advantages can be achieved when energy harvesting power solutions are deployed vs. hard-wired solutions. Additional savings are realised by removing the significant costs of battery replacement.
Energy harvesting devices require low power management circuitry to condition the transducer output power, store energy and deliver power to the rest of the wireless sensor. In most environments, any transducer producing power cannot be relied upon under all circumstances to continuously supply power to the load. While each transducer delivers power at some amplitude and with some regularity, they do not store energy. Consequently, when that source of power is not present, there is no power to supply the load in the absence of an energy storage device. Moreover, the transducers typically do not deliver power at the appropriate voltage to operate the electronic system; therefore, conditioning of transducer power is essential to making the power output useful in operating the sensor, processor and transmitter. In particular, without an energy storage device, it is difficult or impossible to deliver the pulse current necessary to drive the wireless transmitter. Traditional rechargeable energy storage devices such as supercapacitors and coin cell batteries have severe limitations with respect to charge/ discharge cycle life, self-discharge and charge current and voltage requirements.
An energy processor, such as Cymbet’s EnerChip™ EP CBC915 (available across Europe through specialist distributor, Avnet Abacus) provides the energy conversion, energy storage, and load power
management for a zero power wireless sensor. In order to produce high efficiency transducer energy conversion the energy processor performs maximum peak power tracking by emulating the impedance of the transducer. The energy processor also coordinates all the power-up sequencing even from a dead start with no charge in the system and provides power and energy status information to the microcontroller so the system can be made “energy aware”. Figure 1 shows the EnerChip EP Energy Processor and EnerChip solid state batteries on the EVAL-09 universal energy harvesting kit. This kit interfaces to any type of energy harvesting transducer, converts and stores the harvested energy and provides a regulated output voltage to a target system.
solar EM/RF thermal vibration
solid state
batteries
wireless sensor interface
Figure 1: Cymbet EVAL-09 universal energy harvesting kit
Avnet Abacus, one of Europe’s leading interconnect, passive, electromechanical and power distributors, brings together a wealth of innovative sensor technologies and power solutions. The company’s extensive franchise portfolio includes leading sensor manufacturers such as Alps, Bourns, EPCOS, GE Sensing and Murata as well as energy harvesting specialist supplier Cymbet and several traditional
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