RF-Powered Wireless Sensors

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.

The system was developed based on the same core technology as the Powercast P2110 Powerharvester receiver and the P2110-EVAL-01 Energy Harvesting Development Kit, both of which are available for other sensor OEMs to embed Powercast’s technology into their own products.

Product Page |  Press Release |  Product Presentation (PDF)

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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.

Product Link | Press Release

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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.

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Powercast, with the support of Infinite Power Solutions, has released the Lifetime Power® Energy Harvesting Development Kit for Battery Charging. This kit provides long-range, wireless trickle charging of battery-based systems for low-power applications. The kit features the THINERGY® Micro-Energy Cell from Infinite Power Solutions (IPS), and also supports traditional rechargeable batteries including Lithium Ion, Alkaline, and Ni-MH, as well as other solid-state/thin-film batteries.

Components of the kit include:

• 915MHz, 3 watt Power+Data Transmitter (TX91501-3W-ID)
• P2110 Evaluation Boards (P2110-EVB)
• 6dBi directional antenna
• 1dBi omni-directional antenna
• Battery charging board (BAT-EVAL-01)
• THINERGY® Micro-Energy Cell Evaluation Card
• Cable for connecting to THINERGY® ADP
• TI eZ430-RF2500 wireless development tool

The components in the kit enable wireless battery charging at a distance of 40-45 feet (13-15 meters). The charging board can directly charge a THINERGY Micro-Energy Cell or connect to the THINERGY ADP. 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 as a regulated output to pulse-charge a battery.

Product Listing | User’s Manual | Press Release

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Powercast, with the development support of Microchip, has released the Lifetime Power® Energy Harvesting Development Kit for Wireless Sensors.  This kit provides wireless power for remote, battery-free wireless sensor networks (WSN).

The kit (part number P2110-EVAL-01)  includes the following items:
1 - 3W Powercaster Transmitter - 915MHz (TX91501-3W-ID)
2 - P2110 Evaluation Board (P2110-EVB)
2 - Directional, patch antennas - 915MHz
2 - Omni-directional dipole antennas - 915MHz
2 - Wireless Sensor Boards (WSN-EVAL-01)
1 - Microchip XLP 16-bit Development Board
1 - Microchip 802.15.4, 2.4GHz radio
1 - PICkit programmer/debugger

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.

Product Link | Press Release

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Randy Frank has written a good summary of the state of energy harvesting technology for Electronic Design in an article titled “Making Energy Harvesting’s Promise of Free Energy a Reality”.

With its allure of free energy and maintenance-free operation for lifetimes of 10 and even 15 years, energy harvesting (EH) is grabbing the attention of potential users in many markets. Recent EH developments have made great progress, and the pieces appear to be falling into place.

System components such as microcontrollers (MCUs), RFICs, and power-supply ICs have had to drastically reduce their power consumption and increase performance to complete a useful energy-harvesting system. In addition, software that controls the power management, data collection, and transmission processes while avoiding any unnecessary power consumption is essential.

Read more…

The article includes several graphics, including the following general diagram of a wireless sensor node.

Companies mentioned in the article include HP, EnOcean Alliance, Perpetuum, Micropelt, Powercast, Enertia Energy Systems, Tellurex, CYMBET, Infinite Power Solutions (IPS), Perpetua, CAP-XX, Microstrain, Microchip, Texas Instruments, Analog Devices, and Linear Technology.

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The New York Times recently ran an article on various projects and products related to RF energy harvesting, including some commentary on Powercast.

Title: Bye-Bye Batteries: Radio Waves as a Low-Power Source

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A joint article by Powercast (Harry Ostaffe, Charlie Greene) and AVX (Bharat Rawal), titled “Power Module and Double Layer Capacitor Harvest Energy From Radio Signals“  was recently published in Power Electronics Technology.  Combining Powercast’s P2110 Powerharvester receiver with an AVX Double-Layer Capacitor (super-capacitor) results in a battery-free, wireless power supply that can be used for low power applications such as wireless sensors.  The article describes in detail the operation of the P2110 Powerharvester.

Figure 1 shows a general block diagram of the P2110 Powerharvester.  The RF energy is converted to DC and stored into an external capacitor.  For some applications a small electrolytic capacitor may be sufficient, but other cases will require more energy and therefore a larger double-layer capacitor (super-capacitor).  The voltage on the external capacitor is typically managed between the operating range of 1.25V, when the output voltage is turned on, and turned off at the low threshold of 1.05V.  The boost converted is used to provide a regulated output voltage from a range of 2-5.25V to accommodate a wide range of applications.

The timing diagram in Figure 2 provides more detail on the operation.  The INT pin provides a logic-level output to indicate when Vout is active, and the RESET pin enables an external device such as a microtontroller or external timer to turn off Vout.  The RESET function saves energy and allows the P2110 to recharge the capacitor more quickly.

Figure 3 show a system-level implementation that is typical in a wireless sensor, such as HVAC control sensors using ZigBee, WiFi, or other protocols, or industrial sensors using ISA100 or WirelessHART.

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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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