Research On Wireless Fire Alarm System Based On LoRa Technology

With the development of China’s science and technology and rapid economic growth,fire problems caused by natural or human factors occur from time to time,and people have put forward higher requirements for fire alarm systems.In addition,the development of the Internet of Things and wireless communication technology provides technical support for fire alarm systems.Aiming at the shortcomings of the existing fire alarm system functions and low-speed data transmission methods,such as high hardware failure,difficult installation and construction location changes,and poor anti-interference ability,this paper proposes a wireless fire alarm system based on LoRa technology.This article first introduces and analyzes the current research status at home and abroad.Through research and analysis of the fire development status and system function requirements,the design idea and overall plan of the wireless fire alarm system based on LoRa are proposed.The system is mainly composed of a smoke detector and a monitoring host,and the detector and the monitoring host communicate over a long distance through the LoRa network.In the hardware system part,the signal acquisition circuit,wireless communication circuit,and communication interface circuit of the optical smoke detector are designed.The power supply circuit,reset circuit and alarm circuit of the host are monitored.Design and study the work flow of the smoke alarm node,wireless communication node and monitoring host node of the fire alarm system respectively,to realize that when a fire occurs,the smoke detector can collect and process data in real time,and transmit the alarm signal to the wireless transmission method.Monitoring host,the monitoring host sends out an alarm and stores data,the staff on duty can make a judgment and take fire extinguishing measures as soon as possible.In order to improve the sensitivity of the system’s transmission signal and extend the transmission distance of the system signal,this paper uses HFSS,ADS and other electromagnetic simulation software to simulate the antenna,and design the impedance matching network,and studies the best topology of the wireless fire alarm system based on LoRa technology.In the HFSS software,a normal mode helical antenna model is established,and the antenna structure parameters are analyzed using the control variable method to obtain the optimal antenna model.In the ADS software,the antenna matching circuit is simulated by a non-radiative network to realize the simulation of the antenna matching network.The overall simulation results show that the gain of the normal mode helical antenna reaches to,the return loss of the antenna feed port is reduced from to,and the impedance after matching is about 50Ω,which achieves a good matching state.Finally,the wireless fire alarm system was tested for electromagnetic characteristics,functionality,and transmission distance.The test results show that the electromagnetic field characteristics of the LoRa wireless fire alarm system basically meet the requirements of the Ministry of Health on the premise of meeting long-distance and high-reliability wireless transmission.Required human safety standards.