Household appliance water shortage detection circuit and household appliance using same

Abstract

The utility model particularly relates to a household electrical appliance water shortage detection circuit and a household electrical appliance, and the circuit comprises an electrode sensor circuit which is composed of a first electrode E1 and a second electrode E2 which are insulated from each other, and is used for collecting a first AD turn-off value and a second AD turn-on value; the MCU chip is used for being connected to the electrode sensor module and used for calculating the difference value between the first AD turn-off value and the second AD turn-on value, comparing the difference value with a preset threshold value and outputting a water shortage state signal according to a comparison result; and the water pump control circuit is connected with the MCU chip and controls the working state of the water pump M1 according to the electric signal output by the MCU chip. Compared with a traditional detection scheme, the circuit has the advantages that the cost is reduced and the structure is extremely simple; besides, difference judgment between water outlet detection and non-water outlet detection is more reliable than fixed AD value judgment, and the fixed value judgment may cause misjudgment due to different water quality AD values, so that the detection stability can be improved.

Description

TECHNICAL FIELD

[0001] The utility model relates to the technical field of water dispenser or ice maker, specifically a domestic appliance water shortage detection circuit and the domestic appliance of application of this circuit. BACKGROUND

[0002] With the global science and technology progress and innovation at an unprecedented speed, in the field of household appliances, the importance of water shortage detection technology is increasingly prominent, and it has been widely studied and applied in academic and industrial circles. From traditional water dispenser or ice maker, water shortage detection function is the key factor to ensure normal operation of equipment, prolong service life and ensure user safety and convenience.

[0003] At present, there are many water shortage detection technologies on the market. These technologies meet the needs of some household appliances to some extent, but there are still many problems to be solved in terms of cost and stability. For example, some high-end optical detection technology can provide more accurate detection results, but due to the need to use high-precision optical elements and complex signal processing circuit, the cost is high, making the product expensive, limiting its popularization and application in the low-end household appliance market. While the traditional electrode detection method, although the cost is relatively low, the electrode is immersed in water for a long time, which is easily affected by impurities and ions in water, corrosion and electrochemical effect, resulting in reduced electrode life, poor detection stability, frequent misjudgment or failure, which brings many inconveniences to users, and also affects the brand image and market competitiveness of household appliances. The specific problems existing in the prior art are: one cost problem: in the existing water shortage detection technology, some technologies use expensive sensors, chips or special materials, which greatly increases the cost of the entire detection system. For example, the water shortage detection technology based on ultrasonic detection principle, the ultrasonic sensor itself is relatively high in price, and in order to ensure the accuracy of detection, a high-precision signal processing module and a complex algorithm are also needed, which further increases the cost of the system. For some price-sensitive household appliance products, the high detection cost makes the product lack of price competitiveness in the market, and it is difficult to popularize on a large scale. In addition, two stability problems: traditional detection methods have obvious shortcomings in stability. In addition to the short service life of the electrode type detection method mentioned above, some detection methods based on mechanical principles are also easily affected by external environmental factors. For example, the float ball type water level detection device may be stuck by impurities in the water during use, resulting in inaccurate detection results; and with the increase of use time, the wear of mechanical parts will also affect the stability of detection. In addition, some technologies using capacitive detection principle are easily disturbed by surrounding environmental humidity, temperature and other factors, resulting in large fluctuation of detection signal, affecting the accuracy and reliability of detection. SUMMARY

[0004] The utility model aims at at least solving one of prior art technical problems. For this reason, one purpose of the utility model lies in providing a domestic appliance water shortage detection circuit and a domestic appliance applying the circuit, which can provide a low-cost, high-stability detection scheme to meet the market demand of fierce competition of domestic appliances.

[0005] According to the utility model domestic appliance water shortage detection circuit, including following.

[0006] The electrode sensor circuit is composed of the first electrode E1 and the second electrode E2 which are insulated from each other, and is used for collecting the first AD closing value when the water pump M1 is closed and the second AD opening value when the water pump is opened.

[0007] The MCU chip is used for connecting to the electrode sensor module for calculating the difference between the first AD closing value and the second AD opening value and comparing with the preset threshold value, and outputting a water shortage state signal according to the comparison result.

[0008] The water pump control circuit is connected with the MCU chip, and controls the working state of the water pump M1 according to the output electric signal of the MCU chip.

[0009] Further, the alarm and the digital display tube are connected to the MCU chip respectively.

[0010] Further, the electrode sensor circuit is further provided with the first resistor R1, the second resistor R2, the first capacitor C1 and the +5V terminal, the first resistor R1 is connected with the first electrode E1, the common terminal between the first resistor R1 and the first electrode E1 is connected with the second resistor R2 and the first capacitor C1 respectively, the first capacitor C1 is connected with the second electrode E2, and the second resistor R2 is connected with the +5V terminal.

[0011] Further, the water pump control circuit further includes the field effect tube Q1, the third resistor R3 and the fourth resistor R4, the water pump M1 is connected with the D pole of the field effect tube Q1, the G pole of the field effect tube Q1 is connected with the third resistor R3, the common terminal between the G pole of the field effect tube Q1 and the third resistor R3 is connected with one end of the fourth resistor R4, and the other end of the fourth resistor R4 is connected with the S pole of the field effect tube Q1.

[0012] Further, one end of the water pump M1 is connected with the 12V terminal.

[0013] The utility model further discloses a domestic appliance applying the above-mentioned domestic appliance water shortage detection circuit, which comprises a first water tank, a second water tank, a water pump M1, a conveying pipe and the domestic appliance water shortage detection circuit, the domestic appliance water shortage detection circuit is fixed on one side of the first water tank, the second water tank or the conveying pipe, both ends of the conveying pipe are respectively arranged in the first water tank and the second water tank, and the water pump M1 is installed on the conveying pipe.

[0014] Further, the material of the first electrode E1 and the second electrode E2 on the electrode sensor circuit is food-grade stainless steel, and only in the water delivery stage of the delivery pipe, the first electrode E1 and the second electrode E2 are in contact with water.

[0015] Further, one end of the delivery pipe penetrates the inner wall of the first water tank, and the other end of the delivery pipe is connected to the inner wall of the first water tank through a sealing ring.

[0016] The beneficial effects of the utility model are as follows: compared with the traditional detection scheme, the circuit can reduce the cost and has a simple structure; in addition, by fully utilizing the water adding characteristics of the household appliance, the electrode is placed at the water outlet, the contact time with water is greatly reduced, and the service life of the first electrode E1 and the second electrode E2 is increased; furthermore, the difference between the water delivery detection and the non-water delivery detection is used for judgment, which is more reliable than the fixed AD value judgment, the fixed value judgment may be misjudged due to different AD values of different water qualities, and the detection stability can be improved. BRIEF DESCRIPTION OF DRAWINGS

[0017] The above and / or additional aspects and advantages of the utility model will become apparent and more readily appreciated from the following description of the embodiments, with reference to the following drawings.

[0018] Figure 1 is the circuit diagram of the utility model.

[0019] Figure 2 is the connection diagram of the MCU chip, the alarm and the digital display tube of the utility model.

[0020] Figure 3 is the structural diagram of the utility model.

[0021] Figure 4 is the detection process flow chart of the utility model. DETAILED DESCRIPTION

[0022] The embodiments of the utility model will be described in detail below, and examples of the embodiments are shown in the drawings, wherein the same or similar reference numerals represent the same or similar elements or elements with the same or similar functions throughout. The embodiments described below by referring to the drawings are exemplary and are only used to explain the utility model, and cannot be understood as a limitation of the utility model.

[0023] The following will be described with reference to Figures 1 to 2 The water shortage detection circuit of the household appliance according to the embodiments of the utility model includes the following.

[0024] The electrode sensor circuit is composed of the first electrode E1 and the second electrode E2 which are insulated from each other, and is used for collecting the first AD closing value when the water pump M1 is closed and the second AD opening value when the water pump is opened.

[0025] MCU chip, for connecting to the electrode sensor module for calculating the difference between the first AD closed value and the second AD open value and comparing with the preset threshold value, outputting the water shortage state signal according to the comparison result.

[0026] Water pump control circuit, the water pump control circuit is connected with the MCU chip, and controls the working state of the water pump M1 according to the output electric signal of the MCU chip.

[0027] Compared with the traditional detection scheme, the circuit plays a role in reducing cost and extremely simple structure; in addition, the difference between the water detection and the non-water detection is used for judgment, which is more reliable than the fixed AD value judgment, and the fixed value judgment may be misjudged due to different water quality AD values, which can improve the detection stability.

[0028] The circuit further comprises an alarm and a digital display tube, which are respectively connected to the MCU chip. The electrode sensor circuit of the circuit further comprises a first resistor R1, a second resistor R2, a first capacitor C1 and a +5V terminal, the first resistor R1 is connected with the first electrode E1, the common terminal between the first resistor R1 and the first electrode E1 is connected with the second resistor R2 and the first capacitor C1 respectively, the first capacitor C1 is connected with the second electrode E2, and the second resistor R2 is connected with the +5V terminal. The AD detection circuit of the circuit further comprises a field effect tube Q1, a third resistor R3 and a fourth resistor R4, the water pump M1 is connected with the D pole of the field effect tube Q1, the G pole of the field effect tube Q1 is connected with the third resistor R3, the common terminal between the G pole of the field effect tube Q1 and the third resistor R3 is connected with one end of the fourth resistor R4, and the other end of the fourth resistor R4 is connected with the S pole of the field effect tube Q1. One end of the water pump M1 is connected with a 12V terminal.

[0029] The circuit is designed to detect the working state of the water pump M1, and collects the AD value through the electrode sensor circuit, and realizes the water pump control, the water shortage state detection and the alarm through the logical judgment of the MCU chip. The working principle and detailed description are as follows.

[0030] Working principle of the electrode sensor circuit.

[0031] The electrode sensor circuit is composed of the first electrode E1 and the second electrode E2 which are insulated from each other, and the AD value is collected by detecting the conductivity change in water. The specific process is as follows.

[0032] First AD closed value collection: when the water pump M1 is closed, the electrode sensor circuit detects the water state (no water flow) and collects the first AD closed value.

[0033] Second AD open value collection: when the water pump M1 is opened, the electrode sensor circuit detects the water flow state and collects the second AD open value.

[0034] Difference calculation: The MCU chip calculates the difference between the first AD closing value and the second AD opening value, and compares it with a preset threshold value. The change in the difference reflects the change in the water flow state, avoiding the problem of misjudgment of the fixed AD value caused by different water quality.

[0035] A first resistor R1, a second resistor R2, a first capacitor C1 and a +5V terminal are also provided in the electrode sensor circuit to stabilize the working voltage of the circuit and improve the detection accuracy.

[0036] The MCU chip is the core control unit of the circuit, and its main functions include: difference comparison: comparing the calculated AD difference (second AD opening value - first AD closing value) with a preset threshold value. Water shortage state judgment: if the difference is less than the preset threshold value, it indicates that the water pump M1 may be in a water shortage state, and the MCU chip outputs a water shortage state signal. Control signal output: according to the judgment result, the MCU chip outputs corresponding control signals to the water pump control circuit to adjust the working state of the water pump M1.

[0037] Working principle of the water pump control circuit: The water pump control circuit is connected with the MCU chip, and controls the opening or closing of the water pump M1 according to the output signal of the MCU chip. The specific process is as follows: Control of the field effect tube Q1: The G pole of the field effect tube Q1 is connected with the MCU chip through the third resistor R3 and the fourth resistor R4. When the MCU chip outputs a high level signal, the field effect tube Q1 is turned on, and the water pump M1 is opened. When the MCU chip outputs a low level signal, the field effect tube Q1 is cut off, and the water pump M1 is closed. In addition, 12V power supply: one end of the water pump M1 is connected with the 12V terminal to provide stable working voltage.

[0038] Alarm and display function: The circuit also includes an alarm and a digital display tube, which are connected with the MCU chip respectively: alarm: when the MCU chip detects a water shortage state, the alarm is triggered to send an alarm signal to remind the user to handle it in time. Digital display tube: real-time display of the working state of the water pump M1 (such as normal, water shortage, etc.), which is convenient for the user to monitor.

[0039] As shown in Figure 3 The utility model discloses a household appliance of the above-mentioned household appliance water shortage detection circuit, including first water tank 1 and second water tank 3, water pump M1, delivery pipe 2 and household appliance water shortage detection circuit, household appliance water shortage detection circuit is fixed in the one side place of first water tank 1, second water tank 3 or delivery pipe 2, and the both ends of delivery pipe 2 are placed in first water tank 1 and second water tank 3 respectively, and water pump M1 is installed on delivery pipe 2.

[0040] The structure fully utilizes the water adding characteristics of household appliances, places the electrodes at the water outlet, greatly reduces the contact time ratio of water, and increases the service life of the first electrode E1 and the second electrode E2; in addition, the first water tank 1 and the second water tank 3 are plastic water tanks or metal water tanks. The conveying pipe 2 is a plastic conveying pipe or a metal conveying pipe, which is freely selected by the user.

[0041] The material of the first electrode E1 and the second electrode E2 on the electrode sensor circuit of the structure is food-grade stainless steel, and only contacts water during the water delivery stage of the conveying pipe 2. One end of the conveying pipe 2 penetrates the inner wall of the first water tank 1, and the other end of the conveying pipe 2 is connected to the inner wall of the first water tank 1 through a sealing ring.

[0042] The first electrode E1 is an M3 stainless steel screw with a diameter of 0.5 mm, and the second electrode E2 adopts a spiral winding process to form a three-turn ring structure. The spacing between the first electrode E1 and the second electrode E2 is designed to be 2 mm ± 0.1 mm, the contact area ratio is 1:3, and the linear response relationship R = p d / (S k) (k = 0.95) is satisfied.

[0043] The resistance value of the first resistor R1 in the water pump control circuit is 1MΩ, the resistance value of the second resistor R2 is R2 is 470kΩ, and the capacity of the first capacitor C1 is 0.1μF. The first resistor R1, the second resistor R2 and the first capacitor C1 constitute a second-order low-pass filter, which converts the conductivity change between the first electrode E1 and the second electrode E2 of 0.1-10μS into a 0-5V measurable signal, and eliminates high-frequency interference errors.

[0044] Dynamic difference algorithm: adopt double sampling mechanism, get the reference value AD_off (theoretical value 4095) when the pump body M1 is closed, and get the AD_on value when the pump body works. Through ΔAD = |AD_off-AD_on|, the environmental temperature drift (temperature coefficient ≤±0.05% / ℃) is eliminated.

[0045] The adaptive threshold model realizes the weighted history data through the forgetting factor α = 0.85, and establishes the dynamic correction equation T(n) = 0.85T(n-1) + 0.15[ΔAD(n)-σ(n)] combined with the sliding standard deviation σ(n), which effectively tracks the slow changes of water quality.

[0046] In addition, the working mode of the combination of the first electrode E1 and the second electrode E2 is innovative: one, contact time control: by installing the electrode 5mm downstream of the water outlet electromagnetic valve, the daily contact time of the electrode is reduced from 100% in the traditional scheme to 8.3% (according to 5 minutes of water output per hour), and the theoretical service life is increased by 12 times. Two, material compatibility design: select 316L food-grade stainless steel, the corrosion rate is ≤0.002mm / year in pH6-8 water quality environment, cooperate with epoxy resin sealing structure, and reach IP67 protection level.

[0047] Open circuit detection of fault diagnosis mechanism: electrode failure alarm is triggered when AD_off < 3800 (corresponding resistance > 50MΩ): short circuit detection: electrode adhesion failure is judged when ΔAD continues < 50 (threshold value corresponding resistance < 100Ω).

[0048] As Figure 4 The utility model discloses a water shortage detection method of water shortage detection circuit of household appliance, comprising the following steps.

[0049] Step one: water pump is closed and is detected: the water pump M1 is closed through the MCU chip control, and the electrode sensor circuit gathers the first AD closing value at this moment, and the AD value gathered needs to carry out the filtering processing.

[0050] Water pump is opened and is detected: the electrode sensor circuit gathers the second AD opening value after the MCU chip control water pump M1 discharges.

[0051] Step two: difference calculation: the difference of the first AD closing value and the second AD opening value is calculated through the MCU chip in the water discharge stage of water pump M1.

[0052] Water shortage judgment: the difference obtained is compared with the preset threshold value.

[0053] State feedback: when judging as water shortage, the MCU chip exports water shortage state signal, and the water pump control circuit controls the water pump M1 to stop working according to the signal, simultaneously, the alarm connected to the MCU chip sends the alarm, and the digital display tube shows the water shortage state, reminds the user to handle in time.

[0054] Specific further, in the step two, if the difference is greater than the threshold value, judge as having water, and the water pump works normally, if the difference is lower than the threshold value, judge as water shortage.

[0055] The first electrode E1 and the second electrode E2 on the electrode sensor circuit need to adopt food-grade stainless steel material, and only contact water in the water discharge stage of the conveying pipe 2. Install the electrode, ensure that the water flow can contact two electrodes simultaneously when the water pump discharges, and simultaneously fix the water shortage detection circuit of household appliance on one side of the first water tank 1, the second water tank 3 or the conveying pipe 2. The two ends of the conveying pipe 2 are respectively arranged in the first water tank 1 and the second water tank 3, one end of the conveying pipe 2 penetrates the inner wall of the first water tank 1, and the end and the inner wall of the first water tank 1 are connected through a sealing ring, and the water pump M1 is installed on the conveying pipe 2.

[0056] Circuit connection check: check the connection between electrode sensor circuit and MCU chip, ensure that the first AD closed value and the second AD open value can be normally collected. At the same time, check the connection between water pump control circuit and MCU chip, ensure that the working state of water pump M1 can be controlled according to the MCU output electric signal. Also, confirm whether the connection between the alarm and the digital display tube and the MCU chip is normal.

[0057] The working mechanism of the electrode is as follows.

[0058] When water flows through the electrode, water forms an equivalent resistance R as a conductive medium. According to Maxwell's electromagnetic field theory, the electrode spacing d and the contact area S satisfy: R = p·d / (S·k), where p is the water conductivity, and k is the electrode material coefficient. When stainless steel material is used, k = 0.93-0.97, which ensures linear response.

[0059] The AD detection logic is as follows.

[0060] In the absence of water, the resistance between the electrodes is →∞, and AD(off)≈Vcc; when there is water, a voltage divider circuit is formed, and AD(on)=Vcc·R1 / (R1+R2), where R1 is a fixed sampling resistor, and R2 is the water resistance. The temperature drift effect is eliminated by the difference ΔAD.

[0061] The dynamic threshold is calculated as follows.

[0062] Establish an adaptive model: T(n) = α·T(n-1) + (1-α)·[ΔAD(n) - σ(n)], where α=0.85 is the forgetting factor, and σ(n) is the standard deviation of the last m samples, which realizes the tracking of slow changes in water quality.

[0063] The embodiment takes a water dispenser as an example.

[0064] M3 stainless steel screw is used as the first electrode E1, and a 0.5mm diameter stainless steel wire is wound 3 turns of spiral as the second electrode E2, which is installed 5mm downstream of the water outlet solenoid valve.

[0065] Circuit parameters: sampling frequency 10Hz, filter window 20 cycles, and the initial value of the water shortage determination threshold is set to 300 (corresponding to 12-bit AD value).

[0066] In addition, the implementation example and parameter configuration take the water dispenser application as an example.

[0067] I. Installation parameters: the distance between the first electrode E1 and the delivery pipe 2 from the water outlet is 5mm±0.5mm, and the water flow velocity is 1.2m / s to form a stable liquid film contact.

[0068] II. Circuit parameters: sampling frequency: 10 Hz (satisfies liquid film formation time constant τ = 0.1 s); filter window: 20-period moving average (corresponding to 2 seconds of valid sampling); initial threshold: 300 (corresponding to conductivity 150 μS / cm); calibration procedure: perform dry / wet cycle detection when first powered on, automatically calculate the reference ΔAD range.

[0069] Although the embodiments of the present application have been shown and described, those skilled in the art can understand that various changes, modifications, replacements and variations can be made to these embodiments without departing from the principles and purposes of the present application, and the scope of the present application is defined by the claims and their equivalents.

Claims

1. A water shortage detection circuit for a domestic appliance, characterized in that: It comprises: an electrode sensor circuit composed of a first electrode E1 and a second electrode E2 insulated from each other, for collecting a first AD closed value when the water pump M1 is closed and a second AD open value when the water pump is opened; an MCU chip connected to the electrode sensor circuit, for calculating the difference between the first AD closed value and the second AD open value and comparing it with a preset threshold value, and outputting a water shortage state signal according to the comparison result; a water pump control circuit connected to the MCU chip and controlling the working state of the water pump M1 according to the output electrical signal of the MCU chip.

2. The water shortage detection circuit for a household electrical appliance according to claim 1, characterized in that: It also comprises an alarm and a digital display tube, which are respectively connected to the MCU chip.

3. The water shortage detection circuit for a household appliance according to claim 1, characterized in that: The electrode sensor circuit is further provided with a first resistor R1, a second resistor R2, a first capacitor C1 and a +5V terminal, the first resistor R1 is connected to the first electrode E1, the common terminal between the first resistor R1 and the first electrode E1 is connected to the second resistor R2 and the first capacitor C1 respectively, the first capacitor C1 is connected to the second electrode E2, and the second resistor R2 is connected to the +5V terminal.

4. The water shortage detection circuit for a household appliance according to claim 1, characterized in that: The water pump control circuit comprises a field effect transistor Q1, a third resistor R3 and a fourth resistor R4, the water pump M1 is connected to the D terminal of the field effect transistor Q1, the G terminal of the field effect transistor Q1 is connected to the third resistor R3, the common terminal between the G terminal of the field effect transistor Q1 and the third resistor R3 is connected to one end of the fourth resistor R4, and the other end of the fourth resistor R4 is connected to the S terminal of the field effect transistor Q1.

5. The water shortage detection circuit for a household electrical appliance according to claim 4, characterized in that: One end of the water pump M1 is connected to a 12V terminal.

6. A household appliance applying the water deficiency detection circuit of any one of claims 1 to 5, characterized by: It comprises a first water tank (1) and a second water tank (3), a water pump M1, a conveying pipe (2) and a household appliance water shortage detection circuit, the household appliance water shortage detection circuit is fixed to one side of the first water tank (1), the second water tank (3) or the conveying pipe (2), both ends of the conveying pipe (2) are respectively placed in the first water tank (1) and the second water tank (3), and the water pump M1 is installed on the conveying pipe (2).

7. The domestic appliance according to claim 6, characterized in that: The materials of the first electrode E1 and the second electrode E2 on the electrode sensor circuit are food-grade stainless steel, and only in the water delivery stage of the conveying pipe (2) are they in contact with water.

8. The domestic appliance according to claim 6, characterized in that: One end of the conveying pipe (2) penetrates through the inner wall of the first water tank (1), and the one end of the conveying pipe (2) and the inner wall of the first water tank (1) are connected through a sealing ring.

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