Clock hands harvest energy from RF signals

August 28, 2018 | 11:15
Clock hands harvest energy from RF signals. Image: Chaoyun Song, IEEE / Liverpool University.
Clock hands harvest energy from RF signals. Image: Chaoyun Song, IEEE / Liverpool University.
Modern homes are dense with radio signals, mostly from Wi-Fi, cellphone, TV and radio. Though not a lot, it’s free energy and it prompted EW BrightSparks 2018 winner Chaoyun Song from Liverpool University to investigate if the hands of an electronic clock can act as antennas for capturing the wireless energy from ambient signals, possibly to help power smart sensors and IoT/IIoT devices.

The result of Chayun’s research was a battery-free quartz clock with wireless sensing functions.

Chaoyun Song said: “In this project, we have developed the broadband rectifying-antenna (rectenna) technology, which could capture, rectify and convert the RF power of signals over a wide spectrum into DC power. We have significantly overcome the problems on antenna and circuit integration, in particular, a number of novel impedance matching techniques have been developed for such broadband rectennas.”

“More importantly, we have also invented a cutting-edge technique to effectively integrate the antenna to the rectifying and power management circuit without the need of extra matching networks and circuit components, thus reducing the cost, power loss and manufacturing complexity of the product. This technology has been filed to a US patent (US Patent 9,966,656), and bought by a US company.”
The full details of this work have been published on the IEEE, see “Novel Quartz Clock with Integrated Wireless Energy Harvesting and Sensing Functions“, IEEE Transactions on Industrial Electronics (May 2018). “One of our recent achievement on this project is that we have developed the first battery-free quartz clock with wireless sensing functions in the world. The clock hands have been used as antennas to directly sense and capture the wireless energy from ambient signals. Thus the final product of this design only requires the addition of a small piece of simple PCB rectifier circuit on the clock.”

“The clock can be efficiently powered under the coverage of a typical Wi-Fi router. Moreover, the harvested power was used to power a wireless environmental sensor that has been integrated to the clock. The sensor could transmit the data of temperature, humidity, air-pressure, noise level, air-quality and light intensity etc. over a GPRSbee, Bluetooth or LoRaWAN network.”

Potentially the quartz clock is self-powered as well as suitable for use as a smart indoor weather station or for smart home monitoring.

Source: Electronics Weekly.
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