Design And Implementation Of The High-precision Temperature Control System Based On Thermoelectric Cooler

With the rapid development of miniaturized instruments of life science research,physicochemical parameter measurement and semiconductor laser occurs,the application for the rapidity of heating and cooling switch and high-precision temperature control in a small space,needs more and more urgent.However,the traditional control way is often difficult to meet the requirements.Thermoelectric cooler has the advantages of small size,easy to realize high precision and integrated heating and cooling,and it has a wide application prospect in these fields.In this paper,the high precision TEC temperature control system is taken as the research object,and the design and implementation of the system are deeply discussed from the aspects of the overall scheme of the system,the hardware circuit,the software,the temperature control algorithm and the human-computer interaction.In the overall design of the system,starting from the working principle and application conditions of TEC,the analysis and calculation of heat transfer of the system structure are carried out,including the selection and layout of TEC,the material and thickness of the insulation layer,radiator and its fan etc.Combined with system function requirements,the core components of MCU,temperature sensor and AD converter are selected and analyzed.In the design of hardware circuit,the 24 bit of the type of ?-? ADC is used in the temperature acquisition.By applying the technology of exciting commutation and the ratio method to three-wire platinum resistance innovatively,the lead resistance error is eliminated effectively and the measurement precision is improved.Aiming at the present problems of low current,low efficiency and poor reliability of TEC drive circuit,the floating gate drive circuit of 4 NMOS tubes is designed,which realized flexible switching for heating and cooling.For the lack of overload and thermal shock resistance of TEC,high frequency filter and protection circuit are introduced to prolong the life of TEC.In the design of temperature control algorithm,aiming at the complicated problem of temperature control mode near the room temperature,the double direction temperature control mode based on TEC characteristics is designed.In order to solve the problems of time-varying,instability of TEC power and troublesome PID parameter setting,a combination of fitting function parameters of PID,single and double subsection control and variable integral is used in the strategy of temperature control.In the software design,the software programming of temperature acquisition,communication of master and slave system,PWM output and control of TEC driver are completed.In the aspect of human-computer interaction,a development software called LabVIEW is used to design the interface of host computer,and the real-time interaction contain PID parameters and setting temperature is realized.In the experimental verification,the calibration and calibration experiments are carried out,the results show that the temperature measurement error is better than ±0.025 °C.The temperature control range and the control precision of the system are also verified by experiments,the results show that the TEC temperature control system designed in this paper can realize the temperature control in the range of 0 °C to 120 °C,meanwhile the control precision is up to ±0.1 °C.