Dielectric sensor detection circuit for nitrogen content in rice field soil

Abstract

The invention belongs to the technical field of rice field soil element content detection, and relates to a rice field soil nitrogen content dielectric sensor detection circuit. Comprising an STM32 microcontroller, a digital signal synthesizer, a low-pass filter circuit, a measuring circuit, a signal processing module, a booster circuit, a step-down circuit, a charging circuit, a LoRa wireless transmission and a serial port transmission. The STM32 microcontroller controls the digital signal synthesizer to generate an excitation signal; the digital signal synthesizer is connected with the low-pass filter circuit; the low-pass filter circuit is connected with the measuring circuit; the measuring circuit is connected with the signal processing module; the boost circuit is connected with the buck circuit; the charging circuit is connected with the lithium battery. The STM32 microcontroller adopts an STM32F405RGT6 chip as a core controller, and the STM32 microcontroller adopts an STM32F405RGT6 The digital signal synthesizer adopts an AD9859 chip, and the working rate of the chip can be up to 400 MHz. The system has the advantages of good stability, good timeliness, long-distance wireless transmission and the like, and can realize long-term real-time on-line monitoring of the nitrogen content of the rice field soil.

Description

Technical Field

[0001] The invention belongs to the technical field of detecting element content in paddy soil and relates to a dielectric sensor detection circuit for nitrogen content in paddy soil. Background Art

[0002] Nitrogen is a crucial element for rice growth and a key indicator of paddy soil fertility. Therefore, accurate and real-time monitoring of soil nitrogen content is crucial for rice production. Online, real-time monitoring of paddy soil nitrogen content helps conserve agricultural inputs, maintain appropriate soil fertility, prevent excessive nitrogen fertilizer application, and create a favorable environment for rice growth.

[0003] Most soil nitrogen content sensors currently available on the market suffer from common problems such as low precision, high cost, poor environmental adaptability, low portability, and difficulty in data transmission. These sensors are unsuitable for long-term field operation, and their practical application in farmland monitoring remains to be improved. Based on this, the present invention designs a dielectric sensor circuit for detecting nitrogen content in paddy soil. This circuit has the advantages of low power consumption, long service life, stable operation, and real-time and accurate data transmission. It can achieve long-term online monitoring of paddy soil nitrogen content, meeting actual production needs and promising application prospects. Summary of the Invention

[0004] In order to solve the above problems, the present invention mainly provides a dielectric sensor detection circuit for nitrogen content in paddy soil.

[0005] The principle of the present invention is that when the soil contains different substances, the dielectric constant of the soil will also be different. When the paddy field soil contains different nitrogen contents, the dielectric constant of the paddy field soil will also be different.

[0006] The present invention collects data through experiments, processes the collected data, establishes a model, and transplants the model into STM32. In actual use, prediction is made based on the data measured by the measurement circuit to obtain the nitrogen content in the currently monitored paddy field soil.

[0007] In order to achieve the purpose of the present invention, the present invention adopts the following technical solutions:

[0008] A dielectric sensor detection circuit for nitrogen content in paddy soil is used for wirelessly monitoring nitrogen content data in paddy soil. The circuit comprises an STM32 microcontroller, a digital signal synthesizer, a low-pass filter circuit, a measuring circuit, a signal processing module, a boost circuit, a buck circuit, a charging circuit, LoRa wireless transmission, and serial port transmission. The STM32 microcontroller controls the digital signal synthesizer to generate an excitation signal. The digital signal synthesizer is connected to the low-pass filter circuit. The low-pass filter circuit is connected to the measuring circuit. The measuring circuit is connected to the signal processing module. The boost circuit is connected to the buck circuit. The boost circuit is connected to a lithium battery. The charging circuit is connected to the lithium battery to charge the lithium battery. The LoRa wireless transmission is connected to the STM32 microcontroller. The serial port transmission is connected to the STM32 microcontroller.

[0009] The digital signal synthesizer generates an excitation signal, which is smoothed by a low-pass filter circuit. The smoothed excitation signal is transmitted to a measurement circuit for signal acquisition, and the acquired signal enters a signal processing module for processing.

[0010] The signal processing module is connected to the STM32 microcontroller via the PC0 and PC1 pins, and the signal processing module can convert the collected signal into an amplitude ratio voltage and a phase difference voltage.

[0011] The charging circuit connects to the lithium battery via a 2P terminal connector to charge the battery, stabilizes the voltage at 5V through the boost circuit, and provides stable power to the entire circuit. The 5V voltage is then reduced to 3.3V by the buck circuit, and then from 3.3V to 1.8V, providing the required voltage for other circuits.

[0012] The LoRa wireless transmission is connected to the serial port 1 of the STM32 microcontroller through the TXD and RXD pins. At the same time, the STM32 microcontroller controls the LoRa wireless transmission through the M0 and M1 pins, selects the LoRa wireless transmission mode, and realizes the wireless transmission of nitrogen content in paddy soil.

[0013] Preferably, the STM32 microcontroller adopts a 32-bit STM32F405RGT6 single-chip microcomputer with an ARMCortex-M4 core as the core controller, the STM32 minimum system part, the main frequency is provided by an external high-speed clock, and an 8 MHz quartz crystal oscillator is externally connected to pins 5 and 6.

[0014] Preferably, the digital signal synthesizer uses an AD9859 chip, which has a maximum operating speed of 400 MHz and a built-in 10-bit DAC, which can form a complete digitally programmable high-frequency synthesizer to output a sine wave.

[0015] Preferably, the signal processing module adopts an AD8302 chip, and the amplitude measurement range can reach 60dB through two width logarithmic detectors, and the detection range of an independent phase detector can reach 180°.

[0016] In summary, the beneficial effects of the present invention are:

[0017] 1. The circuit uses the AD8302 dual-channel logarithmic detection technology to achieve 0.1mV-level amplitude measurement and 0.1° phase difference detection. Combined with the 0.8mV quantization accuracy of the STM32F405RGT6 built-in 12-bit ADC, the accuracy is more than three times that of traditional conductivity methods.

[0018] 2. Through dynamic power management, the average power consumption of the system is greatly reduced. Combined with a 2000mAh lithium battery, it can achieve three years of maintenance-free operation, which is five times longer than similar sensors and meets the long-term monitoring needs of rice fields.

[0019] 3. The circuit has a reliable data transmission system, and the LoRa wireless plus wired backup dual-mode transmission solution meets different scenarios. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is the overall design diagram of the dielectric sensor detection circuit for nitrogen content in paddy soil of the present invention.

[0021] Figure: 1. STM32 microcontroller; 2. Digital signal synthesizer; 3. Low-pass filter circuit; 4. Measurement circuit; 5. Signal processing module; 6. Boost circuit; 7. Buck circuit; 8. Charging circuit; 9. LoRa wireless transmission; 10. Serial port transmission. DETAILED DESCRIPTION

[0022] Now combined with the attached Figure 1 The embodiments of the present invention are described in detail, and the present invention is further described in detail.

[0023] Unless otherwise specified, the terms used in the text of this document should be interpreted in a broad sense. For example, "connection" in this document can be understood as the connection between circuits and circuits, or between electronic components, to achieve direct electrical connection between the two. If you are unable to understand the above explanation of the term, you can understand the specific meaning of the term according to the specific circumstances in which the term is used in this document.

[0024] The STM32 microcontroller (1) downloads the frequency sweep program to the STM32F405RGT6 single chip microcomputer through pins PA13 and PA14, so as to sweep the paddy soil and obtain the frequency response curves of the paddy soil at different nitrogen contents.

[0025] The digital signal synthesizer (2) is powered by a 1.8V voltage and operates in an external crystal oscillator input source mode. Pin 9 is connected to an external 25MHz active crystal oscillator. Frequency sweep control is achieved by communicating with the STM32 master control via a four-wire SPI protocol. The output signal is output via pin 21 OUT. The output signal then passes through a low-pass filter circuit (3) to achieve a smooth sinusoidal excitation signal.

[0026] The measuring circuit (4) is provided with an IPEX connector, the pins of the IPEX connector are connected to the measuring circuit (4), and the IPEX connector is connected to the digital signal synthesizer (2) via a coaxial cable.

[0027] The INPA and INPB pins of the signal processing module (5) input signals through the measurement circuit (4), thereby obtaining two types of data, namely, amplitude ratio and phase difference. The signal processing module (5) is connected to the PC0 and PC1 pins of the STM32 microcontroller (1) through the VPHS and VMAG pins, and outputs two 0-3.3V analog signals, namely, the phase difference and amplitude ratio of the input signal.

[0028] The boost circuit (6) outputs a stable voltage of 5V from the input lithium battery. A 10uH inductor, a 10uF input capacitor, and a 22uF output capacitor are added to the boost circuit (6) to provide a stable low-noise output voltage.

[0029] The step-down circuit (7) uses the AMS1117CD–3.3 chip to step down +5 V to +3.3 V, and then steps down +3.3 V to +1.8 V through the AMS1117CD-1.8 chip.

[0030] The charging circuit (8) uses a TP5100 chip to charge the device lithium battery via a Type-C interface wired connection.

[0031] The LoRa wireless transmission (9) is adjusted to the configuration mode before the circuit works, and the parameters such as the baud rate, channel and bandwidth of the LoRa wireless transmission (9) are configured. Then, the LoRa wireless transmission (9) is adjusted to the working mode to perform wireless transmission. The STM32 microcontroller provides M0 and M1 pins to control the LoRa communication module. When the M0 and M1 pins are both set to 0, the serial port and wireless functions are turned on, which is the transmission mode; when the M0 pin is set to 1 and the M1 pin is set to 0, the receiver and sender can be defined, which is the WOR mode; when the M0 pin is set to 0 and the M1 pin is set to 1, the register can be accessed through the serial port to write the configuration parameters, which is the configuration mode; when the M0 and M1 pins are both set to 1, the module goes into sleep, which is the deep sleep mode.

[0032] The CH340E chip used in the serial port transmission (10) is a USB bus adapter chip, which can realize USB to serial port conversion and transmit the signal to the host computer.

[0033] The embodiments described above with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be interpreted as limiting the present invention. Those skilled in the art will be able to make modifications and parameter substitutions to the embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is determined by the appended claims and their equivalents.

Claims

1. A dielectric sensor detection circuit for nitrogen content in paddy soil, which is used for wirelessly monitoring nitrogen content data in paddy soil, comprises an STM32 microcontroller (1), a digital signal synthesizer (2), a low-pass filter circuit (3), a measuring circuit (4), a signal processing module (5), a boost circuit (6), a buck circuit (7), a charging circuit (8), a LoRa wireless transmission (9), and a serial port transmission (10); the STM32 microcontroller (1) controls the digital signal synthesizer (2) to generate an excitation signal; the digital signal synthesizer (2) is connected to the low-pass filter circuit (3); the low-pass filter circuit (3) is connected to the measuring circuit (4); the measuring circuit (4) is connected to the signal processing module (5); the boost circuit (6) is connected to the buck circuit (7) and a lithium battery; the charging circuit (8) is connected to the lithium battery to charge the lithium battery; the LoRa wireless transmission (9) is connected to the STM32 microcontroller (1); and the serial port transmission (10) is connected to the STM32 microcontroller (1).

2. The dielectric detection circuit for nitrogen content in paddy soil according to claim 1, characterized in that: The digital signal synthesizer (2) generates an excitation signal, which is smoothed by a low-pass filter circuit (3). The smoothed excitation signal is transmitted to a measurement circuit (4) for signal acquisition, and the acquired signal enters a signal processing module (5) for processing.

3. The dielectric sensor detection circuit for nitrogen content in paddy soil according to claim 1, characterized in that: The signal processing module (5) is connected to the STM32 microcontroller (1) via the PC0 and PC1 pins. The signal processing module (5) can convert the collected signal into an amplitude ratio voltage and a phase difference voltage.

4. The dielectric sensor detection circuit for nitrogen content in paddy soil according to claim 1, characterized in that: The charging circuit (8) is connected to the lithium battery via a 2P terminal connector to charge the lithium battery, stabilizes the voltage at 5V via the boost circuit (6), and provides stable power to the entire circuit; the 5V voltage can be reduced to 3.3V via the step-down circuit (7), and then reduced from 3.3V to 1.8V, providing the required voltages for other circuits.

5. The dielectric sensor detection circuit for nitrogen content in paddy soil according to claim 1, characterized in that: The LoRa wireless transmission (9) is connected to the serial port 1 of the STM32 microcontroller (1) through the TXD and RXD pins. At the same time, the STM32 microcontroller (1) controls the LoRa wireless transmission (9) through the M0 and M1 pins, selects the mode of the LoRa wireless transmission (9), and realizes the wireless transmission of the nitrogen content in the paddy soil.

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