Study On Detection System For Harmful Gas In Granary

China is a agricultural country，with the most population in the world，a plenty of grainreserves is the fundamental for our social to develop stability. Whether the daily life ofpeople or disaster and crisis occured，such as earthquakes and floods，country’s situation couldbe controlled through the grain reserves，especially in the war period，country’s stability wasdecided by the grain reserves. But most of the grain in the granary is stored directly，so thequestion of rot，mildew and insect etc. is very easily occurred，which effects the quality ofgrain reserves. In order to guarantee the quality of grain reserves，granary used a variety ofstorage technologies to manage the grain reserve，such as fumigation，ventilation or taking thereserved grain out of granary to sun. Moreover，grain is life to breath，there are many kinds ofharmful gas in granary，not just only the residual gas of fumigation，but also produced bymolds and the breath of mildewed grain. Many kinds of these toxic gases have fatal effect onhuaman body，even if the granary has been ventilated for a long time，it is also has a badeffect on human health. Therefore， it is very necessary to establish a harmful gasconcentration detect system of granary，so that it could provid a quantification standard onharmful gas concentration for granary workers.The traditional granary environment detect system is mainly used to detect the humidityand temperature，it is still blank about the harmful gas concentration detection，and there aremany deficiencies and limitations when using the traditional system. This project combinedZigBee wireless network technology and CAN field bus technology with modern sensordetect technology，studied and designed a harmful gas detect system with new structure forvertical granary. The system includes as follows:(1) Constructed a distributed intelligent nodedetect system with two layers.(2) Based on ZigBee network technology，studied the methodof building a harmful gas multi-node communication network. Took advantages of low powerconsumption，low cost，high performance of ZigBee equipment to construct a ZigBee acquirenetwork，it could prolong the working time of pre-acqiring network，and reduce the systemcost.(3) Based on the characteristic of long distance transmit data of CAN bus，studied andbuilded a CAN transmission network which connect the coordinator node with data-receiving node of control terminal，use to transmit the data of coordinator node and the command ofcontrol terminal.(4) Set up a quantitative safety threshold value standard in thedada-receiving node of controll terminal. When the data-receiving node received data from acoordinator node，it will make a comparison between the data processed result and the safetythreshold value standard， and provide a quantitative stanard for harmful gas concentrationwhich out of limit.Finally，we make a simulation test to the system，the test result proves that the system isstable，communicat data is reliable and has strong anti-interference. Therefore，the systemconforms to the requirements of designed.