Low power water immersion detection circuit

Abstract

The utility model relates to a kind of low-power water immersion detection circuit, including power end POWER, power end POWER is connected with the one end of resistance R1, the one end of resistance R4 and the one end of capacitor C2 respectively;The other end of resistance R1 is connected with the emitter of triode Q1;The collector of triode Q1 is connected with signal output end TEST_IO, and the positive pole of capacitor C1 and diode D1 is connected with.The negative pole of diode D1 is connected with the one end of resistance R2, the other end of resistance R2 is connected with the one end of capacitor C2, and the other end of capacitor C2 is connected with ground GND1 after water immersion probe;The other end of capacitor C2 and the other end of resistance R4 are connected with ground GND1 after being connected, and capacitor C2 and resistance R4 constitute RC charging network;The one end of triode Q1 is connected with the one end of resistance R3, and the other end of resistance R3 is connected with signal output end TEST_IO, and the other end of water immersion probe is connected with ground GND2.Can avoid the false triggering or missing trigger caused by external interference.Overcurrent can be quickly cut off in the abnormality such as probe short circuit, capacitor breakdown, to protect core component from being damaged.

Description

Technical Field

[0001] This utility model relates to a detection circuit, and more particularly to a low-power water immersion detection circuit. Background Technology

[0002] Water immersion detection technology is a key technology for ensuring the safety of equipment in scenarios such as communication base stations, underground pipe networks, and precision equipment rooms. Among them, electrode-based water immersion detection has become one of the most widely used solutions due to its intuitive principle and controllable cost. Its core is to trigger a detection signal by detecting the change in resistance when the electrode comes into contact with water, thereby realizing early warning of water accumulation or leakage. The electrode-based water immersion detection circuit and water immersion sensor disclosed in the prior art convert and amplify the PWM signal through the first and second electrode signal input units, and realize the water immersion detection technology in conjunction with the comparison unit and signal output unit. It has the characteristics of high detection accuracy and strong anti-interference ability, and is suitable for complex environments such as outdoor charging piles. However, this solution relies on PWM signal processing circuit and multi-stage amplification module, and the overall structure is relatively complex. It has not been specifically optimized for the ultra-low power consumption requirements of battery-powered scenarios, and the standby power consumption is difficult to meet the needs of long-term use without external power supply.

[0003] Meanwhile, there is another type of water immersion sensor that uses a basic alarm circuit built with ordinary discrete components. It achieves cost control by simplifying the circuit structure, but it does not perform power consumption adaptation design on the parameters of key components such as resistors and capacitors. Its standby current is still in the milliampere level, which cannot meet the low power consumption requirements of "microampere level" in battery-powered scenarios. It has poor applicability in scenarios such as remote outdoor monitoring points where it is inconvenient to frequently change batteries.

[0004] From the current technological status quo, the requirements of "low power consumption, high reliability, and simplified structure" for water immersion detection circuits in battery-powered scenarios have not been fully met: on the one hand, existing solutions either rely on complex signal processing modules, resulting in excessive power consumption, or rely on main control chips, increasing cost and complexity, making it difficult to balance "low power consumption" and "low cost"; on the other hand, most solutions do not consider power consumption optimization under continuous water immersion conditions, and the circuit is prone to high power consumption operation under continuous water immersion, shortening battery life; in addition, some solutions lack adaptation design for different external chip IO pins, and the detection signal pulse duration is fixed, making it incompatible with different models of external interrupt detection modules.

[0005] In view of the above-mentioned shortcomings, the designer actively researched and innovated in order to create a low-power water immersion detection circuit, making it more valuable for industrial applications. Utility Model Content

[0006] To solve the above-mentioned technical problems, the purpose of this utility model is to provide a low-power water immersion detection circuit.

[0007] This utility model discloses a low-power water immersion detection circuit, including a power supply terminal POWER, and further comprising a PNP transistor Q1, resistors R1, R2, R3, and R4, capacitors C1 and C2, a diode D1, a water immersion probe, and a signal output terminal TEST_IO. The power supply terminal POWER is connected to one end of resistor R1, one end of resistor R4, and one end of capacitor C2. The power supply terminal POWER is also connected to one end of resistor R1, one end of resistor R4, and the emitter of transistor Q1. The other end of resistor R1 is connected to the base of transistor Q1. The collector of transistor Q1 is connected to the signal output terminal TEST_IO. The base of transistor Q1 is connected to one end of capacitor C1, and the other end of capacitor C1 is connected to the anode of diode D1. The cathode of diode D1 is connected to one end of resistor R2, and the other end of resistor R2 is connected to one end of capacitor C2. The other end of capacitor C2 is grounded to GND1 through a water immersion probe. The other end of capacitor C2 and the other end of resistor R4 are connected together and then grounded to GND1 through a water immersion probe, and capacitor C2 and resistor R4 form an RC charging network. One end of transistor Q1 is connected to one end of resistor R3, and the other end of resistor R3 is connected to the signal output terminal TEST_IO. One end of the water immersion probe is connected to one end of C2 and one end of R4, and the other end is grounded to GND2. The resistance values ​​of resistors R1, R3, and R4 are 1MΩ-20MΩ, the capacitance value of capacitor C1 is 0.5μF-1μF, the capacitance value of capacitor C2 is 0.8μF-2μF, and the capacitance value of capacitor C1 is less than the capacitance value of capacitor C2.

[0008] Furthermore, in the aforementioned low-power water immersion detection circuit, the resistor R1 is 2.2MΩ, the resistor R3 is 1MΩ, the resistor R4 is 10MΩ, the capacitor C1 has a capacitance of 0.68μF, and the capacitor C2 has a capacitance of 1μF.

[0009] Furthermore, in the aforementioned low-power water immersion detection circuit, diode D1 is a 1N4148 silicon diode with a forward voltage drop of 0.5V-0.7V.

[0010] Furthermore, in the aforementioned low-power water immersion detection circuit, the water immersion probe is an electrode-type water immersion sensor with an equivalent resistance of 0-100KΩ when immersed in water, and is disconnected when open-circuited, and the installed probe is equipped with stainless steel electrodes.

[0011] Furthermore, in the aforementioned low-power water immersion detection circuit, the signal output terminal TEST_IO is connected in parallel with a filter capacitor C3, the capacitance of which is 0.01μF-1μF, and the filter capacitor C3 is a multilayer ceramic capacitor (MLCC).

[0012] Further, in the above low-power water immersion detection circuit, the power terminal POWER, triode Q1, resistor R1, resistor R2, resistor R3, resistor R4, capacitor C1, capacitor C2 and diode D1 are all welded on a PCB circuit board, and the water immersion probe is connected to the PCB circuit board through a wire.

[0013] Further, in the above low-power water immersion detection circuit, the triode Q1 is an S8550 PNP triode, and the packaging structure is SOT-23.

[0014] Further, in the above low-power water immersion detection circuit, the power supply voltage of the power terminal POWER is 3V-5V direct current voltage, and a patch fuse with a fusing current of 50mA is connected in series between the power terminal POWER and the resistor R1.

[0015] Still further, in the above low-power water immersion detection circuit, the resistor R1, resistor R2, resistor R3 and resistor R4 are all metal film resistors.

[0016] By means of the above solution, the present utility model has at least the following advantages: 1. The circuit limits the standby current by selecting 1MΩ-20MΩ megohm-level resistors, and combines the capacitance ratio of "capacitance C1 < C2" to ensure complete discharge after water immersion triggering. In a continuous water immersion state, the triode Q1 is turned off and the circuit returns to low power consumption, and the overall standby power consumption is controlled at the level of several microamps. This design is perfectly adapted to battery-powered scenarios, does not require frequent battery replacement, greatly reduces the operation and maintenance cost of equipment, and is especially suitable for application environments such as communication base stations and underground pipe networks where frequent operation and maintenance is inconvenient.

[0017] 2. The filter capacitor C3 can filter out noise at the TEST_IO terminal and avoid false triggering or missing triggering caused by external interference; the water immersion probe adopts stainless steel electrodes, which improves the corrosion resistance in humid and mild acid-base environments and prolongs the service life of the probe. A 50mA patch fuse connected in series at the power terminal can quickly cut off the circuit when abnormal overcurrent occurs such as probe short circuit and capacitor breakdown, so as to protect core components (such as triode Q1 and resistor R1) from damage. Meanwhile, the capacitance design of "C1 < C2" ensures reliable conduction and cutoff of Q1 when triggered by water immersion, and guarantees stable output of alarm signals.

[0018] 3. It can adapt to the IO port interrupt detection characteristics of different external chips, and is also compatible with common power supply specifications such as single-cell lithium batteries and 3-cell dry battery packs. The triode Q1 adopts SOT-23 miniaturized packaging, the PCB circuit board supports lightweight integration, can meet various installation forms such as wall mounting and pasting, and adapts to different installation scenarios such as outdoor equipment cabinets and waterproof cabins for precision instruments.

[0019] 4. It eliminates the need for complex main control chips or additional power conversion modules, reducing hardware costs. Furthermore, the water immersion probe is connected to the PCB via tin-plated copper wires, simplifying the assembly process, ensuring high consistency, and making it suitable for industrial mass production.

[0020] The above description is only an overview of the technical solution of this utility model. In order to better understand the technical means of this utility model and to implement it in accordance with the contents of the specification, the preferred embodiments of this utility model are described in detail below with reference to the accompanying drawings. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of a low-power water immersion detection circuit. Detailed Implementation

[0022] The specific embodiments of this utility model will be described in further detail below with reference to the accompanying drawings and examples. The following examples are used to illustrate this utility model, but are not intended to limit its scope.

[0023] like Figure 1 This low-power water immersion detection circuit includes a power supply terminal (POWER), and its unique feature is that it also includes a PNP transistor Q1, resistors R1, R2, R3, and R4, capacitors C1 and C2, a diode D1, a water immersion probe, and a signal output terminal (TEST_IO). Specifically, the power supply terminal (POWER) is connected to one end of resistor R1, one end of resistor R4, and the emitter of transistor Q1. The other end of resistor R1 is connected to the base of transistor Q1. Furthermore, the collector of transistor Q1 is connected to the signal output terminal (TEST_IO), the base of transistor Q1 is connected to one end of capacitor C1, and the other end of capacitor C1 is connected to the anode of diode D1. The cathode of diode D1 is connected to one end of resistor R2, the other end of resistor R2 is connected to one end of capacitor C2, and the other end of capacitor C2 is grounded to GND1 via the water immersion probe. To facilitate water immersion detection, the other end of capacitor C2 and the other end of resistor R4 are connected together and then grounded to GND1 through the water immersion probe. Capacitor C2 and resistor R4 form an RC charging network. Furthermore, one end of transistor Q1 is connected to one end of resistor R3, and the other end of resistor R3 is connected to the signal output terminal TEST_IO. One end of the water immersion probe is connected to C2 and one end of R4, and the other end is grounded to GND2.

[0024] In a preferred embodiment of this invention, the resistance values ​​of resistors R1, R3, and R4 are 1MΩ-20MΩ. This resistance range satisfies the pull-up and pull-down functions while minimizing current consumption during conduction, achieving low standby power consumption. In practical applications, resistors R1 (2.2MΩ), R3 (1MΩ), and R4 (10MΩ) are preferred. This set of parameters has been verified through simulation and testing, balancing low power consumption and circuit response speed. The resistance value of resistor R2 is set according to the high-level pulse requirement of the signal output terminal TEST_IO, typically 300KΩ-500KΩ, adaptable to the response characteristics of different external chip IO detection pins. Furthermore, resistors R1, R2, R3, and R4 are all metal film resistors with an accuracy of ±5%. Its high precision and small temperature coefficient ensure that the actual resistance value of each resistor in the circuit deviates little from the design value, avoiding instability of key parameters such as RC charging and discharging time and transistor bias current due to resistance value deviation, and ensuring that the low power consumption characteristics and trigger sensitivity of the circuit are not affected.

[0025] Furthermore, the capacitance of capacitor C1 is 0.5μF-1μF, and the capacitance of capacitor C2 is 0.8μF-2μF, with the capacitance of C1 being smaller than that of C2. Preferably, the capacitance of C1 is 0.68μF and the capacitance of C2 is 1μF. This capacitance ratio ensures that C1 discharges completely during water immersion triggering, preventing insufficient discharge of C1 from causing a short conduction time for transistor Q1, thus ensuring that the rising edge level of the signal output terminal TEST_IO can be stably recognized by the external system. Simultaneously, a filter capacitor C3 is connected in parallel to the signal output terminal TEST_IO. The capacitance of filter capacitor C3 is 0.01μF-0.1μF, preferably 0.1μF. Filter capacitor C3 is a multilayer ceramic capacitor (MLCC), which is characterized by its small size, stable capacitance, and good high-frequency characteristics. It can filter out noise interference at the signal output terminal TEST_IO, making the output signal level more stable and reducing the possibility of false triggering or missed triggering by the external system.

[0026] In practical implementation, the transistor Q1 used is an S8550 PNP transistor in an SOT-23 package. The SOT-23 package is compact, reducing PCB space requirements and making it suitable for miniaturized water immersion sensor designs. The S8550 PNP transistor has a forward voltage of approximately 0.2V-0.3V, stable current amplification, and meets the low-power requirements of this circuit. It can quickly conduct when the base is properly biased, enabling level switching at the TEST_IO signal output. Meanwhile, diode D1 is a 1N4148 silicon diode with a forward voltage drop of 0.5V-0.7V, with an optimal forward voltage drop of 0.6V. This diode enables unidirectional conduction, preventing reverse current from flowing into the base of transistor Q1 during capacitor C1 discharge, thus avoiding interference with the operation of transistor Q1 and protecting the base of transistor Q1 from reverse voltage damage.

[0027] To optimize usage, the water immersion probe used in this invention is an electrode-type water immersion sensor. Its equivalent resistance during water immersion is 0-100KΩ, and its equivalent resistance is greater than 10MΩ when open-circuited. The probe is equipped with stainless steel electrodes, which possess excellent corrosion resistance and conductivity, enabling them to adapt to complex operating environments such as humidity and acid / alkali conditions. This prevents the electrodes from corroding due to prolonged water contact, extending the probe's lifespan. When the probe is in contact with water, a conductive path is formed between the electrodes, enabling water immersion detection. When not in contact with water, the electrodes remain open-circuited, ensuring stable standby operation.

[0028] During use, the power supply voltage at the POWER terminal is 3V-5V DC, with 5V being the optimal supply voltage. This voltage range conforms to common battery power specifications, such as a single lithium battery or a three-cell dry cell battery pack. This eliminates the need for an additional power conversion module, reducing installation costs and circuit complexity, and perfectly meets the design requirements of battery-powered water immersion sensors. Furthermore, a 50mA surface-mount fuse is connected in series between the POWER terminal and resistor R1. This small, fast-responding fuse quickly melts in case of abnormal overcurrent, such as probe short circuits or capacitor breakdown, cutting off the power circuit and protecting core components such as transistor Q1 and resistor R1 from damage, thus improving the overall reliability of the circuit.

[0029] In terms of integrated installation, the power supply, transistor Q1, resistors R1, R2, R3, and R4, capacitors C1 and C2, and diode D1 are all soldered to the PCB circuit board. The PCB circuit board is preferably an FR-4 epoxy glass cloth laminate, with a thickness ranging from 0.8mm to 1.6mm, and an optimal thickness of 1.2mm. This type of circuit board has good insulation performance, high mechanical strength, and high temperature resistance, making it suitable for long-term stable operation of electronic components and easy for mass production. Meanwhile, the water immersion probe is connected to the PCB circuit board via wires. Tinned copper wires are used; tinned copper wires have good conductivity and prevent oxidation, avoiding poor contact due to corrosion of the wire joints after long-term use, and ensuring a stable circuit connection between the probe and the circuit board.

[0030] The working period of this utility model can be divided into four stages: standby, water immersion trigger, continuous water immersion, and water removal recovery, as detailed below: 1. Standby Phase. The water immersion probe remains open at both ends. After the power supply (POWER) is powered on, current flows through resistor R4 to capacitor C2, and simultaneously through resistors R1 and R2 to capacitor C1, quickly charging capacitors C1 and C2 to full charge, matching the POWER voltage. At this time, the voltage across capacitor C1 is stable, and the base and emitter potentials of transistor Q1 are close (both close to the POWER voltage). PNP transistor Q1 is off because it does not meet the conduction condition. The signal output terminal TEST_IO is pulled down to ground (GND2) through resistor R3, maintaining a low level. Since resistors R1, R3, and R4 are all in the megaohm range, only a weak leakage current exists in the circuit, and the overall standby power consumption is controlled to a few microamps, achieving ultra-low power standby and effectively extending battery life.

[0031] 2. Water Immersion Trigger Stage. When water immersion occurs, the stainless steel electrodes of the water immersion probe come into contact with water, forming a conductive path between the electrodes. The equivalent resistance of the probe drops to 0-100KΩ. At this time, capacitor C2 discharges rapidly through the conducting water immersion probe, and the voltage across capacitor C2 drops rapidly. Subsequently, capacitor C1 begins to discharge through resistor R2 and diode D1, and the voltage across capacitor C1 gradually decreases, causing the base potential of transistor Q1 to be lower than the emitter potential (the difference satisfies the conduction condition of a PNP transistor). After transistor Q1 is triggered and turned on, current flows from the power supply terminal POWER through resistor R1 and transistor Q1 to the signal output terminal TEST_IO. The signal output terminal TEST_IO is pulled up to the power supply terminal POWER voltage, generating a rising edge signal from low to high level. This rising edge signal can directly trigger the interrupt pin of an external system (such as a microcontroller or alarm controller), causing the external system to generate a water immersion alarm signal, thus completing the water immersion detection function.

[0032] 3. Continuous Water Immersion Stage. Once capacitor C2 is fully discharged to ground GND1, it will not continue to discharge even if the water immersion continues. Simultaneously, after capacitor C1 discharges to a certain level, it is instantly discharged and then recharged. The voltage across C1 is insufficient to maintain the conduction state of transistor Q1. The base potential of transistor Q1 rises back to near its emitter potential, and Q1 turns off. The signal output terminal TEST_IO is pulled down to ground GND2 again through resistor R3, returning to a low level. At this time, the circuit maintains a weak standby current only through resistors R1, R3, and R4, keeping power consumption low and preventing increased power consumption during continuous water immersion from rapidly depleting the battery.

[0033] 4. Water Removal Recovery Phase. Once the water immersion disappears (i.e., the probe is removed from the water), the probe returns to an open circuit, with an equivalent resistance greater than 10MΩ. The power supply (POWER) recharges capacitor C2 through resistor R4, while current flows through resistors R1 and R2 to charge capacitor C1. Furthermore, capacitor C1 is recharged immediately after being fully discharged, maintaining continuous charging during the remaining water immersion phase. Once both capacitors C1 and C2 are fully charged, transistor Q1 remains off, the TEST_IO signal output remains low, and the circuit returns to standby mode, waiting for the next water immersion event to trigger the alarm again.

[0034] Furthermore, the directions or positional relationships described in this utility model are based on the directions or positional relationships shown in the accompanying drawings. They are only for the purpose of facilitating the description of this utility model and simplifying the description, and are not intended to indicate or imply that the device or structure referred to must have a specific orientation, or to operate in a specific orientation. Therefore, they should not be construed as limitations on this utility model.

[0035] The above description is only a preferred embodiment of the present utility model and is not intended to limit the present utility model. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present utility model, and these improvements and modifications should also be considered within the protection scope of the present utility model.

Claims

1. A low-power water immersion detection circuit, including a power supply terminal POWER, characterized in that: It also includes a PNP transistor Q1, resistors R1, R2, R3, and R4, capacitors C1 and C2, diode D1, a water immersion probe, and the signal output terminal TEST_IO. The power supply terminal POWER is connected to one end of resistor R1, one end of resistor R4, and the emitter of transistor Q1; the other end of resistor R1 is connected to the base of transistor Q1. The collector of transistor Q1 is connected to the signal output terminal TEST_IO, the base of transistor Q1 is connected to one end of capacitor C1, and the other end of capacitor C1 is connected to the positive terminal of diode D1. The negative terminal of the diode D1 is connected to one end of the resistor R2, the other end of the resistor R2 is connected to one end of the capacitor C2, and the other end of the capacitor C2 is grounded to GND1 through the water immersion probe. The other end of capacitor C2 and the other end of resistor R4 are connected together and then grounded to GND1 through a water immersion probe. Capacitor C2 and resistor R4 form an RC charging network. One end of the transistor Q1 is connected to one end of the resistor R3, and the other end of the resistor R3 is connected to the signal output terminal TEST_IO. One end of the water immersion probe is connected to C2 and one end of R4, and the other end is grounded to GND2. The resistance values ​​of resistors R1, R3, and R4 are 1MΩ-20MΩ, the capacitance value of capacitor C1 is 0.5μF-1μF, the capacitance value of capacitor C2 is 0.8μF-2μF, and the capacitance value of capacitor C1 is less than the capacitance value of capacitor C2.

2. The low-power water immersion detection circuit according to claim 1, characterized in that: The resistor R1 has a capacitance of 2.2 MΩ, the resistor R3 has a capacitance of 1 MΩ, the resistor R4 has a capacitance of 10 MΩ, the capacitor C1 has a capacitance of 0.68 μF, and the capacitor C2 has a capacitance of 1 μF.

3. The low-power water immersion detection circuit according to claim 1, characterized in that: The diode D1 is a 1N4148 type silicon diode with a forward voltage drop of 0.5V-0.7V.

4. The low-power water immersion detection circuit according to claim 1, characterized in that: The water immersion probe is an electrode-type water immersion sensor with an equivalent resistance of 0-100KΩ when immersed in water, and disconnects when open-circuited. The probe is also equipped with stainless steel electrodes.

5. The low-power water immersion detection circuit according to claim 1, characterized in that: The signal output terminal TEST_IO is connected in parallel with a filter capacitor C3. The capacitance of the filter capacitor C3 is 0.01μF-0.1μF, and the filter capacitor C3 is a multilayer ceramic capacitor (MLCC).

6. The low-power water immersion detection circuit according to claim 1, characterized in that: The power supply terminal POWER, transistor Q1, resistors R1, R2, R3, and R4, capacitors C1 and C2, and diode D1 are all soldered to the PCB circuit board. The water immersion probe is connected to the PCB circuit board via wires.

7. The low-power water immersion detection circuit according to claim 1, characterized in that: The transistor Q1 is an S8550 PNP transistor with an SOT-23 package.

8. The low-power water immersion detection circuit according to claim 1, characterized in that: The power supply voltage of the POWER terminal is 3V-5V DC voltage, and a surface-mount fuse with a fusing current of 50mA is connected in series between the POWER terminal and the resistor R1.

9. The low-power water immersion detection circuit according to claim 1, characterized in that: The resistors R1, R2, R3, and R4 are all metal film resistors.

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