RF-Powered Wireless Sensors

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.

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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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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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