- General description of the system
- Controller selection
- Leakage sensors
- Executive and auxiliary devices
- Circuit assembly and installation
In a country house, especially not intended for permanent residence, a leak from a water supply system can have very serious consequences. There are many ready-made solutions on the security systems market, however, today we will talk about self-construction of a leakage protection scheme.
General description of the system
There are two main topologies for leakage protection systems. The main difference between them is the method of signal transmission between the sensor, controller and actuators. Systems using wire transmission are simpler and more reliable, but they are not always convenient to use when the places of probable leaks are far away from each other, when the signal may not be recognized by the controller due to the length of the cable. In turn, wireless systems do not require cabling, so that decorative finishing coatings will not be damaged during installation, but such protection is more expensive.
In wired systems, communication between the leakage sensor and the controller is carried out over a three-wire wire. In addition, executive devices are connected to the control output of the controller: electric cut-off valves, light and sound alarm devices. If desired, the scheme can be supplemented with communication devices to alert the user via a mobile or home wireless network.
Schematic diagram of protection against water leaks: 1 – control unit; 2 – radio module; 3 – electric ball 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, but the leak detector itself and the transmitter need a stabilized power supply from an external unit or a battery. The locking 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.
The brain of the system is an electronic control unit. Its main function is to accurately recognize the change in the signal level from the sensor and apply voltage to the actuator. In this case, it is important that the controller has the function of restoring 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, three options can be proposed.
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 preservation 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 bypass with manual reset to keep it in the emergency mode. Nevertheless, this is the most budget-friendly option for building a circuit. Suitable solutions include Omron relay modules and Arduino expansion boards, as well as more expensive programmable relays like OVEN PR110 for connecting up to 12 sensors..
Programmable relay ARIES PR110
Programmable logic controllers are the most versatile type of control devices that allow you to implement more complex algorithms for the leakage protection system and interconnect them with other automation systems. For the same purposes, cheap single-board computers such as Arduino can be used, with the help of which functions such as forced draining of water from the tank of a washing machine can be implemented..
One of the channels of a home automation controller or fire and security alarm can be used to connect a flood sensor. The only problem is the mismatch of the type or level of the signal at the output of the sensor, so it often becomes necessary to supplement the circuit with an amplifier or a single-channel discrete converter..
An example of a leakage protection scheme on an Arduino
The simplest control device can be made with your own hands 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 for control (about 2-3 V) and are capable of switching up to 20 A of load current. A 300–500 ohm pull-up resistor is installed between the gate and the source to avoid accidental firing. It is advisable 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 gate to keep the key open. In the open circuit of the shunt, it is necessary to install a trip button for resetting the accident. Such a circuit can have an almost unlimited number of transistors and, accordingly, control a number of executive devices and indicators..
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 is used to transmit the alarm signal to the control unit. Some sensors have built-in sound and light signaling devices, and a galvanically isolated switch in the form of a relay can also be installed in one housing to supply power directly to the actuator.
Device for water leakage sensors GIDROLOCK
The most common sensors, primarily due to their low cost (about 500 rubles / piece), are the sensors “H2O Contact”, “Aquarius-R” and Equation. They have several versions for connection to both 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 able to switch a significant load, that is, they cannot directly control 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 – Ajax LeaksProtect, Ezviz T10, Neptun RSW + and other wireless devices. As a rule, these detectors are powered by a “Krona” type battery, with 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 – beeps or sends a notification via mobile communication when a leak is detected.
Wireless water leakage sensors: 1 – Ajax LeaksProtect; 2 – Ezviz T10; 3 – Neptun RSW+
In everyday life, the most popular are not individual sensors, but kits for installing leak protection systems. They can include up to three sensors, one or two electric valves, a power supply and a central control unit. Such kits are supplied to the market under the trademarks Neptun, Aquastorozh and Gidrolock.
Protection system against water leaks “Aquastorozh Classic 2×20”
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 be used only 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 return contact of the relay or manually through the button – a kind of replacement for resetting the alarm.
Ball valve with electric GIDROLOCK PROFESSIONAL
Normally open electromechanical valves operate once when a control signal is applied and close 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 with a power failure and is manually charged after the leak is eliminated.
Solenoid valve for water
Actuators do not have to be specialized; any taps or valves for plumbing systems will do. However, it is necessary 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.
Also, auxiliary devices may be present in the circuit:
- Radio communication modules – a set of a transmitter and a receiver, for example, the MX series at 433 MHz, will create a wireless connection between the sensor and the control unit using equipment designed for building systems with wired communication.
- Amplifiers and signal modulators are designed to match logic levels between sensors and a control unit. As amplifiers, the most popular single-board modules based on the LM358 microcircuit, for signal conversion – modular DAC / ADC on PCF8591.
- Intermediate relays will be useful if the relay group of the control unit does not allow switching of significant currents. The most preferred relays are designed for low control voltage – 24 or 36 V.
Circuit assembly and installation
There is no difficulty in installing the leakage protection system if a ready-made kit is used: all elements are fully compatible, the connectors fit each other, detailed instructions are available. Assemblies of an individual configuration are more difficult to implement, so consider the topology of a protection system with two sensors and wireless communication.
The “H2O Contact” in four-wire version with a normally open contact will be used as a flood sensor. The brown (+) and white (-) wires are connected to the 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 coiled copper wire to the ANT pad on the transmitter board. The sensor is fixed with screws or on double-sided tape, the electrodes must be firmly pressed to the floor. The wire from the sensor is routed along the wall to a small plastic case that houses the radio transmitter and power supply.
Wiring diagram for anti-leakage system with two sensors and wireless communication
The MX-05V radio receiver is installed near the control device, which will be the FRM01 programmable relay module. 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 5 V power supply. The amplifier module also needs 12 V power through the VCC and GND terminals. The output from the amplifier module is connected to the input terminal of the IN relay module, which also connects to a 12V power supply (the circuit is protected against polarity reversal).
It is recommended to use an NT9047 ball valve with a supply voltage of 24 V as an actuator, which is installed at the inlet of the water main. The neutral wire of the crane is connected to the minus of the power supply, the wire of the closing contact is connected to the normally open output of the relay, the opening contact to the normally closed one. The relay must be configured according to the instructions – set function No. 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.