Research And Design Of A Distributed Methane Concentration Monitoring System Based On Zigbee Antenna Array

With the implementation of "urban-rural integration",the living standard of citizens has been improving and the use of natural gas has been increasing.Because methane is colorless and odorless,highly sensitive methane sensors can miss,misreport,or fail to give early warning when the methane concentration in the air is extremely low.If no one in the room,even if the sensor accurate alarm,gas leakage can not be dealt with in time,once the leakage will lead to safety accidents.Therefore,the wireless monitoring of methane concentration has very important practical significance.The main contents of this paper are as follows:In order to solve the problems such as missing alarm,false alarm or alarm but not being found in time,the distribution of kitchen and the concentration of natural gas in the dining room of a school district were studied,a distributed methane concentration monitoring system based on Zigbee antenna array is designed.The system consists of five modules:Terminal Node,SINK NODE,coordinator node,Serial Port Circuit and Monitoring Center,the methane concentration was monitored by Zigbee wireless network technology.Five Zigbee modules with CC2530 chip are selected for each kitchen as wireless network terminal monitoring points,and four Zigbee modules with MQ-4 methane sensor and external half-wave dipole antenna are selected as terminal nodes,a Zigbee module is outfitted with a set of binary arrays as convergence nodes.The terminal node adopts a Rhombus antenna array,a phase difference detection circuit and a phase shift control circuit,which can make the four electromagnetic wave signals cooperate and transmit in the same direction,so that the signal energy utilization ratio can reach over 90%,the theory of diversity reception is used to overcome the shortcoming that the energy utilization ratio of the traditional Rhombus antenna is only about 50%,thus,it is advantageous for the sink node to receive and send methane concentration signals to the coordinator node in time and effectively.The coordinator node then transmits the methane concentration information to the monitoring center through the serial Port Circuit,wireless Monitoring and early warning of methane concentration.The results of HFSS simulation and system test show that the distributed methane concentration monitoring system based on the Rhombus antenna array has high sensitivity and reliability.When the methane concentration is less than 2%,the absolute error of the system is less than 0.1%,which meets the national standard for indoor methane measurement.