Agricultural protection machine pipeline type liquid level detection circuit and device

Abstract

The utility model relates to a kind of plant protection machine pipeline type liquid level detection circuit, equipment, belong to the technical field of agricultural aviation plant protection equipment circuit design, comprising: MCU circuit, temperature detection circuit, pressure sensor circuit, CAN transceiver, indicator light circuit, external interface circuit and power circuit;MCU circuit, with temperature detection circuit, pressure sensor circuit, CAN transceiver and indicator light circuit connection;External interface circuit, one end is connected with the CAN transceiver and the other end is connected external device.The utility model can be applied in the liquid level detection of plant protection unmanned aerial vehicle medicine box, improve plant protection unmanned aerial vehicle operation precision and efficiency, realize operation accurate control.

Description

Technical Field

[0001] This utility model relates to the field of circuit design technology for agricultural aviation plant protection equipment, and in particular to a pipeline-type liquid level detection circuit and device for plant protection aircraft. Background Technology

[0002] Currently, the liquid level gauges used in agricultural drones include ultrasonic liquid level gauges, millimeter-wave liquid level gauges, Hall effect float liquid level gauges, and pipeline liquid level gauges.

[0003] The accuracy of ultrasonic and millimeter-wave level gauges is significantly affected by installation and air bubbles on the surface of the liquid. In actual use, both ultrasonic and millimeter-wave level gauges exhibit the following problems:

[0004] Foam: Pesticides contain adjuvants that are prone to foaming. If the foam layer is too thick, the reading will be based on the surface of the foam rather than the actual liquid level, resulting in a significantly higher reading.

[0005] Steam and droplets: The hot and humid environment inside the medicine box, filled with steam, affects signal accuracy. Dew condensation on the sensor surface also affects wave transmission and reception.

[0006] Shaking: When the drone flies, turns, or climbs, the liquid shakes violently, creating a tilted, wavy liquid surface, which causes the echo signal to scatter and the measurement value to jump.

[0007] Hall effect float level gauges are a simple, low-cost solution but have relatively poor reliability. Their working principle is based on the fundamental principle of buoyancy, triggering a Hall effect sensor by detecting the presence or absence of liquid. However, they are functionally limited, only determining the presence or absence of liquid, and cannot determine the liquid level. This leads to the following problems during use:

[0008] Pesticide Adhesion: Adjuvants, powders, impurities, etc. contained in pesticides can easily become viscous and adhere to floats, connecting rods, and sliding shafts. Once dried, this can cause moving parts to jam and liquid level indicators to malfunction.

[0009] Mechanical vibration: Continuous high-frequency vibration during drone flight can accelerate the wear of moving parts, causing errors or jamming.

[0010] Reading Delay and Fluctuations: The liquid level in the tank will violently shake and tilt when the drone accelerates, turns, or climbs. The float's response speed cannot keep up with the changes in the liquid level, making it impossible for the operator to read an accurate and stable value in a short time.

[0011] Inconvenient installation and maintenance: It usually needs to be built into the medicine box, which is not easy to install and remove. Every time the medicine box is cleaned or the sensor is inspected, it needs to be removed from the medicine box, which is a cumbersome process. Regular cleaning and maintenance are required to prevent jamming, which increases maintenance costs and time. Utility Model Content

[0012] Based on the above analysis, this utility model aims to provide a pipeline-type liquid level detection circuit and device for plant protection machines, so as to avoid the problem that the accuracy of existing ultrasonic liquid level gauges and millimeter-wave liquid level gauges is greatly affected by installation and air bubbles on the surface of the liquid, thus affecting accuracy; and to avoid the problem of poor reliability of existing Hall effect float-type liquid level gauges.

[0013] The objective of this utility model is mainly achieved through the following technical solutions:

[0014] On the one hand, this utility model embodiment provides a pipeline-type liquid level detection circuit for plant protection machines, the circuit including an MCU circuit, a pressure sensor circuit, and a CAN transceiver;

[0015] The pressure sensor circuit includes a pressure sensor, which is placed in the detection pipe to contact the pesticide solution and obtain the static pressure signal of the liquid in the pesticide tank of the plant protection machine.

[0016] The MCU circuit is connected to the pressure sensor circuit and the CAN transceiver; and interacts with external devices through the CAN transceiver.

[0017] Furthermore, the circuit also includes a temperature detection circuit;

[0018] The temperature detection circuit includes a temperature sensor, which is placed in the detection pipe to contact the liquid medicine and detect the temperature of the liquid medicine; it is connected to the MCU circuit and interacts with external devices through the CAN transceiver.

[0019] Furthermore, the circuit also includes indicator light circuits and / or external interface circuits;

[0020] The indicator light circuit is connected to the MCU circuit and is used to indicate different working states;

[0021] The external interface circuit is connected to the CAN transceiver at one end and to an external device at the other end.

[0022] Furthermore, the MCU circuit includes an MCU chip, a reset circuit, and a crystal oscillator circuit;

[0023] The output of the reset circuit is connected to the reset pin of the MCU chip;

[0024] The input terminal of the crystal oscillator circuit is connected to the external clock output terminal of the MCU chip, and the output terminal of the crystal oscillator circuit is connected to the external clock input terminal of the MCU chip.

[0025] Furthermore, the temperature detection circuit also includes connector J2 and a voltage divider circuit, and the temperature sensor is an NTC thermistor;

[0026] Connector J2 is connected to the NTC thermistor via a lead wire. The output terminal of connector J2 is connected to a voltage divider circuit, which in turn connects to the MCU chip.

[0027] Furthermore, the pressure sensor circuit also includes an I2C interface and a filtering circuit;

[0028] The power supply terminal of the pressure sensor is connected to the power supply through a filter circuit, and the signal output terminal of the pressure sensor is connected to the MCU chip through the I2C interface.

[0029] Furthermore, the CAN transceiver includes a CAN chip, a CAN bus differential circuit, a logic power decoupling circuit, and a CAN transceiver power decoupling circuit.

[0030] The input terminal of the CAN bus differential circuit is connected to the CAN chip, and the output terminal of the CAN bus differential circuit is connected to the external interface circuit.

[0031] One end of the logic power decoupling circuit is connected to the CAN chip, and the other end is grounded.

[0032] One end of the CAN transceiver power decoupling circuit is connected to the CAN chip, and the other end is grounded; it is also connected to the MCU chip through the CAN chip.

[0033] Furthermore, the indicator light circuit includes an LED light and an LED constant current drive circuit;

[0034] The anode of the LED lamp is connected to a 3.3V power supply, the cathode of the LED lamp is connected to the input terminal of the LED constant current drive circuit, and the output terminal of the LED constant current drive circuit is connected to the MCU chip.

[0035] The external interface circuit includes connector J1, TVS diode D1, and ESD diode D2;

[0036] The connector J1 includes a power supply pin, a power ground pin, an EXT_CAN_H pin, and an EXT_CAN_L pin; and connects to external devices through the EXT_CAN_H pin and the EXT_CAN_L pin.

[0037] The TVS diode D1 is connected to a 12V power supply at one end and to ground at the other end; the ESD diode D2 is connected to the EXT_CAN_H pin and the EXT_CAN_L pin of the connector J1 through the EXT_CAN_H pin and the EXT_CAN_L pin.

[0038] Furthermore, the circuit also includes a power supply circuit, which includes a 12V to 5V power supply circuit and a 5V to 3.3V power supply circuit.

[0039] The output terminal of the 12V to 5V power supply circuit is connected to the 5V to 3.3V power supply circuit and the CAN transceiver.

[0040] The output of the 5V to 3.3V power supply circuit is connected to the CAN transceiver, the indicator light circuit, the pressure sensor circuit, the MCU circuit, and the temperature detection circuit.

[0041] On the other hand, this utility model embodiment provides a pipeline-type liquid level detection device for plant protection machines. The device includes a liquid level gauge and a liquid level detection pipeline. The liquid level gauge is fixedly installed at the top of the pipeline. The liquid level gauge includes the pipeline-type liquid level detection circuit for plant protection machines described in the previous embodiment.

[0042] Furthermore, both the pressure sensor and the temperature sensor are located at the bottom of the liquid level detection pipe and are in contact with the liquid.

[0043] The beneficial effects of this technical solution are:

[0044] The device and circuit structure provided by this utility model are simple, flexible in installation, and require no changes to the external piping structure. It accurately measures the total amount of medicine, measuring the static pressure from the bottom of the tank to the liquid surface, unaffected by foam, color, or transparency. The measurement is only related to the static pressure of the liquid column, completely unaffected by measurement accuracy. With no moving parts, it uses a solid-state pressure sensor, eliminating mechanical moving parts, making it vibration-resistant, shock-resistant, long-lasting, and highly reliable. This utility model can replace traditional ultrasonic level gauges, millimeter-wave level gauges, and Hall effect float level gauges, effectively solving the technical problems faced by existing solutions. Furthermore, this utility model also includes a pre-installed medicine liquid temperature sensor, enabling real-time detection of the medicine liquid temperature.

[0045] In this invention, the above-described technical solutions can be combined with each other to achieve more preferred combinations. Other features and advantages of this invention will be set forth in the following description, and some advantages may become apparent from the description or be learned by practicing the invention. The objects and other advantages of this invention can be realized and obtained from the description and drawings, which are particularly pointed out. Attached Figure Description

[0046] The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of the invention. Throughout the drawings, the same reference numerals denote the same parts.

[0047] Figure 1 This is a schematic diagram of the overall circuit structure of this utility model;

[0048] Figure 2 This includes the circuit diagrams for the MCU chip, crystal oscillator, and reset circuit.

[0049] Figure 3 This is a circuit diagram for temperature detection.

[0050] Figure 4 This is a circuit diagram for a pressure sensor.

[0051] Figure 5 This is a circuit diagram for a CAN transceiver.

[0052] Figure 6 This is the circuit diagram for the indicator light.

[0053] Figure 7 This is the circuit diagram for the external interface.

[0054] Figure 8 This is a circuit diagram for a 12V to 5V power supply.

[0055] Figure 9 Circuit diagram for a 5V to 3.3V power supply;

[0056] Figure 10 A schematic diagram of the modular structure of a pipeline-type liquid level detection device for plant protection machines according to an embodiment of this application. Detailed Implementation

[0057] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which constitute a part of this application and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not intended to limit the scope of the present invention.

[0058] A specific embodiment of this utility model discloses a pipeline-type liquid level detection circuit for a plant protection machine, such as... Figure 1 As shown.

[0059] The circuit includes an MCU circuit, a pressure sensor circuit, and a CAN transceiver.

[0060] The pressure sensor circuit includes a pressure sensor, which is placed in the detection pipe to contact the pesticide solution and obtain the static pressure signal of the liquid in the pesticide tank of the plant protection machine.

[0061] The MCU circuit is connected to the pressure sensor circuit and the CAN transceiver; and interacts with external devices through the CAN transceiver.

[0062] Furthermore, the circuit also includes a temperature detection circuit;

[0063] The temperature detection circuit includes a temperature sensor, which is placed in the detection pipe to contact the liquid medicine and detect the temperature of the liquid medicine; it is connected to the MCU circuit and interacts with external devices through the CAN transceiver.

[0064] Furthermore, the pipeline-type liquid level detection circuit of the plant protection machine also includes an indicator light circuit and / or an external interface circuit;

[0065] The indicator light circuit is connected to the MCU circuit and is used to indicate different working states;

[0066] The external interface circuit is connected to the CAN transceiver at one end and to an external device at the other end.

[0067] In principle, this embodiment provides a method to connect the temperature detection circuit, pressure sensor circuit, indicator light circuit, and CAN transceiver to the MCU circuit. The NTC thermistor in the temperature detection circuit is in direct contact with the liquid medicine, and different liquid medicine temperatures correspond to different resistance values. The NTC thermistor is connected to the MCU chip after passing through a voltage divider circuit to obtain the liquid medicine temperature. The pressure sensor in the pressure sensor circuit outputs a differential signal through the MEMS piezoresistive core to obtain a digital static pressure value. The static pressure value is output to the MCU chip through the I2C interface. The MCU chip calculates the liquid level in the medicine tank and estimates the weight of the liquid medicine based on the static pressure value.

[0068] The MCU chip outputs high and low levels to the indicator circuit through designated GPIO pins according to the working status of the liquid level gauge, thus displaying the working status of the liquid level gauge; the CAN transceiver realizes bidirectional conversion between the TTL level signal transmitted by the MCU chip and the differential signal of the CAN bus, ensuring that the data such as "liquid level, liquid weight, and liquid temperature" detected by the liquid level gauge can be exchanged with external devices through the external interface circuit.

[0069] Understandably, the MCU chip in this application has a pre-installed program for calculating the height and weight of the liquid. This program can be any existing program that calculates the liquid height and weight based on liquid pressure. This utility model does not limit the specific program executed in the MCU. The improvement of this utility model lies in the improvement of the circuit hardware structure.

[0070] For example, this embodiment can realize the spraying and low liquid level alarm operation of agricultural drones. First, the MCU chip is initialized, the pressure of the liquid level in the tank is read every 10ms, and the temperature of the liquid in the tank is read every 100ms. Then, the liquid level and the amount of medicine are calculated, packaged and sent to the external flight control device through the CAN transceiver. The flight control device receives the data and performs the spraying operation. When the liquid level is low, an alarm is triggered.

[0071] First, the relevant circuit structure in this embodiment will be explained.

[0072] Furthermore, such as Figure 2 As shown, the MCU circuit includes an MCU chip, a reset circuit, and a crystal oscillator circuit;

[0073] The output of the reset circuit is connected to the reset pin of the MCU chip;

[0074] The input terminal of the crystal oscillator circuit is connected to the external clock output terminal of the MCU chip, and the output terminal of the crystal oscillator circuit is connected to the external clock input terminal of the MCU chip.

[0075] Specifically, the reset circuit is as follows: Figure 2 As shown in the lower right sub-diagram, the NRST terminal of the reset circuit serves as the output terminal of the reset circuit and is connected to the PF2_NRST pin of the MCU chip through the NRST terminal;

[0076] The crystal oscillator circuit is as follows Figure 2 As shown in the lower left sub-diagram, the OSC_IN of the crystal oscillator circuit serves as the input terminal of the crystal oscillator circuit and is connected to the PC15_OSCX_OUT of the MCU chip. The OSC_OUT of the crystal oscillator circuit serves as the output terminal of the crystal oscillator circuit and is connected to the PC14_OSCX_IN of the MCU chip.

[0077] In principle, when an event occurs that pulls the NRST pin low to below 0.8V and lasts for at least 100ns, the reset circuit restores the microcontroller to its initial state; the crystal oscillator circuit includes a crystal oscillator chip, which provides a stable clock signal to the microcontroller, synchronizes the operation of each module inside the crystal oscillator circuit, and latches, counts, samples, or transmits and receives data on the same clock edge.

[0078] Preferably, the MCU chip is an STM32C092GB and the crystal oscillator chip is an AD-CJ16-160001210D80.

[0079] Furthermore, such as Figure 3 As shown, the temperature detection circuit also includes connector J2 and a voltage divider circuit, and the temperature sensor is an NTC thermistor;

[0080] Connector J2 is connected to the NTC thermistor via a lead wire. The output terminal of connector J2 is connected to a voltage divider circuit, which in turn connects to the MCU chip.

[0081] Specifically, connector J2 connects the "upper end" lead of the NTC thermistor to pin 1 of connector J2 via a lead wire, and connects the "lower end" lead of the NTC thermistor to pin 2 of connector J2. Pin 1 of connector J2 serves as the output terminal of connector J2 and is connected to the voltage divider circuit. The voltage divider circuit is connected to pin PA2 of the MCU chip via ADC_NTC.

[0082] In principle, when the temperature of the liquid rises, the resistance of the thermistor decreases exponentially. After being divided by a voltage divider circuit, the voltage is connected to the MCU chip. The MCU samples the temperature every certain period of time to obtain a 12-bit code value. The temperature is calculated according to the thermistor's three-coefficient formula. The density is then corrected based on the calculated temperature to achieve full temperature compensation for liquid level measurement.

[0083] Preferably, the connector J2 model is WAFER-MX1.25-2PLB.

[0084] Furthermore, such as Figure 4 As shown, the pressure sensor circuit also includes an I2C interface and a filtering circuit;

[0085] The power supply terminal of the pressure sensor is connected to the power supply through a filter circuit, and the signal output terminal of the pressure sensor is connected to the MCU chip through the I2C interface.

[0086] Specifically, the filtering circuit includes filter capacitors C7 and C8, which are connected in parallel. One end of the parallel connection is grounded and connected to the ground pin of the pressure sensor, and the other end is connected to the power supply pin of the pressure sensor, which is also connected to a 3.3V power supply.

[0087] The I2C interface includes resistors R11 and R12. One end of R11 and R12 is connected to a 3.3V power supply. The other end of R11 is connected to the SCL pin of the pressure sensor, and the other end of R12 is connected to the SDA pin of the pressure sensor. The I2C interface is connected to the PB3 and PB4 pins of the MCU chip through the SCL and SDA pins.

[0088] In principle, under the action of hydrostatic pressure, the resistance of the internal pressure-sensitive resistor in the MEMS piezoresistive core changes with the pressure, outputting a raw electrical signal that is directly proportional to the applied pressure. The sensor has a built-in conditioning chip that amplifies, compensates for temperature, and compensates for linearity in the raw signal, outputting the conditioned signal as a stable voltage signal. Subsequently, the pressure sensor connects to the MCU via an I2C interface, transmitting the conditioned voltage signal to the MCU in real time. The filtering circuit can filter out high-frequency noise in the transmission path of the I2C interface between the pressure sensor and the MCU chip, suppressing interference and ensuring accurate and stable pressure detection signal.

[0089] Preferably, the pressure sensor is model NSPGD1F010DT10.

[0090] Furthermore, such as Figure 5 As shown, the CAN transceiver includes a CAN chip, a CAN bus differential circuit, a logic power decoupling circuit, and a CAN transceiver power decoupling circuit.

[0091] The input terminal of the CAN bus differential circuit is connected to the CAN chip, and the output terminal of the CAN bus differential circuit is connected to the external interface circuit.

[0092] One end of the logic power decoupling circuit is connected to the CAN chip, and the other end is grounded.

[0093] One end of the CAN transceiver power decoupling circuit is connected to the CAN chip, and the other end is grounded; it is also connected to the MCU chip through the CAN chip.

[0094] Specifically, the CAN bus differential circuit includes resistors R16, R17 and R18. One end of R16 is connected to the CANH pin of the CAN chip, one end of R17 is connected to the CANL pin of the CAN chip, and the two ends of R18 are connected to the other ends of R16 and R17 respectively, and serve as the output terminal of the CAN bus differential circuit connected to the external interface circuit.

[0095] The logic power decoupling circuit includes a filter capacitor C12. One end of C12 is grounded, and the other end is connected to the VIO pin of the CAN chip. This pin is also connected to a 3.3V power supply.

[0096] The CAN transceiver power decoupling circuit includes filter capacitors C10 and C11, which are connected in parallel. One end of the parallel connection is grounded, and the other end is connected to the VCC pin of the CAN chip. This pin is also connected to a 5V power supply. The CAN chip is connected to the MCU chip PB6 and PB5 through the TXD and RXD pins.

[0097] In principle, the CAN chip receives the transmit and receive single-ended logic signals output by the MCU, converts them into differential signals required by the CAN bus through the CAN bus differential circuit, and simultaneously converts the bus differential signals back into single-ended signals to be transmitted back to the MCU, adapting to the signal types of different devices. The output of the CAN bus differential circuit is connected to the external interface circuit to realize data transmission between the level gauge and external devices, transmitting data such as liquid level, weight, and temperature calculated by the MCU back to the external devices to support the operation control of the plant protection machine. The logic power supply decoupling circuit filters out high-frequency noise and voltage fluctuations in the logic power supply, avoiding interference with the clock, reset, and I2C data interaction of the logic module, and ensuring the stability of the logic signal. The CAN transceiver power supply decoupling circuit filters out noise and ripple in the power supply for the CAN transceiver, providing a stable power supply to the transceiver, avoiding power interference that causes signal conversion distortion, and ensuring that there is no packet loss or bit error when the liquid level data is transmitted to the flight controller through the CAN bus, ensuring stable data interaction.

[0098] Preferably, the CAN chip model is SIT1042ATK / 3.

[0099] Furthermore, such as Figure 6 As shown, the indicator light circuit includes an LED light and an LED constant current drive circuit;

[0100] The anode of the LED lamp is connected to a 3.3V power supply, the cathode of the LED lamp is connected to the input terminal of the LED constant current drive circuit, and the output terminal of the LED constant current drive circuit is connected to the MCU chip.

[0101] Specifically, the LED constant current driving circuit includes a MOSFET Q1, with the drain (D) terminal of the MOSFET Q1 serving as the input terminal of the LED constant current driving circuit, and the output terminal LED1 of the LED constant current driving circuit connected to the PB8 pin of the MCU chip.

[0102] In principle, when the MCU outputs a high-level signal, the MOSFET Q1 in the LED constant current drive circuit is turned on, and the LED lights up; when the MCU outputs a low-level signal, the MOSFET Q1 in the LED constant current drive circuit is turned off, the circuit is broken, and the LED lights off. By changing the frequency of the MCU output signal, the flashing speed of the LED lights is changed, providing intuitive feedback on the current working status of the level gauge, which is convenient for operators or maintenance personnel to judge the equipment's operating status.

[0103] Preferably, the LED lamp is model FC-1608UGK-520D, and the MOSFET Q1 is model 2SK3018.

[0104] Furthermore, such as Figure 7 As shown, the external interface circuit includes connector J1, TVS diode D1, and ESD diode D2.

[0105] The connector J1 includes a power supply pin, a power ground pin, an EXT_CAN_H pin, and an EXT_CAN_L pin; and connects to external devices through the EXT_CAN_H pin and the EXT_CAN_L pin.

[0106] The TVS diode D1 is connected to a 12V power supply at one end and to ground at the other end; the ESD diode D2 is connected to the EXT_CAN_H pin and the EXT_CAN_L pin of the connector J1 through the EXT_CAN_H pin and the EXT_CAN_L pin.

[0107] Preferably, the connector J1 is model A1257WV-S-4P, the TVS tube D1 is model SMAJ12CA, and the ESD tube D2 is model SAT03N24AOA.

[0108] Furthermore, such as Figure 8 , Figure 9As shown, the circuit also includes a power supply circuit, which includes a 12V to 5V power supply circuit and a 5V to 3.3V power supply circuit.

[0109] The output terminal of the 12V to 5V power supply circuit is connected to the 5V to 3.3V power supply circuit and the CAN transceiver.

[0110] The output of the 5V to 3.3V power supply circuit is connected to the CAN transceiver, the indicator light circuit, the pressure sensor circuit, the MCU circuit, and the temperature detection circuit.

[0111] Preferably, the 12V to 5V power supply circuit uses the DC-DC power chip SY8113BADC, and the 5V to 3.3V power supply circuit uses the LDO power chip ETA5255V330DS2F.

[0112] Another specific embodiment of this utility model discloses a pipeline-type liquid level detection device for plant protection machines, such as... Figure 10 As shown, the device includes a level gauge and a level detection pipe; the level gauge is fixedly installed at the top of the pipe; the level gauge includes the pipeline-type level detection circuit for plant protection machines described in the previous embodiment.

[0113] Specifically, the air nozzle of the level gauge is connected to the bottom of the medicine tank through the level detection pipe, and it is necessary to ensure that the pipe at the air nozzle end is leak-free. The rise or fall of the liquid level in the medicine tank will correspond proportionally to the change in liquid pressure. Through the high-precision sensor in the level gauge, the liquid level and estimated weight in the medicine tank can be obtained in real time, and then automatic replenishment or delivery of water can be achieved according to the control logic of different operations.

[0114] The liquid level pressure sensor is located at the bottom of the liquid level detection pipe and is in contact with the liquid. It uses a MEMS piezoresistive pressure gauge core as the pressure sensing element, which outputs a raw signal that is directly proportional to the ambient pressure. The built-in conditioning chip drives the sensing element and amplifies, temperature-compensates, and linearizes the raw signal before outputting a voltage signal that is linearly related to the applied pressure.

[0115] The temperature sensor for detecting the liquid temperature is located at the bottom of the liquid level detection pipe and is in contact with the liquid to detect the real-time liquid temperature.

[0116] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A pipeline-type liquid level detection circuit for a plant protection machine, characterized in that, The circuit includes an MCU circuit, a pressure sensor circuit, and a CAN transceiver. The pressure sensor circuit includes a pressure sensor, which is used to be placed in the detection pipe to contact the pesticide solution and obtain the static pressure signal of the liquid in the pesticide tank of the plant protection machine. The MCU circuit is connected to the pressure sensor circuit and the CAN transceiver; and interacts with external devices through the CAN transceiver.

2. The pipeline-type liquid level detection circuit for plant protection machines according to claim 1, characterized in that, The circuit also includes a temperature detection circuit; The temperature detection circuit includes a temperature sensor, which is placed in the detection pipe to contact the liquid medicine and detect the temperature of the liquid medicine; it is connected to the MCU circuit and interacts with external devices through the CAN transceiver.

3. The pipeline-type liquid level detection circuit for plant protection machines according to claim 1, characterized in that, The circuit also includes indicator light circuits and / or external interface circuits; The indicator light circuit is connected to the MCU circuit and is used to indicate different working states; The external interface circuit is connected to the CAN transceiver at one end and to an external device at the other end.

4. The pipeline-type liquid level detection circuit for plant protection machines according to claim 1, characterized in that, The MCU circuit includes an MCU chip, a reset circuit, and a crystal oscillator circuit; The output of the reset circuit is connected to the reset pin of the MCU chip; The input terminal of the crystal oscillator circuit is connected to the external clock output terminal of the MCU chip, and the output terminal of the crystal oscillator circuit is connected to the external clock input terminal of the MCU chip.

5. The pipeline-type liquid level detection circuit for plant protection machines according to claim 1, characterized in that, The temperature detection circuit also includes connector J2 and voltage divider circuit, and the temperature sensor is an NTC thermistor. Connector J2 is connected to the NTC thermistor via a lead wire. The output terminal of connector J2 is connected to a voltage divider circuit, which in turn connects to the MCU chip.

6. The pipeline-type liquid level detection circuit for plant protection machines according to claim 1, characterized in that, The pressure sensor circuit also includes an I2C interface and a filtering circuit; The power supply terminal of the pressure sensor is connected to the power supply through a filter circuit, and the signal output terminal of the pressure sensor is connected to the MCU chip through the I2C interface.

7. The pipeline-type liquid level detection circuit for plant protection machines according to claim 1, characterized in that, The CAN transceiver includes a CAN chip, a CAN bus differential circuit, a logic power decoupling circuit, and a CAN transceiver power decoupling circuit. The input terminal of the CAN bus differential circuit is connected to the CAN chip, and the output terminal of the CAN bus differential circuit is connected to the external interface circuit. One end of the logic power decoupling circuit is connected to the CAN chip, and the other end is grounded. One end of the CAN transceiver power decoupling circuit is connected to the CAN chip, and the other end is grounded; it is also connected to the MCU chip through the CAN chip.

8. The pipeline-type liquid level detection circuit for plant protection machines according to claim 3, characterized in that, The indicator light circuit includes an LED light and an LED constant current drive circuit. The anode of the LED lamp is connected to a 3.3V power supply, the cathode of the LED lamp is connected to the input terminal of the LED constant current drive circuit, and the output terminal of the LED constant current drive circuit is connected to the MCU chip. The external interface circuit includes connector J1, TVS diode D1, and ESD diode D2; The connector J1 includes a power supply pin, a power ground pin, an EXT_CAN_H pin, and an EXT_CAN_L pin; and connects to external devices through the EXT_CAN_H pin and the EXT_CAN_L pin. The TVS diode D1 is connected to a 12V power supply at one end and to ground at the other end; the ESD diode D2 is connected to the EXT_CAN_H pin and the EXT_CAN_L pin of the connector J1 through the EXT_CAN_H pin and the EXT_CAN_L pin.

9. The pipeline-type liquid level detection circuit for plant protection machines according to any one of claims 1-8, characterized in that, The circuit also includes a power supply circuit, which includes a 12V to 5V power supply circuit and a 5V to 3.3V power supply circuit. The output terminal of the 12V to 5V power supply circuit is connected to the 5V to 3.3V power supply circuit and the CAN transceiver. The output of the 5V to 3.3V power supply circuit is connected to the CAN transceiver, the indicator light circuit, the pressure sensor circuit, the MCU circuit, and the temperature detection circuit.

10. A pipeline-type liquid level detection device for plant protection machines, characterized in that, The device includes a level gauge and a level detection pipe; the level gauge is fixedly installed at the top of the pipe; the level gauge includes the pipeline-type level detection circuit for plant protection machines as described in any one of claims 1-9.

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