RF-Powered Wireless Sensors

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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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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