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Powercast Debuts Energy-Harvesting Wireless Sensor System

The technology allows the sensors to receive and harvest RF energy to power their own transmissions, eliminating the need for replaceable batteries.
By Claire Swedberg
May 05, 2011Powercast 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 Corp., based in Pittsburgh, was launched in 2003 to develop a system for harvesting wireless power over distances using RF technology. The solution was intended to allow a tag to receive a continuous RF signal from a transmitter, and to store that signal's energy on a rechargeable battery. The receiving device can then simply utilize the battery's stored energy for its own functionality, or transmit data and an ID number. The Lifetime Power Wireless Sensor System evolved from a Lifetime Power Energy Harvesting Development Kit, which uses Powercast’s P2110 Powerharvester receiver and was made commercially available in October 2010. The kit included a 3-watt transmitter, a receiver with a built-in battery-charging board, and a micro-energy cell evaluation card, and could be employed to charge devices that transmit data similarly to an active RFID tag. "Our core products have been around RF harvesting," says Harry Ostaffe, Powercast's VP of marketing and business development.

Powercaster's TX91501 transmitter emits 915 MHz radio waves that supply power wirelessly to the sensor nodes.
According to Ostaffe, the Lifetime Power Wireless Sensor System eliminates the need to wire the device to an external power source, simplifies installation and negates the need for battery replacement, which is required in the case of conventional active RFID tags (see RF Code Debuts Inexpensive Server Tracking Solution and Visual Data Center Combines RFID With 3-D Thermal Imaging).

The company's Lifetime Power Wireless Sensor System includes a 6.75-inch by 6.25-inch by 1.63-inch RF transmitter box, the TX91501, which sends a 915 MHz signal to power the tags using a proprietary air-interface protocol. The transmitter also transmits fixed, pre-programmed data, amounting to an 8-bit transmitter ID. However, Ostaffe says, a power transmitter could be developed to accept external data input, and then send control information to the sensor nodes. The TX91501 is available with output power of 1 watt for shorter range or 3 watts for longer range.

The wireless sensors can harvest sufficient energy for perpetual operation at a distance of up to 80 feet from the transmitter. The first of the family of sensor devices is the WSN-1001 wireless temperature and humidity sensor. Additional wirelessly powered sensors will follow shortly, the company indicates, designed to measure carbon dioxide, air pressure, light level, motion and other conditions.

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