On The Development Of Full Automatic Control System Of Grain Dryer

Generally, grain contains adequate moisture, and grain moisture is a very important quality indicator in the food administrator all over the world. Grain moisture not only affects the safety of grain storage, but also affects the quality of food products processing. This thesis focuses on the development of a grain humidity-temperature control system, in which the grain humidity is detected on-line and then is sent to the humidity-temperature control system to achieve the automatic control of grain dryer.In this thesis, the capacitive sensor is taken as the grain moisture measure devices. The relative dielectric of capacitive sensor changes with the moisture, and accordingly the capacitance will be changed. A high-frequency sinusoidal excitation signal is imposed across the end of the capacitive sensor, and there will be a response in the output side. The excitation and response signals have the same frequency, but with a phase difference between them. The phase difference is measured to calculate the ratio of the capacitance and the conductance, then the moisture of grain could be calculated.In the automatic temperature control system, AT89C51 is employed as the CPUs, and high-precision digital temperature sensor and control circuitry are used, and high precision and high reliability is achieved.The key of the control system is the speed and the accuracy of Data transmission. In this paper, CAN controller area network is applied to transfer the signal of moisture and temperature,and the single chip is to control the process of grain dryer, which achived intelligent control in the whole system.