Water level detection device and method

Abstract

The application discloses a water level detection device and method, relates to the technical field of water level detection, and solves the technical problem that the existing capacitive water level detection device is greatly influenced by metal and human body and has great limitation on the distance between the capacitive sensor and the container. The device comprises a PCB board, a touch chip, a first capacitive sensing disc and a second capacitive sensing disc; the first capacitive sensing disc is used for detecting the capacitive value change caused by the change of external environment; the second capacitive sensing disc is used for detecting the capacitive value change caused by the change of water level; the touch chip and the first capacitive sensing disc are fixedly connected to the front surface of the PCB board respectively; the second capacitive sensing disc is fixedly connected to the back surface of the PCB board; and the first capacitive sensing disc and the second capacitive sensing disc are electrically connected to the touch chip. The application reduces the detection error caused by environmental change, isolates the influence of the external metal and human body, widens the distance of the air detection, and reduces the requirement on the thickness of the outer wall of the container using the water level detection device.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of water level detection, in particular to a water level detection device and method. BACKGROUND

[0002] Water level detection function is widely used in water dispenser, water purifier, coffee machine, kettle, dishwasher and other related household appliances and electronic products, the traditional water level detection method has electrode type, reed type, pressure type and capacitance type, these detection methods have advantages and disadvantages. For the capacitance type water level detection method, it can be closely attached to the outer wall of the container to realize the detection of the water level, without the need to increase the detection device in the detected liquid, without pollution to the liquid, and without the influence of the color and corrosion of the liquid, with obvious advantages. The capacitance type water level detection is generally composed of a self-capacitance touch chip and a capacitance sensor. The sensor can use copper foil on the PCB to design corresponding patterns, and these patterns are connected to the capacitance detection channel of the touch chip. When the system starts working, the touch chip first reads the capacitance to ground of each channel, which serves as the reference capacitance for water level detection. Then the touch chip starts to scan the capacitance value of each touch channel at a fixed time. If the detected capacitance value is not much different from the reference capacitance value, it is considered that the water level has not changed; when the difference exceeds the pre-set threshold value, it is judged that the corresponding water level is reached.

[0003] Although the capacitance type water level detection realizes the detection of the water level in the air, has simple structure, is convenient to use, and has no pollution, etc., it also has some disadvantages. First, the air capacitance value caused by the change of the water level is very small, so the capacitance detection sensitivity of the touch chip is required to be very high, and high sensitivity means that it is easier to introduce interference signals. Second, the capacitance to ground of the capacitance sensor is affected by many factors. When there is metal, the human body is close, or the temperature, humidity and voltage change, the capacitance to ground of the capacitance sensor will change significantly, sometimes even greater than the capacitance change caused by the change of the water level. For the traditional capacitance type water level detection device, the influence of the temperature, humidity and voltage of the environment can be corrected by certain auxiliary algorithm. However, the change of the capacitance caused by the approach of the metal or the human body to the touch detection channel is the same as the change caused by the change of the water level, and the touch chip cannot distinguish the capacitance data changes caused by the two situations, so the threshold value of the water level detection must be increased to make the capacitance value detected by the change of the water level as far as possible greater than the capacitance value caused by the approach of the metal or the human body.

[0004] In the process of implementing the present application, the inventors found that there are at least the following problems in the prior art:

[0005] The existing capacitance type water level detection device is seriously affected by the approach of the metal and the human body, and has great limitation on the distance between the capacitance sensor and the container. SUMMARY

[0006] The application aims to provide a water level detection device and method to solve the technical problem that the capacitive water level detection device is seriously affected by metal and human body proximity and has a great limitation on the distance between the capacitive sensor and the container in the prior art.

[0007] To achieve the above object, the application provides the following technical solutions.

[0008] The application provides a water level detection device, which comprises a PCB board, a touch chip, a first capacitive sensing disc and a second capacitive sensing disc.

[0009] Preferably, the internal circuit of the touch chip comprises a switch SW1, a switch SW2, a switch SW3, a switch SW4, a first operational amplifier, a second operational amplifier, a first analog-to-digital converter and a second analog-to-digital converter.

[0010] Preferably, one end of the switch SW2 is connected between the switch SW1 and the first capacitive sensing disc, and the other end is grounded.

[0011] Preferably, one end of the switch SW4 is connected between the switch SW3 and the second capacitive sensing disc, and the other end is grounded.

[0012] Preferably, the pin 13 of the touch chip is connected to the first capacitive sensing disc, and the pin 12 is connected to the second capacitive sensing disc.

[0013] Preferably, the capacitive channel wiring of the first capacitive sensing disc and the second capacitive sensing disc is the same, the channel pattern is completely symmetrical, and the size is the same.

[0014] Preferably, the PCB is provided with a front surface with components and a back surface without components; the back surface of the PCB is attached to the outer wall of the liquid container for detecting the change of water level, and the front surface is used for detecting the change of capacitance caused by external interference and isolating external interference.

[0015] A water level detection method for detecting the water level of the water level detection device, comprising:

[0016] S1, obtaining a reference value when the container is empty and the external environment is not interfered;

[0017] S2, obtaining a first capacitance change value, a second capacitance change value and a third capacitance change value respectively when detecting the water level;

[0018] S3, correcting the first capacitance change value according to the second capacitance change value and the third capacitance change value;

[0019] S4, subtracting the corrected first capacitance change value from the reference value; if the difference is greater than a preset threshold value, it is determined that the water level reaches the water level value corresponding to the threshold; otherwise, it is determined that the water level does not reach the water level value corresponding to the threshold.

[0020] Preferably, the internal circuit of the touch chip includes switches SW1, SW2, SW3 and SW4.

[0021] Close the switches SW1 and SW3, and open the switches SW2 and SW4 to obtain the reference value and the first capacitance change value; close the switches SW2 and SW3, and open the switches SW1 and SW4 to obtain the second capacitance change value; close the switches SW1 and SW4, and open the switches SW2 and SW3 to obtain the third capacitance change value.

[0022] Preferably, the reference value, the first capacitance change value, the second capacitance change value and the third capacitance change value are all the differences between the capacitance values detected by the first capacitance sensing disc and the second capacitance sensing disc; the first capacitance sensing disc and the second capacitance sensing disc detect simultaneously in the touch chip.

[0023] Implementing one of the technical solutions in the above-mentioned technical solutions of the present application has the following advantages or beneficial effects:

[0024] The present application changes the design method of the traditional capacitance sensor, not only reduces the detection error introduced by the change of the external environment (such as temperature, humidity, voltage, etc.), but also isolates the influence of the external metal and the human body close to it. Further, it reduces the requirement for the size of the capacitance value caused by the change of water level, widens the distance of the detection in the air, and reduces the requirement for the thickness of the outer wall of the container using the water level detection device. Attached Figure Description

[0025] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying 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. In the drawings:

[0026] Figure 1 This is a first-view structural schematic diagram of the water level detection device according to an embodiment of the present invention;

[0027] Figure 2 This is a second-view structural schematic diagram of the water level detection device according to an embodiment of the present invention;

[0028] Figure 3 This is a circuit diagram of the internal circuit of the touch chip of the water level detection device according to an embodiment of the present invention;

[0029] Figure 4 This is a pin diagram of the touch chip of the water level detection device according to an embodiment of the present invention;

[0030] Figure 5 This is a flowchart of the water level detection method according to an embodiment of the present invention;

[0031] In the diagram: 1. PCB board; 2. First capacitive sensing disk; 3. Second capacitive sensing disk. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of the present invention clearer, various exemplary embodiments described below will be referenced to the accompanying drawings, which form part of the exemplary embodiments, illustrating various exemplary embodiments that may be used to implement the present invention. Unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this disclosure. It should be understood that they are merely examples of processes, methods, and apparatuses consistent with some aspects of the present invention disclosed as detailed in the appended claims, and other embodiments may be used, or structural and functional modifications may be made to the embodiments listed herein without departing from the scope and spirit of the present invention.

[0033] In the description of the present application, it should be understood that the terms "center", "longitudinal", "transverse" and the like indicate the orientation or positional relationship based on the drawings shown, only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the elements referred to must have a particular orientation, be constructed and operated in a particular orientation. The terms "first", "second" and the like are only for the purpose of description, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. The term "a plurality of" means two or more. The terms "connected", "connected" should be broadly understood, for example, it can be fixed connection, detachable connection, integral connection, mechanical connection, electrical connection, communication connection, direct connection, indirect connection through intermediate medium, it can be the internal communication of two elements or the interaction relationship of two elements. The term "and / or" includes any and all combinations of one or more related listed items. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0034] In order to illustrate the technical solutions described in the present application, the following will be described by specific examples, only showing the part related to the embodiment of the present application.

[0035] Example one:

[0036] As Figures 1-2 shown, the present application provides a water level detection device, comprising: a PCB board 1, a touch chip U, a first capacitive sensing disc 2 and a second capacitive sensing disc 3; the first capacitive sensing disc 2 is used for detecting the change of the capacitance value caused by the change of the external environment; the second capacitive sensing disc 3 is used for detecting the change of the capacitance value caused by the change of the water level; the touch chip U and the first capacitive sensing disc 2 are respectively fixedly connected to the front surface of the PCB board 1; the second capacitive sensing disc 3 is fixedly connected to the back surface of the PCB board 1; the first capacitive sensing disc 2 and the second capacitive sensing disc 3 are respectively electrically connected with the touch chip U. The touch chip used in this embodiment can make two touch channels detect the ground capacitance of the capacitive sensing disc on the front and back surfaces of the PCB board at the same time, not only reducing the error caused by the change of the external environment (such as temperature, humidity, voltage, etc.) to the water level detection, but also isolating the influence caused by the proximity of the external metal and human body, widening the distance of the air detection.

[0037] As an alternative embodiment, as Figures 3-4As shown, the internal circuit of the touch chip U includes: switches SW1, SW2, SW3, SW4, a first operational amplifier CA1, a second operational amplifier CA2, a first analog-to-digital converter ADC1, and a second analog-to-digital converter ADC2; the input end of the first operational amplifier CA1 is connected to the first capacitive sensing plate S1 through the switch SW1, and the output end is connected to the input end of the first analog-to-digital converter ADC1; the input end of the second operational amplifier CA2 is connected to the second capacitive sensing plate S2 through the switch SW3, and the output end is connected to the input end of the second analog-to-digital converter ADC2. One end of the switch SW2 is connected between the switch SW1 and the first capacitive sensing plate 2, and the other end is grounded; one end of the switch SW4 is connected between the switch SW3 and the second capacitive sensing plate 3, and the other end is grounded. The pin 13 of the touch chip U is connected to the first capacitive sensing plate 2, and the pin 12 is connected to the second capacitive sensing plate 3. The capacitive channel wiring of the first capacitive sensing plate 2 and the second capacitive sensing plate 3 is the same, the channel pattern is completely symmetrical, and the size is the same. The positions and capacitive channel wirings of the first capacitive sensing plate 2 and the second capacitive sensing plate 3 are completely coincident on the front and back surfaces of the PCB 1. This design makes the direction consistent and the size similar of the ground capacitance change on the two touch channels when the external environment changes, thereby reducing the error caused by the external environment. The surface of the PCB 1 on which the elements are arranged is the front surface, and the surface without elements is the back surface; the back surface of the PCB 1 is attached to the outer wall of the liquid container, which is used for detecting the change of the water level, and the front surface is used for auxiliary detection, which is used for detecting the capacitive change caused by the external interference such as the proximity of metal or human body, and isolating the interference from the outside.

[0038] The embodiment changes the design of the traditional capacitive sensor, not only reduces the detection error introduced by the change of the external environment, but also isolates the influence of the proximity of the external metal and human body, thereby reducing the requirement of the size of the capacitive value caused by the change of the water level, widening the distance of the capacitive detection, and reducing the requirement of the thickness of the outer wall of the container for using the water level detection device. The traditional capacitive water level detection device must be closely attached to the outer wall of the liquid container, and the distance of the capacitive detection from the liquid must not exceed 2 mm, while the distance of the capacitive detection from the liquid of the water level detection device of the embodiment can be 7 mm or more, which greatly reduces the requirement of the thickness of the outer wall of the container.

[0039] The embodiment is only a specific example, and does not mean that the present application is in this way.

[0040] Embodiment two:

[0041] The difference between the second embodiment and the first embodiment is that Figure 5 As shown, a water level detection method is used for water level detection of the water level detection device, which includes:

[0042] S1, obtaining a reference value under the condition that the container is empty and the external environment is not interfered;

[0043] S2, obtaining a first capacitance change value, a second capacitance change value and a third capacitance change value respectively when detecting the water level;

[0044] S3, correcting the first capacitance change value according to the second capacitance change value and the third capacitance change value;

[0045] S4, obtaining a difference between the corrected first capacitance change value and a reference value; if the difference is greater than a preset threshold value, determining that the water level reaches a water level value corresponding to the threshold; otherwise, determining that the water level does not reach the water level value corresponding to the threshold.

[0046] As an optional embodiment, the internal circuit of the touch chip U includes switches SW1, SW2, SW3 and SW4; closing the switches SW1 and SW3 and opening the switches SW2 and SW4, the reference value and the first capacitance change value can be obtained by testing; closing the switches SW2 and SW3 and opening the switches SW1 and SW4, the second capacitance change value can be obtained by testing; closing the switches SW1 and SW4 and opening the switches SW2 and SW3, the third capacitance change value can be obtained by testing. The reference value, the first capacitance change value, the second capacitance change value and the third capacitance change value are all differences between the capacitance values detected by the first capacitance sensing disc 2 and the second capacitance sensing disc 3; the first capacitance sensing disc 2 and the second capacitance sensing disc 3 detect simultaneously in the touch chip U. The first capacitance sensing disc 2 and the second capacitance sensing disc 3 detect the capacitance to ground at the same time, which can ensure that the influence of environmental changes (temperature, humidity, voltage, etc.) or other interference (such as power supply common mode interference) on the two capacitance sensing discs is the same, so that the data detected by the two capacitance sensing discs is disturbed by the same factors, and then using the difference algorithm can eliminate this disturbance.

[0047] With a water level detection point as an example, the detection method of the embodiment is described. In advance, in the case that the container is free of water and the outside is free of interference (such as no metal and human body close to etc.), the switch SW1 and the switch SW3 are closed, the switch SW2 and the switch SW4 are disconnected, and the ground capacitance values of the two ends of the first capacitive sensor 2 and the second capacitive sensor 3 are sampled as Data_S1 and Data_S2 respectively, the scanning waveforms, frequencies and voltage amplitudes of the two ends are completely consistent, the influence of the capacitance change caused by the environment (temperature, humidity, voltage, etc.) change on the sampling of the two ends is the same, and the difference Diff0 = Data_S2-Data_S1 of the two can eliminate the environmental influence, and the difference Diff0 is the obtained reference value. After obtaining the reference value Diff0, the water level detection can be performed. In the detection process (there can be liquid and metal, human body close to etc.), the switch SW1 and the switch SW3 are closed, the switch SW2 and the switch SW4 are disconnected, and the first capacitance change value Diff1 is obtained by testing; then the switch SW2 and the switch SW3 are closed, the switch SW1 and the switch SW4 are disconnected, the ground capacitance value of the second capacitive sensor 3 is sampled, the first capacitive sensor 2 is grounded, and the influence of the external interference change such as metal or human body close to on the second capacitive sensor 3 is isolated, and the second capacitance change value Diff2 obtained at this time only reflects the capacitance change caused by the water level; finally, the switch SW1 and the switch SW4 are closed, the switch SW2 and the switch SW3 are disconnected, the ground capacitance of the first capacitive sensor 2 is sampled, the second capacitive sensor 3 is grounded, and the influence of the water level change on the first capacitive sensor 2 is isolated, and the third capacitance change value Diff3 obtained at this time only reflects the capacitance change caused by the external interference; then the second capacitance change value Diff2 and the third capacitance change value Diff3 are used to correct the first capacitance change value Diff1, and assuming that the preset threshold value is 1000, if Diff1-Diff0>1000, it indicates that the water level reaches the position corresponding to the threshold value, otherwise it does not reach. With the change of the water level, the first capacitance change value Diff1 is constantly detected and updated, and each time the first capacitance change value Diff1 is updated, it is compared with the reference value Diff0, so that the real-time detection of the water level is realized.

[0048] As shown in Table 1, it is the capacitance change of the capacitive sensor at different distances from the water when filled with water. It can be seen that with the increase of the distance, the capacitance change value for detecting the water level change rapidly becomes small, and when the distance is 7mm, the data of the water and the no water only differs by 600. In the traditional water level detection, the capacitance test data caused by the temperature difference change is close to 500, the data change caused by the voltage change is more than 1000, and the data change caused by the metal or human body close to is greater, which is more than 2000 when the distance is 5mm. Therefore, the traditional method of closely adhering to the outer wall of the container (the thickness of the outer wall of the container is less than 2mm) can meet the reliability of the water level detection under various conditions.

[0049]

[0050] Table 1 Influence of distance between capacitive sensing plate and container on capacitive change value

[0051] As shown in Table 2-3, as the temperature increases, the temperature influence is reduced by subtracting the capacitive values of the two capacitive sensing plates, and the influence of temperature change can be controlled within 100 capacitive changes, which is significantly better than the traditional water level testing method.

[0052]

[0053] Table 2 Influence of temperature on capacitive change value in traditional water level testing method

[0054]

[0055] Table 3 Influence of temperature on capacitive change value in water level testing method of the present embodiment As shown in Table 4, as the voltage increases, the difference algorithm of the two capacitive sensing plates can offset the interference on the capacitive test data caused by the voltage change.

[0056]

[0057] Table 4 Influence of supply voltage on capacitive change value

[0058] As shown in Table 5, as the external metal approaches, due to the isolation effect of the first capacitive sensing plate 2, the influence on the second capacitive sensing plate 3 (detecting water channel) is very small when the external metal approaches at different distances, and the maximum influence is about 150 changes, while the traditional testing method cannot distinguish the interference of the external metal or human body approaching.

[0059]

[0060]

[0061] Table 5 Influence of external metal approaching on capacitive change value

[0062] As shown in Table 6, when the capacitive sensing plate is 7mm away from the container outer wall, the water level change data tested can be seen, and as the water level increases, the influence on the first capacitive sensing plate 2 (detecting external interference channel) is relatively small, and the maximum influence change is about 350, which is more easily to judge that the data change is caused by water level change. The difference between the full water level of the first capacitive sensing plate 2 and the second capacitive sensing plate is about 1800, which can be used to judge the water level change after eliminating environmental interference.

[0063]

[0064] Table 6 Influence of water level on capacitive change value

[0065] The application method of the embodiment can not only offset the interference of the external environment, but also eliminate the common-mode interference of the power supply by detecting the earth capacitances of different induction discs and a difference algorithm. By correcting the detected capacitance change value, the influence of the proximity of metal and human bodies is excluded, and more accurate water level change data is obtained.

[0066] The above only describes the preferred embodiments of the present application, and those skilled in the art know that various changes or equivalent replacements can be made to the features and embodiments without departing from the spirit and scope of the present application. In addition, the features and embodiments can be modified to adapt to specific conditions and materials under the guidance of the present application without departing from the spirit and scope of the present application. Therefore, the present application is not limited by the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of the present application are within the protection scope of the present application.

Claims

1. A water level detecting device characterized by comprising: It comprises: PCB board, touch chip, first capacitive sensing disc and second capacitive sensing disc; the first capacitive sensing disc is used for detecting the change of the capacitance value caused by the change of the external environment; the second capacitive sensing disc is used for detecting the change of the capacitance value caused by the change of the water level; the touch chip and the first capacitive sensing disc are fixedly connected to the front surface of the PCB board respectively; and the second capacitive sensing disc is fixedly connected to the back surface of the PCB board; The first capacitive sensing disc and the second capacitive sensing disc are electrically connected to the touch chip respectively; The internal circuit of the touch chip comprises: switches SW1, SW2, SW3, SW4, a first operational amplifier, a second operational amplifier, a first analog-digital converter and a second analog-digital converter; The input end of the first operational amplifier is connected to the first capacitive sensing disc through the switch SW1, and the output end is connected to the input end of the first analog-digital converter; the input end of the second operational amplifier is connected to the second capacitive sensing disc through the switch SW3, and the output end is connected to the input end of the second analog-digital converter; the surface of the PCB board on which the elements are arranged is the front surface, and the surface of the PCB board on which no element is arranged is the back surface; the back surface of the PCB board is attached to the outer wall of the liquid container, and is used for detecting the change of the water level; the front surface is used for detecting the change of the capacitance caused by the external interference, and isolating the external interference.

2. The water level detecting device according to claim 1, wherein One end of the switch SW2 is connected between the switch SW1 and the first capacitive sensing disc, and the other end is grounded; one end of the switch SW4 is connected between the switch SW3 and the second capacitive sensing disc, and the other end is grounded.

3. The water level detecting device according to claim 1, wherein The pin 13 of the touch chip is connected to the first capacitive sensing disc, and the pin 12 is connected to the second capacitive sensing disc.

4. The water level detecting device according to claim 1, wherein The capacitance channel wiring of the first capacitive sensing disc and the second capacitive sensing disc is the same, the channel pattern is completely symmetrical, and the size is the same.

5. The water level detecting device according to claim 4, wherein The positions of the first capacitive sensing disc and the second capacitive sensing disc and the capacitance channel wiring completely coincide on the front and back surfaces of the PCB board.

6. A water level detecting method characterized by comprising: The water level detection of the water level detection device of any one of claims 1-5 comprises: S1, obtaining a reference value under the condition that there is no water in the container and no external interference; S2, obtaining a first capacitance change value, a second capacitance change value and a third capacitance change value respectively during water level detection; S3, correcting the first capacitance change value according to the second capacitance change value and the third capacitance change value; S4, obtaining a difference value between the corrected first capacitance change value and the reference value; if the difference value is greater than a preset threshold value, it is judged that the water level reaches the water level value corresponding to the threshold value; otherwise, it is judged that the water level does not reach the water level value corresponding to the threshold value.

7. The water level detection method according to claim 6, wherein The internal circuit of the touch chip comprises switches SW1, SW2, SW3 and SW4; The reference value and the first capacitance change value can be obtained by closing the switches SW1 and SW3 and opening the switches SW2 and SW4; The second capacitance change value can be obtained by closing the switches SW2 and SW3 and opening the switches SW1 and SW4; Close the switch SW1 and the switch SW4, open the switch SW2 and the switch SW3, and test the third capacitance change value.

8. The water level detection method of claim 6, wherein, The reference value, the first capacitance change value, the second capacitance change value and the third capacitance change value are all differences between capacitance values detected by the first capacitance sensing disc and the second capacitance sensing disc; the first capacitance sensing disc and the second capacitance sensing disc simultaneously detect inside the touch chip.

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