Many of us, and not only avid summer residents, have faced the problem of automation and control of filling containers with water. Most likely, this article is specifically for those who decided to make a simple scheme for monitoring the filling of a container at home. The most cost-effective way to build automation is to use a water control relay. Level control relays (water) are also used in more complex water supply systems for private houses, but in this article we will consider only budget models of conductive liquid level control relays. Controlled liquids include: water (tap, spring, rain), liquids with low alcohol content (beer, wine, etc.), milk, coffee, wastewater, liquid fertilizers. The rated current of the relay contacts is 8-10A, which allows you to switch small pumps without using an intermediate relay or contactor, but manufacturers still recommend installing intermediate relays or contactors to turn pumps on/off. The operating 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, weight no more than 200 grams, DIN-rail mounting, so you will need to think about it in advance placement of the control system.

The principle of operation of the relay is based on measuring the resistance of the liquid located between two immersed sensors. If the measured resistance is less than the response threshold, then the state of the relay contacts changes. To avoid electrolytic effects, alternating current flows across the sensors. The sensor supply voltage is no more than 10V. Power consumption no more than 3W. Fixed sensitivity 50 kOhm.

There are many relays of the same type on the market; let’s consider the most budget models from the manufacturers “Relay and Automation” in Moscow and new products from “TDM” (Morozov Trading House).

Level control relay. ( analogue of RKU-02 TDM)

The TDM level control relay is available in four models:

1. (SQ1507-0002) for connector Р8Ц (SQ1503-0019) on DIN rail
2. (SQ1507-0003) on DIN rail ( analogue of RKU-1M)
3. (SQ1507-0004) on DIN rail
4. (SQ1507-0005) on DIN rail

Relay housings are made of flame retardant materials. Level control sensors are made 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, allowing the use of fill or drain mode. Supply voltage RKU-02, RKU-03, RKU-04 – 230V or 400V.

Scheme for controlling a pump in a tank in the “filling or draining” mode.

Scheme of pumping liquid 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 decreases)

Scheme of alternating or total activation of 2 pumps. The RKU-04 relay is used in places where overfilling of wells, pits, catch basins and other containers is unacceptable. The relay works with 2 pumps, and, for uniform use of their resource, the relay switches them on alternately. In the event of an emergency, both pumps are switched off simultaneously.

The relay cannot be used for the following liquids: distilled water, gasoline, kerosene, oil, ethylene glycols, paints, liquefied gas.

Comparative table of analogues by series:

TDM	F&F	lovato	RiA
RKU-01	PZ-829	LVM20	RKU-1M
RKU-02	PZ-829	LVM20	RKU-1M
RKU-03	-	LVM20	EBR-02
RKU-04	-	LVM20	-

Water supply and drainage is an integral part of everyday life and production. Almost everyone who has been involved in farming or home improvement has at least once encountered the problem of maintaining the water level in one container or another. Some people do this manually by opening and closing valves, but it is much easier and more efficient to use an automatic water level sensor for this purpose.

Types of level sensors

Depending on the tasks assigned, contact and non-contact sensors are used to monitor the liquid level. The former, as one might guess from their name, have contact with the liquid, the latter receive information remotely, using indirect measurement methods - transparency of the medium, its capacity, electrical conductivity, density, etc. According to the principle of operation, all sensors can be divided into 5 main types:

1. Float
2. Electrode.
3. Hydrostatic.
4. Capacitive.
5. Radar.

The first three can be classified as contact-type devices, since they directly interact with the working medium (liquid), the fourth and fifth are non-contact.

Float sensors

Perhaps the simplest in design. They are a float system that is located on the surface of the liquid. As the level changes, the float moves, one way or another closing the contacts of the control mechanism. The more contacts there are along the path of movement of the float, the more accurate the indicator readings:

Operating principle of a float water level sensor in a tank

The figure shows that the indicator readings of such a device are discrete, and the number of level values ​​depends on the number of switches. In the diagram above there are two of them - upper and lower. This, as a rule, is quite enough to automatically maintain the level in a given range.

There are float devices for continuous remote monitoring. In them, the float controls the rheostat motor, and the level is calculated based on the current resistance. Until recently, such devices were widely used, for example, to measure the amount of gasoline in car fuel tanks:

Rheostatic level meter device, where:

• 1 – wire rheostat;
• 2 – rheostat slider, mechanically connected to the float.

Electrode level sensors

Devices of this type use the electrical conductivity of a liquid and are discrete. The sensor consists of several electrodes of different lengths immersed in water. Depending on the level in the liquid, there is one or another number of electrodes.

Three-electrode system of liquid level sensors in the tank

In the figure above, the two right sensors are immersed in water, which means that there is water resistance between them - the pump is stopped. As soon as the level drops, the middle sensor will be dry and the circuit resistance will increase. The automation will start the boost pump. When the container is full, the shortest electrode will fall into the water, its resistance relative to the common electrode will decrease and the automation will stop the pump.

It is quite clear that the number of control points can easily be increased by adding additional electrodes and corresponding control channels to the design, for example, for overflow or dryness alarms.

Hydrostatic control system

Here the sensor is an open tube in which a pressure sensor of one type or another is installed. As the level increases, the height of the water column in the tube changes, and therefore the pressure on the sensor:

Operating principle of hydrostatic liquid level control system

Such systems have a continuous characteristic and can be used not only for automatic control, but also for remote level control.

Capacitive measurement method

Operating principle of a capacitive sensor with a metal (left) and dielectric bath

Induction pointers work on a similar principle, but in them the role of a sensor is played by a coil, the inductance of which changes depending on the presence of liquid. The main disadvantage of such devices is that they are only suitable for monitoring substances (liquids, bulk materials, etc.) that have a fairly high magnetic permeability. Inductive sensors are practically not used in everyday life.

Radar control

The main advantage of this method is the lack of contact with the working environment. Moreover, the sensors can be quite far away from the liquid, the level of which needs to be controlled - meters. This allows radar-type sensors to be used to monitor extremely aggressive, toxic or hot liquids. The principle of operation of such sensors is indicated by their very name - radar. The device consists of a transmitter and receiver assembled in one housing. The first emits one or another type of signal, the other receives the reflected one and calculates the delay time between the sent and received pulses.

Operating principle of ultrasonic radar type level switch

The signal, depending on the assigned tasks, can be light, sound, or radio emission. The accuracy of such sensors is quite high – millimeters. Perhaps the only drawback is the complexity of radar monitoring equipment and its fairly high cost.

Homemade liquid level regulators

Due to the fact that some of the sensors are extremely simple in design, creating a water level switch with your own hands is not difficult at all. Working in conjunction with water pumps, such devices will allow you to fully automate the process of pumping water, for example, into a country water tower or an autonomous drip irrigation system.

Float automatic pump control

To implement this idea, a homemade reed switch water level sensor with a float is used. It does not require expensive and scarce components, is easy to repeat and is quite reliable. First of all, it is worth considering the design of the sensor itself:

Design of a two-level float sensor for water in the tank

It consists of a float 2 itself, which is attached to a movable rod 3. The float is on the surface of the water and, depending on its level, moves together with the rod and the permanent magnet 5 fixed on it up/down in guides 4 and 5. In the lower position, when the liquid level is minimal, the magnet closes reed switch 8, and in the top (the tank is full) – reed switch 7. The length of the rod and the distance between the guides are selected based on the height of the water tank.

All that remains is to assemble a device that will automatically turn the boost pump on and off depending on the state of the contacts. Its diagram looks like this:

Water pump control circuit

Assume that the tank is completely full and the float is in the up position. Reed switch SF2 is closed, transistor VT1 is closed, relays K1 and K2 are disabled. The water pump connected to connector XS1 is de-energized. As the water flows, the float, and along with it the magnet, will lower, the reed switch SF1 will open, but the circuit will remain in the same state.

As soon as the water level drops below the critical level, the reed switch SF1 closes. Transistor VT1 will open, relay K1 will operate and become self-locking with contacts K1.1. At the same time, contacts K1.2 of the same relay will supply power to starter K2, which turns on the pump. Water pumping began.

As the level increases, the float will begin to rise, contact SF1 will open, but the transistor blocked by contacts K1.1 will remain open. As soon as the container is filled, contact SF2 closes and forcibly closes the transistor. Both relays will release, the pump will turn off, and the circuit will go into standby mode.

When repeating the circuit in place of K1, you can use any low-power electromagnetic relay with an operating voltage of 22-24 V, for example, RES-9 (RS4.524.200). An RMU (RS4.523.330) or any other with an operating voltage of 24 V, the contacts of which can withstand the starting current of the water pump, is suitable as K2. Reed switches can be any type that operates to close or switch.

Level switch with electrode sensors

For all its advantages and simplicity, the previous design of a level gauge for tanks also has a significant drawback - mechanical components that operate in water and require constant maintenance. This disadvantage is absent in the electrode design of the machine. It is much more reliable than the mechanical one, does not require any maintenance, and the circuit is not much more complicated than the previous one.

Here, three electrodes made of any conductive stainless material are used as sensors. All electrodes are electrically isolated from each other and from the container body. The design of the sensor is clearly visible in the figure below:

Three-electrode sensor design, where:

• S1 – common electrode (always in water)
• S2 – minimum sensor (tank empty);
• S3 – maximum level sensor (tank full);

The pump control circuit will look like this:

Scheme of automatic pump control using electrode sensors

If the tank is full, then all three electrodes are in water and the electrical resistance between them is small. In this case, transistor VT1 is closed, VT2 is open. Relay K1 is turned on and de-energizes the pump with its normally closed contacts, and with its normally open contacts it connects sensor S2 in parallel with S3. When the water level starts to drop, electrode S3 is exposed, but S2 is still in the water and nothing happens.

Water continues to be consumed and finally electrode S2 is exposed. Thanks to resistor R1, the transistors switch to the opposite state. The relay releases and starts the pump, simultaneously turning off sensor S2. The water level gradually rises and first closes electrode S2 (nothing happens - it is turned off by contacts K1.1), and then S3. The transistors switch again, the relay is activated and turns off the pump, while simultaneously putting sensor S2 into operation for the next cycle.

The device can use any low-power relay that operates from 12 V, the contacts of which can withstand the current of the pump starter.

If necessary, the same scheme can be used to automatically pump water, say, from a basement. To do this, the drainage pump must be connected not to the normally closed, but to the normally open contacts of relay K1. The scheme will not require any other changes.

I recently came across a video on the Internet where they made my childhood dream come true. The video showed how you can assemble a device for automatically filling a container with water. All the work was very clearly demonstrated, but the diagram was not shown.

The fact is that in my childhood, in the summer, I often had to water the garden and I always had ideas for automating this process, but I never succeeded in turning my thoughts into reality. Today I will fulfill part of my dream, although only theoretically for now.

Let’s imagine this situation: you have a container of water at your dacha or at home, for watering the garden or for some other purpose. You pump water into this container using a pump. To pump water, each time you have to turn on the pump and watch until the container is filled with water. Filling a container with water can be automated very easily and quite cheaply.

Below is a structural picture of our device.

To automate filling the container with water, we will have to slightly modify the container. A rod with a height no less than the depth of the container is installed on the top of the barrel, on which two reed switches are fixed. A movable rod with a float is also attached to the rod, which moves depending on the water level in the container. A permanent magnet is attached to the rod to control the reed switches.

In the next picture you can see an example of a rod and a movable rod.

And now the most interesting part: a circuit for automatically filling the container with water.

To implement this device, we need a circuit breaker to protect the pump, an electromagnetic contactor to turn the pump on and off, and two reed switches (sealed magnetic contact) to control the contactor.

The lower reed switch should be a closing switch, the upper one should be a breaking switch. For example, the MKS-27103 reed switch is quite suitable for us, because it has a changeover contact. For low level signaling, the circuit uses a normally open contact, and for high level signaling, a normally closed reed switch contact is used. At the moment when the water level in the tank reaches a critical value, the magnet will be located at the same level with the lower reed switch, which, under the influence of a magnetic field, will switch the contact and thereby send a signal to turn on the pump. After this, the float will begin to rise to the upper level, where the upper reed switch will turn off the pump.

This scheme does not implement a manual mode, although it should be provided in case of failure of our level meters. The easiest way is to use a locking button to manually control the pump. I think it won’t be difficult for you to include a button in the resulting diagram.

Of course, you can buy ready-made level meters and not reinvent the wheel, especially since they are produced by industry. However, one such level gauge will cost you at least $30, and one MKS-27103 reed switch costs $2-3.

This is how you can automatically fill a container with water. I also had an idea for water to be drained from this container for irrigation (for example, tomatoes, cucumbers) through drainage pipes. Perhaps they do this in greenhouses.

I hope someday I will have a dacha where I can fully realize my dream, not because I like to dig in the garden, I just like others to work for me, I mean devices

In summer cottages and gardens, various water storage tanks are often used, designed so that the water in them can be warmed up before watering and saturated with oxygen. They are also used in cases where the supply of water is periodic or not guaranteed. For example, a well or borehole has a very small flow rate (that is, it gives very little water at a “one time” and you need to wait some time for it to fill up again). Or water is supplied through a centralized system at a certain time.

Be that as it may, it is useful to have some kind of device that would automatically replenish the water supply in the water tower or tank, including a booster pump, when the water level in the tank drops below a critical (or set) level.

For those who have a centralized water supply on their site, which is under pressure when water is supplied, it is extremely easy to make such a machine. It is enough to put plumbing fixtures in the container, such as those that are in the toilet cistern. Its float shut-off valve will always keep the tank full.

You can even get by with a simple faucet with a handle. A small lever (stick) is tied to the handle, and 1-2 plastic bottles are attached to its end. The tap is securely strengthened in such a way that when the tank is completely filled, it is closed, and the PET bottles are slightly submerged. If water consumption occurs, the floats - bottles will begin to fall down and open the tap slightly. If there is water in the system, it will begin to flow into the tank. If there is no water in the system, the tap will remain open until water appears and fills the container.

It is much more difficult to organize automatic pumping for those who do not have running water and water is pumped from a well or borehole. Here you need some kind of automatic device that turns on the pump. There are a lot of similar developments. Starting from float switches to electronic water level sensors. A proprietary float switch is quite expensive and is rarely sold separately. You can make it yourself (see the article “Homemade float switch”), and it can be done by fairly handy craftsmen. Yes, and it must be done very carefully - still, a complete guarantee of sealing of wires in water is necessary. Electronic devices are, in general, too tough for a few. And it won't be cheap.

Summer residents need a simple device that anyone can assemble, as they say “from a tin can,” and with the cost of a bottle of beer. Such devices must meet two basic requirements. First - They should not have the so-called. “bouncing” of contacts. And there should be two stable positions - “on” and “off”. This is called the "toggle switch effect." Otherwise, with a smooth connection of the closing contact to the others, breakdown of the microscopic air gap, sparking, and burning of the contacts are inevitable. The pump may even fail for this reason. The second condition is the presence of the so-called. "hysteresis loops". Those. a certain working time “gap” between the on and off events. You won’t be able to track the drop in water level in the tank by 1 mm. Such frequent and short starts can simply kill the motor. Therefore, quite significant drops in level, by several tens of centimeters, are monitored.

That’s why even homemade similar devices that meet these requirements are quite complex and ultimately expensive. Fortunately, I was able to develop a device for such an automatic pump switch, which costs 50 rubles, and which every summer resident can actually make in half an hour.

In fact, it is a movable closing element (contact) that moves vertically depending on the water level. Its secret is the presence of a magnet on it! You can use the simplest magnet - from a magnetic latch.

The design of the switch itself is clear from the sketch. The two contacts of the switch are half rings made of steel. You can cut a massive steel washer M16-M20, preferably reinforced, into two halves. They are glued with epoxy resin or screwed with countersunk screws to the dielectric substrate. Wires from the network and the electric pump are also supplied to them. A hole is drilled in the substrate between these “horseshoes”, through which the float guide rod will move up and down. It should also be made of non-conductive material, preferably not absorbing moisture.

At the end of the rod, the closing contact is secured with a self-tapping screw. This is a round metal plate made of tinned sheet metal, copper, duralumin, aluminum, but quite thin. Its size should be such that it is guaranteed to close both half rings at once, closing the electrical circuit. A magnet is secured on top of the plate (with glue, epoxy resin, bracket...)

The rod is passed through a guide pipe fixed to the wall of the storage tank, and a float is attached to the bottom of it. The float must have a long, elongated shape and be attached vertically to the rod.

The operation of this circuit breaker is based on the fact that the force of pushing the float out of the water (Archimedes' force) has a linear dependence on the depth of the float's immersion. Those. it increases or decreases according to a linear law. And the force of magnetic attraction decreases (increases) according to the quadratic law! It is inversely proportional to the square of the distance between the magnet and what it is attracted to.

It is almost impossible to balance these forces with each other. It is enough to “move” everything by one micron, by 1 nanometer - and immediately an avalanche-like development of events occurs and the victory of one of the forces. No intermediate position is possible.

This is how the switch works. When the tank is full, the float floats at the very top of the water, submerged enough to compensate for the weight of the rod and magnet. The magnet is located quite high above the contact area. As the water is consumed, the float (and the rod and the magnet, naturally) fall lower and lower. Eventually, at some distance from the magnet to the horseshoes, the force of attraction of the magnet towards them begins to appear. And when it becomes greater than the Archimedes force acting on the float, the magnet accelerates very sharply and instantly and reliably sticks to the forgings of the contacts. The contacts, of course, are closed. The pump turns on and water begins to flow into the container.

As its level increases, the float becomes immersed in water more and more. And the buoyancy force of Archimedes also increases. But it is not strong enough to tear the magnet off the horseshoes. But when it exceeds this separation threshold, the magnet will still come unstuck. And it won’t just come unstuck, it will bounce off like a bullet! By the way, you will need to install some kind of damper (spring or sponge) at the bottom of the guide tube.

As you understand, the effect of the toggle switch is absolute, and the hysteresis loop depends on the attractive force of the magnet, the shape and size of the float. Therefore, here you have to experiment, selecting a float for the parameters you need.

Of course, since the switch operates with a voltage of 220 volts, it is necessary to take all measures to prevent contact of the switch with water. It is advisable to close the container, put some kind of spring on the float or place some kind of limiter for the upward “jump” of the rod when opening it above the switch. Close the switch from precipitation.

You can ask questions about this switch and discuss other questions about water automation and automatic irrigation systems on the forum.

To automate many production processes, it is necessary to monitor 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 meters in everyday life; a striking example of this is the shut-off valve of a toilet cistern or an automatic system for shutting off a well pump. Let's look at the different types of level sensors, their design and operating principle. This information will be useful when choosing a device for a specific task or making a sensor yourself.

Design and principle of operation

The design of measuring devices of this type is determined by the following parameters:

• Functionality, depending on this device, is usually divided into alarms and level meters. The former monitor a specific tank filling point (minimum or maximum), while the latter continuously monitor the level.
• The operating principle can be based on: hydrostatics, electrical conductivity, magnetism, optics, acoustics, etc. Actually, this is the main parameter that determines the scope of application.
• Measuring method (contact or non-contact).

In addition, the design features are determined by the nature of the technological environment. It is one thing to measure the height of drinking water in a tank, another to check the filling of industrial wastewater tanks. In the latter case, appropriate protection is necessary.

Types of level sensors

Depending on the principle of operation, alarms are usually divided into the following types:

• float type;
• using ultrasonic waves;
• devices with a capacitive level detection principle;
• electrode;
• radar type;
• working on the hydrostatic principle.

Since these types are the most common, let's look at each of them separately.

Float

This is the simplest, but nevertheless effective and reliable way to measure liquid in a tank or other container. An example implementation can be found in Figure 2.

Rice. 2. Float sensor for pump control

The design consists of a float with a magnet and two reed switches installed at control points. Let us briefly describe the principle of operation:

• The container is emptied to a critical minimum (A in Fig. 2), while the float drops to the level where reed switch 2 is located, it turns on the relay that supplies power to the pump pumping water from the well.
• The water reaches the maximum level, the float rises to the location of reed switch 1, it is triggered and the relay is turned off, respectively, the pump motor stops working.

It’s quite easy to make such a reed switch yourself, and setting it up 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 media and may have an analogue or discrete output. That is, the sensor can limit the filling upon reaching a certain point or monitor it continuously. The device includes an ultrasonic emitter, receiver and signal processing controller. The operating principle of the alarm is demonstrated in Figure 3.

Rice. 3. Operating principle of ultrasonic level sensor

The system works as follows:

• an ultrasonic pulse is emitted;
• the reflected signal is received;
• The duration of signal attenuation is analyzed. If the tank is full, it will be short (A Fig. 3), and as it becomes empty it will begin to increase (B Fig. 3).

The ultrasonic alarm is non-contact and wireless, so it can be used even in aggressive and explosive environments. After initial setup, such a sensor does not require any specialized maintenance, and the absence of moving parts significantly extends its service life.

Electrode

Electrode (conductometric) alarms allow you to monitor 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 example given, a three-level alarm is used, in which two electrodes control the filling of the container, and the third is an emergency one to turn on the intensive pumping mode.

Capacitive

Using these alarms, it is possible to determine the maximum filling of the container, and both liquid and bulk solids of mixed composition can act as the process medium (see Fig. 5).

Rice. 5. Capacitive level sensor

The operating principle of the alarm 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, a “dry contact” design is used, that is, the level gauge operates through the tank wall in isolation from the process medium.

These devices can operate over a wide temperature range, are not affected by electromagnetic fields, and can operate over a long distance. Such characteristics significantly expand the scope of application up to severe operating conditions.

Radar

This type of alarm device can truly be called universal, since it can work with any process environment, including aggressive and explosive ones, and pressure and temperature will not affect the readings. An example of how the device works is shown in the figure below.

The device emits radio waves in a narrow range (several gigahertz), the receiver catches the reflected signal and, based on its delay time, determines how full the container is. The measuring sensor is not affected by pressure, temperature or the nature of the process fluid. Dustiness also does not affect the readings, which cannot be said about laser alarms. 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 maximum and current filling of tanks. Their operating principle is demonstrated in Figure 7.

Figure 7. Fill measurement with gyrostatic sensor

The device is built on the principle of measuring the level of pressure produced by a column of liquid. Acceptable accuracy and low cost have made this type quite popular.

Within the scope of the article, we cannot examine all types of alarms, for example, rotary-flag ones, for identifying granular substances (a signal is sent when the fan blade gets stuck in a granular medium, after first tearing out the pit). It also makes no sense to consider the principle of operation of radioisotope meters, much less recommend them for checking the level of drinking water.

How to choose?

The choice of a water level sensor in a tank depends on many factors, the main ones:

• Composition of the liquid. 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 is to accumulate liquid.
• The need to control the minimum and maximum level, or monitoring of the current state is required.
• Admissibility of integration into an automated control system.
• Switching capabilities of the device.

This is not a complete list for selecting measuring instruments of this type. Naturally, for domestic use it is possible to significantly reduce the selection criteria, limiting them to the volume of the tank, the type of operation and the control circuit. A significant reduction in requirements makes it possible to independently manufacture such a device.

Making a water level sensor in a tank with your own hands

Let's say there is a task to automate the operation of a submersible pump for water supply to a dacha. As a rule, water flows into a storage tank, therefore, we need to make sure that the pump automatically turns off when it is filled. It is not at all necessary to buy a laser or radar level indicator for this purpose; in fact, you don’t need to purchase any. A simple problem 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: a minimum level for closing, a maximum level for opening. The pump connection diagram is simple and, importantly, safe. The principle of operation was described above, but let’s repeat it:

• As the water collects, 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 de-energization of the engine.
• 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 a tank can work for decades, unlike an electronic control system.