Design And Test Of Temperature And Humidity Control System For Plastic Shed Based On STC Single-chip Microcomputer

In recent years, plastic shed of vigorous development has become a key link in the process of agriculturalproduction. In the southern region of Xinjiang, because of the natural climate conditions of largetemperature difference between day and night, drought and desertification, it is control of the increasinglyhigh demand for plastic shed temperature, humidity and other internal factors related to detection. Themathematical model of temperature and humidity in plastic shed internal established through analysis, withSTC89C54as control core, using DHT11as the main temperature and humidity data acquisitioncomponents, ordinary plastic shed temperature and humidity controller is designed by modular. Thehardware part which is composed of module control core, temperature and humidity detection, display,output,alarm. After open the system, temperature and humidity data collected by the sensoranalog-to-digital conversion in its interior, and convert the digital signals to the single chip, and the initialthreshold comparison, get the deviation of data set value and the measured value, combined with PIDcontrol method, the control of external equipment action, release, maintain temperature and humidity inshed a reasonable range. The software mainly analyzes STC89C54MCU internal clock, interrupt control,DHT11startup and the response and LCD1602read, write, read the instructions state data, and write datafour operation timing. The problems of the plastic shed temperature and humidity nonlinear, hysteresismeasurement control were solved by combing with PID control and using the KEIL C programming anddebugging. At the same time, single factor, the comprehensive factors and precision test experiments weremade. Performance test results show that: when the outdoor temperature change at9.2-24.3DEG C range,after the initial time open controller working operation30minutes, the shed temperature is always in thechange set in the range of25-27DEG C, external equipment with internal temperature changes; when theoutside humidity is in the30-86%range changes, after the initial time open controller working operation30minutes, the humidity in shed always changes set the range of50-60%, external equipment with internalhumidity changes; when the outdoor temperature, humidity respectively at10.7-24.7DEG C,30-90%range changes, after the steady state to be the controller working operation, shed temperature and humidityis always in25-27C,50-60%setting range, external equipment with internal temperature and humiditychanges. The accuracy of test results show: the temperature and humidity inside shed value and the averageerror is generally in the true worth of about+/-5%, external equipment opened, closed state stability. Thedesign of the system is economical and practical, the circuit structure is simple and reasonable, the systemis stable and reliable, and can meet the demand of the majority of farmers, and the realization of the basicrequirements for temperature and humidity control.