"Smart" protection against water leaks in the apartment - do not flood your neighbor! Do-it-yourself water leakage protection for the home

Water is life. If it is in a tap, or in a heating radiator, this is good. And if it is on the floor of your apartment, or on the ceiling of a neighbor from below, this is a big financial and moral trouble. Of course, it is necessary to regularly check the water supply and heating system for corrosion or cracks in plastic pipes. However, a water breakthrough usually occurs suddenly, with no signs of impending danger. Well, if at this moment you are at home, and do not sleep. But, according to the law of meanness, leaks occur just at night, or when you are not at home.

Simple rules for dealing with this problem (especially for old housing stock, with worn out networks):

Regularly inspect water pipes and elements of the heating system for defects, pitting, leaks, etc.
When leaving home, close the inlet valve on the riser.
Outside the heating season, close the taps on the batteries (if any).
Use a leak protection system.

Let's take a closer look at the last item on the list.

How to signal a water leak

The solution to the issue came to life from the yachting world. Since the ship's premises of the lower tier (especially the holds) are below the waterline, water regularly accumulates in them. The consequences are clear, the question is how to deal with it. It is irrational to set up a separate watch sailor for control. Then who will give the command to turn on the pump?

There are effective tandems: a water presence sensor and an automatic pump. As soon as the sensor detects the filling of the hold, the pump motor turns on and pumping is performed.

The water sensor is nothing more than a simple swivel float connected to a pump switch. When the water level rises by 1-2 cm, the alarm and the pump motor are activated at the same time.

Comfortable? Yes. Safely? Of course. However, such a system is unlikely to be suitable for a residential building.

Firstly, if the water reaches a level of 1–2 cm over the entire area of the room, it will run through the threshold of the front door to the landing (not to mention the neighbors below).
Secondly, an exhaust pump is completely unnecessary, since it is necessary to immediately find and localize the cause of the breakthrough.
Thirdly, the float system for rooms with a flat floor is inefficient (unlike boats with a keeled bottom shape). While the “necessary” level for triggering is reached, the house will fall apart from dampness.

Therefore, a more sensitive alarm system against leaks is needed. This is a matter of sensors, and the executive part can be of two types:

1. Alarm only. It can be light, sound, or even connected to a GSM network. In this case, you will receive a signal on your mobile phone, and you will be able to call the emergency team remotely.

2. Turning off the water supply (unfortunately, this design does not work with the heating system, only plumbing). After the main valve, which supplies water from the riser to the apartment (it does not matter, before or after the meter), a solenoid valve is installed. When a signal is given from the sensor, the water is blocked, and further flood stops.

Naturally, the water shutdown system also signals a problem in any of the above ways. These devices are offered in a wide range of plumbing stores. It would seem that the material damage from the flood is potentially higher than the price of peace. However, the majority of citizens live by the principle "until the thunder breaks out, the peasant will not cross himself." And more progressive (and prudent) homeowners make a water leakage sensor with their own hands.

The principle of operation of leakage sensors

Speaking of the block diagram - everything is very simple. A certain element fixes the liquid at the point of its placement, and sends a signal to the executive module. Which, depending on the settings, can give light or sound signals, and (or) give a command to close the valve.

How sensors are arranged

We will not consider the float mechanism, since at home it is not effective. Everything is simple there: the base is fixed to the floor, a float is suspended on a hinge, which closes the contacts of the switch when it rises. A similar principle (only mechanical) is used in the toilet bowl.

The most commonly used contact sensor, which uses the natural ability of water to conduct electricity.

Of course, this is not a full-fledged switch through which a voltage of 220 volts passes. A sensitive circuit is connected to two contact plates (see illustration), which detects even a small current. The sensor can be separate (as in the photo above), or built into a common housing. This solution is used on mobile stand-alone sensors powered by a battery or accumulator.

If you do not have a "smart home" system, and water is supplied without any electromagnetic valves, it is the simplest sensor with a sound alarm that can be used as a starting option.

Homemade sensor of the simplest design

Despite the primitiveness, the sensor is quite effective. This model attracts home craftsmen with a penny cost of radio components, and the ability to assemble literally “on the knee”.

The base element (VT1) is an NPN transistor of the BC515 series (517, 618 and the like). It supplies power to the buzzer (B1). This is the simplest ready-made buzzer with a built-in generator, which can be purchased for a penny, or soldered from some old electrical appliance. Power is required on the order of 9 volts (specifically for this circuit). There are options for 3 or 12 volt batteries. In our case, a Krona-type battery is used.

How the scheme works

The secret is in the sensitivity of the collector-to-base transition. As soon as a minimum current begins to flow through it, the emitter opens and power is supplied to the sound element. There is a squeak. An LED can be connected in parallel, adding a visual signal.

The signal for the opening of the collector transition is given by the very water, the presence of which must be signaled. Electrodes are made of non-corrosive metal. It can be two pieces of copper wire that can simply be tinned. On the connection point diagram: (Electrodes).

You can assemble such a sensor on a breadboard.

Then the device is placed in a plastic box (possibly in a soap dish), in the bottom of which holes are made. It is desirable that if water gets in, it does not touch the circuit board. If you want aesthetics, the printed circuit board can be etched.

The disadvantage of such a sensor is different sensitivity to different types of water. For example, distillate from a leaking air conditioner may go unnoticed.

Based on the concept: an inexpensive stand-alone device, it cannot be integrated into a single security system for your home, even a home-made one.

More complex circuit, with sensitivity control

The cost of such a scheme is also minimal. It is performed on the KT972A transistor.

The principle of operation is similar to the previous version, with one difference. The generated signal about the presence of leakage (after the opening of the emitter junction of the transistor), instead of a signaling device (LED or sound element), is fed to the relay winding. Any low-current device, such as RES 60, will do. The main thing is that the supply voltage of the circuit matches the characteristics of the relay. And already from its contacts, information can be submitted to the actuator: the "smart home" system, alarm system, GSM transmitter (to a mobile phone), emergency solenoid valve.

An additional advantage of this design is the ability to adjust the sensitivity. With the help of a variable resistor, the current of the collector-base junction is regulated. You can adjust the response threshold from the appearance of dew or condensate, to the full immersion of the sensor (contact plate) in water.

Leakage sensor on the LM7555 chip

This radio element is an analogue of the LM555 microcircuit, only with lower energy consumption parameters. Information about the presence of moisture comes from the contact pad, indicated in the illustration as a "sensor":

To increase the response threshold, it is better to make it in the form of a separate plate connected to the main circuit with wires with minimal resistance.

The best option in the photo:

If you do not want to spend money on buying such a "limit switch", you can etch it yourself. Just be sure to tin the contact tracks to increase corrosion resistance.

As soon as water appears between the tracks, the plate becomes a closed conductor. An electric current begins to flow through the comparator built into the microcircuit. The voltage quickly rises to the threshold, and the transistor opens (which acts as a key). The right side of the diagram is the command and executive part. Depending on the implementation, the following happens:

Top diagram. A signal is triggered on the so-called "boozer" (tweeter), and the optionally connected LED lights up. There is another use case: several sensors are combined into a single parallel circuit with a common buzzer, and the LEDs remain on each block. When a sound signal is triggered, you will accurately determine (by emergency glow) which block has worked.
Bottom diagram. The signal from the sensor goes to the electromagnetic emergency valve located on the water supply riser. In this case, the water shuts off automatically, localizing the problem. If you are not at home at the time of the accident, the flood will not happen, material losses will be minimal.

Information: Of course, you can also make a shut-off valve with your own hands. However, this complex device is best purchased ready-made.

The circuit can be made according to the PCB layout, which is equally suitable for both LM7555 and LM555. The device is powered by 5 volts.

Important! The power supply must be galvanically isolated from 220 volts so that dangerous voltage does not fall into a puddle of water during a leak.

In fact, the ideal option is to use a charger from an old mobile phone.

The cost of such a homemade product does not exceed 50–100 rubles (for the purchase of parts). If you have an old element base in stock, you can reduce costs to zero.

The body is up to you. With such a compact size, finding a suitable box is not difficult. The main thing is that from the common board to the contact plate of the sensor, the distance should be no more than 1 meter.

General principles for the placement of leakage sensors

Any owner of the premises (residential or office) knows where the water supply or heating communications pass. There are not so many potential leak points:

stopcocks, mixers;
couplings, tees (especially for propylene pipes, which are connected by soldering);
inlet pipes and flanges of the toilet bowl, washing machine or dishwasher, flexible hoses of kitchen faucets;
connection points for metering devices (water meters);
heating radiators (can flow both over the entire surface and at the junction with the main).

Of course, ideally, the sensors should be located under these devices. But then there may be too many of them, even for the option of self-production.

In fact, 1-2 sensors per potentially dangerous room are enough. If it is a bathroom, or a toilet - as a rule, there is a sill of the front door. In this case, water is collected, as in a pan, the layer can reach 1–2 cm, until the liquid spills over the threshold. In this case, the installation location is not critical, the main thing is that the sensor does not interfere with moving around the room.

In the kitchen, sensors are installed on the floor under the sink, behind the washing machine or dishwasher. If a leak occurs, it first forms a puddle in which the alarm will go off.

In other rooms, the device is installed under heating radiators, since water supply pipes are not laid through the bedroom or living room.

It will not be superfluous to install the sensor in a niche along which pipeline and sewer risers pass.

The most critical points of water breakthrough

With uniform working pressure, the risk of leakage is minimal. The same applies to faucets and faucets, if you open (close) the water smoothly. The weak point of the pipeline system manifests itself during water hammer:

the valve for supplying water to the washing machine, when closed, creates a pressure that is 2–3 times the nominal water supply;
the same, but to a lesser extent, applies to the closing fittings of the toilet bowl;
heating radiators (as well as the places of their connection to the system) often do not withstand the test pressing, which is carried out by heat supply companies.

How to place sensors correctly

The contact plate should be located as close as possible to the floor surface without touching it. Optimal distance: 2–3 mm. If the contacts are placed directly on the floor, permanent false alarms due to condensation will occur. Long distance reduces the effectiveness of protection. 20-30 millimeters of water is already a problem. The sooner the sensor is triggered, the lower the loss.

reference Information

Regardless of whether a leak protection system is purchased in a store or made by hand, you need to know the uniform standards for its operation.

Device classification

By the number of secondary protective devices at the facility (stop emergency valves with electromagnetic drive). Leak sensors should not block all water supply if the shut-off systems are separated by consumers. Only the line on which a leak is detected is localized.
According to the method of submitting information about the accident of the water supply (heating system). Local signaling involves the presence of people at the facility. Remotely transmitted information is organized taking into account the prompt arrival of the owner or repair team. Otherwise, it is useless.
Notification method: local sound or light alarm (on each sensor), or information output to a single remote control.
Protection against false positives. As a rule, finely tuned sensors work more efficiently.
Mechanical or electrical protection. An example of mechanics is the Aqua Stop system on the supply hoses of washing machines. There is no alarm on such devices, the scope is limited. Self-manufacturing is not possible.

Conclusion

Having spent a little time and a minimum of funds, you can protect yourself from serious financial problems associated with a flood in the apartment.

General description of the system

There are two main topologies of leak protection systems. The main difference between them is the way the signal is transmitted between the sensor, controller and actuators. Systems using wired transmission are simpler and more reliable, but it is not always convenient to use them when the places of possible leaks are far from each other, when the signal may not be recognized by the controller due to the considerable length of the cable. In turn, wireless systems do not require cabling, so that decorative finishes will not be disturbed during installation, but such protection is more expensive.

In wired systems, the connection between the leakage sensor and the controller is carried out via a three-wire wire. In addition, actuators are connected to the control output of the controller: electric shut-off valves, light and sound signaling devices. If desired, the scheme can be supplemented with communication devices to alert the user through a mobile or home wireless network.

Schematic diagram of protection against water leaks: 1 - control unit; 2 - radio module; 3 - ball electric drive; 4 - inlet taps; 5 - wired sensors; 6 - radio sensors

The main difference between the wireless system is that a radio communication module is installed together with the flood sensor. This does not require a wired connection between the controller and the sensor, however, the leak detector itself and the transmitter need a stabilized power supply from an external unit or a battery. Shut-off valves can also be controlled by radio, but often this is not required, because it is much easier to install the controller next to the actuator.

Controller selection

The brain of the system is the electronic control unit. Its main function is to accurately recognize a change in the signal level from the sensor and apply voltage to the actuator. At the same time, it is important that the controller has the function of recovering from emergency mode after the cause of the leak has been eliminated. As you can see, the logic of the controller is quite simple, and therefore even the simplest devices, including handicraft ones, can be used. In general, there are three options.

Relay modules are the simplest class of control devices for connecting one or two sensors. There are a number of disadvantages: the lack of state retention when the power is turned off, the need to convert the signal from the sensor to the correct level and provide the circuit with a manual reset shunt to hold in the emergency mode. However, this is the most budgetary option for building a circuit. Suitable solutions include Omron relay modules and Arduino expansion boards, as well as more expensive programmable relays such as OWEN PR110 for connecting up to 12 sensors.

Programmable logic controllers are the most versatile type of control devices that allow implementing more complex algorithms for the operation of a leakage protection system and interconnecting them with other automation systems. For the same purpose, cheap single-board computers such as Arduino can be used, with the help of which functions such as forced draining of water from the washing machine tank can be implemented.

One of the channels of a home automation or fire alarm controller can be used to connect a flood sensor. The only problem is that the type or level of the signal at the output of the sensor does not match, so it often becomes necessary to supplement the circuit with an amplifier or a single-channel discrete converter.

An example of a leakage protection circuit on Arduino

The simplest control device can also be made by hand from common electronic components. Amplification of the signal from the sensor can be implemented on transistors marked Logic Level (IRL series), which use very low voltages (about 2-3 V) for control and are capable of switching up to 20 A of load current. To avoid accidental operation, a 300-500 ohm pull-up resistor is installed between the gate and the source. It is desirable to supplement the circuit: limit the control signal with a zener diode to 50-70% of the maximum gate-source voltage, and also provide a shunt with a voltage divider between the source and the gate to hold the key in the open state. It is necessary to install an emergency reset button in the shunt circuit break. Such a circuit can have an almost unlimited number of transistors and, accordingly, control a number of actuators and indicators.

Leak sensors

The leak detector has a simple, if not primitive device. Its two main elements are a pair of electrodes, when wet, which closes the circuit, as well as a signal amplifier, which is usually a bipolar transistor with a low saturation current. The sensor is powered by two wires, the third alarm signal is transmitted to the control unit. Some sensors have built-in sound and light alarms, and a galvanically isolated switch in the form of a relay can be installed in one housing to supply power directly to the actuator.

The most common, primarily due to their low cost (about 500 rubles / piece), are considered to be the sensors "H2O Contact", "Aquarius-R" and Equation. They have several versions for connection both to analog inputs of control devices and to inputs of the "dry contact" type in normally open and normally closed states. The detectors have a built-in signal indication, but their main drawback is that they are not capable of switching a significant load, that is, they cannot directly control the valves.

Water leakage sensors: 1 - "Vodoley-R"; 2 - "H2O Contact"; 3 - Equation

More advanced, but also more expensive (from 1.5 to 2.5 thousand rubles) sensors are Ajax LeaksProtect, Ezviz T10, Neptun RSW + and other wireless devices. As a rule, these detectors are powered by a Krona battery; for some models, the battery life can be up to two years. Most of the detectors are designed to work as part of the protection system of the same manufacturer, for some the operating frequency is indicated and it is possible to configure it for connection to universal radio receivers. A certain part of autonomous models works in the alarm mode - it emits a sound signal or sends a notification via mobile communications when a leak is detected.

Wireless water leakage sensors: 1 - Ajax LeaksProtect; 2 - Ezviz T10; 3 - Neptune RSW+

In everyday life, not individual sensors, but kits for mounting leak protection systems have gained the greatest popularity. They can include up to three sensors, one or two electric valves, a power supply and a central control unit. Similar kits are supplied to the market under the trademarks Neptun, Akvastor and Gidrolock.

Water leakage protection system "Aquastorage Classic 2x20"

Executive and auxiliary devices

The third element of the system is a device that shuts off the water supply when a leak is detected. For this purpose, either motorized ball valves or electromechanical valves are used.

Ball valves with a motor are controlled by a three-wire circuit, so they can often only be used in systems controlled by a full-fledged controller, because in addition to the closing signal, an opening signal must be given when the system is restored to its original state. However, the signal to open can be given through the reverse contact of the relay or manually through the button - a kind of replacement for resetting the alarm.

Electromechanical valves of normally open type act once when a control signal is applied and block the flow. In this case, the voltage on the control channel can remain indefinitely, because during operation the circuit is opened by a contact group mechanically connected to the valve stem. It must be remembered that it is the normally open valve that, after the protection is triggered, remains in this position even in the event of a power failure and is cocked manually after the leakage has been eliminated.

Actuators do not have to be specialized; any taps or valves for plumbing systems will do. However, you need to pay attention to the operating voltage range, because some relay modules cannot control direct current, and the switching outputs of the controllers can only work with limited voltage and current.

Auxiliary devices may also be present in the circuit:

Radio communication modules - a set of transmitter and receiver, for example, the MX series at 433 MHz, will allow you to create a wireless connection between the sensor and the control unit using equipment designed to build systems with wired communication.
Signal amplifiers and modulators are designed to match the logic levels between the sensors and the control unit. As amplifiers, single-board modules based on the LM358 chip are most popular, for signal conversion - modular DAC / ADC based on PCF8591.
Intermediate relays will be useful if the relay group of the control unit does not allow switching currents of significant magnitude. Relays designed for low control voltage - 24 or 36 V are most preferred.

Circuit assembly and installation

There is no difficulty in installing a leak protection system if a ready-made kit is used: all elements are fully compatible, the connectors fit together, there is a detailed instruction. Assemblies of an individual configuration are more difficult to implement, so we will consider the topology of a protection system with two sensors and wireless communication.

The “H2O Contact” will be used as a flood sensor in a four-wire version with a normally open contact. Brown (+) and white (-) wires are connected to a power source - a 9 V battery. One of the remaining wires is connected to the power plus, the other to the TX DATA pin of the MX-FS-03V radio transmitter. Solder 10-15 cm of copper wire coiled into a spiral to the ANT pad on the transmitter board. The sensor is attached with screws or double-sided tape, the electrodes must be firmly pressed to the floor. The wire from the sensor runs along the wall to a small plastic case that houses the radio transmitter and power supply.

Wiring diagram for a leak protection system with two sensors and wireless communication

The radio receiver MX-05V is installed near the control device, which will be used as a programmable relay module FRM01. The RX terminal of the radio receiver is connected to the IN input of the LM358 amplifier module, the GND and VCC terminals are connected to the negative and positive 5V power supply. The amplifier module also needs 12V power through the VCC and GND terminals. The output from the amplifier module is connected to the input terminal of the relay module IN, which is also connected to a 12V power supply (the circuit is reverse polarity protected).

As an actuator, it is recommended to use a ball valve NT9047 with a supply voltage of 24 V, which is installed at the inlet of the water main. The neutral wire of the tap is connected to the minus of the power source, the wire of the closing contact is connected to the normally open output of the relay, the opening one is connected to the normally closed one. The relay must be configured according to the instructions - set function number 10. As you can see, the entire assembly requires three voltage levels for operation, which is solved by purchasing several cheap power supplies for 5, 12 and 24 V, the latter with a current of up to 2 A.

Rules for the installation of a flood protection system

The main advantage of any modern leak protection system is the ease of assembly and the speed of installation work. By purchasing a flood warning system, you get a kind of constructor, the individual parts of which are connected using special connectors.

A significant advantage of factory-made leak and emergency flood alarm systems is the ease of assembly and installation of components (+)

Work on the installation of the system should begin with a detailed diagram, which will clearly indicate the location of each of the components. After developing a plan, it is necessary to check the length of the wires and determine whether it is enough to connect sensors and taps to the control unit.

Installation work is carried out in the following order:

Marking areas where the installation of the controller, cranes and sensors is provided.
Laying and connection of mounting wires.
Insertion of ball valves equipped with shut-off valves with electromechanical or electromagnetic drives.
Installation of leakage sensors.
Installation of the control unit (controller).
Connection and verification.

One of the most difficult moments in the installation of leakage protection is the insertion of ball valves. A mistake when tapping taps can nullify all efforts.

Image gallery

External location. The sensors are laid directly on the floor with the contacts down. The sensor housing can be fixed with construction adhesive or double-sided tape.

The external location of the devices is most often used if the leakage control system is installed after finishing and installing plumbing.

When installing the sensor outdoors, it must be placed with the plates down and fixed with construction glue or adhesive tape. The sensor should be easily removed for maintenance.

Installing a water leak sensor with your own hands will cause even less difficulties if wireless sensors are provided in the system.

In this case, you don’t have to worry about the aesthetic side of the issue, you don’t need to ditch the walls and floor or mask the wires into the baseboard. The wireless sensor is easily mounted on any surface, as it is equipped with fasteners.

Controller Mounting Rules

The controller must be located in a convenient location for maintenance. It is best to place the controller near shut-off valves, it can be mounted on the wall with brackets or hidden in a niche.

Please note that the control unit is powered by the power cabinet, so phase and zero must be connected to the controller.

The controller can be installed in almost any convenient place, but it is best to place it close to electrical wiring and shut-off valves, so there is less need to run wires

After fixing the controller, you can connect it to the mains and connect the electrically controlled valves.

The wires are connected through special terminal connectors, numbered and signed for ease of installation. The controller and the instructions clearly indicate where and which wire should be connected.

It remains to connect the water leakage sensors to the appropriate connectors and the assembly of the system can be considered complete. If the standard length of the wire is not enough, then it is necessary to extend them. Manufacturers guarantee the operation of the system even if the sensor is 100 m away from the control unit.

Checking system operation

After pressing the power button, the controller will carry out diagnostics and confirm its readiness for operation with a green indicator light. Before entrusting the security of your home to the system, it will not be superfluous to diagnose it.

To do this, it is enough to moisten the plates of one of the sensors with water. If the system is working correctly, you will hear a beep, the indicator light will turn on or flash red, and the electric valves will shut off the water supply.

After water gets on the sensor contacts, the controller gives a noise and sound signal, at the same time blocking the solenoid valves in a matter of seconds

To unlock the system, the sensor should be wiped dry and reinstalled. The power to the controller must be turned off and on again. After the self-diagnosis, the water leakage control system is ready for operation again.

How to choose flood protection

In terms of their effectiveness, cheap and expensive devices are almost the same, with the exception of factory defects, which can be in any system. Each of the manufacturers presents their product, but this is just an advertisement and nothing more.

In system of protection against leaks with a logo hydrolock complete delivery provides for the presence of 3 sensors, while you can connect another 40 sensors without installing additional blocks.

Unexpected water leakage not noticed in time can cause a lot of harm. The presented homemade water leakage sensor allows you to detect spilled water on the floor and notify about it anywhere.

The design of the water leakage sensor circuit provides two levels of control: the first triggers an alarm sound signal, the second (built-in relay) can, for example, turn on the pump or shut off the solenoid valve.

The location of the sensor can be arbitrary, while changing the length of the measuring electrodes. The scheme will be active until the flooding is eliminated. It will be enough to use three small pieces of wire as measuring sensors.

Material: ABS + metal + acrylic lenses. LED lights...

Initially, the scheme was designed to pump out water in the basement during flooding. When the first electrodes were closed, the pump in the basement was turned on, which pumped water out of it. But some situations required the intervention of residents, so there was a need for a sound notification. Often these were situations where there was simply too much water for the pump to handle.

The operation of the leakage sensor is based on the detection of a decrease in resistance between the electrodes „E1” and „E2” and „E1” and „E3”, which decreases as a result of current flow through the liquid (water).

In rest mode, there is a low level signal at the bases of the transistors, for this reason the transistors are locked. When water appears between the electrodes, it causes the appearance of a positive voltage at the bases of the transistors and, as a result, the operation of an audible signal or a relay.

An emergency situation that occurs in a cold or hot water supply system always causes a lot of trouble not only to the owner of the apartment, but also to all neighbors, especially those living on the lower floors. After the leakage of the water pipeline, the water flowing from it passes through the building structures, damaging the wallpaper, stretch ceilings, and decorative coatings.

It poses a particular danger to household electrical wiring, violating the state of insulation and creating unforeseen leakage currents, which also reduce houses.

To prevent the development of serious consequences of water leakage, the system of automatic notification of residents, which is promptly triggered when the first signs of moisture appear, allows. Any home craftsman who can solder simple amateur radio devices can assemble it.

bipolar transistor NPN design 2N5551;
microchip K561LA7;
microchip K561LN2.

How to make a humidity sensor

It is a common element for any of the three schemes under consideration and works due to the electrical conductivity of water.

The sensor is made of two electrodes, which can be located in or vertically relative to each other.

Horizontal pad design

The composition includes two dry electrodes, which can be of various configurations. It is convenient to cut them out of a foil fiberglass or getinax board by cutting insulating tracks on it.

You can experiment with the shape and dimensions of the humidity sensor, carefully select them for specific placement conditions. If there is no board at hand, then the contact pads are cut out of ordinary foil or tin, sticking them on a flat dielectric surface.

A positive electrical potential is applied to one electrode, and a negative one to the other. They are equally spaced, separated by an air gap with high dielectric properties.

When moisture appears on the electrodes, an electric current begins to pass through its layer, which changes the state of the electronic circuit of the leakage sensor, causing a light and sound alarm to be triggered.

Vertical pad design

Two strips of foil with dimensions of approximately 10x40 mm (dimensions are arbitrary and not of fundamental importance) are fixed with parallel planes at a small distance so as to exclude their spontaneous contact during operation.

It is better to connect the humidity sensor to the electronic circuit with short wires or use a screen or twisted pair.

Advice! You can increase the sensitivity of a home-made sensor with a simple action - put it with contact pads on a piece of toilet paper or several layers of gauze located in the place where water is likely to leak on the floor. Due to the hygroscopic properties of these materials, even at low humidity, a good conductive layer is formed.

Water leakage sensor on transistor 2N5551

This is the simplest, but quite reliable circuit that even a novice radio amateur can assemble.

Composition of parts

In addition to the humidity sensor, for the electrical circuit to work, you will need:

bipolar NPN transistor 2N5551 or one of its analogues: BC517, BC618, BC 879, 2SD1207, 2SD1853, 2SD2088;
LED VD1;
a 3 volt battery, such as a coin cell lithium battery;
three-volt piezo emitter;
connecting wires.

All these parts are placed in a small plastic box that serves as a housing and are connected by surface mounting by soldering.

The algorithm for triggering the leakage sensor is quite simple. In the dry position of the contact pads, the transistor VT1 is closed and no current passes through its collector-emitter semiconductor junction.

When water appears in the humidity sensor, a short circuit occurs between the electrodes, the positive potential of the battery goes to the base of the transistor and opens the transition from the collector to the emitter.

A current begins to flow through the piezoelectric emitter and the LED connected in parallel. The sound and light signal turns on, notifying residents of high humidity.

The assembly and operation of such a circuit based on the BC517 transistor can be viewed in a short video by the owner of “Hands from Shoulders”.

Water leakage sensor on the K561LA7 chip

It works according to a more complex, but quite affordable scheme, which has higher reliability and sensitivity.

Composition of parts

In addition to the humidity sensor and the K561LA7 microcircuit, assembly will require:

bipolar transistor VT1 series KT315G;
1 MΩ, 100 Ohm and kilo-ohm resistors: 1.5 K, 10 K, 300 K;
two polar capacitors for 2.2 and 47 microfarads for operation under voltage up to 16 volts;
200 picofarad capacitor;
Light-emitting diode;
sound wave generator ЗП-1;
switch SA-1;
power supply.

K561LA7 analogues are K176LA7, 564LA7, 164LA6, HFF4011BP, HCF4011BE, CD4011A, CD4011.

The circuit is not critical to the level of the supply voltage and works reliably within its limits from 5 to 15 volts.

The principle of operation of the electrical circuit

When voltage is supplied to the dry contacts of the humidity sensor from the power source, the LED does not light up, and the sound generator does not produce signals: the emitter-collector transistor junction is in the closed state.

When current appears through the humidity sensor, current will flow through the keys of the microcircuit to the base of the transistor, and it will open. The LED will light up and the buzzer will sound.

When the circuit is powered from the mains, and not from an autonomous source, it is better to switch SA1 to the down position. In this case, the LED will immediately glow, indicating the readiness of the leakage sensor to operate, and it will go out when the transistor is opened.

By changing the capacitance of the capacitor C2, the tone of the sound generator is adjusted.

The current consumption of the electrical circuit is:

approximately 1 mA in standby mode;
25 mA when triggered.

Water leakage sensor on the K561LN2 chip

It works according to a scheme similar to the previous one, it also has high sensitivity and reliability.

Composition of parts

In addition to the humidity sensor and the K561LN2 microcircuit, you will need:

bipolar transistor VT1 series KT3107D;
resistors for 3 MΩ and 30 K three pieces, 430 K - two, 430 K and 57K - one each;
100 microfarad polar capacitor for operation under voltage up to 16 volts;
a capacitor of 0.01 microns - two and 0.1 microns - also two;
sound wave generator ZP-22;
power supply for 6 ÷ 9 volts.

The principle of operation of the electrical circuit

With dry contacts of the humidity sensor, the transistor VD1 is closed, and when water appears on them, its semiconductor junction opens and the sound generator starts, which generates an alarm.

This circuit also has low power consumption. In standby mode, the load current of the voltage source does not exceed 1 mA, and when triggered, it is about 3 mA.

A water leakage sensor, assembled by hand according to any of the above electrical diagrams, can be installed in any problematic place where there is a high probability of creating an emergency in the water supply system under:

washing machine or dishwasher;
sink;
bathroom;
water supply pipeline system.

Its sound warning will promptly notify the residents of the apartment about the beginning of water leakage, but will not ensure its automatic shutdown. Other devices are designed to perform this function, which the owner of the Remontkv.pro video “How not to flood the neighbors” talks about.

"Smart" protection against water leaks in the apartment - do not flood your neighbor! Do-it-yourself water leakage protection for the home

How to signal a water leak

The principle of operation of leakage sensors

How sensors are arranged

Homemade sensor of the simplest design

How the scheme works

More complex circuit, with sensitivity control

Leakage sensor on the LM7555 chip

General principles for the placement of leakage sensors

The most critical points of water breakthrough

How to place sensors correctly

Device classification

Conclusion

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Circuit assembly and installation

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Composition of parts

The principle of operation of the electrical circuit

Water leakage sensor on the K561LN2 chip

Composition of parts

The principle of operation of the electrical circuit