An ultra-low frequency magnet-tethered vibration energy harvester for self-powered sensing

Wireless sensors face challenges regarding power supply and maintenance when batteries are used. To provide an effective solution, this paper presents a bistable energy harvester capable of exploiting ultra-low frequency vibration to energize low-powered devices. The energy harvester uses rotary-translational motion of a spherical rolling magnet contained inside a frame, with two tethering magnets below the rolling magnet's path to enable two stable positions. To examine the performance of the design, a prototype was fabricated and tested under varying excitation conditions and external loads. An output of 7.1 mW at 750 Ω was effectively determined. A power management circuit is integrated with the energy harvester; the harvester can charge a 470 F capacitor to 3.4 V within 82 s at 0.7 g and 2 Hz.