introduction
Temperature and humidity are the main environmental parameters of industrial and agricultural production. It is of great significance to measure it timely and accurately. Use single chip microcomputer to control temperature and humidity. It has the advantages of temperature control, high humidity accuracy, strong function, small size, low price, simple and flexible, etc. It satisfies the process requirements well. This article introduces the intelligent method of temperature and humidity detection and control using AT89S52 microcontroller.
1 System basic scheme
This system uses AT89S52 microcontroller as the control core. Analyze and process the collected humidity analog voltage signal through ADC0809. Realize A / D conversion. So that the digital tube displays its humidity value. This design can manually set the upper and lower limit values ​​of temperature / humidity. If there is one that does not match the set value, that is, if the temperature / humidity is too high or too low, the system will issue a voice alarm and the relay will be cut off immediately power supply. To achieve system protection.
2 The composition of the hardware system
(1) Main control module: AT89S52 single-chip microcomputer is used as the system controller. Pl port controls the digital tube to display temperature and humidity values. P2 port is connected with ADC0809. Realize the conversion of humidity analog voltage to digital for the convenience of single-chip processing. Keyboard control uses PO port. Among them PO. O is the temperature setting, PO. 1 is the humidity setting, PO. 2 / PO. 3 is to set the upper and lower limits of temperature and humidity respectively. P0.4 is the wiring port of DS18820 temperature sensor. PO. 6 is the wiring port of the ISD1420 voice chip. The principle is shown in Figure l:
(2) Display module: The system uses dynamic display mode to drive 6 digital tubes to work, of which 4 digital tubes are used to display temperature values ​​and 2 are used to display detected humidity values. Use the input end of 74LSl38 to select the bit code. The P1 port of the single chip microcomputer controls the broken code of the digital tube. If the detected temperature and humidity change, the nixie tube will change accordingly and play a real-time display function. The circuit is shown in Figure 2.
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