Working switch detection circuit applied to magnetic defect detector and judgment method of working switch detection circuit

Abstract

The invention discloses a working switch detection circuit applied to a magnetic powder flaw detector and a judgment method of the working switch detection circuit, belongs to the technical field of magnetic powder flaw detection, and solves the problems of poor contact and short service life caused by water inflow of a working switch in the prior art. The device mainly comprises a single-chip microcomputer U1, the single-chip microcomputer U1 controls driving of a magnet yoke coil, the single-chip microcomputer U1 and the magnet yoke coil are both arranged in a magnet yoke probe, the single-chip microcomputer U1 is connected with a switch detection circuit, the switch detection circuit comprises a power supply chip U2, the power supply chip U2 is connected with a current-limiting resistor R2, and the current-limiting resistor R2 is electrically connected with a working switch SW1 and a filter circuit. The filter circuit is connected to an AD acquisition module KEYAD of the single-chip microcomputer U1. The influence of inflow water on the working switch can be reduced, and the service life of the working switch is prolonged; on the basis of the circuit, electric leakage detection can be realized through software, and the reliability and the safety of a product are improved.

Description

Technical Field

[0001] The invention relates to the technical field of magnetic particle flaw detection, and in particular to a working switch detection circuit and a judgment method thereof applied to a magnetic particle flaw detector. Background Art

[0002] The working switch is the control switch for starting and stopping the magnetization of the yoke. For easy operation, it is generally installed on the handle of the yoke of the magnetic particle flaw detector. As an important accessory of the yoke, the working switch is also a vulnerable part of the yoke. The reason for the vulnerability is that magnetic suspension is generally required in the process of magnetic particle flaw detection. Magnetic suspension is a suspended liquid formed by mixing magnetic powder and medium liquid in a certain proportion. Usually the medium liquid is water or kerosene. Water conducts electricity and affects the operation of the circuit. The working switch may malfunction if it enters water, and the inside of the switch is prone to rust after being soaked in water for a long time, which eventually leads to damage to the working switch. Even switches with silver contacts are inevitably damaged. After long-term testing and analysis, it was determined that the main cause of damage to the yoke working switch is: after water enters, the detection voltage loaded on the working switch makes the contacts inside the switch become electrodes, and an electrochemical reaction occurs; the switch with silver contacts cannot resist the erosion of electrochemical reactions, while even ordinary copper electrode switches are not easily damaged if they are soaked in water for a long time when they are not powered. According to the conclusion of the test research, the detection voltage on the yoke working switch is reduced so that the electrode potential difference is lower than the decomposition voltage of the electrolyte solution such as the magnetic suspension. The decomposition voltage is the minimum voltage required to decompose the electrolyte on the electrode to generate electrolysis products. If it is lower than the decomposition voltage, the electrolysis reaction can be avoided, and the switch contacts can be prevented from being rapidly corroded after water enters. The actual measurement uses a voltage lower than 0.9V to detect the on and off state of the switch, and the switch can still work normally for a long time when soaked in water. However, the usual switch detection voltage is 5V or 3.3V. After reducing the detection voltage, it cannot be used directly as a switch signal in the original circuit, and the lower voltage signal is more susceptible to interference from the operation of the yoke.

[0003] For example, the application with announcement number CN110213867B discloses a multifunctional switch circuit, a switch switching method and a magnetic particle flaw detector, which simplifies the mechanical structure of the magnetic particle flaw detector to improve the waterproof ability of the magnetic particle flaw detector. However, kerosene is also used in the magnetic suspension commonly used in magnetic particle flaw detection. Kerosene has a certain solvent effect and will produce a swelling reaction with commonly used waterproof rubber materials such as silica gel. Swelling is the phenomenon that the volume of a polymer expands in a solvent, which will destroy the waterproof structure. In addition, organic solvents are sometimes used as cleaning agents to treat the flaw detection surface during magnetic particle flaw detection, which will also be contaminated with the magnetic yoke, causing damage to the sealant of the shell, debonding and other adverse effects. This is also one of the reasons for water ingress to the magnetic yoke. However, due to the limitations of the application of the magnetic yoke, the working switch needs to be together with the magnetic yoke to facilitate the use of the operator, which will inevitably come into contact with liquids such as water or kerosene. There is currently no reliable source of finished switches that are waterproof, oil-proof and organic solvent-proof, so the problem of the fragility of the magnetic yoke working switch has not been effectively solved. Summary of the invention

[0004] The purpose of the present invention is to provide a working switch detection circuit and a judgment method thereof applied to a magnetic particle flaw detector, so as to solve the problem of poor contact and short service life of the working switch due to water ingress in the prior art.

[0005] The present invention is achieved through the following technical solutions: A working switch detection circuit for a magnetic particle flaw detector includes a single-chip microcomputer U1, which controls the driving of a yoke coil. The single-chip microcomputer U1 and the yoke coil are both arranged inside a yoke probe. The single-chip microcomputer U1 is connected to a switch detection circuit, and the switch detection circuit includes a power chip U2. The power chip U2 is connected to a current limiting resistor R2. The current limiting resistor R2 is electrically connected to a working switch SW1 and a filter circuit respectively. The filter circuit is grounded, and the working switch SW1 is grounded; the filter circuit is connected to an AD acquisition module KEY_AD of the single-chip microcomputer U1.

[0006] Furthermore, the filtering circuit includes a filtering resistor R1 and a capacitor C1, one end of the filtering resistor R1 is electrically connected to the current limiting resistor R2, and the other end is electrically connected to the capacitor C1, the current limiting resistor R2 is also connected to the AD acquisition module KEY_AD of the single chip microcomputer U1, and the capacitor C1 is grounded.

[0007] Furthermore, a voltage stabilizing diode D1 is connected in parallel at both ends of the filter circuit. By adding the voltage stabilizing diode D1 to the filter circuit, voltage fluctuations can be effectively clamped to ensure the stability of the circuit operation. The voltage stabilizing diode D1 can be replaced by a TVS diode or an ESD diode.

[0008] Furthermore, the single chip microcomputer U1 is connected to a yoke driving power supply via a communication interface TX, and the yoke driving power supply controls the yoke coil to be energized.

[0009] A method for determining whether a working switch detection circuit of a magnetic particle flaw detector is turned on includes the following steps: S1, single chip computer U1 outputs detection signal KEY_V to power chip U2; S2, the power chip U2 outputs voltage VREF after receiving the detection signal KEY_V; S3, the AD acquisition module KEY_AD of the single-chip computer U1 detects the level KEY+ at the connection between the filter resistor R1 and the capacitor C1, and determines whether the ripple of the level KEY+ is stable, and then determines whether the switch is in a steady state; S4. Calculate the value of the working switch SW1 according to the steady-state level KEY+value, and then determine whether the working switch SW1 is closed.

[0010] Furthermore, in the step S4, if the value of the on-resistance R_KEY is within the valid range of the software setting parameters, the switch closure is deemed to be valid; if the value of the on-resistance R_KEY is outside the valid range of the software setting parameters, the working switch SW1 is deemed to be not closed.

[0011] Furthermore, when it is determined that the working switch SW1 is closed and valid, a start signal is sent to the yoke drive power supply through the communication interface TX, and the yoke drive power supply starts the magnetization work of the yoke coil; when it is determined that the working switch SW1 is not closed, a stop signal is sent to the yoke drive power supply through the communication interface TX, and the yoke drive power supply stops the magnetization work of the yoke coil.

[0012] Furthermore, it also includes a method for judging whether there is leakage inside the yoke probe. When KEY_V outputs a low level, the power chip U2 is turned off, and its output is in a high impedance state. The AD acquisition module KEY_AD continues to detect the level KEY+. If the level KEY+ is greater than the software setting parameter, it can be judged that the yoke coil is leaking. The single-chip computer U1 turns off the yoke drive power supply and issues an alarm. According to the level value of the level KEY+, it can be identified whether there is leakage.

[0013] Furthermore, it also includes a method for judging whether water has entered the yoke probe. When KEY_V outputs a low level, the power chip U2 is turned off, and its output is in a high impedance state. The AD acquisition module KEY_AD continues to detect the level KEY+, and judges whether water has entered according to the waveform of the level KEY+. Identification is performed according to the waveform of the level KEY+. The degree of water ingress and whether there is leakage can be judged. By processing the level KEY+ waveform recognition process, such as software filtering, the problem that low-voltage signals are susceptible to interference can be effectively solved.

[0014] Compared with the prior art, the present invention has the following beneficial effects: 1. The working switch is a consumable part, and the life of the switch affects the service life of the yoke to a certain extent. After the working switch ages, poor contact is prone to occur. This application converts the switch quantity into analog quantity for processing, uses the AD acquisition module KEY_AD to detect the switch state, and calculates the value of the on-resistance R_KEY to determine whether the switch is closed. This method can provide more accurate switch action identification, ensure the reliability of the working switch during magnetic particle inspection, and extend the actual service life of the switch.

[0015] 2. The working switch detection circuit of the present application can not only complete the switch detection work, but also judge whether the magnetic particle flaw detector has water ingress and leakage detection according to the waveform of the level KEY+ in the power-off state. When an abnormal situation is detected, the microcontroller U1 will promptly turn off the yoke drive power supply and sound an alarm, which not only protects the equipment itself, but also ensures the safety of the user. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is a circuit schematic diagram of the present invention; Figure 2 It is the level KEY+ simulation diagram of the present invention when the induced voltage normally exists; Figure 3 It is a level KEY+ simulation diagram when there is an induced voltage in the influent of the present invention; Figure 4 It is the KEY+ simulation diagram of the level when there is slight leakage in the present invention; Figure 5 It is a KEY+ simulation diagram of the level when there is severe leakage of the present invention. DETAILED DESCRIPTION

[0017] In order to enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention is clearly and completely described below in conjunction with the accompanying drawings of the present invention. Based on the embodiments in this application, other similar embodiments obtained by ordinary technicians in this field without making creative work should all fall within the scope of protection of this application. In addition, the directional words mentioned in the following embodiments, such as "up", "down", "left", "right", etc., are only reference to the directions of the accompanying drawings. Therefore, the directional words used are used to illustrate rather than limit the invention.

[0018] The present invention will be further described below in conjunction with the accompanying drawings.

[0019] Embodiment 1: A working switch detection circuit for a magnetic particle flaw detector, such as Figure 1As shown, it includes a single-chip microcomputer U1, which controls the yoke coil drive. The single-chip microcomputer U1 and the yoke coil are both arranged inside the yoke probe. The single-chip microcomputer U1 is connected to a switch detection circuit, and the switch detection circuit includes a power chip U2. The power chip U2 is connected to a current limiting resistor R2, and the current limiting resistor R2 is electrically connected to a working switch SW1 and a filter circuit respectively. The filter circuit is grounded, and the working switch SW1 is grounded; the filter circuit is connected to the AD acquisition module KEY_AD of the single-chip microcomputer U1.

[0020] The yoke flaw detector is generally used in a way that the magnetization stops after 1 to 3 seconds, and then the position of the yoke probe is adjusted before magnetization again. The working switch is frequently triggered. In magnetic particle flaw detection operations, the number of triggering times of the working switch can reach thousands of times per day. Even if a long-life working switch is used, aging is inevitable. Generally, the aging and damage of the switch is manifested by an increase in the on-resistance R_KEY. After the switch is closed, it cannot be effectively turned on and the switch fails. This application uses analog detection, and the microcontroller U1 can calculate the on-resistance R_KEY after the switch is closed. Even if the switch ages and the resistance value increases, the state of the switch can be identified, which can greatly increase the service life of the switch.

[0021] A method for determining whether a working switch detection circuit of a magnetic particle flaw detector is turned on includes the following steps: S1, single chip computer U1 outputs detection signal KEY_V to power chip U2; S2, the power chip U2 outputs voltage VREF after receiving the detection signal KEY_V; S3, the AD acquisition module KEY_AD of the single-chip computer U1 detects the level KEY+ at the connection between the filter resistor R1 and the capacitor C1, and determines whether the ripple of the level KEY+ is stable, and then determines whether the switch is in a steady state; S4. Calculate the on-resistance R_KEY value of the working switch SW1 according to the steady-state level KEY+ value, and then determine whether the working switch SW1 is closed. The single-chip microcomputer U1 calculates the on-resistance R_KEY of the working switch SW1 through the steady-state level KEY+, the input voltage VREF, and the resistance value of the current-limiting resistor R2. If the on-resistance R_KEY value is within the valid range of the software setting parameters, it is determined that the working switch is closed, and the enabling state of the working switch SW1 is sent to the host through the communication interface TX; if the on-resistance R_KEY value is outside the valid range of the software setting parameters, it is determined that the working switch is not closed, and the release state of the working switch is sent to the host through TX communication.

[0022] The detection signal KEY_V is the detection signal of the working switch SW1. It outputs a high level to start the power supply chip U2 only when the state of the working switch SW1 is detected. The output voltage VREF is loaded on the working switch SW1 through the current limiting resistor R2 to minimize the power-on time of the working switch. The voltage VREF is a fixed value, and its range is greater than 0V and less than 1.2V.

[0023] The working switch SW1 is not closed, and the voltage of KEY+ is greater than 0V. When the working switch SW1 is closed, there will be a certain on-resistance R_KEY. The actual detected level KEY+ is equivalent to the voltage divided by the on-resistance R_KEY and the current limiting resistor R2 in parallel with the filter resistor R1. The more serious the aging of the working switch SW1 is, the greater the resistance of the on-resistance R_KEY will be.

[0024] By performing an aging test on the existing switch in the yoke flaw detector, it is found that the contact resistance of a normal switch when closed is about 50mΩ. After aging, the switch contacts gradually increase to a few Ω to a few hundred Ω, but the contact resistance is basically stable each time it is closed. When the contact resistance is greater than 1kΩ, the contact resistance will change each time it is closed, and there will be an unstable state. Therefore, a certain margin can be left to select 500Ω as the upper limit of the parameter of the effective range of the switch on-resistance R_KEY.

[0025] Embodiment 2: A working switch detection circuit for a magnetic particle flaw detector, the filter circuit comprising a filter resistor R1 and a capacitor C1, one end of the filter resistor R1 being electrically connected to a current limiting resistor R2, and the other end being electrically connected to the capacitor C1, the current limiting resistor R2 being also connected to an AD acquisition module KEY_AD of a single-chip computer U1; a voltage-stabilizing diode D1 being connected in parallel to both ends of the filter circuit, by adding the voltage-stabilizing diode D1 to the filter circuit, the voltage fluctuation can be effectively clamped, thereby ensuring the stability of the circuit operation, the voltage-stabilizing diode D1 can be replaced by a TVS diode or an ESD diode; the single-chip computer U1 is connected to a yoke drive power supply via a communication interface TX, and the yoke drive power supply controls the energization of the yoke coil.

[0026] In step S4, if the value of the on-resistance R_KEY is within the valid range of the software setting parameters, the switch closure is deemed to be valid; if the value of the on-resistance R_KEY is outside the valid range of the software setting parameters, the working switch SW1 is deemed to be not closed. When the working switch SW1 is judged to be closed and valid, a start signal is sent to the yoke drive power supply through the communication interface TX, and the yoke drive power supply starts the magnetization work of the yoke coil; when the working switch SW1 is judged to be not closed, a stop signal is sent to the yoke drive power supply through the communication interface TX, and the yoke drive power supply stops the magnetization work of the yoke coil.

[0027] The method for judging whether there is leakage inside the yoke probe is that when KEY_V outputs a low level, the power chip U2 is turned off, and its output is in a high impedance state. The AD acquisition module KEY_AD continues to detect the level KEY+. If the level KEY+ is greater than the software setting parameter, it can be judged that the yoke coil is leaking. The microcontroller U1 turns off the yoke drive power supply and issues an alarm. According to the level value of the level KEY+, it can be identified to determine whether there is leakage.

[0028] The method for judging whether water has entered the yoke probe is that when KEY_V outputs a low level, the power chip U2 is turned off and its output is in a high impedance state. The AD acquisition module KEY_AD continues to detect the level KEY+ and judges whether water has entered based on the waveform of the level KEY+. Identify based on the waveform of the level KEY+. The degree of water ingress and whether there is leakage can be judged. By processing the level KEY+ waveform recognition process, such as software filtering, the problem of low-voltage signals being susceptible to interference can be effectively solved.

[0029] The rest is the same as Example 1.

[0030] The working switch SW1 is the position that is directly touched when the yoke flaw detector is held in hand, and its assembly structure will directly penetrate the yoke shell. It is the main water inlet point on the yoke flaw detector shell and is close to the yoke coil. Therefore, it is basically reasonable to perform leakage detection through the working switch line here.

[0031] Since it is an induced voltage, the waveform is always fluctuating. When there is no water inside the yoke, the level KEY+ has a low amplitude, such as Figure 2 When water enters the yoke housing, the induced voltage on the KEY+ level will also increase because the dielectric constant of water is higher than that of air. Figure 3 When the device has a slight leakage, the amplitude of the KEY+ level will be higher, as shown in Figure 4 As shown; when the device has a serious leakage, the amplitude of the level KEY+ is as follows Figure 5 As shown. The voltage waveform obtained by the specific single-chip microcomputer U1AD acquisition module KEY_AD is also related to the waveform of the yoke drive voltage and the parameters of the filter circuit. The lower the cutoff frequency of the filter circuit, the flatter the waveform tends to be. The peak value of the collected voltage waveform is related to the parameters of D1.

[0032] The present invention has been described in detail above. The above description is only a preferred embodiment of the present invention and should not limit the scope of implementation of the present invention. That is, all equivalent changes and modifications made within the scope of this application should still fall within the scope of the present invention.

Claims

1. A working switch detection circuit for a magnetic particle flaw detector, comprising a single chip microcomputer U1, the single chip microcomputer U1 controls the driving of a yoke coil, the single chip microcomputer U1 and the yoke coil are both arranged inside a yoke probe, and is characterized in that: The single-chip microcomputer U1 is connected to a switch detection circuit, which includes a power chip U2. The power chip U2 is connected to a current limiting resistor R2. The current limiting resistor R2 is electrically connected to a working switch SW1 and a filter circuit respectively. The working switch SW1 is grounded; the filter circuit is connected to an AD acquisition module KEY_AD of the single-chip microcomputer U1.

2. The working switch detection circuit for magnetic particle flaw detector according to claim 1 is characterized in that: The filter circuit includes a filter resistor R1 and a capacitor C1. One end of the filter resistor R1 is electrically connected to the current limiting resistor R2, and the other end is electrically connected to the capacitor C1. The current limiting resistor R2 is also connected to the AD acquisition module KEY_AD of the single chip microcomputer U1.

3. The working switch detection circuit for magnetic particle flaw detector according to claim 2 is characterized in that: A voltage stabilizing diode D1 is connected in parallel at both ends of the filter circuit.

4. The working switch detection circuit for magnetic particle flaw detector according to claim 1 is characterized in that: The single chip microcomputer U1 is connected to a yoke driving power supply via a communication interface TX, and the yoke driving power supply controls the yoke coil to be energized.

5. A judgment method for a working switch detection circuit of a magnetic particle flaw detector, characterized in that: Using the working switch detection circuit for magnetic particle flaw detector according to any one of claims 1 to 4, the method for judging whether the working switch SW1 is turned on includes the following steps: S1, single chip microcomputer U1 outputs detection signal KEY_V to power chip U2; S2, the power chip U2 outputs the voltage VREF after receiving the detection signal KEY_V; S3, the AD acquisition module KEY_AD of the single-chip computer U1 detects the level KEY+ at the connection between the filter resistor R1 and the capacitor C1, and determines whether the ripple of the level KEY+ is stable, and then determines whether the switch is in a steady state; S4. Calculate the on-resistance R_KEY value of the working switch SW1 according to the steady-state level KEY+ value, and then determine whether the working switch SW1 is closed.

6. The judgment method for the working switch detection circuit of the magnetic particle flaw detector according to claim 5 is characterized in that: In the step S4, if the value of the on-resistance R_KEY is within the valid range of the software setting parameters, the switch closure is deemed to be valid; if the value of the on-resistance R_KEY is outside the valid range of the software setting parameters, the working switch SW1 is deemed to be not closed.

7. The judgment method for the working switch detection circuit of the magnetic particle flaw detector according to claim 6 is characterized in that: When it is determined that the working switch SW1 is closed and valid, a start signal is sent to the yoke drive power supply through the communication interface TX, and the yoke drive power supply starts the magnetization work of the yoke coil; when it is determined that the working switch SW1 is not closed, a stop signal is sent to the yoke drive power supply through the communication interface TX, and the yoke drive power supply stops the magnetization work of the yoke coil.

8. The judgment method for the working switch detection circuit of the magnetic particle flaw detector according to claim 5 is characterized in that: It also includes a method for determining whether there is leakage inside the yoke probe. When KEY_V outputs a low level, the power chip U2 is turned off and its output is in a high-impedance state. The AD acquisition module KEY_AD continues to detect the level KEY+. If the level KEY+ is greater than the software setting parameters, it can be determined that the yoke coil is leaking. The microcontroller U1 turns off the yoke drive power supply and issues an alarm.

9. The judgment method for the working switch detection circuit of the magnetic particle flaw detector according to claim 8 is characterized in that: It also includes a method for determining whether water has entered the yoke probe. When KEY_V outputs a low level, the power chip U2 is turned off and its output is in a high-impedance state. The AD acquisition module KEY_AD continues to detect the level KEY+, and determines whether water has entered based on the waveform of the level KEY+.

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