Design And Implementation Of A Self-powered Autoalarming Wireless Sensor Node

The Internet of Things(IOT) is emerging as the third wave of global information industry. The limited energy associated with sensor nodes is a major bottleneck of IOT technologies. Vibration based energy harvester provide a promising power supply solution for this problem. This thesis presents a fully self-powered autonomously alarming wireless sensor node, which can automatically sent out alarm signal when the concerning vibratory event occurs.The proposed sensor node mainly consists of a vibration energy harvester, a dual threshold power management circuit and a RF signal transmitting module. The harvester features a two-stage vibratory structure. Through the magnetic repulsive force between the two stages, the energy harvester thereby realizing frequency up-conversion and threshold triggering function. The energy harvester generates significant electric energy only when the vibration reaches certain amplitude. The generated energy is used to power the RF system through the dual threshold power management circuit that activates and deactivates the RF module based on two independently pre-set threshold voltages. With the hysteresis control strategy of the power management circuit, the energy harvester is able to drive the high power RF system with low power dissipation. Meanwhile, The RF signal transmitting circuit based on CC1110 chip was designed and optimized to achieve high-efficiency wireless transmission.Experimental results showed that the SWASN could autonomously send out RF signals when excited at vibration with a frequency of 42 Hz and peak amplitude of 5g. The waiting time of the system between two consecutive transmission periods is less than 125 s. Within each transmission period, at least two signal transmissions can be finished and the average transmission distance can reach 1.31 Km.The proposed self-powered auto-alarming sensor node will have broad applications in field surveillance wireless networks.