A smart energy-harvester with the action of electric-power generating triggered by pre-set vibration threshold

This paper reports a novel piezoelectric energy-harvesting device that generates electric-power only when the concerned vibration level reaches a critical threshold. The threshold triggering function (equivalent to that of a sensing switch) is achieved by magnetic repulsive coupling between two vibratory stages (namely sensing-stage and generating-stage) integrated in the device. The threshold can be pre-set by adjusting the gap-distance between the two stages. The working mechanism is validated by both theoretical analysis and testing results from the prototyped micro-devices where maximum average power of 15μW can be generated at 4g acceleration. With the self-sensed vibration-amplitude triggered power-generating function, the smart device can be used for fully self-powered autonomous alarming.