Research And Realization Of Gas Alarm System Based On CAN Bus

No matter in petrochemical enterprises, or in business halls, residential buildings, it will endanger the safety of people's life and enterprises' properties if harmful gases such as combustible gas, poisonous gas leak without taking effective measures. Accidents can be avoided if harmful gases can be detected in time and effective measures could be carried before gases enlarge.This paper first investigates the present situation and development of gas alarm products, compares advantages and disadvantages of all kinds of gas alarm products, studies the communication principle of CAN bus. According to the design requirements of gas alarm, the scheme based on CAN bus is proposed. The system combines CAN bus and RS485 bus. CAN bus is the top network used between the master controller and CAN/485 converters. RS485 bus is the lower layer network used between CAN/485 converter and gas detectors, coupled equipments.Secondly, the hardware and software design of the master controller is introduced in detail in this paper. ATmegal28, a high performance MCU is used in the master controller as the center controller. The design of CAN communication module is completed by using MCP2510 (CAN controller) and PCA82C250 (CAN bus transceiver). Information displaying and parameter setting are realized by a 10.4 inch color LCD which has the touch screen. In addition, the master controller also includes the power conversion and detection module, sound and light alarm, printer, real time clock, coupled equipment, extended 32KB RAM and 32KB E~2PROM etc.Thirdly, the hardware and software design of CAN/485 converter is introduced in detail. ATmega16 is used as the controller for designing the CAN interface and RS485 interface. The converter realizes special functions such as communication format conversion, automatic search of different nodes, address modification etc. Then, the paper introduces the design method of gas detector and coupled equipment. Gas detector and coupled equipment both use PIC16FC690 MCU as the controller. Gas detector completed functions such as gas density collection, data processing and transmission etc. Coupled equipment controls valve of fan or gas pipeline.At last, this paper briefly introduces experiments of the system for functions and electromagnetic compatibility and summarizes several methods to improve the communication distance.The gas alarm system can monitor natural gas, liquefied gas, coal gas, organic solvent and other combustible or toxic gas, and accommodate 1024 gas detectors. The master controller can print historical records and the color LCD with touch screen makes the operating interface convenient and perfect. Alarm system based on CAN bus is applied widely in the fire industry but it is just started in gas alarm field. At present, it is rarely to be reported for the gas alarm system's structure based on this paper. This system is a major development trend of bus-based gas alarm system and it will have broad market prospect. This paper is a horizontal cooperation project with JiNan ChangQing computer Co.,Ltd. At present, the product has passed the certification in gas alarm field and is produced to meet challenges of market.