Grain Situation Measurement And Control System Based On RS-485and Gprs

The Grain security is the foundation of national security and it is also the fundamental event relating to national sovereignty. If there is problem of grain, the country will be in dangerous and millions of people will lose their lives. Grain storage is an important part of grain security. How to reduce the grain spoilage in the process of grain storage is one of the research hot spots at home and abroad. There are many factors affecting the grain storage security in the process of grain storage, such as the temperature, humidity, moisture, insects and so on.In this thesis a grain situation measurement and control system was developed, which can implement detection, analysis and control of the grain situation. The system is consisted with software of client grain situation measurement and control system, communication extension of field unit, measurement and control extension, and handheld grain situation detector. The client is connected with the field unit by GPRS to realize collection of temperature and humidity data, the field unit communicate by RS-485. The hardware circuit of communication extension, measurement and control extension is based on STC single chip. The main research contents are as follows:Firstly, for an example of grain storehouse, a scheme of temperature collection, humidity collection, insect detection and mechanical ventilation control was designed. Digital temperature sensor DS18B20was adopted in temperature collection, the digital humidity sensor SHT71was adopted in humidity collection and the photoelectric principle was employed in insect detection.Secondly, wire transmission was adopted in serial communication of field unit. As the communication may be disturbed by lightning stroke or electromagnetic interferences, some anti-jamming measurements was adopted in the hardware circuit to improve the reliability of the system.Then, handheld grain situation detector was designed. The communication with field unit was connected by serial port, which can achieve the data by manual on-site inspection even though GPRS network was disconnected. In this way, the missing error due to untimely detection can be avoided.Finally, measurement and control systems were programmed. The grain situation was gained by handheld device through serial ports in short distance. In long distance, B/S mode was used to measure and control gain situation through GPRS network.The application of GPRS in grain situation measurement and control can achieve low-cost, long-distance transmission, flexible deployment, real-time detection of grain storage status. It is convenient to find abnormal situation and make the corresponding disposition. Therefore, the grain storage security will be guaranteed, the cost of labor will be reduced, and the efficiency of grain situation measurement and control will be increased.