LONDON Leading European chip company STMicroelectronics NV and Micropelt GmbH (Freiburg, Germany), a specialist in Peltier and Seebeck effect devices, have announced an autonomous wireless sensor evaluation kit.
The TE-Power NODE kit combines a thermogenerator from Micropelt with a ST's EnFilm solid-state thin-film battery. Power management and charge monitoring circuitry connect to the included graphical user interface software via a 2.4-GHz wireless link.
The thermoelectric generator exploits the Seebeck Effect, whereby an electric voltage is produced by a temperature differential across a thermoelectric micro-structured layer. A gradient of 10 degrees C generates a voltage of 1.4V. Micropelt's custom power conditioning converts this into sufficient power to drive the wireless sensor node and charge a battery using excess thermal energy. The Micropelt TEG MPG-D751 is housed between a solid aluminum base plate and a finned heatsink. The base is attached to a suitable heat source, so the cooling effect of the heatsink can create a temperature differential across the embedded TEG.
The rechargeable battery used in the enhanced TE-Power NODE kit is ST's EFL700A39 EnFilm(TM) thin film solid state battery, a 700-microamp-hour UL1642-certified rechargeable battery that can deliver high pulsed peak current (up to 10mA) to provide power to the wireless sensor node during its communication with the network. When the base plate of the evaluation kit is in contact with a heat source, the Micropelt TEG provides power to the system and recharges the EnFilm. When the heat source is removed the EnFilm battery powers the wireless sensor.
The battery board includes a BiCMOS linear regulator (STLQ50) specifically designed for operating in environments with very low power consumption constraints, as well as the STC3100 battery management chip, which monitors battery voltage, current and temperature. The circuitry also incorporates a Coulomb counter to keep track of the charge/discharge status.
“Harvesting thermal energy holds enormous potential as a virtually infinite self-sustaining energy source, exploiting free surplus heat that would otherwise be wasted,” said Micropelt's CEO, Fritz Volkert, in a statement issued by ST.
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