesting RF Switch,” manages to grab from 0.2 to 0.5mW from the switch activation (NB: the video below says 200 microjoules). The force required to push the switch is 8 newtons or about 1.8 pounds-force (or, more technically, 8kg·m/s²) — basically you don’t need to pound this switch or rock it back-and-forth for a minute to generate a sufficient amount of power.
The documentation is not clear on how the power is being harvested, aside from noting that “RF-energy is created by the mechanical actuation of the switch.” Cherry and NXP have not been forthcoming with details, but I’ve been told that the switch does not use piezoelectricity to generate the power, rather this is done through magnetic induction.
With 2.45-GHz radio IEEE 802.15.4 compliance this combination is very much ready to be part of the so-called Internet of Things. The setup will be compatible with 6LoWPAN and ZigBee’s Light Link (the protocol used in Philips’ wireless, app-controlled Hue LED lighting system) so it’s ready to be implemented, and similar systems (though more conventionally powered ones) are already in use today. Given its components, the light switch could interact with other networked devices, in addition to the bulb, which would allow it to become part of a larger ecosystem.