One factor that is holding back the widespread use of wireless sensor networks is the hundreds of thousands of batteries potential users must maintain. Micropelt GmbH, specialists in thin film thermoelectrics, may have solved this problem. The TE-Power NODE, a thermo-powered wireless sensor system has a built-in chip thermogenerator that takes a few degrees of temperature differential and harvests that thermal energy to operate the wireless sensor node, enabling unlimited battery-free operation.
The TE-Power NODE consists of a 60 by 27 mm footprint aluminum base plate that carries up to two MPG-D751 thermogenerators, allowing the energy supply to be scaled for the amount needed by the application. An aluminum heat spreader is mounted on top of the thermogenerators and is stabilized and insulated by a PCB that also holds the receptacles for various plug-on modules. The heat spreader has threaded holes for access to various heat sinks, allowing for detailed exploration of the device’s thermal path and easy repair. To convert the variable incoming thermo-voltage into a battery-like constant voltage, the original TE-Power PLUS DC/DC converter was modified to supply a constant 2.4 V and to charge a 100 µF capacitor to feed the duty cycle of the accompanying pluggable wireless system.
The TE-Power NODE evaluation kit transmits multiple channels of digital sensor data helping users and integrators of thermoharvesters better understand many aspects of their implementation in terms of application scenarios and energy budgets.
The kit uses accepted ultra-low-power technology from Texas Instruments (TI), supporting both IEEE 802.15.4 compliant and custom systems.
To operate the wireless sensor node, it must be attached to a suitable heat source. After a few seconds the node begins transmitting information to a PC through TI’s standard eZ430-RF2500 USB receiver module. In about 2 msec, a stack protocol transmits the temperature of the thermogenerator’s hot and cold sides once every second along with the respective operating voltage. An additional I2C standard based digital sensor interface supplies a channel for optional transmission of data such as vibration or pressure values.
Micropelt’s battery-free thermal energy harvesting technology can power ultra-low-power microcontrollers and RF transceivers, enabling many possibilities in the wireless sensor market.
Said Dr. Nurnus, “Our measurements prove that an effective 3.5° C across the thermogenerator can drive applications. This can even be achieved through harvesting body heat.”
Burkhard Habbe, VP business development added, “Thermoharvesters right now represent a viable energy supply for many applications including most IEEE 802.15.4 based systems. Even a few hundred microwatts supplied continuously can easily outperform a good set of batteries. Mass production of devices is scheduled to start in 2010.
Micropelt GmbH
www.micropelt.com
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