An autonomous battery-less sensor module powered by piezoelectric energy harvesting withRF transmission of multiple measurement signals

Abstract

An energy-autonomous battery-less sensor module is presented, entirely powered by apiezoelectric energy converter driven by mechanical vibrations from the environment.The module manages and stores the converted energy, interfaces to one or morepassive sensors and periodically sends the corresponding measurement signalsover a radio-frequency (RF) link. As an additional variant, the module can senda programmable identification (ID) code on the RF carrier, in order to enablemodule tagging and tracking by the external receiver unit. The module’s generalarchitecture is presented and the strategy used for sensor signal conditioning andtransmission is illustrated. The architecture and principle have been experimentallyvalidated on a fabricated prototype including a piezoelectric bimorph converter, twopassive sensors made by a resistive–capacitive sensor pair and purposely designedelectronic circuitry based on low-power off-the-shelf components. In the testedexperimental conditions, the prototype features a typical time interval betweenmeasurement-and-transmission events of a few tens of seconds, with event durations of theorder of tens of milliseconds, corresponding to an operation duty cycle of the order of 0.1%.Peak power consumption during transmission is of the order of 20 mW and operative rangeis of the order of meters in a laboratory environment. The obtained results showthat the proposed approach has attractive characteristics because of the totalabsence of batteries and, despite the inherent intermittent operation, providessignificant measurement performances in terms of achievable sensitivity and resolution.