RF-Powered Wireless Sensors

The P21110 Powerharvester receiver  has some great new features for power management in addition to RF Energy Harvesting.  A battery-free wireless sensor node (shown below) has been designed to demonstrate the improved performance capabilities of the P2110.

The sensor module has a P2110 Powerharvester, 50mF AVX BestCap, 3 sensors (temperature, humidity, light), a PIC24 microprocessor, and a 2.4 GHz radio module. This node was powered by a 4W EIRP, 915 MHz transmitter.  For testing purposes, an antenna was used with a linear gain of 4, or 6 dBi.  The PCB dimensions are approximately 1.5″x2.5″.

When a charge threshold of 1.25V is reached on the supercap, the DC output is turned on to power the MCU and radio.  A quick read of the sensors is performed, the received signal strength (RSSI) from the transmitter is determined, and that data is transmitted using the MiWi P2P protocol.  The PIC24 was programmed to use the new RESET feature to turn off power as soon as the data packet was transmitted.  With the energy management implemented in this node, a significant reduction in energy consumption was achieved from a previously unoptimized, off-the-shelf sensor demo.  The transmitter also has the ability to send low-rate data, such as a transmitter ID, that can be used for location-based applications or to activate only specific end devices.

The performance at different distances is as follows:

10 feet - every second
20 feet - every 6 seconds
30 feet - every 21 seconds
40 feet - every 89 seconds

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New Scientist magazine has written an article titled “Unplugged: Goodbye cables, hello energy beams” which discusses several technologies and companies in the wireless power market, including Powercast.

As it relates to wireless sensors, RF energy is the only controllable, practical technology to provide power over distance to multiple sensors simultaneously.  Other technologies are either too directional for one-to-many powering (i.e. IR LEDs), or have severe range limitations (i.e. induction, MR).  There are the critics that say RF power is not efficient and most of the energy is wasted.  However, using RF to power sensors at long range (e.g. energy management and building automation) is not about the efficiency of the charging mechanism, it’s about enabling applications and achieving greater system-wide efficiency.  Having a transmitter than consumes a few watts but provides power to sensors which feedback data to control thousands (or tens of thousands) of watts or BTUs provides a significant “energy ROI”.

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Sensors Magazine recently published the article “RF Energy Harvesting Enables Wireless Sensor Networks” by Harry Ostaffe of Powercast.  The article is a brief introduction to RF energy harvesting: what it is, what it does, and how it enables wireless sensor networking applications.

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Powercast will be demonstrating RF energy harvesting at the IDTechEx Energy Harvesting & Storage Conference in Denver (USA) on Nov 3-4, 2009.   On display will be Powercast’s RF energy harvesting technology integrated with wireless sensors from Texas Instruments, Jennic, and EnOcean.

All of the demonstration modules are battery-free and are powered by RF energy that is converted to DC by Powercast’s P2100 Powerharvester module and stored in a supercapacitor.  Harry Ostaffe of Powercast will also be giving a presentation on Practical Applications of RF Energy Harvesting.

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Product Design & Development (PDD) magazine profiled energy harvesting in “The Brainstorm” section of their August 2009 issue.  The questions asked of the contributors were:

“What is the future of energy harvesting?  What markets will energy harvesting have the greatest impact upon?”

http://e-ditionsbyfry.com/olive/ODE/PDD/Default.aspx?href=PDD/2009/08/01

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Jennic recently announced collaborations with multiple energy harvesting companies for vibration, solar, thermal, and RF energy harvesting to power wireless sensor networks based on the IEEE802.15.4 standard such as ZigBee PRO and 6LoWPAN.   The companies involved included Micropelt, CYMBET, AdaptivEnergy, and Powercast.

Jennic’s wireless microcontrollers offer exceptionally low-current operation, and with advanced software based monitoring and control of the energy source, they are able to achieve the extreme efficiency demanded by systems powered by sustainable energy sources.

At Powercast, we used a 915 MHz radio transmitter and the P2100 Powerharvester(TM) module to power wirelessly, without batteries, the new JN5148 module which sent ID, voltage, and temperature readings back through the JN5139-based access point to a PC application.

Jimi Simpson, Jennic Product Marketing, explained, “Harvesting energy from sustainable sources presents designers with the ultimate power challenge: the energy supplied is not necessarily continuous and is available at relatively low levels. This means that every element of the design, from the sensor to the microcontroller, must be considered and managed to achieve the highest levels of power efficiency.”

Jennic press release (PDF)

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Product Design & Develpoment is profiling the Gold award winners at the 2009 Sensors Expo, including an article on the Powercast P2100 Powerharvester(TM).

http://www.pddnet.com/news-rf-power-harvesting-070109/

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AutomationWorld has published an article on energy harvesting technologies demonstrated at the 2009 Sensors Expo, including information on Powercast.

Energy Harvesting Advances
http://www.automationworld.com/news-5664

“While vibration energy harvesting may be most common for industrial applications, a different approach was being shown by Pittsburgh-based Powercast Corp. (www.powercastco.com). At its Sensors Expo show booth, the company was demonstrating its Powercaster transmitter, which was beaming a radio frequency (RF) signal toward the company’s Powerharvester receivers mounted in other nearby booths. The receivers were harvesting energy from the RF field and converting it to DC power sufficient to operate low-power sensor devices. Harry Ostaffe, Powercast director of marketing, said the company has so far deployed the technology in custom projects for military and industrial clients, with typical transmission distances “in the 10s of feet” using a three-watt transmitter.”

Power was transmitted to booths for Esensors and Infinite Power Solutions and converted back to DC with the P2100 Powerharvester.  The Esensors wireless sensor was located about 35 feet from the Powercast transmitter.  It was connected to a Powercast Yagi antenna module and was activated about every 90 seconds.  The IPS energy cell was connected to a Powercast sleeve dipole antenna module and was pulse charged at about 25 feet.  Longer charge distances were possible for both devices, but they were mounted for display purposes.

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Powercast won a Gold-level “Best of Sensors Expo” Award at the 2009 Sensors Expo. The award was granted for innovation in sensor components category for the P2100 Powerharvester module.  The P2100 Powerharvester converts radio waves to DC power and enables battery-free wireless sensors.

At the Sensors Expo, Powercast exhibited wireless power demonstrations with components integrated from Texas Instruments, Esensors, CAP-XX, CYMBET, Infinite Power Solutions (IPS), and NTERA.  Devices were also powered remotely from the Powercast booth to the Esensors and IPS booths at distances of 35 feet and 25 feet, respectively.

Powercast participated in the new Energy Harvesting Pavilion, and conference presentations were given by Harry Ostaffe and Charlie Greene of Powercast.

SensorsMag.com Press Release

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At the Darnell nanoPower Forum on May 18th, Powercast and CAP-XX presented a battery-free wireless power module for wireless sensors.  The module uses the Powercast P2100 Powerharvester receiver, a CAP-XX GZ 115 supercapacitor, and the Texas Instruments eZ430-RF2500 wireless board.  The modules work by receiving radio waves and converting them into DC, which is then stored in the supercap.  When a charge threshold is reached on the supercap, the output to the wireless sensor is turned on which activates the sensor.  The sensor can have zero stand-by power instead of using a sleep mode, and power can be sent on demand, o na scheduled basis, or continuously.

The joint press release by Powercast and CAP-XX contains additional details.

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