Design of optimized cantilever form of a piezoelectric energy harvesting system for a wireless remote switch

Abstract

A smart lighting system can be controlled using a smartphone and/or human activated wireless remote switches. We designed a wireless remote switch using a cantilever type piezoelectric energy harvester to make a battery-less IoT node device that has high output power but a small tip displacement through frequency up-conversion. The purpose of this design is to overcome the conventional volume problem of the piezoelectric cantilever beam. In order to apply the high resonance frequency to the model at constant displacement, we set the limiting conditions of maximum vertical displacement of the cantilever beam to be 1 mm and a human input pressing force of 5–8 N, the force generally required when a human presses a switch button. In these limiting conditions, different shapes of steel substrate were used to find the optimal harvester that meets the limiting conditions and generates about 65 μJ of energy at 5 kΩ resistive loads under free vibration. Using this harvester, we designed a wireless remote switch with an impact type mechanical mechanism with two cantilever type energy harvesters to generate 140 μJ of energy, requiring no impedance matching circuit. This energy was then used to power a microcontroller to transmit data packets using ZigBee Green Power communication. Three identical data packets were transmitted by the wireless remote control switch to ensure data reception by the smart LED bulb and to toggle the bulb on or off state. Finally, this study successfully contributed to elevating the possibility of commercialization of the piezoelectric harvester based wireless remote switch for IoT.