The Design Of PCR Temperature Control System In STC

PCR instrument is widely used in the medical engineering, the temperature control system is its key technology, which is able to achieve rapid, precise temperature control and several thermal cycles to complete gene amplification. A thermal cycle generally comprises three phases:denaturation, annealing and extension. At present, foreign PCR instrument is more advanced in technically, which is larger and more expensive in the price. The purpose of this design is to produce one kind of PCR instrument,which is simple structure, lower prices, smaller, precise performance and temperature uniformity to meet the requirements.Paper introduces the principle of the current PCR instrument and development status at home and abroad, raised some questions about PCR instrument,and discussed,then propose significance of the study, content,and design features of the paper. The main contents of the study is as follows.(1)The module of temperature measurement and variable temperature,which is the key elements in the hardware circuit,and related to accuracy and reliability of the temperature control system. The system of temperature measurement circuit composed by the AD590as a thermal sensor, both to improve the accuracy and reduce the complexity of the hardware. The module of variable temperature,which primary role is to control the temperature and used TEC to control, both to reduce the size of the design and improve the accuracy.Other, added a cooling fan to improve cooling rate.(2) The control circuit of MCU is incuding the module of man-machine communication, AD and DA conversion, serial communication, reset the unit, etc.The hardware circuit is mainly describesed in this section,which is the basis of temperature control normal operation.The protection of temperature measurement precision is AD converter, so we need ensure its voltage stability and multiple sampling to reduce errors in software. Differential amplifier circuit is built by DA conversion to control TEC.(3) The design of temperature controlalgorithm. Software algorithms is adaptive fuzzy PID in the system.This algorithms is combined of PID controland fuzzy contro,using proportional control when the temperature deviation is large,and using adaptive fuzzy PID when the temperature deviation is in a smaller range.Then simulation and comparison the Software algorithms in MATLAB.Simulation and improvement of the temperature uniformity.Reaction tank is a vector of the temperature variation,which directly affects the tube of the temperature uniformity and final test results.The paper using finite element analysis for the reactor,and obtained the temperature distribution,then propose the improved Method of the temperature uniformity.Then demonstrate the improved results using the finite element analysis and actual measurement.The design of software.The system programming language is C language,major programs include the program of the PID algorithm, temperature acquisition and Digital filtering,etc.The PCR instrument was initially achieved,which is small,lost cost and fast,throughing simulation and debugging. And the implementation show the temperature accuracy about0.3℃,the heating and cooling rate is4℃/S,and the temperature uniformity is0.4℃.Its functionality to meet the needs of hospital and Research Institute.