The embedded slides were presented by Powercast at the Sensors Expo in Chicago on June 6, 2012. The presentation covers how RF power harvesting enables passive wireless sensor tags (PWST) and high-function RFID. What is high-function RFID? There’s no official definition, but view it as a class of devices that uses RFID for communications but also includes numerous other components for advanced functionality. The additional components may require significantly more power than is available from a regular RFID chip, and a battery may not be desired. RF power harvesting from and RFID reader can provide the extra power needed for these devices.
Both ECN and Wireless Design & Development (WD&D) have published a recent article by Powercast titled “RF energy Harvesting Perpetually Powers Wireless Sensors”, which looks at using broadcasted RF energy as a reliable long-term power source for battery-less wireless sensors.
An article in RFID Journal recently reviewed the Powercast Lifetime Power Wireless Sensor System which has battery-less wireless sensors (passive wireless sensor tags) powered by RF energy.
“Powercast Corp. is marketing active RFID sensor tags that harvest power from RF signals. The system includes an RF transmitter that provides power signals to sensor tags, and a gateway that receives information transmitted by those tags. The company’s focus is on developing solutions for the wireless transmission of sensor data, such as what is required by data centers. In this case, rather than using wired sensors or traditional active RFID tags to send sensor data regarding a room’s conditions, the Powercast system simply uses continuous RF signals to charge a battery or capacitor built into a sensor tag. The solution, known as the Lifetime Power Wireless Sensor System, targets the heating, ventilating and air conditioning (HVAC) sector, as well as other building-controls industries, by providing a solution for acquiring data from sensors for heating and air-conditioning, lighting controls, access controls or other building automation.”
Powercast has released a battery-less, wirelessly-powered sensor system for building and industrial automation - the Lifetime Power® Wireless Sensor System. The sensor units can be powered at a range of 60-80 feet (18-24 m) from Powercast’s 3W, 915MHz transmitter (TX91501). The initial sensor unit is for temperature and humidity and is to be followed by other types such as CO2, light, and motion.
Powercast Lifetime Power® Wireless Sensor System
The access point (WSG-101 BAS gateway) supports up to 100 sensors and 800 sensor points for large-scale and high-density deployment of sensors. The sensors are battery-free and operate when sufficient charge is stored to take sensor readings and send a data packet. Wireless communication from the sensor nodes to the access point is 2.4GHz using industry-standard 802.15.4 radios. The BAS gateway supports several physical interfaces and a range of BAS protocols to interface with nearly every major type of wired BAS network, including BACnet, Modbus, Metasys N2, and LonWorks.
As announced back in October 2010, Powercast released a development kit to showcase using RF energy for remotely powering battery-free wireless sensors. Jon Titus of Design News was gracious enough to review the kit and gave Powercast ratings of 5 out of 5 in all four areas of the review: Ease of Set-up, Quality and Clarity of Documentation, Overall Experience, and Meets Expectations.
The article is titled “Kit Harvests RF Energy” and we appreciate the subtitle “Engineers who must implement low-power devices that cannot run on local power need this kit from Powercast Corp.”
The components in the kit enable wireless and battery-free operation of the sensor nodes at a distance of 40-45 feet (13-15 meters). Each sensor board can measure temperature, humidity, light, and an external sensor. This can be used for a number of applications including building automation, energy management and industrial monitoring. Power is provided by Powercast’s new 3W transmitter (TX91501-3W-ID), which also sends factory-set data. The P2110 Powerharvester receiver converts the RF energy from the receiving antenna and stores it into a capacitor, which is then boosted to operate the wireless sensor board. The Microchip XLP 16-bit Development Board with the 802.15.4 radio is the access point.
In an earlier post we demonstrated an iPhone powering LEDs in close proximity using Powercast’s RF energy harvesting technology.
The video below demonstrates the use of a standard iPhone in 2G mode to generate RF energy that is used to power a battery-free wireless sensor node. The sensor node is part of Powercast’s Lifetime Power (TM) Energy Harvesting Development Kit for Wireless Senors (P2110-EVAL-01), the receiving board is based on the P2110 Powerharvester Receiver, and the antenna was slightly modified from it’s original tuning for 915MHz.
The wireless sensor node was designed by Powercast and Microchip for ultra-low power operation. At a distance of 2 feet from the iPhone packets are transmitted from node every every 1-2 seconds. As this video shows, mobile phones can be a practical, portable source of wireless power for a wide range of applications.
Broadcasted RF energy creates a predictable, controllable power source to provide power-over-distance and one-to-many charging. Unlike potentially unreliable or intermittent solar, heat or vibration micro-power energy sources, the TX91501 transmitter sends power to enable wireless devices to charge and operate completely untethered from the power source, and power can be sent on-demand, scheduled, or continuously. End-devices can be inherently dormant, with zero-standby power, until power is sent to operate the device, or batteries can be trickle-charged remotely. The operating distance for wireless power transfer (wireless charging) from the TX91501 transmitter to a device with the P2110 Powerharvester Receiver is about 40 feet with a reasonable size receiving antenna.