Wireless Sensor Node Powered by Broadband Low-Frequency Vibration Energy Harvester

A self-powered wireless sensor node for temperature and humidity measurement was developed. It is mainly composed of a vibration energy harvester, power management circuit, microcontroller, temperaturehumidity sensor and a wireless transmitter. The node is powered by a broadband low-frequency vibration energy harvester with a rolling mass. The measured output power of the piezoelectric bimorph on an 140 k? resistor is 0.51 m W under base acceleration with the amplitude of 9.8 m/s2 and frequency of 18.4 Hz, and the half power bandwidth is about 17.8% or 3.8 Hz. The power management circuit mainly consists of LTC3588-1, LT3009 and a 2 200 μF capacitor. The microcontroller and the wireless transmitter are MSP430F149 and n RF24L01, respectively. Experimental results show that, under the base acceleration excitation with a constant amplitude of 1 g, the wireless sensor node works normally when the excitation frequency increases from 5 Hz to 18 Hz, whereas the time interval for the node to measure and send out the temperature and humidity decreases from 848 s to 60.2 s. The broadband and low-frequency properties of the harvester makes this wireless sensor node can be used in many environments.