Monitoring And Control System Based On PLC For Intelligent Greenhouse

As the biggest agricultural country in the world, China’s agricultural production hasa pivotal position in national economy.With the improvement of living standards,demand for green vegetables are growing,therefore our country agriculture developpingfrom extensive to intensive has become an inevitable trend,and as one of the importantways of the developing,agricultural facilities are receiving much more attention. Cropgrowth is mainly affected by temperature, humidity, light intensity, carbon dioxideconcentration and other environmental factors, so the purpose of building intelligentgreenhouse is to automatically control these environmental parameters.Through the analysis of controlled object and environmental quality ofgreenhouse,we determine the structure of the control system and control programs. Inthis paper, we design a distributed intelligent greenhouse control system,which haslower computer-programmable logic controller and upper computer-a personalcomputer with kingview. Hardware mainly includes the PLC and its special functionmodule, all kinds of sensor circuit, power supply and execution unit;software mainlyincludes kingview and Mitsubishi PLC programming software-GX Developer.The control system has two control modes-manual control and automatic control. Inthe automatic control mode, lower computer-PLC collected environmental parametersby sensors and compared with the minimum maximum environmental parameters whichare set by the users to control the start and stop of the corresponding execution unit toadjust the parameters of greenhouse environment. In manual control mode, userscontroll analogue switch in the kingview’s manually screen according to the need，whichcontroll PLC to give out switch order to controll the corresponding execution unitregulating the greenhouse environment. Upper computer communicate with lowercomputer-PLC to complete the function of the human-computer interaction. Kingviewcan real-time display the current environment parameter values collected by lowercomputer-PLC, the states of the execution units,alarms and so on. In themeantime,users can view the trend curves,operate report forms or Access data base bykingview. Users setting the minimum maximum environmental parameters,switching manual/automatic control and controlling analogue switch in manual control mode arealso can be operated in kingview.Through system testing experiment,the intelligent greenhouse monitoring systemachieves the expected design requirements,but it also need to continue to improve inorder to be used in practical greenhouse.