| Temperature is a very important parameter in chemical reaction process, and many types of chemical reactions are required to be conducted under the conditions of constant temperature. If they are not satisfied, chemical reactions may not get the reaction results due, so the temperature must be precisely controlled.The microwave chemical reactor is a chemical reaction device that uses the microwave heating, its calefaction possesses high speed, small inertia, selectivity, also can promote the rate of chemical reaction. So it can not be replaced by the conventional chemical reaction device, and be widely applied in the organic synthesize, extraction and correlative occasion in material, chemical industry, pharmacy, lab research, and correlative teaching field, and so on.In this thesis, on the base of analyzing the working principle of microwave power sources and introducing two-way thyristor technology, designed and realized the temperature control system of microwave chemical reactor based on two-way thyristor technology, PID control algorithm of variable proportion and integral coefficient. The whole control system takes the ATmega128 single-chip processor as core of hardware, through the real-time sampling, processing towards temperature of reactants within microwave chemical reactor, and calculate the amount of volume controlled by the system by using PID control algorithm, triggering the two-way thyristor according to zero-crossing of volume controlled, to control the turn-on time within its cycle-time, therefore to control the average output power of microwave within the cycle of microwave power source, to ultimately realize the constant temperature heating of the reactants inside the microwave chemical reactor by microwave. This thesis has completed the design and debugging towards the hardware and software of the system, obtained the experiment result, and finally achieved the adjustable constant temperature within range of 40-150℃, the control precision achieved±1℃. |
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