Power harvesting sensors

| Information and Communication Technology

Smart sensor tags harvest energy from RF reader antennas

Jonathan Newell discovers a passive sensing and data acquisition system that harvests power from the RF antennas that gather the data.

With more processing work being done on the “edge” of the internet of things, there’s an ever-increasing need to be able to sense such parameters as temperature, pressure and levels and gather that data as well as process it before passing it on to cloud storage systems for further processing.

The devices used for gathering the data need to be small, cheap, have a low physical profile and consume as little power as possible – they need to be “invisible” in all respects except at the moment that they provide the vital function they’re designed for.

Wireless and battery free

ON Semiconductor has now developed a complete wireless battery free sensing kit that allows Smart Passive Sensors (SPS) to be rapidly integrated into Internet-of-Things (IoT) applications. The kit is plug and play ready for users to immediately measure, aggregate and analyse the data for various IoT applications.

SPS wireless and battery-free sensors enable the monitoring of various parameters such as temperature, pressure, moisture or proximity at the network edge where running wires or replacing batteries may be impractical.

When interrogated by an RF reader, the SPS “harvests” energy from the measuring signal and then delivers a rapid and highly accurate reading from the sensor. This cost-effective method has significant benefits over other technologies and offers the potential to significantly change low-power IoT sensing designs.

The development kit is a complete sensing system that includes a UHF SPS reader hub, eight UHF antennas, 50 sensors, a 12 V DC power supply and an Ethernet cable. Also included is ON Semiconductor’s TagReader software, an application specifically developed for reading SPS that enables the full functionality of the tags.

Different tag types

With options for pressure, temperature, moisture detection and proximity, the TagReader software automatically detects the type of tag that is connected and reads sensor data graphically over time. A Graphical User Interface (GUI) allows all system parameters related to the measurement process to be configured and re-configured as needed. As a result, even first-time users can quickly and easily configure a system to measure, aggregate and analyse data for multiple fully wireless, battery-free IoT applications.

Commenting on the launch of the kit, Gary Straker, Vice President of the Protection and Signal Division at ON Semiconductor, said: “This comprehensive system removes the need to source IoT sensors from multiple vendors and saves both time and money due to the ability to rapidly configure and modify multi-sensor IoT applications. Our SPS sensors allow reading over greater distances than is possible with NFC and do not require a battery – a limitation of Bluetooth-based technologies. With this kit, both experienced and inexperienced designers can rapidly configure and deploy advanced energy-harvesting sensing systems at the network edge.”

Automotive leak detection

One application that’s taking advantage of the Smart Passive Sensor kit, it automotive leak detection to analyse motor body sealing as new vehicles roll off the production line. Fitted with low-profile SPS tags hidden in typical water ingress points, the vehicle is guided through a water sprayer.

Wicking whiskers extend the detection range of the smart sensors and any water that enters the body is quickly detected by the sensors. Two portals located at the entrance and exit of the spray booth are configured with RF reader antennas which supply power to the sensors and gather their data.

A comparison between the readings of the two portals discloses any leaks that may be present. In line with good IoT edge processing practice, all the data is processed at the point of acquisition and only relevant data giving Vehicle Identification Number, location of leak and other data is passed on for further processing.

Jonathan Newell
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