Automatic water level control. Simple homemade indicators of the level of water (liquid) in the tank. How to check the water level in a barrel. Wastewater level control
When it becomes necessary to control the liquid level, many do this work manually, but this is extremely inefficient, takes a lot of time and effort, and the consequences of an oversight can be very expensive: for example, a flooded apartment or a burned-out pump. This can be easily avoided by using float switches. These devices are simple in design and principle of operation, affordable.
At home, sensors of this type allow you to automate processes such as:
- control of the liquid level in the supply tank;
- pumping out ground water from the cellar;
- turning off the pump when the level in the well falls below the permissible level, and some others.
The principle of operation of the float sensor
An object is placed in a liquid that does not sink in it. It can be a piece of wood or styrofoam, hollow plastic sphere or metal and much more. When the liquid level changes, this object will rise or fall with it. If the float is connected to the actuator, it will act as a water level sensor in the tank.
Equipment classification
Float sensors can independently control the liquid level or send a signal to the control circuit. According to this principle, they can be divided into two large groups: mechanical and electrical.
Mechanical devices
Mechanical valves include a wide variety of float valves for the water level in the tank. The principle of their operation is that the float is connected to the lever, when the liquid level changes, the float moves up or down that lever, and he, in turn, acts on the valve, which shuts off (opens) the water supply. Such valves can be seen in toilet cisterns. They are very convenient to use where you need to constantly add water from central system water supply.
Mechanical sensors have a number of advantages:
- simplicity of design;
- compactness;
- safety;
- autonomy - do not require any sources of electricity;
- reliability;
- cheapness;
- ease of installation and configuration.
But these sensors have one significant drawback: they can control only one (upper) level, which depends on the installation site, and regulate it, if possible, then within very small limits. On sale such a valve can called "float valve for tanks".
Electrical sensors
An electric liquid level sensor (float) differs from a mechanical one in that it does not shut off the water itself. The float, moving when the amount of liquid changes, acts on the electrical contacts that are included in the control circuit. Based on these signals, the automatic control system decides on the need for certain actions. In the simplest case, such a sensor has a float. This float acts on the contact through which the pump is turned on.
Reed switches are most often used as contacts. A reed switch is a sealed glass bulb with contacts inside. The switching of these contacts occurs under the action of magnetic field. Reed switches are miniature in size and can be easily placed inside a thin tube made of non-magnetic material (plastic, aluminum). A float with a magnet moves freely along the tube under the action of the liquid, when it approaches, the contacts are triggered. The whole system is installed vertically in the tank. By changing the position of the reed switch inside the tube, you can adjust the moment of operation of the automation.
If you need to monitor the upper level in the tank, then the sensor is installed at the top. As soon as the level falls below the set level, the contact closes and the pump turns on. Water will start to increase and when the water level reaches the upper limit, the float will return to its original state and the pump will turn off. However, such a scheme cannot be applied in practice. The fact is that the sensor is triggered at the slightest change in level, after which the pump turns on, the level rises, and the pump turns off. If the water flow from the tank is less than supply, a situation arises when the pump constantly turns on and off, while it quickly overheats and fails.
Therefore, water level sensors to control the pump work differently. The container has at least two contacts. One is responsible for the upper level, it turns off the pump. The second defines the position of the lower level, upon reaching which the pump turns on. Thus, the number of starts is significantly reduced, which ensures reliable operation of the entire system. If the level difference is small, then it is convenient to use a tube with two reed switches inside and one float that switches them. With a difference of more than a meter, two separate sensors are used, installed at the required heights.
Despite more complex structure and the need for a control circuit, electric float sensors allow you to fully automate the process of controlling the liquid level.
If you connect light bulbs through such sensors, then they can be used to visually control the amount of liquid in the tank.
Homemade float switch
If you have the time and desire, then the simplest float water level sensor can be made by hand, and the cost of it will be minimal.
mechanical system
In order to make it as easy as possible design, we will use a ball valve (faucet) as a locking device. The smallest valves (half-inch and smaller) work well. Such a faucet has a handle with which it closes. To convert it into a sensor, it is necessary to lengthen this handle with a strip of metal. The strip is attached to the handle through holes drilled in it with appropriate screws. The cross section of this lever should be minimal, but at the same time it should not bend under the action of the float. Its length is about 50 cm. The float is attached to the end of this lever.
Can be used as a float use a two-liter plastic bottle from soda. The bottle is half filled with water.
You can check the operation of the system without installing it in the tank. To do this, install the crane vertically, and put the lever with the float in a horizontal position. If everything is done correctly, then under the influence of the mass of water in the bottles, the lever will begin to move down and take a vertical position, and the valve handle will turn with it. Now submerge your device in water. The bottle should pop up and turn the valve handle.
Since the valves vary in size and the force required to switch them, it may be necessary to adjust the system. If the float cannot turn the valve, you can increase lever length or take a larger bottle.
We mount the sensor in the tank at the required level in horizontal position, while in vertical position float valve must be open, and in the horizontal - closed.
Electrical type sensor
For self-manufacturing of the sensor of this type, in addition to the usual tool, you will need:
The manufacturing sequence is as follows:
When the liquid level changes, the float moves with it, which acts on the electrical contact to control the water level in the tank. The control circuit with such a sensor may look like the one shown in the figure. Points 1, 2, 3 are the connection points for the wire that comes from our sensor. Point 2 is the common point.
Consider the principle of operation homemade device. Let's say when the tank is turned on empty, the float is in the low position (LL), this contact closes and energizes the relay (P).
The relay is activated and closes contacts P1 and P2. P1 is a self-locking contact. It is needed so that the relay does not turn off (the pump continues to work) when the water starts to arrive and the NU contact opens. Contact P2 connects the pump (H) to the power supply.
When the level rises to the upper value, the reed switch will work and open its VU contact. The relay will be de-energized, it will open its contacts P1 and P2, and the pump will turn off.
With a decrease in the amount of water in the tank, the float will begin to descend, but until it takes the lower position and closes the HL contact, the pump will not turn on. When this happens, the cycle of work will repeat again.
This is how it works float switch water level control.
During operation, it is necessary to periodically clean the pipe and the float from contamination. Reed switches withstand a huge number of switchings, so such a sensor will last for many years.
To automate many production processes, it is necessary to control the water level in the tank, the measurement is carried out using a special sensor that gives a signal when the process medium reaches a certain level. It is impossible to do without level gauges in everyday life, a prime example this - shut-off valves toilet cistern or automation to turn off the well pump. let's consider different kinds level sensors, their design and principle of operation. This information will be useful when choosing a device for a specific task or making a sensor with your own hands.
Design and principle of operation
Design of measuring devices of this type defined by the following parameters:
- Functionality, depending on this device, is usually divided into signaling devices and level gauges. The former monitor a specific tank filling point (minimum or maximum), the latter continuously monitor the level.
- The principle of operation, it can be based on: hydrostatics, electrical conductivity, magnetism, optics, acoustics, etc. Actually, this is the main parameter that determines the scope.
- Measurement method (contact or non-contact).
In addition, the design features determine the nature of the process environment. It's one thing to measure the height drinking water in the tank, the other is to check the filling of industrial wastewater tanks. IN last case appropriate protection is required.
Types of level sensors
Depending on the principle of operation, signaling devices are usually divided into the following types:
- float type;
- using ultrasonic waves;
- devices with capacitive level detection principle;
- electrode;
- radar type;
- operating on the hydrostatic principle.
Since these types are the most common, we will consider each of them separately.
float
This is the most simple, but, nevertheless, effective and reliable way measuring liquid in a tank or other container. An example implementation can be found in Figure 2.
Rice. 2. Float switch for pump control The design consists of a float with a magnet and two reed switches installed at control points. Briefly describe the principle of operation:
- The tank is emptied to a critical minimum (A in Fig. 2), while the float drops to the level where the reed switch 2 is located, it turns on the relay that supplies power to the pump that pumps water from the well.
- The water reaches the maximum mark, the float rises to the location of the reed switch 1, it works and the relay turns off, respectively, the pump motor stops working.
It is quite simple to make such a reed switch on your own, and its setting comes down to setting on-off levels.
Note that if you choose the right material for the float, the water level sensor will work even if there is a layer of foam in the tank.
Ultrasonic
This type of meter can be used for both liquid and dry applications and can have an analog or discrete output. That is, the sensor can limit the filling to a certain point or monitor it constantly. The device includes an ultrasonic emitter, a receiver and a signal processing controller. The principle of operation of the signaling device is shown in Figure 3.
Rice. 3. Working principle ultrasonic sensor level The system works as follows:
- an ultrasonic pulse is emitted;
- reflected signal is received;
- the duration of the signal attenuation is analyzed. If the tank is full, it will be short (A fig. 3), and as it empties it will begin to increase (B fig. 3).
The ultrasonic signaling device is non-contact and wireless, so it can be used even in aggressive and explosive environments. After the initial adjustment, such a sensor does not require any specialized maintenance, and the absence of moving parts significantly extends the service life.
Electrode
Electrode (conductometric) signaling devices allow you to control one or more levels of an electrically conductive medium (that is, they are not suitable for measuring the filling of a tank with distilled water). An example of using the device is shown in Figure 4.
Figure 4. Liquid level measurement with conductometric sensors In the above example, a three-level signaling device is used, in which two electrodes control the filling of the tank, and the third one is an emergency one, to enable the intensive pumping mode.
capacitive
With the help of these signaling devices, it is possible to determine the maximum filling of the container, and both liquid and loose substances of a mixed composition can act as a technological medium (see Fig. 5).
Rice. 5. Capacitive level sensor The principle of operation of the signaling device is the same as that of a capacitor: the capacitance is measured between the plates of the sensitive element. When it reaches the threshold value, a signal is sent to the controller. In some cases, the “dry contact” version is involved, that is, the level gauge works through the tank wall in isolation from the process medium.
These devices can operate over a wide temperature range and are not affected by electromagnetic fields, and operation is possible at a great distance. Such characteristics significantly expand the scope of application up to difficult conditions operation.
Radar
This type of signaling devices can really be called universal, since it can work with any process medium, including aggressive and explosive ones, and pressure and temperature will not affect the readings. An example of the operation of the device is shown in the figure below.
The device emits radio waves in a narrow range (several gigahertz), the receiver catches the reflected signal and determines the capacity of the container by its delay time. The measuring transducer is not affected by pressure, temperature, or the nature of the process fluid. Dust also does not affect the readings, which cannot be said about laser signaling devices. It is also necessary to note the high accuracy of devices of this type, their error is no more than one millimeter.
Hydrostatic
These alarms can measure both the limit and the current filling of tanks. Their principle of operation is shown in Figure 7.
Figure 7. Filling measurement with a gyro sensor The device is built on the principle of measuring the pressure level produced by a liquid column. Acceptable accuracy and low cost made this species quite popular.
Within the framework of the article, we cannot examine all types of signaling devices, for example, rotary-flag ones, for determining bulk solids (there is a signal when the fan blade gets stuck in a loose medium, after the pit has been pulled out). It also makes no sense to consider the principle of operation of radioisotope meters, all the more so to recommend them for checking the level of drinking water.
How to choose?
The choice of a water level sensor in the tank depends on many factors, the main ones are:
- Liquid composition. Depending on the content of foreign impurities in the water, the density and electrical conductivity of the solution may change, which is likely to affect the readings.
- The volume of the tank and the material from which it is made.
- The functional purpose of the container for the accumulation of liquid.
- The need to control the minimum and maximum levels, or monitoring of the current state is required.
- Admissibility of integration into the automated control system.
- Switching capabilities of the device.
This is far from full list to select measuring devices of this type. Naturally, for household purpose it is possible to significantly reduce the selection criteria by limiting them to the volume of the tank, the type of operation and the control scheme. A significant reduction in requirements makes it possible independent production similar device.
We make a water level sensor in the tank with our own hands
Suppose there is a task to automate the operation of a submersible pump for the water supply of a summer residence. As a rule, water enters the storage tank, therefore, we need to make sure that the pump turns off automatically when it is full. It is not at all necessary to buy a laser or radar level indicator for this purpose; in fact, you do not need to purchase any. A simple task requires a simple solution, it is shown in Figure 8.
To solve the problem, you will need a magnetic starter with a 220-volt coil and two reed switches: the minimum level - for closing, the maximum - for opening. The connection diagram of the pump is simple and, importantly, safe. The principle of operation was described above, but we repeat it:
- As the water fills, the float with the magnet gradually rises until it reaches the maximum level reed switch.
- The magnetic field opens the reed switch, turning off the starter coil, which leads to a de-energization of the motor.
- As the water flows, the float drops until it reaches the minimum mark opposite the lower reed switch, its contacts close, and voltage is supplied to the starter coil, which supplies voltage to the pump. Such a water level sensor in the tank can work for decades, unlike electronic system management.
In industry and everyday life, there is a constant need to control the levels of liquids in containers. Measuring devices are classified as contact and non-contact. For both options, the water level sensor is located at a certain height of the tank, and it works, signaling or giving a command to change the mode of its supply.
Contact devices operate on the basis of floats that switch circuits when the liquid reaches predetermined levels.
Non-contact methods are divided into magnetic, capacitive, ultrasonic, optical and others. The devices have no moving parts. They are immersed in controlled liquid or granular media or attached to tank walls.
float switches
Reliable and cheap devices for controlling the level of liquids using floats are the most common. Structurally, they may differ. Let's look at their types.
Vertical arrangement
A float water level sensor with a vertical stem is often used. Inside it is a round magnet. The rod is a hollow plastic tube with reed switches located inside.
A float with a fixed magnet is always located on the surface of the liquid. Approaching the reed switch, the magnet field triggers its contacts, which is a signal that the container is filled to a certain volume. When the contact pairs are connected in series through resistors, you can constantly monitor the water level by the total resistance of the circuit. The standard signal then changes from 4 to 20 mA. The water level sensor is most often placed in the upper part of the tank in a section up to 3 m long.
Electrical circuits with reed switches may differ in the external similarity of the mechanical part. Sensors are located on one, two and more levels, signaling how full the tank is. They can also be linear, transmitting the signal continuously.
Horizontal arrangement
If it is not possible to install the sensor from above, it is fixed horizontally to the tank wall. A magnet with a float is mounted on a lever with a hinge, and a reed switch is placed in the housing. When the liquid rises to the upper position, the magnet approaches the contacts and the sensor is triggered, signaling that the limit position has been reached.
In case of increased contamination or freezing of the liquid, a more reliable float water level sensor on a flexible cable is used. It consists of a small sealed container placed at a depth with a metal ball with a reed contact or a toggle switch inside. When the water level coincides with the position of the sensor, the container is turned over and the contact is activated.
One of the most accurate and reliable float sensors are magnetostrictive. They contain a float with a magnet that slides over a metal rod. The principle of operation is to change the duration of the passage of an ultrasonic pulse through the rod. The absence of electrical contacts significantly increases the clarity of operation when the interface between media reaches a given position.
Capacitive sensors
The non-contact device responds to the difference between the dielectric constant of different materials. The water level sensor in the tank is installed outside the side wall of the tank. In this place, there should be an insert made of glass or fluoroplast so that the interface between the media can be distinguished through it. The distance at which the sensitive element detects a change in the controlled environment is 25 mm.
Sealed design capacitive sensor makes it possible to place it in a controlled environment, for example, in a pipeline or in a tank lid. However, it may be under pressure. Thus, the presence of liquid in the closed reactor is maintained during the process.
Electrode sensors
The water level sensor with electrodes placed in the liquid responds to changes in the electrical conductivity between them. To do this, they are fastened with clamps and placed at the maximum upper and lower levels. With a longer pair, another conductor is installed, but usually the metal body of the tank is used instead.
The water level sensor circuit is connected to the pump motor control system. When the tank is full, all electrodes are immersed in liquid and a control current flows between them, which is a signal to turn off the water pump motor. Water also does not enter unless it touches the bare top conductor. The signal to turn on the pump is when the level drops below the long electrode.
The problem with all sensors is the oxidation of contacts in water. To reduce its influence, stainless steel or graphite rods are used.
DIY water level sensor
The simplicity of the device makes it possible to make it yourself. To do this, you need a float, a lever and a valve. The whole structure is placed at the top of the tank. A float with a lever is connected to a rod that moves the piston.
When the water reaches the upper limit level, the float moves the lever, which acts on the piston and closes the flow through the lower pipe.
As the water flows, the float lowers, after which the piston reopens the hole through which the tank can be refilled.
At right choice and manufacturing, a self-assembled water level sensor works reliably in the household.
Conclusion
The water level sensor is indispensable in the private sector. With it, time is not lost when monitoring the filling of the tank in the garden, the level in the well, well or septic tank. A simple device without the help of the owner will start or turn off the water pump in time. Just do not forget about its prevention.
Water level sensor in conditions modern technology performs the function of one of the human senses. The correct operation of the entire mechanism depends on how correctly it is possible to manage and control the state of the water flow. It is difficult to overestimate the importance of the reliability of the sensor device, if only because the device that controls water, as a rule, becomes the very "narrow" link in modern technology.
Design and principle of operation
Regardless of what principle of operation the device is based on, whether it works only in the signaling mode or simultaneously performs the functions of a watchman, automatic machine or control mechanism, the design of the device always consists of three main components:
- A sensing element capable of responding to the characteristics of the water flow. For example, the actual presence of water, the height of the column or the level in the tank, the fact of the movement of water flow in a pipe or line;
- A ballast element that balances the sensor part of the sensor. Without the ballast, the sensitive sensor would be triggered by the slightest jolt or the occasional drop of water;
- Transmitting or actuating part that converts the signal of the sensor mounted in the water sensor into a specific signal or action.
Approximately 90% of all water technology, one way or another, is connected with electric actuators - pumps, valves, heaters and electronic control machines. It is clear that such a device operating with water flows must be safe in the first place.
Of all signaling systems a sensor that monitors the state of water is considered the simplest and most affordable to set up and repair. Unlike sensors and devices that work with temperature, pressure or flow measurements, the water sensor is very easy to control using the simplest devices, or, in extreme cases, see the level or pumped flow with your own eyes.
Types of level sensors
One of the conditions for the successful operation of the sensor is the high sensitivity of the sensor, the higher the better, the more accurately it is possible to read the controlled water parameter. Therefore, as the value measured by the sensor, they try to choose the one that changes the most during the measurement.
Today there are about two dozen various ways and methods for measuring the mechanical characteristics of water, but all of them are used to obtain information:
- The height of the water column in the container or tank;
- The speed of the flow or flow of water;
- The fact of the presence or absence of water in a closed container, tank, pipe or heat exchanger.
Of course, industrial sensors can be quite complex structurally, but the principles of operation used in them are the same as in household, garden or automotive equipment.
Float type overflow sensor
The easiest way to measure the water level is used in a simple mechanical design, consisting of a sealed float, a rocker or backstage and a shut-off valve. IN this case the float is the sensor, the spring and the float weighting are considered the ballast, and the valve itself acts as the actuator.
In all float systems, the sensor or float is adjusted to a specific response height. The water that has risen in the tank to the control level raises the float and opens the valve.
The float system can be equipped with an electric actuator. For example, a magnet insert is installed inside the float sensor, when the water rises to the working level, the magnetic field causes the vacuum reed switch to close the contacts, and thereby turns on or off the electrical circuit.
The float switch can also be made according to free scheme as, for example, in submersible pumps. In this case, the reed switch closes not under the influence of the magnetic field of the liner, but only due to the pressure difference inside the pump housing and at the level of the float. Today, a magnetic float sensor with an electric actuator is considered one of the safest and most reliable options for monitoring the liquid level.
Ultrasonic sensor
The design of the water sensor provides for the presence of two devices - an ultrasound source and a signal receiver. The sound wave is directed to the surface of the water, reflected and returned to the receiver.
At first glance, the idea of using ultrasound to make a sensor for controlling the level or speed of water movement does not look very successful. Ultra sound wave can be reflected from the walls of the tank, refract and interfere with the operation of the receiving sensor, and in addition, complex electronic equipment will be required.
In fact, an ultrasonic sensor for measuring the level of water or any other liquid is placed in a box a little more than a pack of cigarettes, while using ultrasound as a sensor provides certain advantages:
- The ability to measure the level, and even the speed of water at any temperature, in conditions of vibration or movement;
- The ultrasonic sensor can measure the distance from the sensor to the water surface even under heavy pollution, with variable liquid level.
In addition, the sensor can measure the level of water located at a considerable depth, while the measurement accuracy is 1-2 cm for every 10 m of height.
Electrode water control principle
The fact that water is electrically conductive has been successfully used to make liquid level contact sensors. Structurally, the system consists of several electrodes installed in a container at different heights and connected into one electrical circuit.
As the container is filled with water, the liquid closes a pair of contacts in series, which turns on the pump control relay circuit. As a rule, the water sensor has two or three electrodes, so the measurement of the water flow is too differentiated. The sensor signals only when the minimum level is reached and starts the pump motor, or when the tank is full and turns it off, so such systems are used to control reserve or irrigation water tanks.
Capacitive type water sensor
Capacitive or capacitive type of sensor is used to measure the water level in narrow and deep tanks, it can be a well or a well. Using a capacitive sensor, you can determine the height of the water column in the well with an accuracy of tens of centimeters.
The sensor design consists of two coaxial electrodes, in fact a pipe and an internal metal electrode, immersed in the wellbore. Water fills part inner space system, thereby changing its capacity. Using the connected electronic circuit and the quartz oscillation coil, the capacitance of the sensor and the amount of water in the well can be accurately determined.
radar meter
A wave or radar sensor is used to work in the most difficult conditions, for example, if you need to measure the level or volume of liquid in a tank, an open reservoir, a well of an asymmetric and irregular shape.
The principle of operation does not differ from the ultrasonic device, and the use of an electrical pulse allows you to perform a measurement with great accuracy.
Hydrostatic sensor option
One of the variants of the hydrostatic sensor is shown in the diagram.
For your information! A similar sensor is used in washing machines and boilers, where it is very important to control the height of the water column inside the tank.
The hydrostatic sensor is a box with an elastic spring-loaded membrane that divides the sensor body into two compartments. One of the sections is connected with a strong polyethylene tube with a fitting soldered into the bottom of the tank.
The pressure of the water column is transmitted through the tube to the membrane and causes the contacts of the starting relay to close, most often to start executive mechanism a pair is used - a magnetic insert and a reed switch.
Water pressure sensor
Hydrostatic pressure is determined when a flow or a certain volume of water is at rest. Most often, the hydrostatic sensor is used in heating and heating appliances- boilers, heating boilers.
Water pressure sensor device
Such devices most often operate in trigger mode:
- At high pressure water sensor closes the relay contacts and allows the pump or heater to work;
- At low pressure even the physical possibility of turning on the actuator is blocked in the sensor, that is, no shocks or temporary surges in pressure will make the device work.
With a good water pressure sensor, the sensor will give a signal to start the motor only if the load on the bellows is maintained for more than three seconds.
A typical device of a "smart" sensor is shown in the diagram.
The sensitive element of the system is a diaphragm connected to the bellows, the central rod can rise and fall depending on the pressure, and thereby change the capacitance of the built-in capacitor.
Connecting the water pressure sensor
A simplified sensor model is used in home systems "hydroaccumulator - borehole pump". Inside the instrument is a box with a membrane connected to a rocker arm and two balancing springs.
The design is screwed onto the outlet fitting of the accumulator. With an increase in internal pressure, the membrane rises and opens the main pair of contacts so that the system responds properly to water pressure;
Water leakage sensor
Already from the name it becomes clear that we are talking about a device that detects the presence of water leakage from water supply lines. The principle of operation of the device resembles an electrode system. Inside the plastic box, one or more pairs of electrodes are installed in a special pocket. In the event of an accident, water accumulating on the floor flows into the pocket and closes the contacts. Works electronic circuit, and at the signal of the sensor, ball valves with electric drive come into operation.
It is clear that the sensor, by itself, is a useless thing if used without a control system and automatic water cut-offs installed at the entrance to the house or on one of the branches of the water supply.
An example is one of the most popular protection systems - the Neptune water leakage sensor. The system includes three main blocks:
- The Neptune leak sensor itself is in wired or wireless modification, usually three separate sensors are included in the kit;
- Ball valve with electric drive, manufactured by the Italian company Bugatti, in the amount of two pieces;
- Control unit «Neptun Base».
The most valuable part of the kit - automatic cranes, they are produced for installation on half-inch and inch pipe threads. The design withstands pressure up to 40 atm., and Italian quality drive guarantees at least 100 thousand opening-closing cycles.
The sensor itself looks like two brass plates in a box, to which a low-voltage voltage with a very high input resistance is connected, when the sensor is closed, the current is limited to 50 mA. The design itself is made according to the IP67 protocol, therefore it is absolutely safe for humans.
Installation of wireless water leakage sensors
In the Neptune system, the sensor can be removed from the control unit at a distance of more than 50 m. In more advanced NEPTUN PROW + wireless systems, water leakage sensors equipped with the WF module are used instead of a wire system.
The control unit is equipped with a channel protected from interference and moisture, a system for turning on and off ball valves. It is believed that no interference or accidental drops of moisture, condensate affect the operation of the sensors.
Boxes with a leakage sensor are installed at a distance of no more than 2 m from pipes; sensors cannot be shielded with metal plumbing or furniture.
Wireless water sensor
The design of a wireless meter is more complex than a conventional two-electrode variant with wired connection. A controller is installed inside, which continuously compares the current flowing between the electrodes with the reference value stored in the memory. In this case, the dry floor reference value can be set according to your own choice.
Very convenient solution, given that the humidity level in the bathroom can be very high, and regular condensation can lead to false alarms.
As soon as the controller determines the level corresponding to flooding, the water control device sends an alarm signal to the base unit. The most advanced models are able to duplicate the command with an SMS message over the GSM channel.
Water flow sensor
In many cases, for stable and trouble-free operation of equipment, a water presence sensor is not enough; information is required on whether the flow is moving through the pipeline, what is its speed and pressure. For these purposes, water flow sensors are used.
Types of water flow sensors
In household and the simplest industrial equipment, four main types of flow sensors are used:
- Pressure gauge;
- Petal sensor type;
- Blade measurement scheme;
- Ultrasonic system.
The older pitot tube design is sometimes used, but requires at least a clean and laminar flow of water to function reliably. The first three sensors are mechanical, so they are often subject to clogging or water erosion of the sensing element. The last type of sensor, ultrasonic, is able to work in almost any conditions.
The principle of operation of an ultrasonic meter can be understood from the diagram. Inside the tube is a wave emitter and a receiver. Depending on the flow velocity, the sound wave may deviate from its original direction, which is the basis for measuring the flow characteristics.
Device and principle of operation
The simplest petal flow sensors work on the principle of a rowing oar. A petal suspended on a hinge is immersed in the stream. The higher the flow velocity, the more the sensor lobe deviates.
More accurate paddle sensors use an impeller or impeller made of polyamide or aluminum alloy. In this case, it is possible to measure the flow velocity from the frequency of rotation of the moving element. The only drawback is the increased resistance created by the petals and blades in the water flow.
The pressure sensor works using dynamic flow pressure. Under the pressure of water, the movable element with a magnetic insert is squeezed upwards, thereby freeing up space for the movement of fluid. The reed switch installed in the head instantly reacts to the magnetic field of the insert and closes the circuit.
Application area
Water flow sensors are used exclusively in heating systems and automation systems of single-circuit heat exchangers. Most often, the failure of the flow sensor leads to burnout and severe damage to hot radiators and heaters.
DIY water level sensor
The simplest version of a device capable of signaling the filling of a tank or any other container with water is shown in the diagram below.
Structurally, the level detector consists of three metal electrodes mounted on a textolite plate. The circuit, assembled on a conventional low-power transistor, allows you to determine the maximum permissible upper and lower water levels in the tank.
The design is absolutely safe to use and does not require any expensive parts or control devices.
Conclusion
Water level sensors are widely used in household appliances, therefore, most often for the auxiliary needs of a garage or garden equipment use ready-made designs from old technology, reworked and adapted to new conditions. At correct connection such a device will last much longer than a home-made circuit.
Many of us, and not only avid summer residents, faced the problem of automation and control of filling containers with water. Most likely this article is for those who decide to do the simplest circuit container filling control living conditions. Most budget way building automation is the use of a water control relay. Level control relays (water) are also used in more complex systems water supply of private houses, but in this article we will consider only budget models of a conductive liquid level control relay. Controlled liquids include: water (tap, spring, rain), liquids with a low alcohol content (beer, wine, etc.), milk, coffee, waste water, liquid fertilizers. The rated current of the relay contacts is 8-10A, which allows switching small pumps without using an intermediate relay or contactor, but manufacturers still recommend installing intermediate relays or contactors to turn the pumps on / off. The temperature range of the devices is from -10 to +50C, and the maximum possible wire length (from the relay to the sensor) is 100 meters, there are LED operation indicators on the front panel, the weight is not more than 200 grams, it is mounted on a din rail, so you will need to think in advance placement of the control system.
The principle of operation of the relay is based on measuring the resistance of a liquid located between two immersed sensors. If the measured resistance is less than the threshold value, then the state of the relay contacts changes. To avoid an electrolytic effect, alternating current flows across the sensors. The supply voltage of the sensor is not more than 10V. Power consumption is not more than 3W. Fixed sensitivity 50 kOhm.
There are many relays of the same type on the market, let's consider the most budgetary models from the manufacturers "Relays and Automation" in Moscow and the novelties of "TDM" (Trading House named after Morozov).
Level control relay . ( analogue of RKU-02 TDM)
The TDM level control relay is represented by four models:
- (SQ1507-0002) for connector Р8Ц(SQ1503-0019) on DIN rail
- (SQ1507-0003) on DIN rail analogue of RKU-1M)
- (SQ1507-0004) on DIN rail
- (SQ1507-0005) on DIN rail
Relay housings are made of flame retardant materials. Level sensors are made of of stainless steel. (DKU-01 SQ1507-0001).
The operation of the relay is based on the conductometric method for determining the presence of liquid, which is based on the electrical conductivity of liquids and the occurrence of microcurrent between the electrodes. The relays have changeover contacts, which allows the filling or draining mode to be used. Supply voltage RKU-02, RKU-03, RKU-04 - 230V or 400V.
Tank pump control circuit in "fill or drain" mode.
Scheme of pumping fluid from a well/reservoir to a reservoir, level control in both media, i.e. the relay performs a protective shutdown of the pump in dry running mode (when the liquid level in the well/reservoir drops)
Scheme of sequential or total inclusion of 2 pumps. The RKU-04 relay is used in places where overflow of wells, pits, catchment and other containers is unacceptable. The relay works with 2 pumps, and, for uniform use their resource, the relay switches them on one by one. When emergency both pumps are switched off at the same time.
The relay cannot be used for the following liquids: distilled water, gasoline, kerosene, oil, ethylene glycols, paints, LPG.
Comparative table of analogues by series:
| TDM | F&F | lovato | R&A |
|---|---|---|---|
| RKU-01 | PZ-829 | LVM20 | RKU-1M |
| RKU-02 | PZ-829 | LVM20 | RKU-1M |
| RKU-03 | - | LVM20 | EBR-02 |
| RKU-04 | - | LVM20 | - |
