Multi-path switching value detection method with high interference resistance

Abstract

The invention discloses a multi-path switching value detection method with strong interference resistance, and relates to the technical field of low-voltage motor control, and the method comprises the steps: connecting an external control switch through a first DC power supply, and after the switch is closed, controlling a current to flow through a two-stage RC low-pass filter, and inputting the current to an optical coupler isolation circuit; the input end of the optocoupler is connected in parallel with a transient voltage suppression diode to suppress high-frequency interference; after the optocoupler is conducted, a second direct-current voltage signal is introduced into the microcontroller through the electronic switch module; the microcontroller continuously samples a signal at a high frequency, a sampling value is processed by a third-order Butterworth digital low-pass filter and a sliding window mean filtering algorithm, and a voltage effective value is obtained through calculation; the voltage effective value is compared with an environment noise real-time calibration threshold value, so that the switch state can be accurately acquired; the circuit required by the method is simple in structure, high in adaptability and high in anti-interference capability; the problem of accurate signal acquisition of common-cable or common-slot wiring of the control line and the power line in the prior art is solved.

Description

Technical Field

[0001] This invention relates to the field of low-voltage motor control technology, and in particular to a multi-channel switching quantity detection method with strong anti-interference capabilities. Background Technology

[0002] In the field of low-voltage motor control, in order to achieve remote control of the motor, multiple control cables are usually laid between the motor control box and the distribution cabinet. The motor control box controls the electrical circuit in the distribution cabinet through switching signals. The switching signals are transmitted in DC level or pulse form, thereby realizing the motor's start-stop, speed regulation and other functions. This type of control system has a simple structure and fast response, and is widely used in industrial automation, water pump control, fan systems and other occasions.

[0003] However, in practical engineering applications, since some motor control boxes are far from the distribution cabinet, in order to reduce wiring costs and construction complexity, the control line and the motor power line are often connected by a single cable or laid in the same cable tray. Although this wiring method saves material and construction costs, it also brings significant electromagnetic interference problems.

[0004] Because the control line runs parallel to the AC power line in close proximity, the control line is highly susceptible to interference from AC currents with a power frequency of 50Hz or 60Hz and high-frequency electric fields generated during the operation of high-power equipment. During transmission, this interference will induce voltage in the adjacent control line. After such interference signals are coupled into the control loop, they will be superimposed on the original switching signal, which may cause abnormal fluctuations in the switching signal detection level, reduce the accuracy of switching signal recognition, and lead to signal recognition errors. This can then cause motor malfunctions (such as unexplained start-stop), resulting in safety hazards such as motor mis-start and mis-stop, which seriously affects the safety and reliability of equipment operation.

[0005] Especially in multi-channel parallel control scenarios, interference signals not only have high superposition intensity, but are also often difficult to completely suppress through simple hardware filtering or software debouncing. At the same time, traditional anti-interference measures provided by different manufacturers, such as adding optocouplers, filters, and surge arresters, although improving signal quality to some extent, are difficult to adapt to the ever-changing construction needs and operation and maintenance environment on site, and also increase system costs and maintenance difficulty.

[0006] Therefore, there is an urgent need for a multi-channel switch detection method with stronger anti-interference capabilities, which can effectively identify real switching actions under low-cost wiring structures and accurately filter out background noise such as 50Hz / 60Hz power frequency interference and electric field induced interference, thereby ensuring the stability and safety of low-voltage motor control systems.

[0007] In summary, the existing technology has at least the following technical problems: When existing control lines and power lines are wired together in the same cable or in the same slot, there are technical problems such as weak anti-interference capability of switch signals, low signal recognition accuracy, and low adaptability of anti-interference structure. Summary of the Invention

[0008] The purpose of this invention is to provide a multi-channel switch quantity detection method with strong anti-interference capabilities to solve the technical problems of weak anti-interference capability, low signal recognition accuracy, and low adaptability of anti-interference structure when control lines and power lines are wired together or in the same slot.

[0009] The preferred technical solutions among the many technical solutions provided by this invention can produce a variety of technical effects, which are described in detail below.

[0010] To address the aforementioned technical problems, the present invention provides the following technical solution: This invention provides a multi-channel switch quantity detection method with strong anti-interference capabilities, comprising the following steps: S1, providing DC power to each detection path through a first DC power supply, and connecting an external control switch through the first DC power supply; when the control switch is closed, current flows through a two-stage RC low-pass filter, and the two-stage RC low-pass filter performs analog filtering processing on the signal given by the control switch; S2. Two stages of RC low-pass filters are connected in parallel to the input of the optocoupler. A transient voltage suppression diode is connected in parallel between the input of the optocoupler and the two stages of RC low-pass filters. One end of the transient voltage suppression diode is grounded to absorb high-frequency spike voltage interference and improve surge immunity. The current output from the two-stage RC low-pass filter reaches the emitter of the optocoupler; S3. After the optocoupler is turned on, the output of the optocoupler pulls down the corresponding input pin of the electronic switch module, controls the formation of a conduction path in the electronic switch module, and then sends the voltage signal of the second DC power supply to the microcontroller through the conduction path. S4. The microcontroller periodically samples the signals driven by the optocoupler and electronic switch modules of each detection path. The sampling frequency is 250Hz×n, and 100×n points are sampled continuously, where n is the number of detection paths. S5. The sampled signal is processed by a third-order Butterworth low-pass digital filter with a cutoff frequency of 10Hz, and combined with a sliding window mean filtering algorithm to extract the effective voltage value of the signal. S6. Compare the effective voltage value with the real-time calibration threshold of the ambient noise to determine the control switch signal and obtain the state of the control switch.

[0011] In one embodiment, in step S1, the two-stage RC low-pass filter is a hardware filter with a total cutoff frequency of 28.4Hz, used to effectively filter out 50Hz / 60Hz power frequency induced signals.

[0012] In one embodiment, the two-stage RC low-pass filter is composed of a first RC unit consisting of a first resistor and a first capacitor, and a second RC unit consisting of a second resistor and a second capacitor.

[0013] In one embodiment, the first resistor has a resistance of 2KΩ and the matching first capacitor has a resistance of 1.8nF / 50V; the second resistor has a resistance of 3KΩ and the matching second capacitor has a resistance of 1.2nF / 50V.

[0014] In one embodiment, in step S2, a transient voltage suppression diode is connected in parallel between the circuit of the anode and cathode of the two-stage RC low-pass filter and the input of the optocoupler; the clamping voltage of the transient voltage suppression diode is higher than the operating voltage, and it is used to absorb the spike voltage in AC induction and electric field interference.

[0015] In one embodiment, in step S3, the electronic switch module is a three-to-one switch chip with multiple input channels; the input terminals of the electronic switch module are respectively connected to the output terminals of the optocouplers of each detection path to receive signal input; the electronic switch module transmits the voltage signal of the second DC power supply to the analog-to-digital conversion pin of the microcontroller through the conduction path according to the signal of the optocoupler, forming a sampling signal.

[0016] In one embodiment, the microcontroller’s analog-to-digital conversion pin has a resolution of 12 bits or more to enhance the ability to identify low-amplitude signals.

[0017] In one embodiment, in step S5, the window length of the sliding window mean filtering algorithm is adjustable to adaptively adjust the smoothness of the filtering according to the actual level of environmental interference.

[0018] In one embodiment, in step S6, the real-time environmental noise calibration threshold is obtained through a dynamic threshold algorithm; wherein, the dynamic threshold algorithm uses a statistical model based on the maximum value, minimum value, standard deviation and average value of historical sampling data to update the high and low level judgment threshold in real time.

[0019] In one embodiment, in step S6, when the effective voltage value is greater than the first threshold, it is determined to be a high level; when the effective voltage value is less than the second threshold, it is determined to be a low level.

[0020] The beneficial effects of this invention are as follows: (1) Improve anti-interference capability: The combined effect of two-stage RC analog low-pass filter and third-order Butterworth digital filter can effectively filter out 50Hz / 60Hz AC induction signal and high-frequency interference, and improve the stability and reliability of control signal transmitted by control line when power line and control line are wired together or in the same slot.

[0021] (2) Enhance signal recognition accuracy: The method adopts a high-frequency sampling strategy of 250Hz×n and a continuous sampling strategy of 100×n points. Combined with the sliding window mean filtering algorithm and dynamic threshold algorithm, the effective state of the control switch can be accurately judged and extracted in an electrical noise environment, effectively avoiding safety threats such as false triggering and false recognition.

[0022] (3) Enhance surge and spike resistance: Connecting a transient voltage suppression diode in parallel at the input of the optocoupler can significantly improve the surge resistance of the circuit and protect key components from high voltage spike damage.

[0023] (4) Strong structural versatility and high adaptability: This method constructs a multi-channel switching detection circuit through standard RC filter units, voltage interference absorption, voltage isolation, microcontroller and other general circuit components. It is suitable for various industrial control environments, easy to deploy on a large scale, and adaptable to complex field wiring structures.

[0024] (5) Controllable system cost: By combining hardware filtering, voltage interference absorption, voltage isolation, high-frequency continuous sampling and dynamic threshold judgment of the algorithm, the hardware structure is simple while ensuring high reliability. It does not require expensive anti-interference devices or shielded wiring. Combined with the algorithm, the accuracy of signal acquisition can be improved. It has good cost performance and is suitable for a wide range of industrial control projects.

[0025] In summary, the multi-channel switch quantity detection method of the present invention has significant improvements over the prior art in terms of anti-interference capability, signal recognition accuracy, structural versatility, and system cost. It solves the technical problems of weak anti-interference capability, low signal recognition accuracy, and low adaptability of anti-interference structure when control lines and power lines are wired together or in the same slot, and achieves accurate acquisition of switch quantity signals. Attached Figure Description

[0026] To more clearly illustrate the technical solution of the present invention, the 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.

[0027] Figure 1 This invention relates to a multi-channel switch quantity detection circuit. Detailed Implementation

[0028] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings.

[0029] A specific implementation provides a multi-channel switch quantity detection method with strong anti-interference capabilities. The method includes: connecting an external control switch via a first DC power supply; when the switch is closed, the control current flows through a two-stage RC low-pass filter and is input to an optocoupler isolation circuit; a transient voltage suppression diode is connected in parallel at the input of the optocoupler to suppress high-frequency interference; after the optocoupler is turned on, a second DC voltage signal is introduced into a microcontroller through an electronic switch module; the microcontroller continuously samples the signal at high frequency, and the sampled value is processed by a third-order Butterworth digital low-pass filter and a sliding window mean filtering algorithm to calculate the effective voltage value; the effective voltage value is then compared with a real-time environmental noise calibration threshold to accurately obtain the switch state. This method requires a simple circuit structure, strong adaptability, and high anti-interference capability, and can be widely applied in large-scale industrial control equipment such as motor control. It effectively solves the technical problems of weak anti-interference capability, low signal recognition accuracy, and low adaptability of anti-interference structure when existing control lines and power lines are wired together or in the same slot.

[0030] An embodiment of a multi-channel switch quantity detection method includes the following steps: S1, providing DC power to each detection path through a first DC power supply, and connecting an externally located control switch through the first DC power supply; when the control switch is closed, current flows through a two-stage RC low-pass filter, and the two-stage RC low-pass filter performs analog filtering processing on the signal given by the control switch; S2. Two stages of RC low-pass filters are connected in parallel to the input of the optocoupler. A transient voltage suppression diode is connected in parallel between the input of the optocoupler and the two stages of RC low-pass filters, and one end of the transient voltage suppression diode is grounded to absorb high-frequency spike voltage interference and improve surge resistance. The current output by the two stages of RC low-pass filters reaches the emitter base of the optocoupler. S3. After the optocoupler is turned on, the output of the optocoupler pulls down the corresponding input pin of the electronic switch module, controls the formation of a conduction path in the electronic switch module, and then sends the voltage signal of the second DC power supply to the microcontroller through the conduction path. S4. The microcontroller periodically samples the signals driven by the optocoupler and electronic switch modules of each detection path. The sampling frequency is 250Hz×n, and 100×n points are sampled continuously, where n is the number of detection paths. S5. The sampled signal is processed by a third-order Butterworth low-pass digital filter with a cutoff frequency of 10Hz, and combined with a sliding window mean filtering algorithm to extract the effective voltage value of the signal. S6. Compare the effective voltage value with the real-time calibration threshold of the ambient noise to determine the control switch signal and obtain the state of the control switch; specifically, when the effective voltage value is greater than the first threshold, it is determined to be high level; when the effective voltage value is less than the second threshold, it is determined to be low level.

[0031] When applying the technology, if the first threshold is 3.2V and the effective voltage value is greater than the first threshold, it is determined to be a high level; if the second threshold is 0.4V and the effective voltage value is less than the second threshold, it is determined to be a low level.

[0032] The multi-channel switch detection method of this technical solution has the following advantages in terms of anti-interference and signal acquisition accuracy: (1) Improved anti-interference capability: The synergistic filtering effect generated by the combination of two-stage RC analog low-pass filter and third-order Butterworth digital filter can effectively filter out 50Hz / 60Hz AC induction signal and high-frequency interference, and improve the stability and reliability of the control signal transmitted by the control line when the power line and control line are wired together or in the same slot.

[0033] (2) Enhance signal recognition accuracy: The method adopts a high-frequency sampling strategy of 250Hz×n and a continuous sampling strategy of 100×n points. Combined with the sliding window mean filtering algorithm and dynamic threshold algorithm, the effective state of the control switch can be accurately judged and extracted in an electrical noise environment, effectively avoiding safety threats such as false triggering and false recognition.

[0034] (3) Enhance surge and spike resistance: Connecting a transient voltage suppression diode in parallel at the input of the optocoupler can significantly improve the surge resistance of the circuit and protect key components from high voltage spike damage.

[0035] (4) Strong structural versatility and high adaptability: This method uses standard RC filter units to form two-stage RC low-pass filters, transient voltage suppression diodes, optocouplers, microcontrollers and other general circuit components to build a multi-channel switching detection circuit, realizes hardware filtering, peak interference voltage absorption, voltage isolation, signal acquisition and judgment and other functions. It is suitable for various industrial control environments, easy to deploy on a large scale and adaptable to complex field wiring structures.

[0036] (5) Controllable system cost: By combining hardware filtering, voltage interference absorption, voltage isolation, high-frequency continuous sampling and dynamic threshold judgment of the algorithm, the hardware structure is simple while ensuring high reliability. It does not require expensive anti-interference devices or shielded wiring. Combined with the algorithm, the accuracy of signal acquisition can be improved. It has good cost performance and is suitable for a wide range of industrial control projects.

[0037] In summary, the multi-channel switch quantity detection method of the present invention has significant improvements over the prior art in terms of anti-interference capability, signal recognition accuracy, structural versatility, and system cost. It solves the technical problems of weak anti-interference capability, low signal recognition accuracy, and low adaptability of anti-interference structure when control lines and power lines are wired together or in the same slot, and achieves accurate acquisition of switch quantity signals.

[0038] As one alternative implementation method In step S1, the two-stage RC low-pass filter is a hardware filter with a total cutoff frequency of 28.4Hz, which is used to effectively filter out 50Hz / 60Hz power frequency induced signals.

[0039] Specifically, the two-stage RC low-pass filter consists of a first RC unit composed of a first resistor and a first capacitor, and a second RC unit composed of a second resistor and a second capacitor.

[0040] In application, the first RC unit consists of a first resistor with a resistance of 2K and a matching first capacitor of 1.8nF / 50V; the second RC unit consists of a second resistor with a resistance of 3K and a matching second capacitor of 1.2nF / 50V.

[0041] In step S2, the transient voltage suppression diode is connected in parallel between the circuit of the two-stage RC low-pass filter and the anode and cathode of the optocoupler input.

[0042] In applications, the clamping voltage of the transient voltage suppressor diode is higher than the operating voltage to absorb voltage spikes in AC induction and electric field interference.

[0043] In step S3, the electronic switch module is a three-to-one switch chip with multiple input channels.

[0044] The input terminal of the electronic switch module is connected to the output terminal of the optocoupler of each detection path to receive signal input. The electronic switch module transmits the voltage signal of the second DC power supply to the analog-to-digital conversion pin of the microcontroller through the conduction path according to the signal of the optocoupler, forming a sampling signal.

[0045] When used in applications, the microcontroller’s analog-to-digital conversion pins have a resolution of 12 bits or more to enhance the ability to recognize low-amplitude signals.

[0046] In step S5, the window length of the sliding window mean filtering algorithm is adjustable.

[0047] When applied, this allows the microcontroller to adaptively adjust the smoothing level of the filter based on the actual level of interference in the environment.

[0048] In step S6, the real-time environmental noise calibration threshold is obtained through a dynamic threshold algorithm.

[0049] Specifically, the dynamic threshold algorithm updates the high and low level judgment thresholds in real time, and uses a statistical model based on the maximum, minimum, standard deviation and average values ​​of historical sampling data for calculation.

[0050] Based on the above embodiments of the multi-channel switch quantity detection method, such as Figure 1As shown, a multi-channel switch quantity detection circuit is provided, comprising an externally mounted control switch, a first DC power supply, multiple detection paths, an electronic switch module, a second DC power supply, and a microcontroller.

[0051] The detection path can be set to N lines according to the number of control switches; a single detection path consists of a two-stage RC low-pass filter, a transient voltage suppression diode, and an optocoupler.

[0052] exist Figure 1 In the process, multiple control switches are provided, each connected to a corresponding detection path; the first DC power supply is DC24V, which simultaneously powers multiple detection paths; one end of the first DC power supply is connected to multiple detection paths, and the other end is grounded; One side of the two-stage RC low-pass filter is connected to the detection path, and the other side is connected in parallel to the input terminal of the transient voltage suppression diode and the optocoupler. One end of the transient voltage suppression diode is grounded. Among them, the two-stage RC low-pass filter is composed of Figure 1 In the diagram, the first resistor has a resistance of 2KΩ, and the first capacitor has a resistance of 1.8nF / 50V; the second resistor has a resistance of 3KΩ, and the second capacitor has a resistance of 1.2nF / 50V; the transient voltage suppression diode is... Figure 1 TVS (Transient Voltage Suppressor) element in the middle; The output of the optocoupler is connected to the signal input of the electronic switch module, which has N signal inputs; the second DC power supply is... Figure 1 The DC 3.3V in the power supply provides voltage signals to the output terminals of the optocouplers for multiple detection paths; one end of the second DC power supply is connected to a resistor and then connected to the circuit where the output terminal of the optocoupler is connected to the electronic switch module. The 0 terminal of the electronic switch module is connected to the analog-to-digital converter (ADC) pin of the microcontroller (MCU).

[0053] The MCU samples at a frequency of 250Hz×n, collecting 100 points per channel. After processing by a digital third-order Butterworth low-pass filter, a sliding window mean filter is applied to finally obtain the effective voltage value.

[0054] The microcontroller (MCU) uses a dynamic threshold judgment mechanism to compare the effective voltage value with upper and lower thresholds (such as 3.2V and 0.4V) to determine whether the control switch of each detection path is in a high-level or low-level state.

[0055] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described.

Claims

1. A method for detecting multi-channel switch quantities with strong anti-interference capabilities, characterized in that, Includes the following steps: S1. Provide DC power to each detection path through the first DC power supply, and connect the control switch set externally through the first DC power supply; when the control switch is closed, the current flows through a two-stage RC low-pass filter, and the two-stage RC low-pass filter performs analog filtering processing on the signal given by the control switch. S2. Two stages of RC low-pass filters are connected in parallel to the input of the optocoupler. A transient voltage suppression diode is connected in parallel between the input of the optocoupler and the two stages of RC low-pass filters. One end of the transient voltage suppression diode is grounded to absorb high-frequency spike voltage interference and improve surge immunity. The current output from the two-stage RC low-pass filter reaches the emitter of the optocoupler; S3. After the optocoupler is turned on, the output of the optocoupler pulls down the corresponding input pin of the electronic switch module, controls the formation of a conduction path in the electronic switch module, and then sends the voltage signal of the second DC power supply to the microcontroller through the conduction path. S4. The microcontroller periodically samples the signals driven by the optocoupler and electronic switch modules of each detection path. The sampling frequency is 250Hz×n, and 100×n points are sampled continuously, where n is the number of detection paths. S5. The sampled signal is processed by a third-order Butterworth low-pass digital filter with a cutoff frequency of 10Hz, and combined with a sliding window mean filtering algorithm to extract the effective voltage value of the signal. S6. Compare the effective voltage value with the real-time calibration threshold of the ambient noise to determine the control switch signal and obtain the state of the control switch.

2. The multi-channel switch quantity detection method according to claim 1, characterized in that, In step S1, the two-stage RC low-pass filter is a hardware filter with a total cutoff frequency of 28.4Hz, which is used to effectively filter out 50Hz / 60Hz power frequency induced signals.

3. The multi-channel switch quantity detection method according to claim 2, characterized in that, The two-stage RC low-pass filter consists of a first RC unit composed of a first resistor and a first capacitor, and a second RC unit composed of a second resistor and a second capacitor.

4. The multi-channel switch quantity detection method according to claim 3, characterized in that, The first resistor has a resistance of 2KΩ, and the matching first capacitor is 1.8nF / 50V; the second resistor has a resistance of 3KΩ, and the matching second capacitor is 1.2nF / 50V.

5. The multi-channel switch quantity detection method according to claim 1, characterized in that, In step S2, the transient voltage suppression diode is connected in parallel between the circuit of the two-stage RC low-pass filter and the anode and cathode of the optocoupler input terminal; Transient voltage suppressor diodes have a clamping voltage higher than their operating voltage and are used to absorb voltage spikes in AC induction and electric field interference.

6. The multi-channel switch quantity detection method according to claim 1, characterized in that, In step S3, the electronic switch module is a three-to-one switch chip with multiple input channels; The input terminals of the electronic switch module are connected to the output terminals of the optocouplers of each detection path to receive signal input. The electronic switch module transmits the voltage signal of the second DC power supply to the analog-to-digital conversion pin of the microcontroller through the conduction path according to the signal of the optocoupler, forming a sampling signal.

7. The multi-channel switch quantity detection method according to claim 6, characterized in that, The analog-to-digital conversion pins of the microcontroller have a resolution of 12 bits or more to enhance the recognition of low-amplitude signals.

8. The multi-channel switch quantity detection method according to claim 1, characterized in that, In step S5, the window length of the sliding window mean filtering algorithm is adjustable, which is used to adaptively adjust the smoothness of the filtering according to the actual level of environmental interference.

9. The multi-channel switch quantity detection method according to claim 1, characterized in that, In step S6, the real-time environmental noise calibration threshold is obtained through a dynamic threshold algorithm; The dynamic threshold algorithm uses a statistical model based on the maximum, minimum, standard deviation, and average of historical sampled data to update the high and low level judgment thresholds in real time.

10. The multi-channel switch quantity detection method according to claim 1, characterized in that, In step S6, if the effective voltage value is greater than the first threshold, it is determined to be a high level; if the effective voltage value is less than the second threshold, it is determined to be a low level.

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