PLC In Circulating Grain Dryer Control System’s Application

China is a large population country, the major grain-producing countries, a foodconsumption big country also, the total annual production capacity to about500million tons of grain. According to statistics, China’s grain harvest in threshing, drying,storage losses in the process of transportation, processing, consumption is as high as18percent annually due to climate reasons, grains and dried too late or do not meetthe safe moisture causing mildew, sprouting and loss up to5%of food grain receivedreduce losses to the lowest point, in this sense, we need to use the new technology toreduce the loss. This grain drying control system came into being.Grain drying automatic control technology in everyday life has an importantposition, with the advance of the process of agricultural industrialization, agriculturalmechanization and automation has improved continuously, various forms of graindryer market continuously. I believe that grain drying function play a better role in thelife and production in the future.Grain dryer is an electro mechanical device, it is used to post-harvest graindrying and it must have high standards of automation. Technology is not developed,which uses a relay logic control mode to control its operation. Over those years, withthe rapid development of technology of PLC, PLC in control and hardware costsmake it more widely used in the area of control. Grain dryer also abandoned with thepast relay logic control technology which is "system failure rate is high, longmaintenance cycle", instead of using simple and convenient PLC control technologyto control its operation. Because of the comprehensive advantages of PLC technologyin the field of control shown by other control methods cannot match, it will graduallyreplace other control mode, control of AC Electrical mainstream control mode. Now,in the international market in the field of industrial control PLC has become the mostpopular best-selling products. This thesis discusses the programmable logic controllerPLC: mainly introduces the dryer process, PLC control system design and thestructure, procedures etc.