Water Level Control System Based on AT89S52 Single Chip Microcomputer

　　In order to achieve accurate control of the water level in the container, it is proposed to use AT89S52 as the main control chip, and the 24-bit high-precision A/D conversion chip HX711 processes the changes in the weak voltage signal output by the weighing sensor and converts it into a digital signal. The digital signal converted by ADHX711 is converted into the corresponding water level value and displayed on the LCD screen 12864 through software. The test results show that the error between the water level display value and the actual value is ≤0.2 mm, and the error between the set water level value and the actual value is ≤0.4 mm. The experimental results show that the system has good test stability and high accuracy.

　　With the widespread application of water tanks in modern life, such as domestic water storage, solar water heater water storage equipment, etc., if manual control is used, it is not only inefficient and cumbersome to operate, but also easy to cause "empty tank" and "overflow" phenomena. Based on this, this paper uses a single-chip microcomputer to design a master-slave water level control system. The slave is a water level controller. The host can remotely control the slave through the serial communication port. At the same time, it can read and display the water level setting value and current water level value of the slave, and can also remotely modify the water level setting value of the slave.

　　1 Working principle of single chip microcomputer water level control system

　　The system uses AT89S52 single-chip microcomputer as the control chip of the master and slave machines, and the 24-bit high-precision A/D conversion chip Hx711 processes the changes of the weak voltage signal output by the weighing sensor and converts it into a digital signal. The digital signal converted by ADHX711 is converted into the corresponding water level value and displayed on the LCD screen 12864 through software. The water level control device is shown in Figure 1, and the water level control system is shown in Figure 2.

    The system uses a ruler as a measuring tool for actual values; the host button module is used to set the water level in the water tank; the host display module displays the water pump status, water tank water level value, and current water level value; the serial port module transmits data and control signals; the slave display module displays the same status as the host display module.

2 System Test
    According to the water level control device in Figure 1 and the water level control system block diagram in Figure 2, a master-slave water level control system was designed and manufactured. This system was used for data testing, and the test results are shown in Table 1.

　　As can be seen from Table 1, there is a certain error between the set water level value and the water level display value and the actual water level value. The main reasons are: (1) The scale used by the system is not a high-precision scale and has a certain error. (2) The human eye has visual accidental errors when distinguishing small distances. (3) In the program, the chip has calculation errors when processing floating-point data.

　　3 Conclusion

　　The system uses AT89S52 single-chip microcomputer as the main control chip, and the 24-bit high-precision A/D conversion chip HX711 processes the changes in the weak voltage signal output by the weighing sensor, and obtains good results. The test results show that the error between the water level display value and the actual value is ≤0.2 mm, and the error between the set water level value and the actual value is ≤0.4 mm. The results show that the system has good test stability, high precision and low cost, and has certain application value in water level automatic control technology.