Dielectric sensor detection circuit for nitrogen content in rice field soil

Abstract

The utility model 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 rice field soil nitrogen content on-line monitoring 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 rice field soil nitrogen content.

Description

TECHNICAL FIELD

[0001] The utility model belongs to paddy field soil element content detection technical field relates to a kind of paddy field soil nitrogen content dielectric sensor detection circuit. BACKGROUND

[0002] China paddy field soil scale is larger, and nitrogen is an important element required in the growth process of rice, and is also an important indicator for measuring the fertility of paddy field soil. Therefore, it is of great significance to accurately and timely grasp the nitrogen content of soil for rice production practice. Through online real-time monitoring of the nitrogen content of paddy field soil, it is beneficial to save agricultural investment, maintain appropriate soil fertility and prevent excessive nitrogen application, thereby creating a good environment for rice growth.

[0003] Most of the soil nitrogen content sensors on the market currently have low precision, high cost, poor environmental adaptability, low portability, and data transmission difficulties, which are not suitable for long-term work in the field and have yet to improve the actual application effect in the field of farmland monitoring. Based on this, the present application designs a kind of paddy field soil nitrogen content dielectric sensor detection circuit, which has the advantages of low power consumption, long service life, stable operation, real-time and accurate data transmission, and can realize long-term online monitoring of the nitrogen content of paddy field soil, meet the actual production needs, and has good application prospect. CONTENT OF THE UTILITY MODEL

[0004] In order to solve the above problems, the utility model mainly provides a kind of paddy field soil nitrogen content dielectric sensor detection circuit.

[0005] The principle of the utility model is that when the soil contains different substances, the dielectric constant of the soil will also be different, and when the paddy field soil contains different content of nitrogen, the dielectric constant of the paddy field soil will also be different.

[0006] The utility model collects data through test, processes the collected data, establishes a model, transplants the model to STM32, and in actual use, predicts according to the data measured by the measurement circuit, so as to obtain the nitrogen content of the currently monitored paddy field soil.

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

[0008] A kind of nitrogen content dielectric sensor detection circuit in rice field soil, for wirelessly monitoring nitrogen content data in rice field soil, including STM32 microcontroller, digital signal synthesizer, low pass filter circuit, measurement circuit, signal processing module, boost circuit, buck circuit, charging circuit, LoRa wireless transmission, serial transmission;The STM32 microcontroller controls digital signal synthesizer to generate excitation signal;Digital signal synthesizer is connected with low pass filter circuit;Low pass filter circuit is connected with measurement circuit;Measurement circuit is connected with signal processing module;Boost circuit is connected with buck circuit;Boost circuit is connected with lithium battery;Charging circuit is connected with lithium battery, charges lithium battery;LoRa wireless transmission is connected with STM32 microcontroller;Serial transmission is connected with STM32 microcontroller.

[0009] The digital signal synthesizer generates excitation signal, and the excitation signal becomes smooth through the low pass filter circuit, and the smooth excitation signal is transmitted to the measurement circuit for signal acquisition, and the acquired signal enters the signal processing module for processing.

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

[0011] The charging circuit is connected with the lithium battery through 2P terminal connector, charges the lithium battery, and the voltage is stabilized at 5V through the boost circuit, and the whole circuit is stably powered. 5V voltage can be reduced to 3.3V by buck circuit, and then reduced from 3.3V to 1.8V, to provide the voltage required by other parts of the circuit.

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

[0013] The serial transmission is connected with the STM32 microcontroller through PA9 and PA10 pins, and the serial transmission can quickly and stably transmit data to the host computer to realize data visualization.

[0014] Preferably, the STM32 microcontroller uses a 32-bit STM32F405RGT6 single-chip microcomputer with ARM Cortex-M4 core as the core controller, and the STM32 minimum system part uses an external high-speed clock to provide the main frequency, and an 8 MHz quartz crystal oscillator is connected to pins 5 and 6.

[0015] Preferably, the digital signal synthesizer adopts AD9859 chip, the chip working rate is up to 400 MHz, a 10-bit DAC is built-in, a complete high-frequency synthesizer can be formed, and a sine wave is output

[0016] Preferably, the signal processing module adopts AD8302 chip, through two width log detectors, the amplitude measurement range can reach 60dB, and the independent phase detector detection range can reach 180°.

[0017] In conclusion, the beneficial effects of the utility model are:

[0018] 1. The circuit adopts AD8302 double-channel logarithmic detection technology, realizes 0.1mV-level amplitude measurement and 0.1° phase difference detection, and in combination with the 0.8mV quantization precision of the built-in 12-bit ADC of STM32F405RGT6, the precision is improved by more than 3 times compared with the traditional conductivity method.

[0019] 2. Through dynamic power management, the average power consumption of the system is greatly reduced, and in cooperation with a 2000mAh lithium battery, 3-year maintenance-free operation can be realized, the endurance time is prolonged by 5 times compared with similar sensors, and the long-term monitoring demand of paddy fields is met.

[0020] 3. The circuit has a reliable data transmission system, and the LoRa wireless plus wired backup dual-mode transmission scheme meets different scenes. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 It is the overall design drawing of the detection circuit of the dielectric sensor for nitrogen content in paddy field soil of the utility model

[0022] In the drawing: 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 transmission. DETAILED DESCRIPTION

[0023] The embodiments of the utility model are described in detail, and the utility model is further described in detail. Figure 1 The embodiments of the utility model are described in detail, and the utility model is further described in detail.

[0024] The term used in the text description herein should be interpreted in a broad sense unless otherwise specifically stated, for example, "connection" can be understood as the connection between circuits and circuits, electronic components and electronic components in this text, realizing the direct electrical connection of the two, if the above-mentioned term cannot be understood, the specific meaning of the term can be understood according to the specific situation of the term used in this text.

[0025] The STM32 microcontroller (1) downloads the frequency sweep program to the STM32F405RGT6 single-chip microcomputer through pins PA13 and PA14, and can sweep the rice field soil to obtain the frequency response curve of the rice field soil with different nitrogen contents.

[0026] The digital signal synthesizer (2) is powered by 1.8V voltage, and the external crystal oscillator input source works in the mode, the 9th pin is connected with 25MHz active crystal oscillator, and the frequency sweep control is realized by four-wire SPI protocol and STM32 master communication, and the output signal is output through the 21st OUT pin. The output signal is further filtered by the low-pass filter circuit (3) to realize the smooth sine excitation signal.

[0027] The measuring circuit (4) is designed with an IPEX connector, the IPEX connector pin is connected with the measuring circuit (4), and the IPEX connector is connected to the digital signal synthesizer (2) through a coaxial cable.

[0028] The signal processing module (5) inputs signals through the measuring circuit (4) through the INPA and INPB pins, so as to obtain two types of data, amplitude ratio and phase difference, and the signal processing module (5) is connected to the PC0 and PC1 pins of the STM32 microcontroller (1) through the VPHS and VMAG pins. Two analog signals of 0-3.3V are output, that is, the phase difference and amplitude ratio of the input signal.

[0029] The boost circuit (6) stabilizes the input voltage of the lithium battery to 5V, and a 10uH inductor, a 10uF input capacitor and a 22uF output capacitor are added to the boost circuit (6) to provide stable low-noise output voltage.

[0030] The buck circuit (7) uses AMS1117CD-3.3 chip to reduce +5V to +3.3V, and then reduces +3.3V to +1.8V through AMS1117CD-1.8.

[0031] The charging circuit (8) uses TP5100 chip to charge the lithium battery of the device through Type-C interface.

[0032] The LoRa wireless transmission (9) is adjusted to a configuration mode before the circuit works, and the baud rate, channel and bandwidth and other parameters of the LoRa wireless transmission (9) are configured, then the LoRa wireless transmission (9) is adjusted to a 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 0, the serial port and the wireless function are turned on, which is a transmission mode; when the M0 pin is 1 and the M1 pin is 0, a receiving and sending side can be defined, which is a WOR mode; when the M0 pin is 0 and the M1 pin is 1, a register can be accessed through the serial port to write configuration parameters, which is a configuration mode; when the M0 and M1 pins are both 1, the module is in a sleep mode, which is a deep sleep mode.

[0033] The CH340E chip adopted by the serial port transmission (10) is a USB bus conversion chip, which can realize USB to serial port conversion and transmit signals to the host computer.

[0034] The above-described embodiments described by the drawings are exemplary and are only used to explain the utility model, and cannot be explained as the limitation of the utility model; for the person skilled in the art, the embodiments can be modified and parameter replaced without departing from the principles and spirits of the utility model, and the scope of the utility model is determined by the appended claims and equivalents.

Claims

1. A dielectric sensor detection circuit for nitrogen content in paddy field soil for wireless monitoring of nitrogen content data in paddy field soil, comprising an STM32 microcontroller (1), a digital signal synthesizer (2), a low-pass filter circuit (3), a measurement circuit (4), a signal processing module (5), a voltage boosting circuit (6), a voltage reducing circuit (7), a charging circuit (8), a LoRa wireless transmission (9), 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 with the low-pass filter circuit (3); the low-pass filter circuit (3) is connected with the measurement circuit (4); the measurement circuit (4) is connected with the signal processing module (5); the voltage boosting circuit (6) is connected with the voltage reducing circuit (7) and the lithium battery; the charging circuit (8) is connected with the lithium battery for charging the lithium battery; the LoRa wireless transmission (9) is connected with the STM32 microcontroller (1); the serial port transmission (10) is connected with the STM32 microcontroller (1).

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

3. The dielectric sensor detection circuit for nitrogen content in soil of paddy field according to claim 1, wherein, The signal processing module (5) is connected with the STM32 microcontroller (1) through PC0 and PC1 pins, and the signal processing module (5) can convert the collected signal into amplitude ratio voltage and phase difference voltage.

4. The dielectric sensor detection circuit for nitrogen content in soil of paddy field according to claim 1, wherein, The charging circuit (8) is connected with the lithium battery through a 2P terminal connector to charge the lithium battery, and the voltage is stabilized at 5V through the voltage boosting circuit (6), and the whole circuit is stably powered; the 5V voltage can be reduced to 3.3V through the voltage reducing circuit (7), and then from 3.3V to 1.8V, to provide the voltage required by other parts of the circuit.

5. The dielectric sensor detection circuit for nitrogen content in soil of paddy field according to claim 1, wherein, The LoRa wireless transmission (9) is connected with the serial port 1 of the STM32 microcontroller (1) through TXD and RXD pins, and the STM32 microcontroller (1) controls the LoRa wireless transmission (9) through M0 and M1 pins to select the mode of the LoRa wireless transmission (9), realizing wireless transmission of nitrogen content in paddy field soil.

6. The dielectric sensor detection circuit for nitrogen content in soil of paddy field according to claim 1, wherein, The serial port transmission (10) is connected with the STM32 microcontroller (1) through PA9 and PA10 pins, and the serial port transmission (10) can quickly and stably transmit data to the host computer to realize data visualization.

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