A method and a device for monitoring the electrical condition of a floor drain

Abstract

The application discloses a kind of shell floor drain electric monitoring method and monitoring device, including the following steps: obtaining shell ground voltage;According to the size of the shell ground voltage, a plurality of levels of monitoring module is monitored to obtain the output variable of each level monitoring module;The output variable is input into the action module to make the action module execute corresponding action according to the output variable combination of each level.This application realizes different voltage protection modes according to the size of shell ground voltage, ensures the reliability, adopts ladder protection, and balances the accuracy and quickness in different voltage protection range;The application measures voltage instead of traditional leakage current measurement, improves safety, ensures that the condition of shell forming pressure difference to ground is monitored without forming a loop, and ensures the accuracy of shell ground voltage detection at low voltage by using software and hardware processing.

Description

Technical Field

[0001] This invention relates to the field of casing ground leakage monitoring technology, and in particular to a casing ground leakage monitoring method and monitoring device. Background Technology

[0002] With the development of technology, electrical appliances have become an indispensable part of our lives. However, as electrical products, improper operation or prolonged use due to aging can lead to electrical leakage. Leakage detection devices provide timely warnings and protection to avoid property damage and personal injury. Automated robots are now used in various industries. Most robots are powered by batteries. In harsh environments, power sources can be susceptible to leaks, incorrect wiring, or other issues that could cause the outer casing to become electrified, connecting it to various power sources in the circuit. If someone touches the robot, they could suffer an electric shock, endangering their life and health. Summary of the Invention

[0003] To address the issue of electric shock caused by a live casing, this invention provides a method and device for monitoring leakage current in the casing. Different voltage protection methods are implemented based on the casing ground voltage to ensure reliability. A tiered protection approach is employed to balance accuracy and speed within different voltage protection ranges.

[0004] To achieve the above objectives, the present invention employs the following technical solution: a method for monitoring leakage current in an enclosure, comprising the following steps:

[0005] Obtain the casing ground voltage;

[0006] Based on the magnitude of the outer casing ground voltage, a preset multi-level monitoring module is used to monitor the voltage and obtain the output variables of each level of the monitoring module.

[0007] The output variables are input into the action module so that the action module performs the corresponding action based on the combination of output variables at each level.

[0008] As a further improvement of the present invention, the monitoring method further includes the following steps:

[0009] A multi-level monitoring module is pre-set, including a first-level fast hardware monitoring module, a second-level latency monitoring module, and a third-level computation monitoring module;

[0010] Based on the magnitude of the ground voltage, a multi-level monitoring module is used to monitor the voltage, and the output variables of each monitoring module are obtained, including:

[0011] The first-level rapid hardware monitoring module monitors whether the voltage of the casing is greater than or equal to 36V;

[0012] The second-level delay monitoring module monitors whether the voltage of the casing is greater than or equal to 3.3V and exceeds a set time;

[0013] The third-level operation monitoring module monitors whether the voltage of the casing is greater than or equal to 0.5V and exceeds the set number of operations.

[0014] As a further improvement of the present invention, the monitoring steps of the monitoring module of the first rapid monitoring module include:

[0015] When the voltage of the casing ground is less than 36V, the input voltage is lower than the Vgs of MOSFET Q1 after being divided by the resistor, so MOSFET Q1 is not turned on. At the same time, MOSFET Q3 connected to MOSFET Q1 is lower than the turn-on threshold voltage and is not turned on. At this time, the Vgs of MOSFET Q2 is greater than the turn-on threshold voltage and is turned on, so that LED1 lights up. The output variable of the output terminal OUT1 of the first fast monitoring module is low level.

[0016] When the voltage of the casing ground is greater than or equal to 36V, the input voltage is greater than the Vgs of MOSFET Q1, so MOSFET Q1 is turned on. At the same time, MOSFET Q3 is turned on to complete the self-locking. At this time, the Vgs of MOSFET Q2 is less than the turn-on threshold voltage and it is not turned on. LED1 is turned off, and the output variable of the output terminal OUT1 of the first fast monitoring module is high level.

[0017] As a further improvement of the present invention, the monitoring steps of the second-level delay monitoring module include:

[0018] When the casing ground voltage is less than 36V, the monitoring of the continuous charging delay stage and the delay trigger stage are divided according to the charging and discharging process of the timer and the capacitor C2 of the input section.

[0019] The continuous charging delay phase monitoring includes obtaining a set time based on the charging time of capacitor C2 when the voltage is greater than or equal to 3.3V. At this time, the timer input pin is greater than or equal to 3.3V, and the output variable of the output pin OUT2 is low during the set time.

[0020] The delay trigger phase monitoring includes setting the output variable of the timer's output pin OUT2 to a high level when the voltage is continuously greater than or equal to 3.3V and after a set time has elapsed.

[0021] As a further improvement of the present invention, the monitoring steps of the second-level delay monitoring module further include:

[0022] When the casing ground voltage is greater than or equal to 3.3V, MOSFET Q4 is turned on because the gate voltage after the voltage divider circuit is greater than 2V. When capacitor C2 is first connected, it is considered to be turned on. After passing through capacitor C2, the input voltage connected to the timer input pin is greater than or equal to 3.3V. The timer's VCC pin input is 5V, corresponding to a 2 / 3VCC voltage of approximately 3.3V. According to the timer's monostable state, the output variable of the output pin OUT2 is low.

[0023] As the voltage of the casing ground charges capacitor C2, the input voltage of the input pin begins to drop. When the input voltage drops from 2 / 3VCC to 1 / 3VCC, the output variable of the output terminal OUT2 remains at a low level.

[0024] When the input voltage is less than 1 / 3VCC, the output variable of the timer output pin OUT2 is high, completing the delay trigger.

[0025] As a further improvement of the present invention, the monitoring steps of the second-level delay monitoring module further include:

[0026] The set time is obtained based on the capacitor charging time. When the casing ground voltage is greater than or equal to 3.3V, the actual time has not exceeded the set time. MOSFET Q5 does not conduct because the input voltage drops below the turn-on threshold voltage. At this time, the RST terminal of the timer is at a low level, so the delay protection is canceled and it waits for the next time.

[0027] As a further improvement of the present invention, the monitoring steps of the third-level operation monitoring module include:

[0028] When the voltage of the outer casing ground is less than 3.3V and greater than 0.5V, the third-level operation monitoring module activates the ADC acquisition protection circuit to acquire the signal of the outer casing ground in DMA mode;

[0029] After the acquired signal is converted into a floating-point voltage and loaded into ADC_VALUE(1024), it waits. After the acquired value is loaded into the corresponding FFT loading array, the next acquisition is performed. The number of samplings n is calculated, and the number of samplings n = n + 1 is updated in the next acquisition.

[0030] The FFT function module processes the data, performing a Fast Fourier Transform to obtain the amplitude values ​​at different frequencies. A comparison function is then used to check whether the amplitude values ​​at different frequencies exceed 0.5V.

[0031] If the voltage is greater than or equal to 0.5V, then the count value N = number of samplings n + 1 is obtained;

[0032] If it is less than 0.5V, then keep the count value N = the number of samplings n;

[0033] After looping m times, if m ≥ 3, then determine the result based on the count value N:

[0034] If N is greater than or equal to m*2, the output variable of the output terminal OUT3 is high level;

[0035] If N is less than m*2, the output variable of the output terminal OUT3 is low.

[0036] As a further improvement of the present invention, the monitoring method further includes the following steps:

[0037] The output variables are input into the action module, which is divided into two parts based on the combination of the output variables: displaying the current leakage current and alarming.

[0038] The section displaying the current leakage status includes:

[0039] When the leakage voltage of the casing does not exceed 0.5V, the third action module receives a low-level input variable from the OUT3 terminal of the multi-level monitoring module and controls LED2 to light up, indicating that the casing is currently in a safe condition and can be touched.

[0040] When the leakage voltage to ground of the casing exceeds 0.5V, LED2 of the third action module will turn off, indicating that there is a leakage current issue with the casing.

[0041] When the leakage voltage of the casing exceeds 3.3V, the second action module receives a high-level input variable from the OUT2 terminal of the multi-level monitoring module, and the LED4 of the second action module lights up, indicating that the casing is currently in a safe condition below 36V.

[0042] When the leakage voltage of the casing exceeds 36V, the first action module receives a high-level input variable from the OUT1 terminal of the multi-level monitoring module, and the LED3 of the first action module lights up, indicating that the casing is currently in a state of leakage that endangers the human body and should not be touched directly.

[0043] As a further improvement of the present invention, the alarm portion includes:

[0044] Each output terminal of the multi-level monitoring module is connected to the buzzer circuit through a MOSFET;

[0045] When the output variable of one of the output terminals is high, the buzzer circuit is activated to make the buzzer sound an alarm until the circuit fault is cleared.

[0046] On the other hand, the present invention also provides the following technical solution: a casing ground leakage current monitoring device, which regards the fixing screw connected to the metal casing as the casing ground input terminal, leads out to a multi-level monitoring module to obtain the casing ground voltage, and performs the casing ground leakage current monitoring method as described above in the method for monitoring the casing ground voltage.

[0047] Compared with the prior art, the present invention has the following beneficial effects:

[0048] This invention implements different voltage protection methods based on the different voltage levels of the casing and ground, ensuring reliability. It adopts tiered protection to ensure a balance between accuracy and speed of action within different voltage protection ranges.

[0049] This invention measures voltage instead of the traditional method of measuring leakage current, which improves safety and ensures that the voltage difference between the casing and ground is monitored even when no circuit is formed. It uses a combination of software and hardware to ensure accurate detection of the casing ground voltage under low voltage conditions. Attached Figure Description

[0050] To more clearly illustrate the technical solution, the accompanying drawings used in the embodiments 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 these drawings without creative effort.

[0051] Figure 1 This is a schematic diagram of the monitoring process of the present invention.

[0052] Figure 2 This is a schematic diagram of the circuit structure of the first-level fast hardware monitoring module in the embodiment.

[0053] Figure 3 This is a schematic diagram of the circuit structure of the second-level delay monitoring module in the embodiment.

[0054] Figure 4 This is a schematic diagram of the ADC acquisition and protection circuit structure of the third-level operation monitoring module in the embodiment.

[0055] Figure 5 This is a schematic diagram of the STM32 chipset circuit structure of the third-level operation monitoring module in the embodiment.

[0056] Figure 6 This is a schematic diagram of the circuit structure of the first action module in the embodiment.

[0057] Figure 7 This is a schematic diagram of the circuit structure of the second action module in the embodiment.

[0058] Figure 8 This is a schematic diagram of the circuit structure of the third action module in the embodiment.

[0059] Figure 9 This is a schematic diagram of the alarm circuit structure of the action module in the embodiment. Detailed Implementation

[0060] In order to clearly and completely understand the technical solution, the present invention will be further described in conjunction with the embodiments and accompanying drawings. Obviously, the embodiments described are only some embodiments of the present invention. All other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0061] It should be understood that, when used in this specification and the appended claims, the terms "comprising" and "including" indicate the presence of the described features, integrals, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or collections thereof.

[0062] It should also be understood that the terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the invention. As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms unless the context clearly indicates otherwise.

[0063] It should also be further understood that the term "and / or" as used in this specification and the appended claims refers to any combination of one or more of the associated listed items and all possible combinations, and includes such combinations.

[0064] This invention provides an embodiment, such as Figure 1 As shown, a method for detecting leakage current in an enclosure includes the following steps:

[0065] The voltage of the casing is obtained. The screws used for fixing the metal casing are regarded as the input terminal of the casing ground. They are led out and connected to the multi-level monitoring module to obtain the voltage of the casing ground. When there is no voltage difference between the casing and ground, the action module is not used and no other actions are performed. The monitoring continues.

[0066] A multi-level monitoring module is pre-set, including a first-level fast hardware monitoring module, a second-level latency monitoring module, and a third-level computation monitoring module;

[0067] Based on the magnitude of the ground voltage, a multi-level monitoring module is used to monitor the voltage, and the output variables of each monitoring module are obtained, including:

[0068] The first-level rapid hardware monitoring module monitors whether the voltage of the casing is greater than or equal to 36V;

[0069] The second-level delay monitoring module monitors whether the voltage of the casing is greater than or equal to 3.3V and exceeds a set time;

[0070] The third-level operation monitoring module monitors whether the voltage of the outer casing is greater than or equal to 0.5V and exceeds the set number of operations;

[0071] The output variables are input into the action module so that the action module performs the corresponding action based on the combination of output variables at each level.

[0072] Through the above steps, the first rapid monitoring module outputs a high-level or low-level output variable based on whether the casing ground voltage is greater than or equal to 36V. The safe voltage for the human body does not exceed 36V. Therefore, in order to ensure timely response when the casing leakage exceeds 36V, it is necessary to ensure speed. The system can react quickly to the situation through hardware processing. At the same time, the interference and ripple effects are reduced by adding a capacitor at the output end.

[0073] To better understand, the above steps can be performed in multiple ways. In one optional embodiment, the monitoring steps of the first rapid monitoring module include:

[0074] like Figure 2 As shown, when the casing ground voltage is less than 36V, due to the voltage division through the resistor, the gate voltage of MOSFET Q1 is lower than 2V after being divided by resistor R2. Therefore, it is lower than Vgs(th) = 2V, which is lower than Vgs of MOSFET Q1 and MOSFET Q1 is not turned on. At the same time, MOSFET Q3 connected to MOSFET Q1 is lower than the turn-on threshold voltage and is not turned on. At this time, Vgs of MOSFET Q2 is greater than the turn-on threshold voltage and it is turned on to make LED1 light up. The output variable of the output terminal OUT1 of the first fast monitoring module is low level, and the buzzer of the action module does not alarm, indicating that the casing ground voltage is within the safe voltage range for the human body.

[0075] When the casing ground voltage is greater than or equal to 36V, the input voltage is greater than Vgs of MOSFET Q1, causing MOSFET Q1 to conduct. At the same time, MOSFET Q3 is turned on to complete the self-locking. At this time, Vgs of MOSFET Q2 is less than the turn-on threshold voltage and does not conduct. LED1 is off, the output variable of the first fast monitoring module OUT1 is high, the buzzer of the action module sounds an alarm, indicating that the casing ground voltage is in a dangerous range. When the casing ground voltage is divided and the input voltage of MOSFET Q1 is lower than 2V, it is automatically released.

[0076] Furthermore, the second-level delay monitoring module outputs a high or low level variable based on whether the voltage of the casing ground is greater than or equal to 3.3V and exceeds a set time. When the voltage does not exceed 36V, the harm of leakage to the human body is reduced. To ensure that the voltage of the casing ground actually exists and is not a transient voltage peak caused by ripple or interference, delay protection is used to ensure reliability and reduce the possibility of accidental activation. The delay protection function of the second-level delay monitoring module achieves the delay through the charging and discharging process of capacitor C2 in the input section of the 555 timer.

[0077] In some embodiments, the monitoring steps of the second-level delay monitoring module include:

[0078] like Figure 3 As shown, when the casing ground voltage is less than 36V, the charging and discharging process of the timer and the input capacitor C2 is divided into continuous charging delay stage monitoring and delay trigger stage monitoring.

[0079] The continuous charging delay phase monitoring includes obtaining a set time based on the charging time of capacitor C2 when the voltage is greater than or equal to 3.3V. At this time, the timer input pin is greater than or equal to 3.3V, and the output variable of the output pin OUT2 is low during the set time.

[0080] The delay trigger phase monitoring includes setting the output variable of the timer's output pin OUT2 to a high level when the voltage is continuously greater than or equal to 3.3V and after a set time has elapsed.

[0081] Furthermore, in an optional embodiment, the monitoring steps of the second-level delay monitoring module further include:

[0082] When the casing ground voltage is greater than or equal to 3.3V, MOSFET Q4 conducts because the gate voltage after the voltage divider circuit is greater than 2V. The casing ground voltage is input to the second-stage delay monitoring module. When capacitor C2 is first connected, it is considered to be conducting. After passing through capacitor C2, the input voltage connected to the input pins 2 and 6 of the timer is greater than or equal to 3.3V. Since the VCC pin input of the 555 timer is 5V, the corresponding 2 / 3VCC voltage is approximately 3.3V. According to the timer monostable state, the output variable of the output terminal OUT2 of the output pin 3 is low.

[0083] As the voltage of the casing ground charges capacitor C2, the input voltages at input pins 2 and 6 begin to drop. When the input voltage drops from 2 / 3VCC to 1 / 3VCC, the output variable at output terminal OUT2 remains at a low level.

[0084] When the input voltage is less than 1 / 3VCC, the output variable of the output terminal OUT2 of the timer output pin 3 is high, completing the delay trigger.

[0085] It should be noted that the charging time t of capacitor C2 is determined by t = 1.1 * R5 * C2. In this embodiment, t = 1.1s is determined. That is, the set time is 1.1s. When the voltage of the casing ground is greater than or equal to 3.3V, capacitor C2 is charging. That is, the output variable of OUT2 is low level within 1.1s. When the set time of 1.1s is exceeded, the output variable of the output terminal OUT2 of the timer output pin 3 is high level, completing the delay trigger.

[0086] In this embodiment, the monitoring steps of the second-level delay monitoring module further include:

[0087] The set time is obtained based on the capacitor charging time. When the casing ground voltage is greater than or equal to 3.3V, the actual time has not exceeded the set time. MOSFET Q5 does not conduct because the input voltage drops below the turn-on threshold voltage. At this time, the RST terminal of the timer is at a low level, so the delay protection is canceled and it waits for the next time.

[0088] Furthermore, the third-level operation monitoring module monitors whether the voltage of the casing is greater than or equal to 0.5V and exceeds the set number of operations, and outputs a high-level or low-level output variable. In this embodiment, for example... Figure 4 and 5 As shown, the STM32 chipset is used for computation. Its output terminal is an ADC acquisition and protection circuit and a data feedback circuit. It is activated when the casing ground voltage is less than 3.3V and greater than 0.5V.

[0089] In an optional embodiment, the monitoring steps of the third-level operation monitoring module include:

[0090] It will be activated when the casing ground voltage is less than 3.3V and greater than 0.5V;

[0091] After power-on, initialize the program;

[0092] Connect to the network and send initial data to the cloud via ESP8266 according to the protocol;

[0093] Upon receiving a signal from the cloud, ADC1 is used to acquire the voltage signal of the casing ground in DMA mode;

[0094] The acquired signal is converted into a floating-point voltage and loaded into ADC_VALUE(1024), then waits.

[0095] After loading the collected values ​​into the corresponding FFT loading array, the next collection is performed. The number of samples n is calculated, and the number of samples n = n + 1 is updated in the next collection.

[0096] The FFT function module processes the data, performing a Fast Fourier Transform to obtain the amplitude values ​​at different frequencies. A comparison function is then used to check whether the amplitude values ​​at different frequencies exceed 0.5V.

[0097] If the voltage is greater than or equal to 0.5V, then the count value N = number of samplings n + 1 is obtained;

[0098] If it is less than 0.5V, then keep the count value N = the number of samplings n;

[0099] After looping m times, if m ≥ 3, then determine the result based on the count value N:

[0100] If N is greater than or equal to m*2, the output variable of the output terminal OUT3 is high level;

[0101] If N is less than m*2, the output variable of the output terminal OUT3 is low.

[0102] In some embodiments, the monitoring steps of the third-level operation monitoring module further include:

[0103] After looping m times, the optimization is performed 5 times. That is, after looping 5 times, a judgment is made based on whether the count value exceeds 10. If it exceeds 10, the pin outputs a high level and modifies the corresponding position data according to the set data packet format, while triggering the near-ground alarm.

[0104] Data is sent to the ESP8266 via serial communication, and the ESP8266 sends it to the cloud via WiFi. The cloud remotely controls the system based on the alerts to detect the third-level leakage.

[0105] The process restarts from when the cloud signal is received, using ADC1 to acquire the voltage signal of the casing ground in DMA mode.

[0106] Furthermore, in some embodiments, the monitoring method further includes the following steps:

[0107] The output variables are input into the action module, which is divided into two parts based on the combination of the output variables: displaying the current leakage current and alarming.

[0108] The section displaying the current leakage status includes:

[0109] like Figure 6-8 As shown, when the leakage voltage of the casing does not exceed 0.5V, the third action module receives a low-level input variable from the OUT3 terminal of the multi-level monitoring module and controls the green LED2 to light up, indicating that the casing is currently in a safe condition and can be touched.

[0110] When the leakage voltage of the casing exceeds 0.5V, the STM32 chipset judges the situation by processing the data of the third-level operation monitoring module and the output variables of the first-level fast hardware monitoring module and the second-level delay monitoring module. If any variable reaches the corresponding protection status action value, the green LED 2 will turn off, indicating that there is a leakage safety situation.

[0111] In other words, when the leakage voltage of the casing exceeds 0.5V, the LED2 light of the third action module goes out, indicating that there is a leakage safety situation in the casing. After the first-level fast hardware monitoring module and the second-level delay monitoring module reach the action value, the corresponding LED red light of the action module lights up, indicating that the current leakage safety level has been exceeded. Moreover, the corresponding red light will not go out after the leakage voltage disappears and needs to be reset by pressing the button.

[0112] Specifically, in an optional embodiment, when the leakage voltage of the casing exceeds 3.3V, the second action module receives a high-level input variable from the OUT2 terminal of the multi-level monitoring module, and the red LED4 of the second action module lights up, indicating that the current casing is in a safe condition of exceeding 3.3V but below 36V;

[0113] When the leakage voltage of the casing exceeds 36V, the first action module receives a high-level input variable from the OUT1 terminal of the multi-level monitoring module, and the LED3 red light of the first action module lights up, indicating that the current leakage voltage of the casing is greater than the safe voltage for the human body and should not be touched directly. Therefore, when both LED3 and LED4 red lights are lit, it indicates that the current leakage is dangerous to the human body and should not be touched directly. The power should be turned off to eliminate the danger.

[0114] If all LEDs are lit, it indicates that the leakage voltage has been temporarily eliminated, but there is still a risk, and the problem needs to be resolved. In other words, if LED3 and LED4 are red, it means that there was a problem in the past where the casing voltage exceeded the leakage level and the issue has not yet been resolved. However, the current casing ground voltage is below 0.5V, and LED2 is green, it means that the casing is currently in a safe condition and can be touched.

[0115] The alarm section includes:

[0116] like Figure 9 As shown, each output terminal of the multi-level monitoring module is connected to the buzzer circuit through a MOS transistor;

[0117] When the output variable of one of the output terminals is high, the buzzer circuit is activated to make the buzzer sound an alarm until the circuit fault is cleared.

[0118] On the other hand, embodiments of the present invention also provide a casing ground leakage current monitoring device, which regards the fixing screw connected to the metal casing as the casing ground input terminal, leads out to a multi-level monitoring module to obtain the casing ground voltage, and performs a casing ground leakage current monitoring method as described in any of the above embodiments.

[0119] It should be noted that the embodiments described above are only some embodiments of the present invention, and not all embodiments. In some embodiments, within a specified measurement range, a voltage divider resistor circuit is used to convert a large voltage into a voltage within the measurable range of the STM32 ADC. After internal conversion to an actual voltage value, the collected value is calculated using an FFT algorithm, and protection and alarm functions are implemented based on the results to achieve monitoring. This also falls within the scope of the present invention.

[0120] The above disclosures are merely one or more preferred embodiments of the present invention, intended to help understand the inventive concept of the technical solution, and are not intended to limit the present invention in any other way. Any other equivalent or conventional substitution schemes made by those skilled in the art based on the features defined by the present invention shall still fall within the scope of the present invention.

Claims

1. A method for detecting leakage current in an enclosure, characterized in that, Includes the following steps: Obtain the casing ground voltage; A multi-level monitoring module is pre-set, including a first-level fast hardware monitoring module, a second-level latency monitoring module, and a third-level computation monitoring module; Based on the magnitude of the ground voltage, a multi-level monitoring module is used to monitor the voltage, and the output variables of each monitoring module are obtained, including: The first-level rapid hardware monitoring module monitors whether the voltage of the casing is greater than or equal to 36V; The second-level delay monitoring module monitors whether the voltage of the casing is greater than or equal to 3.3V and exceeds a set time; The third-level operation monitoring module monitors whether the voltage of the outer casing is greater than or equal to 0.5V and exceeds the set number of operations, and outputs a high-level or low-level output variable. The output variables are input into the action module so that the action module performs the corresponding action according to the combination of output variables at each level; The monitoring steps of the second-level delay monitoring module include: When the casing ground voltage is greater than or equal to 3.3V, MOSFET Q4 is turned on because the gate voltage after the voltage divider circuit is greater than 2V. When capacitor C2 is first connected, it is considered to be turned on. After passing through capacitor C2, the input voltage connected to the timer input pin is greater than or equal to 3.3V. The timer's VCC pin input is 5V, corresponding to a 2 / 3VCC voltage of approximately 3.3V. According to the timer's monostable state, the output variable of the output pin OUT2 is low. As the voltage of the casing ground charges capacitor C2, the input voltage of the input pin begins to drop. When the input voltage drops from 2 / 3VCC to 1 / 3VCC, the output variable of the output terminal OUT2 remains at a low level. When the input voltage is less than 1 / 3VCC, the output variable of the timer output pin OUT2 is high, completing the delay trigger.

2. The method for monitoring leakage current in an enclosure according to claim 1, characterized in that, The monitoring steps of the first-level rapid hardware monitoring module include: When the ground voltage is less than 36V, the input voltage is lower than the Vgs of MOSFET Q1 after being divided by the resistor, so MOSFET Q1 is not turned on. At the same time, MOSFET Q3 connected to MOSFET Q1 is lower than the turn-on threshold voltage and is not turned on. At this time, the Vgs of MOSFET Q2 is greater than the turn-on threshold voltage and is turned on, so that LED1 lights up. The output variable of the output terminal OUT1 of the first-stage fast hardware monitoring module is low level. When the casing ground voltage is greater than or equal to 36V, the input voltage is greater than the Vgs of MOSFET Q1, causing MOSFET Q1 to conduct. At the same time, MOSFET Q3 is turned on to complete self-locking. At this time, the Vgs of MOSFET Q2 is less than the turn-on threshold voltage and does not conduct. LED1 is turned off, and the output variable of the first-stage fast hardware monitoring module OUT1 is high.

3. The method for monitoring leakage current in a casing according to claim 1, characterized in that, The monitoring steps of the second-level delay monitoring module include: When the casing ground voltage is less than 36V, the monitoring of the continuous charging delay stage and the delay trigger stage are divided according to the charging and discharging process of the timer and the capacitor C2 of the input section. The continuous charging delay phase monitoring includes obtaining a set time based on the charging time of capacitor C2 when the voltage is greater than or equal to 3.3V. At this time, the timer input pin is greater than or equal to 3.3V, and the output variable of the output pin OUT2 is low during the set time. The delay trigger phase monitoring includes setting the output variable of the timer's output pin OUT2 to a high level when the voltage is continuously greater than or equal to 3.3V and after a set time has elapsed.

4. The method for monitoring leakage current in an enclosure according to claim 3, characterized in that: The monitoring steps of the second-level delay monitoring module also include: The set time is obtained based on the capacitor charging time. When the casing ground voltage is greater than or equal to 3.3V, the actual time has not exceeded the set time. MOSFET Q5 does not conduct because the input voltage drops below the turn-on threshold voltage. At this time, the RST terminal of the timer is at a low level, so the delay protection is canceled and it waits for the next time.

5. The method for monitoring leakage current in a casing according to claim 1, characterized in that, The monitoring steps of the third-level operation monitoring module include: When the voltage of the outer casing ground is less than 3.3V and greater than 0.5V, the third-level operation monitoring module activates the ADC acquisition protection circuit to acquire the signal of the outer casing ground in DMA mode; After the acquired signal is converted into a floating-point voltage and loaded into ADC_VALUE(1024), it waits. After the acquired value is loaded into the corresponding FFT loading array, the next acquisition is performed. The number of samplings n is calculated, and the number of samplings n=n+1 is updated in the next acquisition. The FFT function module processes the data, performing a Fast Fourier Transform to obtain the amplitude values ​​at different frequencies. A comparison function is then used to check whether the amplitude values ​​at different frequencies exceed 0.5V. If the voltage is greater than or equal to 0.5V, then the count value N = number of samplings n + 1 is obtained; If the value is less than 0.5V, then maintain the count value N = the number of samples n; After looping m times, if m ≥ 3, then determine the result based on the count value N: If N is greater than or equal to m*2, the output variable of the output terminal OUT3 is high level; If N is less than m*2, the output variable of the output terminal OUT3 is low.

6. The method for monitoring leakage current in an enclosure according to claim 1, characterized in that: The monitoring method also includes the following steps: The output variables are input into the action module, which is divided into two parts based on the combination of the output variables: displaying the current leakage current and alarming. The section displaying the current leakage status includes: When the leakage voltage of the casing does not exceed 0.5V, the third action module receives a low-level input variable from the OUT3 terminal of the multi-level monitoring module and controls LED2 to light up, indicating that the casing is currently in a safe condition and can be touched. When the leakage voltage to ground of the casing exceeds 0.5V, LED2 of the third action module will turn off, indicating that there is a leakage current issue with the casing. When the leakage voltage of the casing exceeds 3.3V, the second action module receives a high-level input variable from the OUT2 terminal of the multi-level monitoring module, and the LED4 of the second action module lights up, indicating that the casing is currently in a safe condition below 36V. When the leakage voltage of the casing exceeds 36V, the first action module receives a high-level input variable from the OUT1 terminal of the multi-level monitoring module, and the LED3 of the first action module lights up, indicating that the casing is currently in a state of leakage that endangers the human body and should not be touched directly.

7. The method for monitoring leakage current in an enclosure according to claim 6, characterized in that, The alarm section includes: Each output terminal of the multi-level monitoring module is connected to the buzzer circuit through a MOSFET; When the output variable of one of the output terminals is high, the buzzer circuit is activated to make the buzzer sound an alarm until the circuit fault is cleared.

8. A device for monitoring leakage current in an outer casing, characterized in that: The screws used for fixing the metal casing are regarded as the input terminal of the casing, and are led out to a multi-level monitoring module to obtain the casing voltage. The method for monitoring the casing voltage is to perform the casing leakage current monitoring method as described in any one of claims 1-7.

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