Precision detection circuit is adopted, which can detect the relative humidity of ambient air accurately, and send the measured data to the processor (AT89C51) after A/D conversion. Then the relative humidity of the current environment is converted to decimal digits through software programming, and then displayed by digital tube. Moreover, through software programming, coupled with the corresponding control circuit, automatic adjustment is designed. Relative humidity of current environment.
With the development of science and technology and the improvement of people’s living standards, greenhouse industry in China has developed rapidly. Greenhouse is one of the indispensable facilities for vegetable and other plants in cultivation and production.
Different kinds of vegetable have different requirements for growth conditions such as humidity. It provides them with a closed and good living environment more suitable for their growth, so it can be raised. Early or delayed flowering will eventually bring us great economic benefits. Based on this design, a humidity control system based on 89C51 single-chip computer control is designed. This system realizes humidity detection through single-chip AT89C51 and its various interface circuits. Its working principle is that the capacitance of the capacitive relative humidity sensor changes linearly with the change of humidity. The capacitance of the sensor is transformed into the corresponding voltage by signal detection and conversion circuit.
Then the analog voltage signal is converted into digital signal by A/D converter and sent to the single chip computer. The single chip computer filters the collected signal and gets the reality by looking up the table. After measuring the humidity value, the humidity value is displayed through the external interface circuit of the single chip computer, or it is sent to the upper computer through its interface to save and print.
Serial communication is widely used because of its low cost and fewer lines. Especially in long-distance transmission, it avoids the inconsistency of the characteristics of multiple lines. In serial communication, both sides of communication are required to adopt a standard interface, so that different devices can be easily connected to communicate. RS-232-C interface (also known as EIARS-232-C) is currently the most commonly used serial communication interface. It is a standard for serial communication developed in 1970 by the EIA in conjunction with Bell Systems, modem manufacturers and computer terminal manufacturers. Its full name is “Technical Standard for Serial Binary Data Exchange Interface between Data Terminal Equipment (DTE) and Data Communication Equipment (DCE)”, which stipulates that a 25-foot DB25 connector is used to specify the signal content of each pin of the connector and the level of various signals. Fig. 1 is the schematic diagram of the system structure, in which the lower computer is based on AT89C51, and is composed of humidity detection and transmission circuit, A/D conversion circuit, memory circuit, clock circuit, watchdog reset circuit, serial communication circuit, keyboard and LED display circuit and power supply circuit. Sampling: Single-chip AT89C51 can control the sampling procedure of TLC1549 working normally.
After filtering, binary-decimal conversion and decimal 4-bit precision display program.
Communication: MCU AT89C51 can transmit the displayed data to the upper IBM-PC of management level through serial communication port, and then the upper computer can process the received data. The flow chart of the main program is shown in Figure 2. Testing is the final review of software requirements analysis, design specifications and coding before the system is put into operation. It is the key step to ensure the quality of the system. If you want to define a test, you can do this. System testing is the process of executing a program to discover errors. The purpose of testing is to reflect the inconsistencies between functions and requirements, and the inconsistencies of logical thinking to the quality testing department. The quality testing department allocates the requirements department to be unified, thermostatic element and then the developers modify and supplement it. The goal of testing is to identify potential errors and defects in the system with minimal time and effort. This test is strictly in accordance with the design process.
Through this test, we can better understand the design process framework and test design principles, and can solve various problems in the test, and better solve them. Corresponding adjustments are made by changing humidity. The system uses a high precision capacitive relative humidity sensor.
When the system runs stably, the range of humidity measurement is 0-100% RH. The system also makes full use of the software and hardware resources of AT89C51 single chip computer, and has the advantages of intelligence, programmability and small portable. So as long as different humidity sensors are selected and the corresponding software control procedures are modified, the detection system can be applied to environmental protection, industrial control, agricultural production and military affairs, which shows that it has a very wide application prospect.