The Design Of New Fire Alarm System's Signal Processor

In accordance with the fact that the number of probes in the present optical fiber grating temperature sensing fire detecting system can not meet the need of supervising outsize and complicated objectives, and according to the drawback that the fire alarming temperature data of individual sensor can not be installed separately, this paper researches and designs a new signal transforming processor for fire detecting system by applying the I~2C bus virtual technology into optical fiber grating temperature sensing fire detecting system, which bridges over the above two defaults. It can not only enable the objectives supervised by the fire detecting system to break through the number limited by the present demodulator technology and to reach the possibilities of being only controlled by the biggest electric capacity, 400PF, of the I~2C bus so that the number of probes could be increased in duplication from that at present, but also realize the possibility that the data of different sensors' fire alarming temperature can be set separately at random, which is the outstanding creativity of this paper.The main tasks of this paper are as follows:1,The resolution that optical fiber should be used as the probe of fire detectingsystem and that I~2C bus as the intelligent digital node should be worked out in research of such problems as the lack of the existing measuring points of our country's fire detecting system, the tardiness of data processing and so on;2,The number of the mounted probes can be increased in duplication from that at present through the parameter setting up of I~2C bus to the intelligent node. Moreover, the possibilities can be realized that the fire alarming temperature data of the different sensors can be separately intercalated at random and self-examined. In this way, the digital node's ability of processing information can be scaled up by applying the I~2C bus, the memorizer and the modulus transition circuit carried inside the PIC16F877 CMOS chip;3,The new signal processor researched in this paper will transform, process and build up the fire alarming threshold data identifying modules enacted in the intelligent node through the 10 bit A/D transition channel mounted inside the PIC16F877 CMOS chip, and at the same time adjusting the cavity length of the optical fiber F-P by the simulated voltage output by D/A to reach the aim of setting fire alarming temperature;4,A new experimental simulation system formed with digifax transition module, liquid crystal displaying module, keyboard circuit and some other hardware and the relevant software can be exploited by using the temperature node CMOS chip DS18B20. Validated by the experiment for the reliability and the delicacy of the system, the fire detecting system researched in this paper works stably and credibly.