RF-Powered Wireless Sensors

Powercast demos prelude to mobile network RF energy harvester
Directed RF energy harvester demo is stepping stone to full ambient RF harvesters that can siphon energy from ubiquitous mobile networks

“After setting up an RF energy-harvesting demo at this week’s Sensors Expo collocated with ESC Chicago, Powercast’s director of marketing Harry Ostaffe presented a paper that outlined the concepts and paths to what he believes to be the endgame: full ambient RF harvesting capabilities that sip power from ubiquitous mobile networks and eliminate batteries and direct RF power sources completely.”  Read more…

Powercast presentation - Power Out of Thin Air (PDF)

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Powercast will participate as an exhibitor at the 2010 Sensors Expo & Conference.  At the event Power will be demonstrating a battery-free wireless sensor module powered by RF energy and designed for ultra-low power consumption.  The sensor module provides temperature and humidity data to an access point along with the received signal strength (RSSI) and the ID number of the Powercaster™ transmitter from which it is receiving power.

Powercast has recently released the P1110 and P2110 Powerharvester™ Receivers which are capable of converting radio waves in the range of 850-950 MHz into DC power.  The demonstration sensor module uses the P2110 Powerharvester receiver to store the received energy into a capacitor, and then performs a voltage boost to supply the module components will a regulated voltage.  Both the P1110 and P2110 enable a microcontroller to determine the signal strength of the received power, as well as to recover low-rate data encoded in the power broadcasted from the power transmitter.

Harry Ostaffe, Director of Marketing and Business Development for Powercast, will also be delivering two presentations during the event.  During the pre-conference symposium on June 7, 2010 he will speak on “Design Techniques for RF Energy Harvesting Devices”, and during the main conference on June 8, 2010 he will also present “Power Out of Thin Air: Ambient RF Energy Harvesting for Wireless Sensors”.

Powercast’s exhibit and wireless sensor demonstration will be located at Booth 1022 in the exhibition hall.

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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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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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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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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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Pittsburgh, PA – April 30, 2009 – Powercast, a leader in the commercialization of RF energy harvesting and wireless power solutions, announced it has joined the Texas Instruments Developer Network to support wireless powering of devices driven by TI’s MSP430.  The MSP430 is a market leading, low power microcontroller embedded in numerous portable and low-power wireless devices.

Powercast’s RF energy harvesting technology and embedded wireless power solutions enable controllable wireless power, over distance, between one or more sources and multiple receivers.  Devices with Powercast components can be designed for battery-free or battery-minimized operation, thereby eliminating disposable batteries and their adverse environmental impact.  These devices can be dormant, with zero stand-by power, and activated remotely with power being sent on-demand, on a scheduled basis, or continuously.

“We are pleased to have Powercast join TI’s Developer Network,” said Eric Siegel, MCU developer network manager at Texas Instruments.  “Combining wireless power technology with the ultra-low power consumption of the MSP430, Powercast’s innovative solutions eliminate the need to replace batteries by providing constant, unattended charge for applications in the low-power RF market.”

Powercast has also developed an integrated module for demonstrating battery-free wireless sensors.  The Powercast module contains an integrated power receiving antenna, a Powerharvester™ module, energy storage, and space for a low-power wireless module like Texas Instruments eZ430-RF2500T.

“The wireless sensor market is rapidly expanding and today’s wireless sensors are predominantly powered by disposable batteries.  Battery replacement creates a significant operational challenge that will greatly impact the willingness of end-users to scale sensor networks or deploy wireless sensors in hard to service locations.” said Harry Ostaffe, Director of Marketing for Powercast.  “Powercast’s wireless power solutions enable battery-free designs for wireless sensor devices, and allow for lifetime operation without changing batteries.”

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An article by Harry Ostaffe of Powercast was recently published in Industrial Embedded Systems.

The article is titled “Wireless power energizes wireless sensor networks”, and discusses how wireless power enabled by RF energy harvesting can provide a controllable and perpetual source of energy for wireless sensors.  The opening paragraphs are included below.

Battery replacement in wireless sensors is a key factor in limiting device location and scale. Through RF energy harvesting, wireless power can recharge wireless sensors remotely and eliminate battery replacement.

Wireless sensor applications and installations continue to grow as the technology evolves. The ability to add remote sensing points without the cost of running wires is resulting in numerous benefits, including energy and material savings, process improvements, and productivity increases.

Disposable, primary batteries typically supply the main power source for wireless sensors. Primary batteries are a readily available power source and have proven to be useful in many applications. However, with primary batteries as the source of power, sensor and component companies have had to focus on decreasing power consumption to overcome the objections of maintenance cost and disruption from repeated battery changes. The resulting benefit is that wireless sensors and protocols are now sufficiently low power as to be powered from sources of energy other than primary batteries.

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