To make a sensor or indicator of the water level in a tank, tank, swimming pool or other container, you can use the 4093 microcircuit (domestic 561TL1) or on an Arduino microcontroller. Let's start with the first option.
Materials required for the sensor
- 2 4093 chips;
- 2 sockets for microcircuits;
- 7 x 500 ohm resistors;
- 7 x 2.2 MΩ resistors;
- battery 9 V;
- battery socket;
- circuit board 10 x 5 cm;
- 8 brass sensor screws;
- double-sided tape or screws for attaching the box to the wall;
- network cable. The length of the cable depends on the distance from the water tank to the location where the display will be located.
So the base is CI4093, which has four elements. This project uses two chips. Here we have ports with one input per high level, and others connected through a resistor, providing a high logic level. By placing a zero input signal into this logic, the inverter output will go high and turn on the LED. A total of seven out of eight elements were used due to cable network limitations.
There is a line of LEDs on the side different colors, indicating the water level. Red indicators - there is very little water, yellow - the tank is half empty, green - full. The central large button is used to connect the pump and inflate the tank.
The circuit only works when you press the center button. The rest of the time she is in standby mode. But even when the indication circuit is triggered, the current is minimal and the battery will last for a long time.
Sensor connection diagram
The wires run inside the pipes. Try to position the sensors in such a way that water entering the field using the float valve cannot pass by the sensors. Sand was poured inside the pipe with sensors to create the required weight.
Once assembled, the circuit is in a box and mounted on the wall.
Second version of the level sensor circuit
This is completely function controller water level controlled by Arduino MK. The circuit displays the water level in the tank and switches the motor when the water level drops below a preset level. It automatically turns off the motor when the tank is full. Water level and other important data are displayed on a 16x2 dot LCD display. In the author's version, the circuit controls the water level in the drainage tank (reservoir). If the tank level is low, the pump motor will not turn on, which protects the engine from idling. Additionally, an audible alarm is generated when the level in the drain tank is too low.
The water level circuit using an Arduino controller is shown above. The sensor assembly consists of four aluminum wires 1/4, 1/2, 3/4 long and a full level in the tank. The dry ends of these wires are connected to the analog inputs A1, A2, A3 and A4 of the Arduino respectively. The fifth wire is located at the bottom of the tank. Resistors R6 - R9 reduce the potential of the inputs. The dry end of the wire is connected to +5V DC. When water touches a specific probe, it occurs electrical connection between the probe and +5V, because water has some electrical conductivity. As a result, current flows through the probe and this current is converted into a voltage proportional to it. The Arduino reads the voltage drop across each of the input resistors to sense the water level in the tank. Transistor Q1 turns on the buzzer, resistor R5 limits the base current of Q1. Transistor Q2 drives the relay. Resistor R3 limits the base current of Q2. Variable R2 is used to adjust the contrast of the LCD display. resistor R1 limits the current through its LED backlight. Resistor R4 limits the current through the power LED. Full
Hi all. Today we will talk about a very simple set for self-assembly device for monitoring 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 sorry 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 summer season, an attempt was made to apply collected fee 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 about 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 confidently in 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.
The sensors used were homemade sensors conductometric type level. This is roughly what they look like assembled:
On the side of the board where the parts are installed, there is silk-screen printing, 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 payment does not match the one that was sent to me and judging by the comments, many are sent two different options fees. This does not affect the functionality. Both boards are functional.
Results: The simplest set, is available for schoolchildren, also has practical use. 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 +47In 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. In this place there should be an insert made of glass or fluoroplastic 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.
Hermetically sealed capacitive sensor makes it possible to place it in a controlled environment, such as a pipeline or a tank lid. However, it may be under pressure. In this way, the presence of liquid in the closed reactor is maintained during 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.
At making the right choice and manufacturing 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.
In industry and everyday life, there is always a need to determine various levels in containers. Level sensors are used for these tasks various designs. Depending on the filling environment of the tank, one or another sensor is used; sometimes, for the sake of simplicity and saving money and time, combined sensors are used, that is, made by hand. These are simple designs that use completely different types of sensors. Basically, such sensors are used where there is no easy access to the measurement environment or the measurement location is very aggressive for human health.
Types of level sensors
Most modern level sensors have an electronic relay with a converter in their design. Electronic circuit designed to convert the measured value into a standard signal. The signal can be analog or discrete. Analog can be a current 0..20mA and a signal called a current loop 4..20mA or a voltage 0...5V, 0..10V.
Level sensors are used to protect the pump motor from dry running, regulate the motors of well pumps that fill any containers with water and more in the cold and hot water supply system.
DIY water level sensor
Let's see, using the example of pumping water from a pit, how we can control the automatic cycle of maintaining the water level not higher than the required one.
We have a pit with very little clean look a liquid consisting of water and coolant impurities for the cutters of a metal-cutting machine.
All types of sensors were considered, however, in terms of price and ease of execution, a combined design consisting made of wire three meters long(depth of the pit), attached to a float (large plastic container with air), on the surface the wire is attached to a spring with a petal.
The signal is taken as a conventional discrete 24V signal from a conventional inductive sensor. He works on the petal. When the water level in the pit rises, the float rises, weakening the spring. A petal is attached to the end of the spring; it rises due to the extension force of the spring. The petal, in turn, receives feedback from the inductive sensor, feeding the pump motor relay to the coil, causing it to pump out water from the pit. In order to avoid frequent switching on and off of the engine, in the sensor-coil circuit there is a switch-off delay relay set to 10 minutes.
Thus, the next time the sensor is triggered, the relay will work again and the cycle will repeat.
Of course, to protect the engine from dry running it is advisable install a leakage sensor in the pipe, through which the emulsion is pumped out. But in our case, simplicity of design was important. Instead of an inductive sensor, you can use two plates in contact with each other, which will be even more economical.
If water or other liquid has a homogeneous composition, then a metric single-electrode level sensor can be used.
For example, DU-1N manufactured by Relsib, designed for measuring levels in various types liquids. The sensor can operate over a wide temperature range. The body is not subject to corrosion, consists of high quality of stainless steel. Ceramic and fluoroplastic are used as insulation, this provides excellent insulating protection. Resistant to many mechanical loads. The measurements are independent of liquid density. And does not require additional care during operation.
To control the operation of vehicle mechanisms and systems, special devices are required. One of the main such devices is a liquid level sensor.
Varieties
Reed switch A coolant level sensor is a device that is necessary for measuring coolant in an expansion tank or other container (PMP-066, DRU-1PM and others). Fundamentally, the contact sensor is a reed switch with a resistance of up to 3300 Ohms. The design of the device consists of a housing, a plastic float and a magnetic ring. It is also called a liquid level switch (RSF).
Photo - float sensor DRUThe device also has two contacts, which close and open depending on the liquid level. The contacts are connected to a monitor displayed on the dashboard. If the system malfunctions, a signal is immediately sent to this display. Depending on the type of your car, this can be a mechanical dial (VAZ-2101, MAZ) or an electronic monitor (Ford Focus, Kia, Opel Passat, Audi, Mercedes, BMW, Mazda, Volvo).
Photo - liquid level sensor for cars In addition to this, it also happens contactless optical sensor, this device is not used to measure the brake fluid level. It is mainly used to determine the level of liquid in a tank in the production of, say, acid, oil, etc. It is installed on the side of the tank and determines the level using a laser or ultrasonic signal. Laser devices can be seen at water stations, oil plants, chemical plants, etc.
Photo - operating principle of sensor-relays Often used in everyday life electrode liquid level sensors in the boiler DUZHE, DUZH, DU-200. They are necessary for monitoring the operation of boiler equipment and its settings. In industry, various inductive sensors are needed that measure the level of electrically conductive liquids. Their connection diagram is as follows:
Photo - connection diagram of an inductive sensor Any washer, fuel, coolant sensors are divided into threshold and linear:
- A cooling alarm in a car is often a discrete magnetic two-position sensor of the KSL-35 or LFL type (BMW, Ford, Rio, Opel Astra and Passat, Priora, Audi, Kia, Mercedes);
- An ultrasonic sensor for the maximum liquid pressure level in a tank is, in most cases, a linear meter (Siemens alarm level switch, etc.).
Less common are vibration and hydrostatic sensors. They are mainly needed to measure fluid pressure levels.
Operating principle and measurement
Mainly used in cars float sensors liquid level. When the coolant is at normal levels, the magnetic ring acts on the reed switch (this is a magnetic switch equipped with contacts). At this moment, the sensor contacts open, the resistance is within 3300 Ohms. When the washer fluid level drops, the float together with the magnet drops to the level of the reed switch, and it closes the sensor contacts. At this moment a signal sounds dashboard, the contacts of which are closed to ground.
Photo - sensor readings In this case, conductometric sensors and other coolant measuring devices are polled by the control unit every second. If the meter malfunctions or there is insufficient resistance, there is not enough data to determine the level.
Photo - fuel level sensor Diagnostics and repair
Checking the functionality of the sensor is quite simple. In most cases, the system immediately notifies you if it malfunctions using a light signal on the dashboard. Typical symptoms of malfunction temperature and coolant level sensor:
- Atypical mechanical pointer position or certain codes when automatic control car;
- Interruptions in engine operation at idle speed;
- Inability to start the engine;
- The radiator lights up during operation;
- Loud, unusual engine sounds during operation.
Capacitive liquid level sensors are located in front of the outlet on the fuel tank, sometimes it is located at its inlet. If you do not notice problems in its operation in time, the car will begin to consume more fuel, overheat, and stop working.
Photo - emergency brake fluid level sensor You can also check the sensor using an ohmmeter; the price of such diagnostics, even at a professional service station, is up to 300 rubles. Its wires are connected to the contacts of the meter, and then the engine is started. Make sure that there are no moving parts of the car within the measurement range. If the resistance is of a non-standard value, then repair or replacement of the sensors is necessary.
To repair the liquid level sensor, you need to remove it:
- Disconnect the cable from the battery;
- The plug from the sensor in the tank is unscrewed counterclockwise;
- Afterwards it must be carefully removed from the hole;
- Wipe the removal area and the signaling device for further work.
Repair of liquid level sensors for many cars (VAZ-2114 and VAZ-2110, MAZ, and others) does not always require complete replacement. Often the problem is the expansion of the plastic parts that make up the alarm housing. During their heating, microcracks form on the plastic, which allow fuel to pass through and, accordingly, the sensor float is always lowered. To fix this, you need to remove the sensor and disassemble it. After the joint, lubricate with sealant and press to better strengthening. If desired, burn the area around a little with a soldering iron and put it in place.
If the problem is that the reed switch has begun to leak fuel, you need to replace it. To do this, you can buy a special part for the liquid level sensor (sold in OWEN-Auto or other stores) or replace this plate with a plastic one. With such an analog device, the car will become quieter and more reliable.
Photo - different liquid sensors Video: sensor device
How to make a sensor yourself
Making a simple liquid level sensor with your own hands is quite simple, and installation can be done in almost any container. Certainly, homemade device will be somewhat inferior in accuracy to the branded ones, but it will cost you pennies.
After this, sensors of this type are connected to the circuit and connected to the indicator. To do this, you can use a pointer dial or a special monitor. Such a device is suitable for monitoring the water level of a pump or tank. You can install two or more devices in a container.