Rainfall sensor applied to agricultural greenhouse

Abstract

The invention relates to a rainfall sensor applied to an agricultural greenhouse, and belongs to the technical field of rainwater detection, the rainfall sensor comprises a detection electrode plate, a power supply module, a negative voltage conversion module, a signal processing module, a control module, a communication module and a heating module, the power supply module converts an externally input direct current voltage into a stable positive working voltage; alternating oscillation signals are applied to the detection electrode plate, electrolytic reaction caused by the fact that the electrode bears unipolar voltage for a long time is avoided, electrode oxidation is effectively prevented, damage to the detection electrode plate is further reduced in cooperation with the heating module, and the detection stability and reliability of the rainfall sensor are guaranteed; and meanwhile, the rainfall false alarm caused by condensation of the detection electrode plate can be effectively eliminated, the detection accuracy is greatly improved, and the false alarm of the sensor caused by condensation is effectively reduced.

Description

Technical Field

[0001] This invention relates to the field of rainwater detection technology, and in particular to a rain sensor for use in agricultural greenhouses. Background Technology

[0002] In recent years, with the rapid development of facility agriculture, greenhouse cultivation has become an important way to ensure high and stable crop yields. In greenhouse environmental control systems, temperature and humidity are key factors affecting crop growth, typically requiring timely opening and closing of the greenhouse film to achieve cooling and dehumidification or heat preservation and moisture retention. However, if rainfall occurs during environmental control, opening the greenhouse can easily lead to rainwater intrusion, causing crop flooding damage; conversely, if ventilation is not restored promptly after the rain stops, excessively high temperature and humidity may cause crop scorching or disease. Therefore, existing technologies commonly use rainfall sensors as the sensing unit for greenhouse environmental control to automatically detect rainfall signals and link them with the environmental control system to control the opening and closing of the greenhouse film.

[0003] However, in practical applications, the rain sensors currently on the market have many defects: First, they have low detection accuracy and slow response, and are prone to missed or false alarms; second, the sensor detection electrodes are prone to oxidation during long-term use, leading to performance degradation or even complete failure, which seriously affects the reliability of greenhouse operations during the rainy season and causes planting accidents; in addition, in high humidity environments, condensation is prone to form on the sensor surface, which can be misinterpreted as a rain signal, causing the system to close the greenhouse incorrectly, affecting normal dehumidification and cooling, and thus adversely affecting crop growth.

[0004] Therefore, existing rainfall sensors have significant shortcomings in terms of antioxidant capacity, prevention of false alarms due to condensation, and long-term operational stability, making it difficult to meet the high reliability and precision requirements of modern agricultural environmental control systems. There is an urgent need to develop a rainfall sensor that is sensitive, accurate, antioxidant, condensation-resistant, and reliable in operation to improve the intelligence level of greenhouse environmental control and ensure the safety and efficiency of crop cultivation. Summary of the Invention

[0005] To overcome the problems existing in the background technology, the present invention provides a rainfall sensor for agricultural greenhouses. The present invention has high sensitivity and high detection accuracy, as well as excellent anti-oxidation and anti-condensation capabilities, thereby ensuring the reliability and stability of long-term operation.

[0006] To achieve the above objectives, the present invention is implemented through the following technical solution: This invention provides a rainfall sensor for use in agricultural greenhouses, comprising a detection electrode plate, a power supply module, a negative voltage conversion module, a signal processing module, a control module, a communication module, and a heating module. The power supply module converts an externally input DC voltage into a stable positive operating voltage. The negative voltage conversion module is connected to the power supply module, and the negative voltage conversion module converts the positive operating voltage into a negative operating voltage; The signal processing module is powered by positive and negative operating voltages; the signal processing module is connected to the detection electrode plate; the signal processing module includes a signal oscillator circuit and a signal conditioning circuit, the signal oscillator circuit outputs an alternating oscillation signal to the detection electrode plate, and the signal conditioning circuit rectifies, filters and amplifies the signal output by the detection electrode plate.

[0007] The control module is connected to the heating module, and its ADC acquisition channel is connected to the signal processing module. The control module pre-stores a heating threshold and a rainfall confirmation threshold that exceeds the heating threshold. The control module compares the acquired status signal with the heating threshold. When the status signal exceeds the heating threshold, the control module outputs a control signal to control the heating module to heat. The control module also compares the acquired post-heating status signal with the rainfall confirmation threshold. When the post-heating status signal exceeds the rainfall confirmation threshold, the control module confirms the rainfall status and outputs a rainfall signal. The communication module is connected to the control module and is used to send the signal output by the control module to the target end.

[0008] In the above technical solution, the signal oscillator circuit includes a precision operational amplifier and an RC feedback network. The precision operational amplifier and the RC feedback network are connected to form an oscillation circuit. The oscillation circuit is used to generate an alternating oscillation signal with a frequency of 2KHz. The output terminal of the oscillation circuit is connected to the first electrode of the detection electrode plate. The oscillation circuit applies the alternating oscillation signal to the first electrode of the detection electrode plate.

[0009] In the above technical solution, the signal conditioning circuit includes dual operational amplifiers; the dual operational amplifiers include a first operational amplifier and a second operational amplifier; the inverting input terminal of the first operational amplifier is connected to the second electrode of the detection electrode plate; the output terminal of the first operational amplifier is connected to a rectifier filter circuit, the rectifier filter circuit includes a rectifier diode and a filter capacitor; the output terminal of the rectifier filter circuit is connected to the inverting input terminal of the second operational amplifier, and the output terminal of the second operational amplifier is connected to the ADC acquisition channel of the control module after being adjusted by a feedback resistor.

[0010] In the above technical solution, the heating threshold and rainfall confirmation threshold are stored in the memory of the control chip of the control module; the serial communication terminal of the control module is connected to the signal transceiver terminal of the communication module; the control pin of the control module is connected to the mode control terminal of the communication module for switching the transceiver mode of the communication module; a high-frequency filter capacitor and a low-frequency filter capacitor are connected in parallel between the power supply terminal and ground of the control module; the control module is provided with a debugging interface for connecting debugging circuits.

[0011] In the above technical solution, the communication module includes an RS485 transceiver, a bidirectional ESD protection device, a transient suppression diode, a fuse, and a matching resistor; the differential signal pins of the RS485 transceiver are divided into terminals A and B; the fuse is connected in series between terminals A and B and the external bus interface of the RS485 transceiver; the matching resistor is connected in parallel between terminals A and B; the bidirectional ESD protection device is connected in parallel between terminals A and B and ground; the transient suppression diode is connected in parallel between terminals A and ground, and between terminals B and ground.

[0012] In the above technical solution, the power module includes a Schottky diode, a transient voltage suppressor diode, a linear regulator, and a filter capacitor. The Schottky diode is connected in parallel in the input circuit, with its anode facing the input voltage terminal and its cathode facing the subsequent circuit, to achieve reverse connection protection. One end of the transient voltage suppressor diode is connected to the positive power supply bus, and the other end is grounded to achieve overvoltage protection. The input terminal of the linear regulator is connected to the input voltage after reverse connection and overvoltage protection. The adjustment pin of the linear regulator is connected to an external voltage divider resistor to form a feedback circuit. The output terminal of the linear regulator outputs a stable DC voltage. The filter capacitor includes an input filter capacitor connected in parallel to the input terminal of the linear regulator and an output filter capacitor connected in parallel to the output terminal of the linear regulator.

[0013] In the above technical solution, the negative voltage conversion module adopts a charge pump type DC-DC converter. The input terminal of the charge pump type DC-DC converter is connected to the output terminal of the power supply module. An external flying capacitor is connected to the flying capacitor connection terminal of the charge pump type DC-DC converter. The output terminal of the charge pump type DC-DC converter outputs a negative voltage.

[0014] In the above technical solution, the heating module includes an electronic switch and a heating unit. The controlled end of the electronic switch is connected to the control pin of the control module. The input end of the heating module is connected to the output end of the power module. The output end of the heating module is connected in series with the heating unit and then grounded.

[0015] In the above technical solution, the heating unit is a thin-film heating element, which is attached to the back of the detection electrode plate.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. This invention avoids electrolytic reactions caused by the electrodes being subjected to unipolar voltage for a long time by loading an alternating oscillation signal onto the detection electrode plate, effectively preventing electrode oxidation and corrosion; in conjunction with the heating module, it can further reduce the damage to the electrodes caused by the humid environment, extend the service life of the sensor, and ensure the detection stability and reliability of the sensor during long-term use.

[0017] 2. This invention relies on the dual threshold judgment logic and the synergistic effect of automatic heating to accurately distinguish between condensation and time-based rainfall. When condensation is detected, heating is activated in time to eliminate interference. Combined with the high-precision amplification and filtering conditioning of the signal processing module, the detection accuracy is greatly improved and the false alarms caused by the sensor are effectively reduced.

[0018] 3. The detection electrode plate of the present invention has an automatic heating and drying function, which can quickly remove residual moisture on the surface after the rain stops, avoid moisture residue interfering with subsequent detection, and ensure that the rain stop signal is captured in a timely and accurate manner. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0020] Figure 1 This is a schematic diagram illustrating the principle of the present invention; Figure 2 This is a circuit structure diagram of the signal processing module of the present invention; Figure 3 This is a circuit structure diagram of the control module of the present invention; Figure 4 This is a circuit structure diagram of the communication module of the present invention; Figure 5 This is a circuit structure diagram of the power module of the present invention; Figure 6 This is a circuit structure diagram of the negative power conversion module of the present invention. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of this application will be described in further detail below with reference to the accompanying drawings.

[0022] Where the following description relates to the accompanying drawings, unless otherwise indicated, the same numbers in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present invention. Rather, they are merely examples of apparatuses and methods consistent with some aspects of the invention as detailed in the appended claims.

[0023] In the description of this invention, it should be understood that the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance. Those skilled in the art can understand the specific meaning of these terms in this invention according to the specific circumstances. Furthermore, in the description of this invention, unless otherwise stated, "multiple" refers to two or more. "And / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. The character " / " generally indicates that the preceding and following related objects have an "or" relationship.

[0024] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0025] like Figures 1 to 6 As shown, a rainfall sensor for agricultural greenhouses includes a detection electrode plate, a power supply module, a negative voltage conversion module, a signal processing module, a control module, a communication module, and a heating module. The power supply module converts the externally input DC voltage into a stable positive operating voltage. The negative voltage conversion module is connected to the power supply module, and the negative voltage conversion module converts the positive working voltage into a negative working voltage. The signal processing module is powered by positive and negative operating voltages; the signal processing module is connected to the detection electrode plate; the signal processing module includes a signal oscillator circuit and a signal conditioning circuit. The signal oscillator circuit outputs an alternating oscillation signal to the detection electrode plate, and the signal conditioning circuit rectifies, filters and amplifies the signal output by the detection electrode plate.

[0026] The control module is connected to the heating module, and the ADC acquisition channel of the control module is connected to the signal processing module. The control module has a pre-stored heating threshold and a rainfall confirmation threshold that is higher than the heating threshold. The control module compares the acquired status signal with the heating threshold. When the status signal exceeds the heating threshold, the control module outputs a control signal to control the heating module to heat. The control module compares the acquired post-heating status signal with the rainfall confirmation threshold. When the post-heating status signal exceeds the rainfall confirmation threshold, the control module confirms the rainfall status and outputs a rainfall signal. The communication module is connected to the control module and is used to send the signals output by the control module to the target end.

[0027] During operation, the control module continuously acquires status signals from the signal processing module via the ADC acquisition channel. When the status signal exceeds a pre-stored heating threshold, it enters the first-level judgment stage: detecting moisture on the surface of the detection electrode plate. However, this could be rainwater, condensation, fog, or other interference. At this time, the control module sends a control signal to the heating module to start the heating function. After the heating operation is executed, the control module again acquires the post-heating status signal via the ADC acquisition channel. The control module compares this post-heating status signal with a pre-stored rainfall confirmation threshold, which is set higher than the heating threshold. If the post-heating status signal exceeds the rainfall confirmation threshold, it proves that moisture is continuously replenishing, and the control module determines that the rainfall state is established, and then outputs a rainfall signal. If the post-heating status signal does not exceed the rainfall confirmation threshold and returns to normal, it is determined that the interference has been eliminated, and the control module returns to the detection state without outputting a signal. This invention utilizes the heating module to assist electronic judgment, effectively avoiding false alarms caused by condensation, etc., and ensuring the reliability of rainfall state judgment.

[0028] like Figure 2 As shown, the signal oscillator circuit includes a precision operational amplifier U6 and an RC feedback network. The precision operational amplifier U6 and the RC feedback network are connected to form an oscillation circuit, which generates an alternating oscillation signal with a frequency of 2kHz. The RC feedback network includes resistors RS1 and RS2 and capacitors C15 and C13. The output terminal of the oscillation circuit is connected to the first electrode RS1 of the detection electrode plate. The oscillation circuit applies the alternating oscillation signal to the first electrode RS1 of the detection electrode plate. Applying the alternating oscillation signal to the detection electrode plate avoids the electrolytic reaction caused by the long-term application of unipolar voltage to the detection electrode plate, effectively prevents electrode oxidation and corrosion, extends the service life of the sensor, and ensures the stability and reliability of its long-term detection.

[0029] The signal conditioning circuit includes dual operational amplifiers; the dual operational amplifiers include a first operational amplifier U5A and a second operational amplifier U5B; the inverting input terminal of the first operational amplifier U5A is connected to the second electrode RS2 of the detection electrode plate; the output terminal of the first operational amplifier U5A is connected to a rectifier and filter circuit, which includes rectifier diodes D2 and D4 and a filter capacitor C16; the output terminal of the rectifier and filter circuit is connected to the inverting input terminal of the second operational amplifier U5B, and the output terminal of the second operational amplifier U5B is connected to the ADC acquisition channel of the control module after being adjusted by feedback resistors R1 and R2.

[0030] The first electrode RS1 and the second electrode RS2 of the detection electrode plate are rainfall detection electrodes. During rainfall, a conductive path is formed between the electrodes. After the alternating oscillation signal is resistively coupled between the first electrode RS1 and the second electrode RS2, the amplitude of the coupled alternating oscillation signal changes accordingly with the amount of rainfall: the heavier the rainfall, the higher the signal amplitude; the lighter the rainfall, the lower the signal amplitude. The coupled alternating oscillation signal is rectified, filtered, and amplified by the signal conditioning circuit U5 and converted into a stable DC voltage output to the control module, thereby realizing accurate detection of rainfall intensity.

[0031] like Figure 3 As shown, the ADC acquisition channel of the control module is used to acquire the status signal of the detection electrode plate after processing by the signal processing module; the control chip of the control module is an STM32G030F6P6 chip, and the heating threshold and rainfall confirmation threshold are stored in the memory of the control chip; the serial communication terminal of the control module is connected to the signal transceiver terminal of the communication module; the control pin of the control module is connected to the mode control terminal of the communication module to switch the transceiver mode of the communication module; a high-frequency filter capacitor C3 and a low-frequency filter capacitor C4 are connected in parallel between the power supply terminal and ground of the control module; the control module is equipped with a debugging interface SWD1, which is used to connect the debugging circuit to realize program download and online debugging.

[0032] like Figure 4As shown, the communication module includes an RS485 transceiver, a bidirectional ESD protection device TV1, transient voltage suppressor diodes TV2, TV3, and TV4, fuses F1 and F2, and a matching resistor R6. The differential signal pins of the RS485 transceiver are divided into terminals A and B. Fuses F1 and F2 are connected in series between terminals A and B and the external bus interface of the RS485 transceiver, respectively. The matching resistor R6 is connected in parallel between terminals A and B to achieve impedance matching. The bidirectional ESD protection device TV1 is connected in parallel between terminals A and B and ground, which can quickly absorb transient currents generated by static electricity and prevent static electricity from damaging the RS485 transceiver. Transient voltage suppressor diodes TV2, TV3, and TV4 are connected in parallel between terminals A and ground and between terminals B and ground, respectively. When a surge voltage or spike pulse occurs on the bus, the transient voltage suppressor diodes will quickly conduct, clamping the overvoltage within a safe range and protecting the subsequent circuits from damage.

[0033] like Figure 5 As shown, the power supply module includes a Schottky diode, a transient voltage suppressor diode, a linear regulator, and a filter capacitor. The Schottky diode is connected in parallel in the input circuit, with its anode facing the input voltage terminal and its cathode facing the subsequent circuit, providing reverse connection protection. When the power supply polarity is correct, the Schottky diode conducts; when the power supply polarity is incorrect, the Schottky diode is cut off, blocking reverse current and preventing damage to subsequent circuits due to reverse power supply polarity. One end of the transient voltage suppressor diode is connected to the positive power supply bus, and the other end is grounded, providing overvoltage protection. The transient voltage suppressor diode can suppress input voltage spikes, such as surges and static electricity. When the voltage exceeds the clamping value, the transient voltage suppressor diode quickly conducts, clamping the voltage within a safe range to ensure safety. The power supply module protects the downstream circuitry. The input of the linear regulator is connected to the input voltage after reverse connection and overvoltage protection. External voltage divider resistors RA1 and RB1 connected to the adjustment pin form a feedback circuit, and the output of the linear regulator provides a stable DC voltage. The filter capacitors include an input filter capacitor connected in parallel to the input of the linear regulator and an output filter capacitor connected in parallel to the output of the linear regulator. The input filter capacitors include capacitor C6 and electrolytic capacitor E1, and the output filter capacitors include capacitor C7 and electrolytic capacitor E2. The power module converts the DC voltage into a stable +3.3V DC voltage, providing reliable power to the downstream circuitry. Simultaneously, protection and filtering measures ensure power quality and stable operation of the downstream circuitry.

[0034] like Figure 6As shown, the negative voltage conversion module uses a charge pump type DC-DC converter. The input terminal of the charge pump type DC-DC converter is connected to the output terminal of the power supply module. An external flying capacitor C8 is connected to the flying capacitor connection terminal of the charge pump type DC-DC converter. The output terminal of the charge pump type DC-DC converter outputs a negative voltage. An input filter capacitor C12 is connected in parallel between the input terminal of the charge pump type DC-DC converter and ground. An output filter capacitor C10 is connected in parallel between the output terminal of the charge pump type DC-DC converter and ground. The negative voltage conversion module realizes the conversion from positive voltage to negative voltage through the alternating charging and discharging of the flying capacitor.

[0035] In this embodiment, the heating module includes an electronic switch and a heating unit. The controlled terminal of the electronic switch is connected to the control pin of the control module, and the output terminal of the heating module is connected in series with the heating unit and then grounded.

[0036] In this embodiment, the heating unit is a thin-film heating element, which is attached to the back of the detection electrode plate.

[0037] In this embodiment, the sensor is installed on the top of an agricultural greenhouse. Its workflow is as follows: First, the sensor is powered on and initialized. The power module and negative voltage conversion module provide stable positive and negative operating voltages to the signal processing module. The signal processing module continuously applies a 2kHz alternating oscillation signal to the detection electrode plate and monitors the status signal between the electrodes in real time. When the ambient humidity changes, the electrical characteristics of the detection motor plate change. This change is collected, amplified, and filtered in real time by the signal processing module and converted into a status signal, which is then sent to the control module. The control module compares the current status signal with a pre-stored heating threshold. If the threshold is exceeded, then… The system detects the presence of surface moisture, but to avoid false alarms caused by morning dew or other interference, the control module first activates the heating module to briefly heat the electrode plates to evaporate non-rainfall moisture. After heating, the control module immediately collects a new status signal and compares it a second time with a higher rainfall confirmation threshold. If the signal still exceeds the confirmation threshold, it is confirmed as a valid rainfall event. At this point, the control module generates a rainfall command and sends it to the greenhouse main control system through a communication module with anti-interference protection, triggering linked operations such as closing the skylight, activating the alarm, or draining water. The entire process achieves reliable and automatic identification of rainfall, effectively ensuring the stability of the greenhouse's internal environment.

[0038] In the accompanying drawings of this embodiment, the same or similar reference numerals correspond to the same or similar components. In the description of this application, it should be understood that if terms such as "upper," "lower," "left," "right," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, they are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the terms used to describe positional relationships in the drawings are only for illustrative purposes and should not be construed as limiting this application. For those skilled in the art, the specific meaning of the above terms can be understood according to the specific circumstances.

[0039] Finally, it should be noted that the above preferred embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail through the above preferred embodiments, those skilled in the art should understand that various changes can be made to it in form and detail without departing from the scope defined by the claims of the present invention.

Claims

1. A rainfall sensor for use in agricultural greenhouses, characterized in that, It includes a detection electrode plate, a power supply module, a negative voltage conversion module, a signal processing module, a control module, a communication module, and a heating module. The power supply module converts the externally input DC voltage into a stable positive operating voltage. The negative voltage conversion module is connected to the power supply module, and the negative voltage conversion module converts the positive operating voltage into a negative operating voltage; The signal processing module is powered by positive and negative operating voltages; the signal processing module is connected to the detection electrode plate; the signal processing module includes a signal oscillator circuit and a signal conditioning circuit, the signal oscillator circuit outputs an alternating oscillation signal to the detection electrode plate, and the signal conditioning circuit rectifies, filters and amplifies the signal output by the detection electrode plate. The control module is connected to the heating module, and its ADC acquisition channel is connected to the signal processing module. The control module pre-stores a heating threshold and a rainfall confirmation threshold that exceeds the heating threshold. The control module compares the acquired status signal with the heating threshold. When the status signal exceeds the heating threshold, the control module outputs a control signal to control the heating module to heat. The control module also compares the acquired post-heating status signal with the rainfall confirmation threshold. When the post-heating status signal exceeds the rainfall confirmation threshold, the control module confirms the rainfall status and outputs a rainfall signal. The communication module is connected to the control module and is used to send the signal output by the control module to the target end.

2. A rainfall sensor for agricultural greenhouses as described in claim 1, characterized in that, The signal oscillator circuit includes a precision operational amplifier and an RC feedback network. The precision operational amplifier and the RC feedback network are connected to form an oscillation circuit. The oscillation circuit is used to generate an alternating oscillation signal with a frequency of 2KHz. The output terminal of the oscillation circuit is connected to the first electrode of the detection electrode plate. The oscillation circuit applies the alternating oscillation signal to the first electrode of the detection electrode plate.

3. A rainfall sensor for agricultural greenhouses as described in claim 1, characterized in that, The signal conditioning circuit includes dual operational amplifiers; the dual operational amplifiers include a first operational amplifier and a second operational amplifier; the inverting input terminal of the first operational amplifier is connected to the second electrode of the detection electrode plate; the output terminal of the first operational amplifier is connected to a rectifier filter circuit, the rectifier filter circuit includes a rectifier diode and a filter capacitor; the output terminal of the rectifier filter circuit is connected to the inverting input terminal of the second operational amplifier, and the output terminal of the second operational amplifier is connected to the ADC acquisition channel of the control module after being adjusted by a feedback resistor.

4. A rainfall sensor for agricultural greenhouses as described in claim 1, characterized in that, The heating threshold and rainfall confirmation threshold are stored in the memory of the control chip of the control module; the serial communication terminal of the control module is connected to the signal transceiver terminal of the communication module; the control pin of the control module is connected to the mode control terminal of the communication module for switching the transceiver mode of the communication module; a high-frequency filter capacitor and a low-frequency filter capacitor are connected in parallel between the power supply terminal and ground of the control module; the control module is provided with a debugging interface for connecting debugging circuits.

5. A rainfall sensor for agricultural greenhouses as described in claim 1, characterized in that, The communication module includes an RS485 transceiver, a bidirectional ESD protection device, a transient suppression diode, a fuse, and a matching resistor. The differential signal pins of the RS485 transceiver are divided into terminals A and B. The fuse is connected in series between terminals A and B and the external bus interface of the RS485 transceiver. The matching resistor is connected in parallel between terminals A and B. The bidirectional ESD protection device is connected in parallel between terminals A and B and ground. The transient suppression diode is connected in parallel between terminals A and ground and between terminals B and ground.

6. A rainfall sensor for use in agricultural greenhouses as described in claim 1, characterized in that, The power supply module includes a Schottky diode, a transient voltage suppressor diode, a linear regulator, and a filter capacitor. The Schottky diode is connected in parallel in the input circuit, with its anode facing the input voltage terminal and its cathode facing the subsequent circuit, to achieve reverse connection protection. One end of the transient voltage suppressor diode is connected to the positive power supply bus, and the other end is grounded to achieve overvoltage protection. The input terminal of the linear regulator is connected to the input voltage after reverse connection and overvoltage protection. The adjustment pin of the linear regulator is connected to an external voltage divider resistor to form a feedback circuit. The output terminal of the linear regulator outputs a stable DC voltage. The filter capacitor includes an input filter capacitor connected in parallel to the input terminal of the linear regulator and an output filter capacitor connected in parallel to the output terminal of the linear regulator.

7. A rainfall sensor for use in agricultural greenhouses as described in claim 1, characterized in that, The negative voltage conversion module adopts a charge pump type DC-DC converter. The input terminal of the charge pump type DC-DC converter is connected to the output terminal of the power supply module. An external flying capacitor is connected to the flying capacitor connection terminal of the charge pump type DC-DC converter. The output terminal of the charge pump type DC-DC converter outputs a negative voltage.

8. A rainfall sensor for use in agricultural greenhouses as described in claim 1, characterized in that, The heating module includes an electronic switch and a heating unit. The controlled terminal of the electronic switch is connected to the control pin of the control module. The input terminal of the heating module is connected to the output terminal of the power module. The output terminal of the heating module is connected in series with the heating unit and then grounded.

9. A rainfall sensor for use in agricultural greenhouses as described in claim 1, characterized in that, The heating unit is a thin-film heating element, which is attached to the back of the detection electrode plate.

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