| In the process of thermal disinfestation, the pests in agricultural products should be killedquickly and effectively.At the same time, the quality of agricultural products should not beaffected seriously. In order to achieve this aim, we need to understand the thermal resistantcharacteristics of pests in products to obtain the optimal heating rate, holding temperature andholding time in the condition of pest killing rate of100%, minimum energy consumption andimpact on the quality of agricultural products. For this reason, it is need to develop a set ofexperimental device of studying the thermal resistant characteristics of pests.In this study, a set of research system which has the function of temperature sensing andcontrol was designed according to the thermal resistant characteristics of agricultural productspests. And during this design, the technology which has been used mainly contained sensortechnologies, temperature detection technology and temperature control technology. TheAVR microcontroller was selected as the control core. C language and VB language wereused as software development platform. The main contents and conclusions of this researchwere as follows:(1) Firstly, the overall structure of the research system of thermal resistant characteristicsof agricultural products pests was designed. Secondly, specific control requirements and workprocesses were proposed and drawn up respectively. At last, the temperature control methodswere made.(2) The hardware system was designed in this paper. System hardware was mainlycomposed of heating device and hardware circuits. The heating device was mainly consistedof upper aluminum plate, lower aluminum plate, sealing fin, heating plate, thermal insulationmaterial, temperature sensor and stainless steel shell. In the design of hardware circuit, the8-bit single chip microcomputer (SCM) Atmega16was selected as microcontroller. AndPt100was selected as temperature sensor.Signal conditioning circuit was designed by bridgecircuit and op amplifier INA114. Analog to digital converter circuit was designed based on A/D converter TLC2543. Temperature control circuit was designed through the transistor andsolid state relays. Power supplies of the whole hardware circuits were designed by voltagestabilizing chips (for example: LM317and Ref5050).Finally the hardware system of devicewas designed and produced.(3) The software which was mainly written by C language and VB software wasdeveloped for the device. And the C language was used to write SCM program. VB softwarewas used to write PC software. The program of lower machine part was mainly consisted ofA/D conversion subroutine, PWM control subroutine and serial communication subroutine.The PC software was mainly consisted of data processing subroutine, temperature outputsubroutine, PID control subroutine, heating speed control subroutine and dead zonetemperature control subroutine.(4) The debugging and verification of the system were completed. The hardware systemand software system were debugged jointly after the design and produce of the two parts werecompleted. Next temperature sensors of the upper plate and lower plate were calibrated. Theresult of temperature measurement error was less than0.2℃. Followed on the system'scontrol parameters were fixed, and the heating rate and temperature control accuracy wereverified. The experimental results showed that: the error of heating rate and temperature werelimited to±0.3°C/min and±0.1°C respectively.This paper studied about developing a thermal resistant detection system according to thecharacteristics of thermal resistant of agricultural products pests with the AVR single chipmicrocomputer as microcontroller. In order to simulate the thermal disinfestation environmentand get the optimal thermal disinfestation scheme according to the seted heating rate, holdingtemperature and holding time. The system provided conditions to master the thermal resistantcharacteristics of agricultural products pests. And it will supply valuable reference to thethermal disinfestation technology. |
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