Hi all. Today we will talk about a very simple kit for self-assembly of a device to control the water level. This set can be successfully soldered by a student in grades 5-7 in one evening. Of course, you can do it completely yourself, including the board, but I decided to save time, so I ordered a kit.
The set was purchased with the goal of somehow automating the collection of water into a barrel at the dacha. Moreover, this is not exactly a barrel, but rather a pipe going down 2.5-3 meters, so the water reserves there are decent (for simplicity, let there be a barrel). The idea was simple, while there is no regular water supply, the electric valve opens and fills the barrel with water at a given level. Consumption of water in buckets as needed and automatic refilling into the barrel. To ensure that the valve does not often operate due to water fluctuations, several levels are designed. The lower one at which the valve turns on and the upper one at which it turns off. Those. there is a certain dead zone in which there is water flow, but there is still no water supply to the barrel. By the way, this dead zone is actually such a thing as hysteresis.
Last year, this function was performed by such a device as a float mechanism from the toilet cistern. It worked properly and occasionally became clogged, since the water comes through pipes straight from the river. But in the end, it didn’t survive the winter because it was made of plastic and fell apart from the frost.
This set was intended to replace a failed mechanism.
While storing the assembled board and waiting for the summer season, an attempt was made to use the assembled board in production, on this installation. 
This is just a large saucepan with a heating element type heater with a power of 27 kW. The products are taken out of the refrigerator in whole pallets and placed in a saucepan. It all needs to be heated to 90 C. Can you imagine how much electricity is wasted every day?!
To estimate the volumes, I will attach a couple of photos:
The products, by the way, are pork stomachs and curly (part of the intestines).
As far as I know, the stomachs are stuffed with something and eaten, and the intestines are roughly the same - including sausages.
This thing is cooked and re-frozen. Next it goes to China. This is the cycle of goods in nature. We give them natural by-products, and in return we give them electronics...
The question has arisen to switch the heating of the pan to steam. It's more economical and the power is higher. Productivity increases significantly. This is where a level sensor was needed so that no one would be scalded by the steam and steam would be supplied only when there was at least a minimal amount of water in the container.
However, I realized it in time and refused the final installation, although tests showed that the board was working. It is contraindicated to use homemade products in production. Therefore, we found a less quickly needed device that performs the same functions, but also has a certificate. The operating principle of the factory device practically corresponds to the set from the online store and, in a particular case, performs the same functions.
This device is a domestic production Aries SAU-M7. 
Delivery and packaging:
Bangood is very stable, a small package and several layers of polyethylene foam. 
In a small bag there is a “bunch” of parts, a board and wires.
I didn’t sort by denominations, I just laid them out for clarity.
The scheme is not simple, but very simple. 4 2I-NOT elements are used, with two of them serving as a trigger. It is needed to form a hysteresis loop.
Pins 1 and 2 of J3 provide a low level signal and turn on the relay. Contacts J4 1 and 2 are the upper level and emergency; when any of them is triggered, the relay turns off. The relay operation is duplicated by lighting the LED. The scheme works reliably on tap water and just as reliably on water after water treatment, which contains less salts.
I assembled the board almost without looking at the diagram, except to look at the resistor values.
It is unlikely that the pins will be mixed up, and even the installation of parts such as connectors or transistors will be prevented by the silk-screen printing.
The only drawback during installation is that I mixed up the LEDs. But this is so, little things do not affect performance.
Homemade conductometric type level sensors were used as sensors. This is roughly what they look like assembled:
Silk-screen printing is applied on the board on the installation side of the parts, which is quite high quality. 
The process of unsoldering parts will not be of interest to you, since I am not an assembler and do not know the specifics of the board assembly process. Whatever came into my hand from the edge, I soldered it.
The printed circuit board is covered with a protective mask on the solder side. There is no metallization. The fee is one-sided.
I used solder type POS 61 with rosin. I screwed up a little. 
I fixed the power wires with sealant so that they would not break off at the exit from the holes. The wires that came with the kit seemed too short to me. 
I washed the board with a solvent and alcohol and covered it with a layer of Plastik 70. I immediately noticed the difference between my previous boards and this one. The surface is shiny and the contacts are covered with a layer of film.
There was some inconvenience, which is actually a plus. I wanted to make a video about the operation of the board using a multimeter, but I got a problem in the form that the chips simply do not push through the protective coating. That's why there is no multimeter in the video. 
Video demonstrating the board's operation:
Upd: While I was writing the review, I didn’t even pay attention to the product page, as usual. And only after writing the review did I pay attention to the product. The board does not match the one that was sent to me and judging by the comments, many are sent two different versions of the board. This does not affect the functionality. Both boards are functional.
Results: The simplest set, available for schoolchildren, also has practical applications. I recommend it for purchase. There was a slight residue left due to the fact that the board received was not the one in the description.
In my case, the wires turned out to be redundant. They were probably planned to output LEDs from the board to the front panel and connect a power source.
I'm planning to buy +52 Add to favorites I liked the review +25 +47I have published many reviews about dacha automation, many of which involved manipulation of water. Often you need to find out the fluid level, or the fact that it is missing. It is convenient to use such information in your crafts aimed at getting rid of routine procedures. To find out the level, many people, including me, use float sensors on reed switches, the main problem when using them is the need to make holes in the container; you must agree, this does not add reliability and versatility to the use of the container, and drilling with subsequent sealing is not the most pleasant manipulation . The device under review (which went on sale recently) is designed to get rid of this, ensuring scalability and configurability of the system... Let's see what kind of beast is under the cut.
The sensors arrived in 14 days and were packaged quite well. The sensors themselves in bags: 
Unpacking: 
Lace length is about 45 cm: 
Dimensions: 
The sensor is very light, weight: 
The connector has 4 contacts: 
From left to right:
- brown - food
- yellow - signal
- blue - earth
- black setting
The sensor has an indicator that, when water is detected, should light up, judging by the seller’s description. The sensor can be powered in the range from 5 to 24 Volts, which is very convenient. The housing is waterproof (ip67), which allows you to place the sensor outdoors or in a damp room without worrying about its protection. In order not to immediately break the connector, let’s connect the model wiring: 
At my dacha I have a homemade adjustable power supply built into the wall, let’s connect the power, 12 Volts: 
We bring it to a bottle of water, the indicator lights up: 
If you raise it above the water level, the indicator goes out: 
By the way, if you lean your hand, the indicator also lights up: 
Connect the multimeter to the power cables and make sure it works 
Next: minus to ground, and plus to signal output: 
We bring it to the bottle and see the supply voltage at the output: 
If you remove the sensor, the voltage at the signal output disappears: 
The output current of the sensor is in the range of 1-50 mA.
The seller claims that it works when powered in the range of 5-24 Volts, let's try to reduce the supply voltage to 4 Volts: 
The sensor works great, let's try to reduce it to 3 Volts: 
The reliable operation of the sensors allows us to conclude that it can be successfully used with the esp8266 without any conversions - and this is great news!
At other voltages, the sensor also works well: 
I did not dare to go beyond 24 Volts.
Let's set it to 5 Volts: 
The sensor reacts to its bag: 
The side of the bottle cap also reacts: 
Glue it to the bottle with 3M double-sided tape: 
The sensor responds well. With two layers of tape, the sensor does not always work: 
Consumption is about 5-6 mA: 
And of course, we’ll try to apply it in real conditions, working with a controller. Let's take an Arduino Nano as a controller, and also add an indicator LED, so we get the following kit: 
We will connect the LED to pin D3 and ground, and the signal output of the sensor to pin A0 (D14 - since we will use it in digital mode), and we will also supply power to the sensor from the controller: 
Considering that the sensor is designed for water, when working with it it is very important to protect yourself from contact chatter, for example during waves when the pump is running. Also, I will show how to organize such protection without using delays in the program, the actual code:
// Current sensor state bool SensorState = false; // Shift start time unsigned long SensorStartChange = 0; // Guard interval between state changes unsigned long TIMEOUT = 3000; // Current time unsigned long CurrentTime = 0; void setup() ( // The LED is the output pinMode(LED_PIN, OUTPUT); // Do not turn on the light at first digitalWrite(LED_PIN, LOW); // The sensor is the input pinMode(SENS_PIN, INPUT); ) void loop() ( // Set current time CurrentTime = millis(); // read the sensor boolean CurrentState = digitalRead(SENS_PIN); // if the current state of the sensor differs from the read one if (CurrentState != SensorState) ( // if the state change timer has not started, start if (SensorStartChange == 0) SensorStartChange = CurrentTime; // if the new state took on its value in a time greater than the timeout time if (CurrentTime - SensorStartChange > TIMEOUT) ( // change the sensor state SensorState=! SensorState; // reset the start time of the state change SensorStartChange = 0; // if the current sensor state is 1, then turn on the LED if(SensorState)( digitalWrite(LED_PIN, HIGH); // if the current sensor state is 0, then turn off the LED )else( digitalWrite(LED_PIN, LOW); ) ) // the state change did not take place, reset the timer )else( SensorStartChange = 0; ) )
I commented on all the lines to make everything clear. We initialize the outputs and check the change in the state of the signal output of the sensor with contact bounce protection. In this code, the guard interval is 3000 ms = 3 seconds, often it is advisable to increase this interval to a minute to eliminate the influence of waves from the pump. The code is simple, but on its basis it is easy, for example, to organize protection against dry running of the pump (it is very undesirable for most pumps to operate without water), such devices cost an unreasonable amount of money, but here you can get by with little expense, and even implement automatic recovery of the pump when water and a number of other pleasant goodies - such as indication. To do this, you need to glue such a sensor or somehow secure it closer to the bottom of the container, and connect the pump through a relay controlled by the controller. By default, the pump will be turned on, as the sensor recognizes the lack of water - the controller will turn off the pump, and when water appears, it will turn it on. It is also possible to organize protection against leaks on this sensor, especially considering its moisture resistance; in general, everyone can adapt this simple code to their needs. And most importantly, the sensors can be moved around the container without damaging it - by adjusting the levels to suit you.
Video illustrating the operation of the sensor and controller with the specified code:
I put together this layout for testing different capacities: 
I walked around the dacha plot with the model, and the sensor was able to detect water in all non-metallic containers, including a rather thick-walled bucket. Therefore, at the current stage I can fully recommend it; time will tell about its reliability.
The sensor response time is about 500 ms. The wall thickness of a dielectric vessel can reach 1 cm.
They asked to check the sensitivity, so this illustration is better than any words: 
It will work great as a leak sensor.
Various photos upon request
There’s no way with this at all - left-handed alcohol: 
fairy: 
thick canister 40 liters: 
distilled water: 
strong drinks: 
cooler bottle at its thickest point: 
white spirit - no: 
Through the ceramic toilet tank it is easy to find water: 
I opened the lid, the inside was filled with compound, but there was a potentiometer output; after twisting it to the right, the sensor stopped responding to water; after twisting it to the left, it began to respond to lateral finger touches, it looks like this is adjusting the sensitivity. 
If there is interest, I will continue to write about my country crafts.
Thanks to everyone who read this review to the end, I hope someone finds this information useful. Full control over your water resources and goodness to everyone!
When the need arises to control the fluid level, many do this work manually, but this is extremely ineffective, takes a lot of time and effort, and the consequences of oversight can be very expensive: for example, a flooded apartment or a burnt out pump. This can be easily avoided by using float water level sensors. These are devices that are simple in design and operating principle and are affordable.
At home, sensors of this type allow you to automate processes such as:
- monitoring the liquid level in the supply tank;
- pumping groundwater from the cellar;
- turning off the pump when the level in the well falls below the permissible level, and some others.
Operating principle of a float sensor
An object is placed in the liquid and does not sink in it. This could be a piece of wood or foam, hollow sealed 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 monitor 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 a lever; when the liquid level changes, the float moves up or down this lever, and it, in turn, acts on the valve, which shuts off (opens) the water supply. Such valves can be seen in toilet flush tanks. They are very convenient to use where you need to constantly add water from the central water supply system.
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 location, and regulate it, if possible, then within very small limits. Such a valve can be sold called “float valve for containers”.
Electrical sensors
An electric liquid level sensor (float) differs from a mechanical one in that it itself does not shut off the water. The float, moving when the amount of liquid changes, affects the electrical contacts that are included in the control circuit. Based on these signals, the automatic control system makes a decision 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. Switching of these contacts occurs under the influence of a 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 influence of liquid, and when it approaches, the contacts are activated. This entire system is installed vertically in the tank. By changing the position of the reed switch inside the tube, you can adjust the moment the automation operates.
If you need to monitor the upper level in the tank, then the sensor is installed at the top. As soon as the level drops below the set level, the contact closes and the pump turns on. The water will begin 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, in practice such a scheme cannot be used. The fact is that the sensor is triggered by the slightest change in the 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 the supply, a situation arises when the pump is constantly turned on and off, while it quickly overheats and fails.
Therefore, water level sensors to control the pump they work differently. There are at least two contacts in the container. One is responsible for the upper level; it turns off the pump. The second determines 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 connects them. If the difference is more than a meter, two separate sensors are used, installed at the required heights.
Despite their more complex design and the need for a control circuit, electric float sensors allow fully automated liquid level control.
If you connect light bulbs through such sensors, then they can be used to visually monitor the amount of liquid in the tank.
Homemade float switch
If you have the time and desire, then you can make a simple float water level sensor with your own hands, and the costs for it will be minimal.
Mechanical system
In order to simplify as much as possible design, we will use a ball valve (faucet) as a locking device. The smallest valves (half-inch or smaller) work well. This type of faucet has a handle that closes it. To convert it into a sensor, you need to extend this handle with a strip of metal. The strip is attached to the handle through holes drilled in it with the appropriate screws. The cross-section of this lever should be minimal, but it should not bend under the influence of the float. Its length is about 50 cm. The float is attached to the end of this lever.
As a float you can 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 faucet vertically and place 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 the device in water. The bottle should float up and turn the valve handle.
Since valves vary in size and the amount of force required to switch them, the system may need to be adjusted. If the float cannot turn the valve, you can increase lever length or take a larger bottle.
We mount the sensor in the container at the required level in a horizontal position, while in the vertical position of the float the valve should be open, and in the horizontal position it should be closed.
Electric type sensor
For self-production 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 along with it, which acts on an electrical contact to control the water level in the tank. A 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 a common point.
Let's consider the principle of operation of a homemade device. Let's say at the moment of switching on the tank empty, the float is in the low level position (LL), this contact closes and supplies power to the relay (P).
The relay operates 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 begins to rise and the contact of the low pressure unit opens. Contact P2 connects the pump (H) to the power source.
When the level rises to the upper value, the reed switch will operate and open its contact VU. The relay will be de-energized, it will open its contacts P1 and P2, and the pump will turn off.
As the amount of water in the tank decreases, the float will begin to fall, but until it takes the lower position and closes the NU contact, the pump will not turn on. When this happens, the work cycle will repeat again.
This is how a water level control float switch works.
During operation, it is necessary to periodically clean the pipe and float from dirt. Reed switches can withstand a huge number of switchings, so this sensor will last for many years.
" It happens that you need to find out how much water is left in some opaque container. For example, a tank, barrel or any other, buried in the ground or raised to a height so that its contents are not visible. Then a water level sensor will come to the rescue. The circuit is so simple that even someone who has just picked up a soldering iron can repeat it. It consists of only 10 resistors, 3 transistors and 3 LEDs.
Let's start building the sensor circuit. First, we cut the board 30 mm by 45 mm. Then we will draw the paths, as in the photo. It is advisable to paint with paint or nail polish. But I only had a marker on hand (I would like to note that only a permanent marker will do). If you draw with a marker, then a marker purchased from a CD or computer store will hold up best. Once you've drawn, start etching.
I poisoned with hydrogen peroxide, since there is no ferric chloride or copper sulfate. I poured 50 ml of 3% hydrogen peroxide, then added 1 tablespoon of salt and 2 tablespoons of citric acid. Mixed until everything was dissolved. With occasional gentle rocking, I etched the board in about 50 minutes.
Let's start soldering the circuit. For this we need: 3 resistors with a resistance of 10 kOhm, 3 resistors with a resistance of 1 kOhm, 2 green and 1 red LEDs, 4 resistors of 300 Ohms. Having carefully soldered everything in, solder the wires and connect the battery. We cut the wires every 2 centimeters.
Ready! Now we lower the wires into the glass and gradually pour water. For clarity, I slightly tinted the water. As you can see, everything works great.
When the glass contains 1/3 of water, only the red LED lights up. When 2/3, the green light also lights up. And when the glass is filled to the top line, all the LEDs light up. in my case, I assembled a circuit with only 3 LEDs, but you can do more - at least 10. Then the water level will be visible more accurately. I would also like to add that the case was used under a corrector. I assembled the diagram: bkmz268
Discuss the article WATER LEVEL INDICATOR
In industry and everyday life, there is a constant need to monitor 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 is triggered, 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 specified 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 fixed to the walls of tanks.
Float sensors
Reliable and cheap devices for monitoring liquid levels 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 rod is often used. There is a round magnet placed inside it. The rod is a hollow plastic tube with reed switches located inside.
A float with an attached magnet is always located on the surface of the liquid. Approaching the reed switch, the magnetic field triggers its contacts, which is a signal that the container is filled to a certain volume. By connecting contact pairs in series through resistors, you can constantly monitor the water level based on the total resistance of the circuit. The standard signal varies from 4 to 20 mA. The water level sensor is most often placed at the top of the tank in an area up to 3 m long.
Electrical circuits with reed switches may differ even if the mechanical part is similar in appearance. Sensors are located at one, two or more levels, giving a signal about how full the tank is. They can also be linear, transmitting a signal continuously.
Horizontal arrangement
If it is not possible to install the sensor from above, it is attached horizontally to the wall of the tank. A magnet with a float is installed 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 located at depth with a metal ball with a reed contact or toggle switch inside. When the water level coincides with the position of the sensor, the container turns over and the contact is activated.
One of the most accurate and reliable float sensors is magnetostrictive. They contain a float with a magnet that slides along a metal rod. The principle of operation is to change the duration of passage of an ultrasonic pulse through the rod. The absence of electrical contacts significantly increases the clarity of operation when the interface 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. There should be an insert made of glass or fluoroplastic in this place so that the interface between the media can be distinguished through it. The distance at which the sensitive element detects changes in the controlled environment is 25 mm.
The sealed design of the 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. In this way, the presence of liquid is maintained in the closed reactor during the implementation of the technological process.
Electrode sensors
A water level sensor with electrodes placed in a liquid responds to changes in electrical conductivity between them. To do this, they are secured with clamps and placed at the extreme upper and lower levels. Another conductor is installed in pair with the longer one, but usually a metal tank body 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 flow unless it touches the exposed upper conductor. The signal to turn on the pump is a decrease in the level below the long electrode.
The problem with all sensors is the oxidation of contacts in water. To reduce its influence, use stainless steel or graphite rods.
DIY water level sensor
The simplicity of the device makes it possible to make it yourself. This requires a float, a lever and a valve. The entire structure is located 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 a lever that acts on the piston and closes the flow through the lower pipe.
As the water flows, the float lowers, after which the piston again opens the hole through which the tank can be refilled.
With the correct selection and manufacture, a water level sensor, assembled with your own hands, works reliably in the household.
Conclusion
The water level sensor is indispensable in the private sector. With it, no time is wasted when monitoring the filling of the tank in the garden, the level in the well, borehole or septic tank. A simple device will start or turn off the water pump in time without the help of the owner. Just don’t forget about its prevention.