A Study On WSN Node Power Supply Based On Supercapacitor

In recent years, with the development of science and technology, wireless sensor network(WSN: Wireless Sensor Network) technology has been becoming more mature applied to all areas of life such as military detection, medical treatment of sensorineural, soil testing etc.The main power supply for WSN node is battery, and the life and constraints of the battery and often limit the use of WSN, battery replacement and quality defects not only directly affect the sensor node but also the entire life of wireless sensor network. This thesis studies a power supply method for WSN nodes which uses mechanical vibration energy and solar energy harvesting techniques the supercapacitors for storing electrical energy, this power supply method can effectively use the environment energy, make it longer, safer and adapt to wider environments, make full use of resources and energy saving and also extend the life of wireless sensor network.Firstly, this thesis has studied the basic construction and the mathematical model of supercapacitor as an energy storage element, highlighted the advantages of high charging efficiency, wide scope of working conditions and can be repeatedly used almost infinitely.Theoretical calculation has proved that it is suitable as an energy storage element for power supply of low power WSN node, and its main parameters for WSN node power supply is calculated. Then a detailed study on solar energy and mechanical vibration energy harvesting techniques has been made and the mechanisms of energy conversion of solar panel and piezoelectric cantilever beam have been analyzed. The combination of two energy harvest methods makes it possible for charging the supercapacitor which provides the power of WSN node continuously in different environment. The charging and discharging properties of supercapacitor have been studied in detail and a high power charging circuit using the s8050 and LM317 adjustable regulator has been designed, the stability, rapidity and efficiency of charging of supercapacitor when using relatively large current have been proved through the test. Finally to meet the power supply need of current WSN node, a multisource charging power generator has been designed, five 2.7V 500 F supercapacitor have been used as the core energy storage elements, a MSP430 microcontroller has been used to choose the harvesting energy source for supercapacitor, as well as an voltage regulator which compares the voltage supply of the WSN node(3.3V) and adjust the boost circuit output with PWM wave using PID control algorithm, making the output voltage stable. Through the actual hardware circuit construction, debugging and final test data analysis, the designed power supply system based on supercapacitor energy storage can meet the need of requirements for stable voltage supply of WSN node.