A Motion-Powered Piezoelectric Pulse Generator for Wireless Sensing via FM Transmission

A motion-powered pulse generator using piezoelectric transduction is reported in this paper for wireless sensing devices. A metallic rolling ball is implemented in the prototype as an inertial proof mass excited by external motions at random low frequency. Taking advantage of the metallic proof mass, magnetic coupling can be achieved to actuate the piezoelectric cantilever by attaching tip magnets to the free end. In addition, self-synchronous switching is achieved by applying electrodes to the track of the rolling ball. A new passive prebiasing mechanism is introduced to improve the performance of the pulse generator. Both simulation and experimental results were conducted to demonstrate the improvement. Experimental results show that 76% more energy can be extracted by the prebias mechanism compared to the unbiased case. A transmission circuit based on a Colpitts oscillator was built to test the performance of the capacitor-powered oscillator, which is designed as the load of the pulse generator. By adding a voltage control component, the transmission circuit is capable of encoding a sensor signal by frequency modulation, which demonstrates the feasibility of implementing a motion-powered wireless sensing prototype based on the piezoelectric pulse generator.