Environmental Factors Regulating System Development Of Greenhouse Plants Growth Based On PLC

The growth quality of greenhouse plants is closely related to the environmental factors in the greenhouse,ensure plants grow in the appropriate temperature,humidity,light,CO₂ concentration,moisture and nutrient conditions can make plants grow well and promote increased production,therefore,the regulation to the key environmental factors of plants growth in the greenhouse is very necessary.The current large-scale greenhouse intelligent control systems often have characteristics such as bulky,expensive,complicated installation and so on.This paper in view of modern small intelligent greenhouse,designed a kind of key environmental factors regulating system of greenhouse plant growth which based on PLC,it can monitor environmental factors in the greenhouse in real time,and automatically control the corresponding devices according to the changes of environmental parameters,and then achieve the regulation to the key environmental factors of greenhouse plants growth.The system has easy installation,low cost,good stability,strong expansion and other advantages.The system mainly used programm logic controller?PLC?to develop the next crew software,and combined with human machine interface?HMI?touch screen to achieve the control mode set of entire system.The system collected functions of collect,display,storage,control,and developed LED light-fill module,spray irrigating-cooling integration module,wind feed type of CO₂ add module.The system use PLC controller to regulate lighting,temperature,humidity,water,fertilizer and CO₂ concentration inside the greenhouse.PLC controller is used to control the work of various regulatory modules according to the real-time value of each sensor detected.LED light-fill module is used to fill light for plants during the day when lack of natural light intensity or at night to ensure the light needs of plants growth.Spray irrigating-cooling module can on one hand irrigate plants to ensure water and nutrients needs of plants growth,on the other hand lower the temperature of greenhouse in summer when the indoor temperature is high to ensure the temperature and humidity needs of plants growth.CO₂ add module is used to fill CO₂ gas when the CO₂ concentration in the greenhouse is low to ensure the needs of plants photosynthesis to CO₂.In this paper,the control performances of three modules were tested,the test contents were:the effect of LED light-fill at night to the growth of fall and winter capsicums,cooling and humidification performance tests of spray cooling system,compensation effect tests of wind feed type of CO₂ add module.The results of LED light-fill at night tests showed that:After the red blue ratio of 6:3,8:1 and time of 2 hours,4 hours,6 hours light-fill processing at night to the fall and winter capsicums,the light-fill group capsicums' plant height,stem diameter,number of leaves,total number of blossoms,total number of fruits,plant dry weight and so on all have varying degrees of growth compared with the group which did not fill light,and in the tested groups,the group of capsicums which filled light with red and blue ratio of 6:3 and time of 6 hours grew best.The results of spray cooling-humidification tests showed that:The greater spray pressure can cause more obvious cooling/humidification effect.When ensure the other equipments in the greenhouse running in the same states,after the time of 5 minutes and the respective pressure of 120kPa,80kPa,50kPa spray cooling operations,the cooling/humidification rates were 2.58?/33.10%RH,1.52 ?/18.65%RH,0.88 ?/3.55%RH respectively,and the spray flow rates of each nozzle were 292mL/min,246mL/min,190mL/min respectively.The results of CO₂ add tests showed that:Using the CO₂ add system applied in this paper to compensate CO₂ gas in the greenhouse can reach a fast and efficient result.After the time of 3 minutes CO₂ gas compensation under the pressure of 0.4MPa,the CO₂ gas concentration in the greenhouse can increase about 300ppm than the CO₂ concentration without compensation.By detecting the CO₂ concentration changes of four test points at different distances from the compensation point,verified that the entire system can make CO₂ concentration at each point in the greenhouse achieve close within 360s,which ensure the wind feed type of CO₂ add system can make the CO₂ compensation gas in the greenhouse catch even distribution in a fast time.