#the4thLichuangcompetition# Soil moisture detection sensor

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[Please fill in during the registration stage↓] * Brief introduction to the work: This entry is a soil moisture sensor with modbus protocol with calibration function, which can complete the measurement of moisture content of soil of different soil types and provide a variety of data communication interfaces. The design structure is simple and the cost is low.

[Please fill in ↓ during the competition stage]   1. Details of the work; For soil with different humidity, its conductivity will change, and then its soil resistance value will change. It is connected to the soil resistance through an AC signal, and then it can match different The voltage under conductivity is then used to fit the data and establish a function. By fitting the matching voltage with the soil moisture, the soil moisture can be measured for soil with the same soil quality and different moisture.   2. Describe the challenges faced by the work and the problems it solves; Existing soil moisture sensors have low accuracy and are expensive. In order to support PLC, most sensors usually only support the modbus protocol. The sensor is always working and consumes high power.   3. Describe the key points involved in the hardware and software parts of the work; For soil with different humidity, the voltage of the soil is matched through AC signals drawn from the two contactor ports. For soil with different humidity, the soil resistance is inconsistent. Therefore, through The check port detects a basically unique voltage. The voltage detection is obtained through the AD conversion inside the microcontroller, and on this basis, the relationship between humidity and voltage is established. Part of the experimental data is as shown below:     After the data detection is completed, a functional relationship needs to be established, that is, the humidity and detection voltage are matched. The data of this design is fitted using MATLAB software. The function of soil moisture is generated through MATLAB, and a basic table is established Function image. As shown in the figure below:     After obtaining the fitting function through MATLAB, the function needs to be written into the microcontroller, and the function is established through the microcontroller programming tool KEIL so that it can return soil moisture for different matched voltage values. So as to achieve the purpose of soil moisture measurement. At the hardware level, STC's 15F series microcontroller is directly used in this design. The microcontroller integrates multiple 10-bit precision ADs and can quickly complete digital-to-analog conversion. And there is no need for an external crystal oscillator (through the internal RC oscillator) to obtain the clock source, and the clock can reach up to 24MHz. It can meet the requirements of this design to a certain extent. In order to facilitate the transmission of 485 data, hardware 485 support is provided during the design. The chip uses Maxim's MAX3485 chip as the 485 level conversion chip.   4. List of materials for the work; Quick sealant; Stainless steel rod; Several wires; Circuit board; Resistor; Capacitor; Inductor; STC8A8K microcontroller; etc....;   5. Upload pictures of the work; (The competition logo must be on the PCB and taken photos Upload,   if not, it will be deemed as giving up the competition) 6. Demonstrate your work and record it as a video for upload; (The video content must include: introduction of the work; function demonstration; performance test; close-up shot of the competition logo on the PCB, if not, it will be considered as giving up the competition) https ://www.bilibili.com/video/av68304315#reply1971398425    7. Open source documents. The project is in Lichuang EDA, the link is as follows