Application And Research Of PLC On The Temperature Control For The Multi-span Glass Greenhouse

Facilities agriculture is the most energy new industry in the 21st century,and greenhouse is a typical representation.In modern intelligent greenhouse,auto measure-control system is a very important. The domestic and overseas planting practices show that it improve the auto control and manage level can fully exert the efficiency of greenhouse.The thesis have made use of sensor techniques,communication techniques, auto-measure techniques and computer techniques to designed a distributed system.This system based on the PLC is an intelligent-control system on temperature of greenhouse,it adopts the idea of distributional control and consists of hypogyny-system, epigynous-system.Epigynous-system is based on the model FX2N-48MR-ES/UL of Mitsubishi PLC which is the main controller in the scence,a distributed control network formed by using of PLC networking function in epigynous-system.The main function of the epigynous-system is collecting and storing of temperature parameters of greenhouse,starting or pausing the executing agency,and giving light alarm when parameters overrun.Hypogyny-system uses the computer,utilizes RS-485 to communicate with Epigynous-system provide a good interface and it is convenient for people to use the system.The main functions of the hypogyny-system is showing and storing the data of the temperature,querying the historical data,printing the data report,giving alarm when parameters overrun and displaying the running states in and out of each greenhouse.The system contains these characteristics below:1) Aiming at the climate characteristic of the Yunnan Province,it analyses the temperature characteristic of multi-span glass greenhouse.It put forward the method of lowering or rising temperature which suits the local climate condition on the basis of the previous studies,realized the development of economy and cost-saving.2)It adopts PLC as master-control unit in the scene control and it fully uses the advantage of PLC to make the temperature controlling more convenient and reliable.3) Using distributed configuration can realize expediently the management of large-size glass greenhouse group,as each of Epigynous-systems is independent from each other,the reliability is good.4) Using VB6.0 programmed the software that is suitable for controlling the temperature of greenhouse.lt can effectively administrate and analyses the history data,moreover,on the basis of the analysis we can worked out reasonable monitoring plan,which carries on more effective management on the temperature of multi-span glass greenhouse.The research on the system has been summarized at the end of the thesis,at the same time,the insufficiencies in research and the direction of further study are proposed.