Design Of Fire Alarm System Applied To EMUs

With the development of technology, Electric Multiple Units (EMUs) with the characters such as high-speed, comfort, economical and environment harmlessness have gradually become the focus of the development in China's high speed railway and play a more and more important role in the national economy. As an integral part of traffic safety system, Fire alarm on EMUs can warn potential fires in time and ensure passengers safety. But the fire alarm systems used in EMUs completely rely on imports. Because of the intellectual property of those foreign equipments, the problems such as high price and difficult maintenance have greatly limited the application and development of fire alarm systems in our country.In this paper, an intelligent fire alarm system used for high-speed EMUs is designed with PIC series microcontroller units(MCU) by analyzing fire alarm needs and the actual operating environment of CRH5 EMUs.Firstly, the principles of fire detection and the design of smoke chamber are described in detail referenced to a comprehensive analysis of different types of fire alarm systems. The automatic monitoring and alarm of the system are carried out with smoke-temperature compound detection technology and signals processing algorithm based on "Floating threshold + Change rate of temperature". Secondly, under the overall design of the system, each functional module of the fire detectors and controllers are completed using PIC16F876A and PIC16F630 as MCUs. Finally, the measures to improve system reliability are proposed in the both aspects of the hardware and software on the analysis of system reliability in detail. A monitor circuit for MCU based on Monostable Multivibrator is designed, and a passive fault diagnosis system is designed which can find out the fault in the detector, based on the basic composition and principle of detector. With the help of the system, the maintenance cost is effectively reduced and reliability is enhanced.The debugging for each functional module of the system is accomplished under the lab environment, and a comprehensive test of the system under the conditions of the actual operation of CRH5 EMUs is done. The results show that the fire alarm system developed by our project which is fully compatible with the connection of foreign products, and has reached the fire early warning requirements of EMUs stability and applicability.