Anti-polarization liquid level detection circuit

Abstract

The utility model discloses an anti-polarization liquid level detection circuit, and relates to the technical field of liquid level detection, the liquid level detection circuit comprises a control module, an interface module and an anti-polarization liquid level detection module, the control module is respectively connected with the interface module and the anti-polarization liquid level detection module, and the interface module is connected with the anti-polarization liquid level detection module. The control module achieves liquid level detection and prevents electrode polarization by controlling the potential direction and the power supply time of the electrode in the anti-polarization liquid level detection module, the polarization phenomenon caused by the fact that the electrode is in a single potential for a long time is effectively avoided, and the performance of the liquid level detection system is improved.

Description

TECHNICAL FIELD

[0001] The utility model relates to liquid level detection technical field, concretely is a liquid level detection circuit of polarization prevention. BACKGROUND

[0002] In many industries, such as household appliances, medical equipment and industrial control field, the accurate detection of liquid level is crucial, for example, in the water purifier industry, the liquid level of the water tank needs to be accurately monitored, so as to timely prompt the user to add water or automatically start the water replenishment program, and guarantee the continuous operation of the equipment; in the medical equipment field, the high and low of the liquid level in the reagent box is directly related to the accuracy and process of experiment or detection, and has a key influence on the result.

[0003] The traditional liquid level detection method mostly adopts the way of inserting metal probe into liquid, which is relatively common, but still has defects. In the detection process, the metal probe needs to be electrified, and with the passage of time, the electric charge is accumulated on the surface of the probe, thereby causing the polarization of the metal needle, which not only accelerates the corrosion of the metal probe itself and shortens its service life, but also leads to the instability of the detection system. For example, in the long-term use of water purifier, the polarization corrosion of the metal probe may cause the decrease of the liquid level detection accuracy, and the false alarm or the failure to timely detect the change of the liquid level; in the medical equipment, the polarization of the probe may interfere with the detection result and affect the accuracy of diagnosis. SUMMARY

[0004] The utility model aims at providing a liquid level detection circuit of polarization prevention to solve the problems in the above background.

[0005] In order to solve the above technical problems, the utility model provides the following technical scheme: a liquid level detection circuit of polarization prevention, the liquid level detection circuit includes control module, interface module and polarization prevention liquid level detection module, the control module is connected with interface module and polarization prevention liquid level detection module respectively, the control module realizes liquid level detection by controlling the potential direction and power supply time of the electrode in the polarization prevention liquid level detection module and prevents the polarization of the electrode.

[0006] The polarization prevention liquid level detection module includes resistance R1, resistance R2, resistance R3, resistance R4, resistance R5, resistance R6, resistance R7, power supply VCC, capacitor C1, capacitor C2, diode D1, diode D2, diode D3, bidirectional diode D4, triode Q1, triode Q3, field effect tube Q2, metal detection electrode PAD1, metal detection electrode PAD2;One end of resistance R2 is connected with control module, the other end of resistance R2 is connected with the grid of field effect tube Q2, one end of resistance R1 is connected with power supply VCC, the other end of resistance R1 is connected with the grid of field effect tube Q2, the drain of field effect tube Q2 is connected with power supply VCC;

[0007] The source of the field effect tube Q2 is connected with one end of the resistor R3, the other end of the resistor R3 is connected with the positive electrode of the capacitor C2, the negative electrode of the capacitor C2 is grounded, the anode of the diode D1 is connected with the other end of the resistor R3, the cathode of the diode D1 is connected with one end of the capacitor C1, the anode of the diode D2 is connected with one end of the capacitor C1, the cathode of the diode D2 is grounded, the other end of the C1 is connected with one end of the resistor R4, the other end of the resistor R4 is connected with the emitter of the transistor Q1, the transistor Q1 is an NPN type transistor, the collector of the transistor Q1 is connected with the power supply VCC, one end of the resistor R5 is connected with the base of the transistor Q1, the other end of the resistor R5 is connected with the control module, the transistor Q3 is a PNP type transistor, the emitter of the transistor Q3 is connected with the other end of the resistor R4, the collector of the transistor Q3 is grounded, one end of the resistor R5 is connected with the base of the transistor Q3.

[0008] One end of the resistor R6 is connected with the source of the field effect tube Q2, the other end of the resistor R6 is connected with the anode of the diode D3, the cathode of the diode D3 is connected with one end of the resistor R7, the other end of the resistor R7 is connected with the control module, the bidirectional diode D4 is formed by two reverse series connected zener diodes, one end of the bidirectional diode D4 is connected with the other end of the resistor R6, the other end of the bidirectional diode D4 is grounded, the metal detection electrode PAD1 is connected with the anode of the diode D3, the metal detection electrode PAD2 is connected with the other end of the bidirectional diode D4.

[0009] In the above scheme, according to the signal of the control module, the potential of the metal detection electrode PAD1 is alternately changed, in different working stages, the metal detection electrode PAD1 presents a positive voltage or a negative voltage state, which avoids the polarization of the electrode due to long-term at a single potential, prolongs the service life of the electrode; when the metal detection electrodes PAD1 and PAD2 are in contact with the liquid, the resistance between the electrodes will change, the circuit converts the resistance change into voltage change through resistance voltage division, and transmits the signal to the pin W_AD of the control module through the diode D3, realizing the conversion of liquid level information into electrical signal; the circuit part composed of the transistor Q1 and the transistor Q3 processes and amplifies the detected signal, enhances the strength and stability of the signal, so that the control module can more accurately detect the liquid level change; the bidirectional diode D4 is connected between the metal detection electrode PAD2 and the ground, when abnormal overvoltage appears on the electrode, the bidirectional diode D4 will be turned on, limiting the amplitude of the voltage, protecting other elements in the circuit from being damaged by overvoltage.

[0010] The control module includes a single-chip microcomputer U1 and a capacitor C3, a pin 1 of the single-chip microcomputer U1 is connected with a power supply VCC, a pin 3 of the single-chip microcomputer U1 is grounded, a positive electrode of the capacitor C3 is connected with the pin 1 of the single-chip microcomputer U1, a negative electrode of the capacitor C3 is connected with the pin 3 of the single-chip microcomputer U1, a pin SWCLK and a pin SWDIO of the single-chip microcomputer U1 are connected with an interface module, a pin W_SW of the single-chip microcomputer U1 is connected with one end of a resistor R2, a pin W_AD of the single-chip microcomputer U1 is connected with the other end of the resistor R7, and a pin W_SW2PWM of the single-chip microcomputer U1 is connected with the other end of a resistor R5.

[0011] In the above scheme, the single-chip microcomputer U1 is connected with the interface module through the pins SWCLK and SWDIO to realize communication with external equipment, so that the circuit can interact with a host computer or other systems for data, facilitating remote monitoring and control. The single-chip microcomputer U1 outputs a control signal to control the working state of the anti-polarization liquid level detection module, and outputs different level signals through the pin W_SW and the pin W_SW2PWM to alternately change the positive and negative voltage states of the metal detection electrode PAD1, effectively eliminating the polarization phenomenon of the electrode and ensuring the long-term stability and accuracy of the liquid level detection. In addition, the single-chip microcomputer U1 detects the voltage state through the pin W_AD to determine whether there is liquid contacting the metal detection electrode. When there is liquid contacting, the resistance between the electrodes changes, thereby causing a change in the voltage at the pin W_AD.

[0012] The interface module includes a connector CN1, a bidirectional diode D5 and a bidirectional diode D6, a pin 1 of the connector CN1 is connected with a power supply VCC, a pin 4 of the connector CN1 is grounded, a pin 2 of the connector CN1 is connected with a pin SWCLK of the single-chip microcomputer U1 in the control module, a pin 3 of the connector CN1 is connected with a pin SWDIO of the single-chip microcomputer U1 in the control module, the pin 2 of the connector CN1 is connected with one end of the bidirectional diode D5, the other end of the bidirectional diode D5 is grounded, the pin 3 of the connector CN1 is connected with one end of the bidirectional diode D6, and the other end of the bidirectional diode D6 is grounded.

[0013] In the above scheme, the connector CN1 provides a physical connection interface for the circuit and external equipment, which can conveniently access power supply, communication lines and the like; the bidirectional diode D5 and the bidirectional diode D6 are connected between the pin 2 and the pin 3 of the connector CN1 and the ground, respectively, to play a role in overvoltage protection. When an external signal appears abnormal overvoltage, the bidirectional diode will be turned on to introduce the overvoltage signal into the ground, preventing the single-chip microcomputer U1 in the control module from being damaged by excessively high voltage, and improving the anti-interference ability and reliability of the circuit.

[0014] Compared with the prior art, the utility model has the advantages of:

[0015] The utility model discloses a positive and negative pressure alternation mode is realized to prevent electrode polarization liquid level detection function, thereby avoid metal probe polarization easy to corrode short service life, system is not stable and so on problem, with low cost, high precision, strong reliability's characteristics can be applied to home appliance, medical treatment, industry and so on many fields. BRIEF DESCRIPTION OF DRAWINGS

[0016] The accompanying drawings are included to provide a further understanding of the present utility model, and constitute a part of the specification, and are used together with the embodiments of the present utility model to explain the present utility model, and do not constitute the limitation to the present utility model.In the drawings,

[0017] Figure 1 It is a kind of control module circuit diagram of the liquid level detection circuit of polarization prevention;

[0018] Figure 2 It is the interface module circuit diagram of the liquid level detection circuit of polarization prevention;

[0019] Figure 3 It is the polarization prevention liquid level detection module circuit diagram of the liquid level detection circuit of polarization prevention;

[0020] Figure 4 It is the application circuit diagram of the liquid level detection circuit of polarization prevention. DETAILED DESCRIPTION

[0021] The technical scheme in the embodiments of the present utility model will be clearly and completely described below in conjunction with the drawings in the embodiments of the present utility model, obviously, the described embodiments are only part of the embodiments of the present utility model, not all the embodiments.Based on the embodiments in the present utility model, all other embodiments obtained by the person skilled in the art without making creative labor are within the scope of the present utility model.

[0022] Please refer to Figures 1-4 The utility model provides technical scheme: a kind of liquid level detection circuit of polarization prevention, the liquid level detection circuit includes control module, interface module and polarization prevention liquid level detection module, the control module is connected with interface module and polarization prevention liquid level detection module respectively, the control module realizes liquid level detection by controlling the potential direction and power supply time of electrode in polarization prevention liquid level detection module and prevents electrode polarization.

[0023] The anti-polarization liquid level detection module includes resistors R1, R2, R3, R4, R5, R6, R7, a power supply VCC, capacitors C1 and C2, diodes D1, D2 and D3, a bidirectional diode D4, transistors Q1 and Q3, and a field effect transistor Q2, and metal detection electrodes PAD1 and PAD2; one end of the resistor R2 is connected to a control module, the other end of the resistor R2 is connected to the gate of the field effect transistor Q2, one end of the resistor R1 is connected to the power supply VCC, the other end of the resistor R1 is connected to the gate of the field effect transistor Q2, and the drain of the field effect transistor Q2 is connected to the power supply VCC;

[0024] The source of the field effect transistor Q2 is connected to one end of the resistor R3, the other end of the resistor R3 is connected to the positive electrode of the capacitor C2, the negative electrode of the capacitor C2 is grounded, the anode of the diode D1 is connected to the other end of the resistor R3, one end of the capacitor C1 is connected to the cathode of the diode D1, one end of the capacitor C1 is connected to the anode of the diode D2, the cathode of the diode D2 is grounded, the other end of the C1 is connected to one end of the resistor R4, the emitter of the transistor Q1 is connected to the other end of the resistor R4, the transistor Q1 is an NPN type transistor, the collector of the transistor Q1 is connected to the power supply VCC, one end of the resistor R5 is connected to the base of the transistor Q1, the other end of the resistor R5 is connected to the control module, the transistor Q3 is a PNP type transistor, the emitter of the transistor Q3 is connected to the other end of the resistor R4, the collector of the transistor Q3 is grounded, and one end of the resistor R5 is connected to the base of the transistor Q3.

[0025] One end of the resistor R6 is connected to the source of the field effect transistor Q2, the other end of the resistor R6 is connected to the anode of the diode D3, one end of the resistor R7 is connected to the cathode of the diode D3, the other end of the resistor R7 is connected to the control module, the bidirectional diode D4 is formed by two reverse series connected zener diodes, one end of the bidirectional diode D4 is connected to the other end of the resistor R6, the other end of the bidirectional diode D4 is grounded, the metal detection electrode PAD1 is connected to the anode of the diode D3, and the metal detection electrode PAD2 is connected to the other end of the bidirectional diode D4.

[0026] In the above scheme, the potential of the metal detection electrode PAD1 is alternately changed according to the signal of the control module, and the metal detection electrode PAD1 presents a positive voltage or a negative voltage state in different working stages, thereby avoiding polarization of the electrode due to long-term presence at a single potential and prolonging the service life of the electrode; when the metal detection electrodes PAD1 and PAD2 are in contact with the liquid, the resistance between the electrodes changes, the circuit converts the resistance change into a voltage change through resistance voltage division, and transmits the signal to the pin W_AD of the control module through the diode D3, thereby realizing conversion of the liquid level information into an electrical signal; the circuit part composed of the triode Q1 and the triode Q3 processes and amplifies the detected signal, thereby enhancing the strength and stability of the signal and enabling the control module to more accurately detect the liquid level change; the bidirectional diode D4 is connected between the metal detection electrode PAD2 and the ground, and when an abnormal overvoltage appears on the electrode, the bidirectional diode D4 will be turned on to limit the amplitude of the voltage and protect other elements in the circuit from being damaged by overvoltage.

[0027] The control module comprises a single-chip microcomputer U1 and a capacitor C3, the pin 1 of the single-chip microcomputer U1 is connected with a power supply VCC, the pin 3 of the single-chip microcomputer U1 is grounded, the positive electrode of the capacitor C3 is connected with the pin 1 of the single-chip microcomputer U1, the negative electrode of the capacitor C3 is connected with the pin 3 of the single-chip microcomputer U1, the pin SWCLK and the pin SWDIO of the single-chip microcomputer U1 are connected with an interface module, the pin W_SW of the single-chip microcomputer U1 is connected with one end of a resistor R2, the pin W_AD of the single-chip microcomputer U1 is connected with the other end of a resistor R7, and the pin W_SW2PWM of the single-chip microcomputer U1 is connected with the other end of a resistor R5.

[0028] In the above scheme, the single-chip microcomputer U1 is connected with the interface module through the pins SWCLK and SWDIO, communication with external devices is realized, the circuit can interact with the upper computer or other systems, and remote monitoring and control are facilitated. The single-chip microcomputer U1 outputs a control signal to control the working state of the anti-polarization liquid level detection module, different level signals are output through the pin W_SW and the pin W_SW2PWM, the positive and negative voltage states of the metal detection electrode PAD1 are alternately changed, the polarization phenomenon of the electrode is effectively eliminated, and the long-term stability and accuracy of the liquid level detection are ensured; in addition, the single-chip microcomputer U1 detects the voltage state through the pin W_AD to determine whether the metal detection electrode is in contact with the liquid, when the metal detection electrode is in contact with the liquid, the resistance between the electrodes changes, and the voltage at the pin W_AD changes.

[0029] The interface module comprises a connector CN1, a bidirectional diode D5 and a bidirectional diode D6, a pin 1 of the connector CN1 is connected with a power supply VCC, a pin 4 of the connector CN1 is grounded, a pin 2 of the connector CN1 is connected with a pin SWCLK of a single-chip microcomputer U1 in the control module, a pin 3 of the connector CN1 is connected with a pin SWDIO of the single-chip microcomputer U1 in the control module, the pin 2 of the connector CN1 is connected with one end of the bidirectional diode D5, the other end of the bidirectional diode D5 is grounded, the pin 3 of the connector CN1 is connected with one end of the bidirectional diode D6, and the other end of the bidirectional diode D6 is grounded.

[0030] In the above scheme, the connector CN1 provides a physical connection interface for the circuit and external devices, and can conveniently access the power supply, communication lines and the like; the bidirectional diode D5 and the bidirectional diode D6 are connected between the pin 2 and the pin 3 of the connector CN1 and the ground, respectively, and play a role of overvoltage protection; when an external signal appears abnormal overvoltage, the bidirectional diode will be turned on to introduce the overvoltage signal into the ground, thereby preventing the single-chip microcomputer U1 in the control module from being damaged by excessively high voltage, and improving the anti-interference ability and reliability of the circuit.

[0031] Working principle of the utility model:

[0032] In the utility model, the model of field effect tube Q2 is AO2301, the model of diode D1, diode D2 and diode D3 is BAT54WS, the model of triode Q1 is S8050 of NPN type triode, the model of triode Q3 is S8550 of PNP type triode, the model of bidirectional diode D4 is ESDA0603-05, the model of bidirectional diode D5 and bidirectional diode D6 is ESDA0402-05, the model of single-chip microcomputer U1 is PY32T020, the model of connector CN1 is DIP-2.54-4P, and the parameters of relevant resistance and capacitor are as follows: resistance R1 (100K-5%), resistance R2 (1K-5%), resistance R3 (10K-1%), resistance R4 (5.1R-1%), resistance R5 (1K-5%), resistance R6 (300K-1%), resistance R7 (100R-5%), capacitor C1 (100nF-10%-50V), capacitor C2 (1uF-10%-16V).

[0033] Step one: control module outputs control signal, sets the output level of pin W_SW2PWM to low level, sets the output level of pin W_SW to low level, opens diode D1, at this time, power supply starts to power the whole detection circuit, and the circuit enters the preparation detection state; after opening diode D1, sets the delay time to 10ms, and the purpose is to make the circuit reach the stable state and ensure the accuracy of subsequent voltage detection.

[0034] Step two: the anti-polarization liquid level detection module is connected with the single-chip microcomputer U1 in the control module through the pin W_AD, at this time, the voltage at the pin W_AD is obtained by dividing the resistance Rx between the resistance R6 and the two metal detection electrodes (PAD1 and PAD2), and then subtracting the voltage between the two ends of the diode D3; if there is no liquid contacting the electrode, the voltage value is VCC-0.2V; if there is liquid contacting, the conductivity of the liquid will make the Rx resistance value smaller, and the voltage value is VCC*Rx / (R6+Rx)-0.2V, when the voltage is detected, the delay time is set to 1ms;

[0035] Step three: the output level of the pin W_SW is set to high level, the diode D1 is turned off, the output level of the pin W_SW2PWM is set to PWM mode, and a PWM signal with a frequency of more than 1Mhz is output, at this time, the metal detection electrode PAD1 is in a negative voltage state, in order to prevent the pin W_AD from becoming negative voltage and causing damage to the single-chip microcomputer U1, a diode D3 is connected in series in the circuit, due to the unidirectional conductivity of the diode, when the pin W_AD may appear negative voltage, the diode D3 is cut off, preventing the negative voltage signal from entering the single-chip microcomputer; the delay time is set to 10ms to ensure that the negative voltage state of the metal detection electrode PAD1 can effectively eliminate the polarization phenomenon that may be generated in the previous positive voltage state;

[0036] Step four: the output level of the pin W_SW is set to high level, the output level of the pin W_SW2PWM is set to low level, the metal detection electrode PAD1 is not powered on and is in a power-off state, and the delay time is set according to the actual polling time.

[0037] Step five: the above steps one to four are repeated, and the liquid level detection is continuously cycled to monitor the change of the liquid level in real time.

[0038] Finally, it should be noted that the above is only the preferred embodiment of the present application and is not intended to limit the present application, although the present application has been described in detail with reference to the foregoing embodiments, for those skilled in the art, the technical solutions recorded in the foregoing embodiments can be modified, or some technical features can be replaced. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A polarization-resistant liquid level detection circuit, characterized in that: The liquid level detection circuit includes a control module, an interface module, and an anti-polarization liquid level detection module. The control module is connected to both the interface module and the anti-polarization liquid level detection module. The control module detects the liquid level and prevents electrode polarization by controlling the potential direction and power supply time of the electrodes in the anti-polarization liquid level detection module.

2. The anti-polarization liquid level detection circuit according to claim 1, characterized in that: The anti-polarization liquid level detection module includes resistors R1, R2, R3, R4, R5, R6, and R7, a power supply VCC, capacitors C1 and C2, diodes D1, D2, D3, a bidirectional diode D4, transistors Q1 and Q3, a field-effect transistor Q2, and metal detection electrodes PAD1 and PAD2. One end of resistor R2 is connected to the control module, and the other end of resistor R2 is connected to the gate of field-effect transistor Q2. One end of resistor R1 is connected to the power supply VCC, and the other end of resistor R1 is connected to the gate of field-effect transistor Q2. The drain of field-effect transistor Q2 is connected to the power supply VCC.

3. The anti-polarization liquid level detection circuit according to claim 2, characterized in that: The source of the field-effect transistor Q2 is connected to one end of resistor R3, and the other end of resistor R3 is connected to the positive terminal of capacitor C2. The negative terminal of capacitor C2 is grounded. The anode of diode D1 is connected to the other end of resistor R3, and the cathode of diode D1 is connected to one end of capacitor C1. The anode of diode D2 is connected to one end of capacitor C1, and the cathode of diode D2 is grounded. The other end of C1 is connected to one end of resistor R4, and the other end of resistor R4 is connected to the emitter of transistor Q1. Transistor Q1 is an NPN transistor. The collector of transistor Q1 is connected to power supply VCC. The base of transistor Q1 is connected to one end of resistor R5, and the other end of resistor R5 is connected to the control module. Transistor Q3 is a PNP transistor. The emitter of transistor Q3 is connected to the other end of resistor R4, the collector of transistor Q3 is grounded, and the base of transistor Q3 is connected to one end of resistor R5.

4. The anti-polarization liquid level detection circuit according to claim 2, characterized in that: One end of resistor R6 is connected to the source of field-effect transistor Q2, and the other end of resistor R6 is connected to the anode of diode D3. The cathode of diode D3 is connected to one end of resistor R7, and the other end of resistor R7 is connected to the control module. Bidirectional diode D4 is formed by two Zener diodes connected in reverse series. One end of bidirectional diode D4 is connected to the other end of resistor R6, and the other end of bidirectional diode D4 is grounded. Metal detection electrode PAD1 is connected to the anode of diode D3, and metal detection electrode PAD2 is connected to the other end of bidirectional diode D4.

5. The anti-polarization liquid level detection circuit according to claim 1, characterized in that: The control module includes a microcontroller U1 and a capacitor C3. Pin 1 of the microcontroller U1 is connected to the power supply VCC, and pin 3 of the microcontroller U1 is grounded. The positive terminal of the capacitor C3 is connected to pin 1 of the microcontroller U1, and the negative terminal of the capacitor C3 is connected to pin 3 of the microcontroller U1. Pins SWCLK and SWDIO of the microcontroller U1 are connected to the interface module. Pin W_SW of the microcontroller U1 is connected to one end of resistor R2, pin W_AD of the microcontroller U1 is connected to the other end of resistor R7, and pin W_SW2PWM of the microcontroller U1 is connected to the other end of resistor R5.

6. The anti-polarization liquid level detection circuit according to claim 1, characterized in that: The interface module includes connector CN1, bidirectional diode D5, and bidirectional diode D6. Pin 1 of connector CN1 is connected to power supply VCC, pin 4 of connector CN1 is grounded, pin 2 of connector CN1 is connected to pin SWCLK of microcontroller U1 in the control module, pin 3 of connector CN1 is connected to pin SWDIO of microcontroller U1 in the control module, pin 2 of connector CN1 is connected to one end of bidirectional diode D5, and the other end of bidirectional diode D5 is grounded, and pin 3 of connector CN1 is connected to one end of bidirectional diode D6, and the other end of bidirectional diode D6 is grounded.

7. The anti-polarization liquid level detection circuit according to claim 5, characterized in that: In the control module, the microcontroller U1 outputs a control signal to eliminate polarization by alternately changing the positive and negative voltage states of the electrodes in the anti-polarization liquid level detection module, and determines whether there is liquid contact by detecting the voltage state at the W_AD pin.

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