Research On The System Of Automatic Monitor And Control With Microcomputer Of Grain Drying Machine

China is not only densely populated, but depends heavily on agriculture as well. In recent years, China's average total yield is about 500 million tons, of which 20 % has a moisture content higher than that for safe storage and around 85 millions tons needs drying. Normally, these grains are dried by drying machines. In China, improving the drying machines becomes increasingly important, because the old and less automatic model-drying machines cannot satisfy us with its poor quality of dryness.By using microcomputer, I studied the monitoring system of drying machines about the content of water, the temperature of grains and the position of grains in the machine. The conclusions are as follows. The improved monitoring system contains three parts: sensors, controllers and executors. Sensors are used to detect the content of water and the temperature of grains, to measure the velocity of influx and to position the grains in the drying machines respectively. Thermal sensors are thermocouples to monitor the temperature of heated air current and thermo resistances to measure the temperature of grains on different surfaces; water sensors include neutron probes and condensates to measure the content of water of grains before and after drying respectively; the velocity of flow of grains is measured by the indicators of flow. All of the variables are conveyed into a single chip microcomputer through RS-485 interfaces and are processed there. Two microcomputers are used. The upper one is a IPC 610 industrial controlling microcomputer in which variables can be set; the lower one, (a PLC), by processing data from the single chip computer, mediates the velocity of outflow of grains and keeps it in the most suitable range by controlling the speed of motor. Turbo C language is used in the program that is easy to be understood and is operative.This system can be used on both old and new model-drying machines. The improvement of drying machines can certainly promote the efficiency of the grain drying machines and the quality of grains in storage.