A fuel level sensor is an indispensable thing for any car. It allows you to monitor the remaining fuel in the tank in real time, and, therefore, not to stall at the most inopportune moment. The capacitive sensor is immersed in the tank, and the readings obtained from it are displayed on the instrument panel.
Types of sensors
Modern sensors are based on a potentiometric design. It is quite simple, gives accurate measurements and is affordable. Such sensors are divided into lever and tubular. But they cannot be used in all types of cars.
Advanced non-contact sensors are able to determine the volume of fuel without diving into the tank. There are several types of such devices:
- Magnetic;
- Radio controlled;
- Ultrasonic.
They are quite complex in design, so they can only be manufactured in a factory. But a simple do-it-yourself capacitive contact sensor can be done by an avid radio amateur who has the skill of working with a soldering iron and understands the principles of operation of a car’s fuel system.
The main principle of operation of such a sensor is that a signal is sent for a specific fuel level value. Of course, the float does not drop immediately as soon as the fuel level goes down, but after some time. In this regard, the device may give a slight error, which also depends on the design of the tank and fluctuations in gasoline or diesel. Data is displayed on the dashboard in digital or analogue form. The digital value is more accurate and has minimal error.
How to make a capacitive sensor
The operating principle of a capacitive sensor is to compare electrical capacitance data. In essence, the device is a regular capacitor. You can make such a device by having two metal tubes or plates on hand. The manufacturing rules are as follows:
1.Both electrodes are isolated from electrical contact.
- When the sensor is immersed in fuel, the space between the electrodes is freely filled with fuel, and when the level drops, the electrodes remain in the air.
- The meter is not installed level in the tank, but slightly inclined.
- The power supplied to the device should not be more than 5 W, otherwise the gasoline will ignite from a spark.
- The circuit itself is located close to the sensor, the closer the better.
- The length of the wires from the circuit to the sensor should not be more than 2 cm.
- The capacitive sensor consists of two modules connected by three wires: the sensor module itself and the display module. Two wires supply power to the sensor module, and the third carries the signal from the sensor to the display module.
If there is a lot of fuel in the tank, then the capacity of the sensor is higher, and it takes longer to charge. This measurement principle can be implemented using a built-in microcontroller. Part of the voltage is supplied to the input by a resistive motor. When the meter receives voltage, the microcontroller turns on. When the voltage reaches the peak level, the timer starts. From the timer, data is sent to the reflection module.
Revealing the internal aspects of production and work in general. In this article I want to talk about the full production cycle of such a very important element of GPS monitoring and control systems as a fuel level sensor (search engines know it as FLS). There will be a theory, all the drawings and diagrams for assembling this product. For those interested, read on.
0. Introduction
Looking ahead, I will say that there will be three articles, in this one I will talk about the simplest option for determining the level of diesel fuel (diesel only, use on gasoline vehicles is absolutely prohibited, as it is explosive). In the following articles, if of course the reader is interested, we will consider a digital fuel level sensor, and at the very end I plan to post the circuit diagram and firmware of the monitoring device that I described in this article.1. A little theory
The most popular fuel level measurement sensors are an electric capacitor consisting of two tubes placed inside each other; a tank with fuel is installed, the level of which is measured. Diesel freely penetrates into the space between the tubes; a change in the fuel level in the tank is signaled by a change in the electrical capacitance of the sensor.When the fuel level in the tank changes, the relative dielectric constant of the space between the capacitor plates changes, since the dielectric constant of fuel and air are generally different. And since the capacitance is directly proportional to the dielectric constant of the insulator, the electrical capacitance of the sensor also changes as a result. Sensors are mostly made of aluminum or copper because they are least susceptible to aggressive environments. Of the many ways to measure the capacitance value of a capacitor and then convert its capacitance into a proportional change in the DC voltage at the output, the pulse-width method was chosen as quite simple and reliable, but at the same time providing the necessary level of measurement accuracy. A disclaimer is immediately required, this is the simplest method in terms of finances and quite simple in terms of assembling the FLS method for determining the level of diesel fuel.
2. Description of the operation of the electrical circuit of the fuel level sensor
Fig 2. Schematic diagram of the fuel level sensor (FLS) ()
To increase the stability and accuracy of readings, all circuit elements are used with a minimum temperature coefficient. Resistors are used with a 1% tolerance, microcircuits are selected with improved parameters in contrast to household analogues, for example: SE555N instead of NE555N, and LM358D instead of LM258D.
A master oscillator is assembled on the U1 SE555N chip and elements R1, R2 and C1. Since the stability of the reading greatly depends on it, a precision polystyrene capacitor K71-7 1% is used as capacitor C1; they were usually installed in Soviet color TVs as master horizontal oscillators. It can be replaced with something modern, but the availability and price of these capacitors makes them very attractive, and they were born back in the distant year, when the USSR was very good at monitoring the quality of the elements produced.
From the output of the 3rd microcircuit U1, rectangular pulses trigger a one-shot device assembled on the U2 SE555N microcircuit. As a single-vibrator capacitor, a sensor placed in the fuel is used, so its capacity will depend on the fuel level, and therefore, the pulse width at output 3 of the U2 microcircuit will also change on the fuel level.
To ensure a linear dependence of the pulse width on the level of fuel filling of the sensor, the fuel sensor receives charging current from a current stabilizer made on the U3.2 chip and transistor Q1 BC856BT. Also, by changing the charging current, the circuit is adjusted to different sensor sizes. The circuit is configured by selecting resistors R6 and R7 to obtain 1.8-1.9 Volts at the output of the circuit, with a “dry” sensor.
From output 3 of microcircuit U2, pulses are sent to an integrator assembled on elements R8 and C6.
Next, the integrated voltage formed on capacitor C6 is supplied to the low-pass filter made on R10 and C10.
Then the constant voltage is supplied to the direct current amplifier, made on the U3.1 chip.
From the output of the 1st microcircuit U3.2, the signal, through a filter made on elements R17, C12, C14 and C15, goes to the output.
Resistor R16 is used to prevent self-excitation of the amplifier when operating a capacitive load.
The divider is made of resistors R9 and R11 and provides the necessary constant bias for the DC amplifier to operate in linear mode.
The voltage stabilizer for powering the electronic circuit is placed according to the classical circuit on the U4 LM317MDT chip.
As a result, at the output, we receive an analog signal empty tank 1.8V full 6.0V (there is a dependence on the height of the FLS), which is linear and directly proportional to the fuel level in the tank\tank\storage. Then, using the Kalman filter, you can remove fuel surges, calculate the average consumption, etc.
In reality it will look something like this:
Fuel level graph + speed.
3. Drawing of the fuel level sensor, materials
FIG 3. Drawing of the fuel level sensor (link to large drawing)
It has already been mentioned that aluminum is mainly used, as can be seen from the drawing, the outer tube is soldered in any convenient way into the “head” of the FLS. When producing our sensors, we use welding, because... we have access to it, although not the most aesthetically beautiful option, but it is reliable and time-tested. An aluminum rod is used inside, to fix which a thread is cut in the upper part. The bushings are made of special fluoroplastic, which is maximally tolerant of diesel fuel.
4. Summary
The vast majority of fuel level sensors presented on the GPS market in the CIS and around the world are built on this solution. Each manufacturer makes its own changes to increase the accuracy of fuel level measurement, such as an accelerometer, temperature sensors, digital signal processing, etc. The scheme I presented is the simplest, ready to work, as they say, in the fields without any difficulties. Dear reader with straight hands, it is quite possible to make any modifications that can be used both for your own purposes and for commercial needs.PS. A little erotica about how such goodness can be installed on equipment.
Good day, our dear readers. In today's article we will talk about such a useful device as a fuel level sensor, the low readings of which definitely upset every driver.
Still would! When gasoline (or other fuel) runs out, the vehicle owner has little choice: either refuel the car again, and today this is an expensive pleasure, or start leading an active lifestyle and walking. Of course, basically everyone always chooses the first option, but you probably shouldn’t put yourself in situations where you have to make a decision immediately. This is where the fuel level sensor is designed to help.
Functional features of the device
Fuel level sensor (FLS)- a device designed for measuring and monitoring fuels and lubricants (gasoline, diesel fuel, oil) in vehicles and related warehouses. We will not consider its functions in warehouse work conditions and will focus our attention on cars, where it is used to indicate the fuel level, convert the level into volume, and transmit the resulting value via an analog or digital path.
The device can be used as an addition to display devices or controllers, with the possibility of programming, having the characteristics of input electrical signals corresponding to its technical requirements.
The main purpose of a vehicle fuel level sensor is to measure the volume and level of fuel in tanks, most often gas tanks (except for diesel and gas cars). This device consists of a metal rod installed in a container with fuel (tank), through a standard hole, or a specially made hole of suitable diameter. The sensor is connected to the machine’s monitoring system, to which the necessary information is transmitted.
Most often, they are high-precision devices of a universal type, which makes it possible to use them not only on cars, but also on other equipment and even stationary objects (warehouses, factories). This device “cooperates” with the fuel level indicator, which is located on the dashboard.
Nowadays, there are several options for fuel level sensors (electronic, digital, float, ultrasonic, universal), but they all have one common goal - to correctly determine the flow rate of the tank contents, so that each driver can control their fuel costs. In addition, the device will allow you to monitor the volume of drainage (a particularly useful function for managers of enterprises, taxi services and other organizations where employees can drain government gasoline) and fuel refills (where, when and in what quantity they were made).
In order to be able to monitor the fuel level in more detail, an appropriate device with increased sensitivity and minimal error should be installed on the vehicle, which will ensure the most accurate readings.
Operating principle of the sensor
You can place a fuel level sensor in any car tank, including those with a diesel system. The readings will be displayed on the vehicle’s dashboard, where a special indicator is provided for these purposes.
Modern tanks have a wide variety of shapes and designs, which is something you should definitely pay attention to, since this fact affects the amount of fuel. A sensor placed in the tank does not immediately begin to give correct signals about its filling, since for some time it displays the filling of the entire tank and only then the numbers drop to the correct level. True, if you believe the statistics, not a single such device provides absolutely accurate readings.
The principle of operation of the sensor is based on the correspondence of the fuel level value to a certain signal, depending on which devices with a digital and analog signal are distinguished. Analog sensors have a high percentage of unreliability, which is why they are practically not used anymore. A digital sensor “translates” the analog signal into a “digital” signal, and then corrects and equalizes measurement errors caused by uneven fuel levels and tank geometry. It is this type of device that provides the most accurate indicators, and errors can only be present at the stage of physical measurement of the fuel level.
Modern vehicles mainly use a potentiometric displacement sensor as a fuel level sensor. Its advantages are expressed in simplicity, reliability and low cost. Among the disadvantages is the mobility of contacts, which is why it is more susceptible to wear and oxidation.
There are two types of potentiometric sensors used in cars today: lever and tubular. Both types are equipped with a float, which is always on the surface of the fuel. Such an element is made from foam plastic, thin, light metal or hollow plastic. Of course, each type has its own characteristics.
So, in the lever sensor the float is connected to the moving contact of the potentiometer (a device that creates resistance to current) thanks to a metal lever and can be used either separately or as part of the fuel supply unit. Due to their design, sensors of this type are universal and can be used in any fuel tank.
Tubular sensor consists of a tube in which the float moves along a guide, and resistance wires with slip rings that close on the float are located parallel to it. The main advantage of this type of sensor is its resistance to changes in fuel level when turning, ascending and descending the vehicle. The negative point is that there are restrictions in use due to the geometric parameters of the fuel tank.
The described types of fuel level sensors are contact types, which are completely impractical when using new types of fuel: ethanol, methanol and biodiesel. It's all about their aggressive influence on the surface of the device, which is why it wears out quickly. In such cases, it is recommended to use non-contact fuel level sensors, such as an inactive magnetic position sensor, the sensing element of which is hermetically sealed and does not come into contact with the fuel.
The fuel level is calculated using a traditional float connected by a lever with a permanent magnet, which moves along a sector with fixed metal plates of different lengths. The created magnetic field generates a specific electrical signal corresponding to different types of fuel.
Possible device problems
The fuel level sensor, like any other part of the car, periodically fails and requires repair work. Now we will describe the most common causes of this phenomenon. If the sensor readings change all the time (“jump”), the reason for this may be wear on the contact tracks on the board, which are erased over time due to the constant movement of the device’s slider along them. If the worn area is not large, you can try to bend the slider so that it becomes higher than the worn area, but if the worn area is large, then the problem can only be solved by replacing the sensor.
Sometimes, when the tank is full, the indicator needle returns to zero. A possible cause for this is incorrect placement of the float stop.
When the ignition is on and the engine is running, the indicator needle remains motionless. Most often, the reason lies in a blown fuse, a malfunction of the pointer receiver (sensor), damage to the connecting wires or oxidation of their tips.
If the fuel level needle often drops to zero, and in the process also twitches, then it is worth checking the current collector; perhaps it is weakly touching the sensor resistor, or the winding of the resistor has broken.
Also, the warning light about the minimum amount of fuel in the tank may stop working completely, or work intermittently. In this case, most likely the problem is with the resistor and it is quite possible that it will have to be replaced.
The most common problem with potentiometric sensors is their rapid wear and oxidation of the tracks, which determines the occurrence of the problems described above.
DIY fuel level sensor repair
We have already named the possible causes of breakdowns of the fuel level sensor, now we will consider ways to deal with them.
So, what should you do if the fuel level indicator overestimates (underestimates) the actual amount of fuel in the tank? First of all, you should try to adjust the sensor. You can do this in two main ways:
move the float pin to its extreme positions, and the arrow on the indicator should also fall into these positions (0 - empty and 1 - full). If the arrow at the extreme position does not want to be set to “0” or “1”, bend the pin, leaving it movable and adjust;
you need to disassemble the dashboard and, having reached the sensor through it, remove the arrow and connect the wires back to the device. After this, start the car and let it run for about 10 minutes, and then you should set the indicator axis to position “1” and reconnect the indicator arrow.
If the sensor hangs at zero, you should disassemble the dashboard and find the contact wires leading to the device. All nuts must be unscrewed and sanded, removing any possible oxidation there, and then installed in their original places, tightening them tightly. The same should be done with all the masses on the body (paying special attention to the mass under the handbrake).
To find out exactly what the problem is: in the sensor itself or in the indicator, a special device - a multimeter - will help. With its help, the indicator is diagnosed: with a full tank, the approximate resistance value should be about 7 Ohms (possibly a little less), if half is filled, the resistance will fluctuate from 108 to 128 Ohms; and in the complete absence of fuel, the multimeter will show a value of 315-345 Ohms.
To check the sensor, disconnect the wires going to it and connect a 330 Ohm resistance, then add a 10 Ohm resistor to the circuit; start the engine and you can start measuring the resistance on the resistor using the slider (the arrow floats from the “empty” value to the “full” value).
Before you begin to repair or replace a failed sensor part, you need to know exactly where it is located and how to repair it in the event of a low pressure level. And it is located at the bottom of the gas tank, so to dismantle it you will have to jack up the car (or use an inspection hole) and disconnect the contacts. After removing the sensor, first of all you should pay attention to the condition of the tracks, because they are often the first to be erased under the influence of the slider.
What to do if the fuel level sensor in the tank shows incorrectly, is buggy or lying? Of course, immediately repair it or replace it with a new one, since this device not only predicts our fuel costs, but also saves the family budget by controlling its consumption.
Basic functions of the device
All capacitive fuel level sensors are designed to measure the amount of liquid in a container, or more precisely, in a gas tank. They are connected to the vehicle monitoring system, to which they transmit the corresponding signals. Basically, these are high-precision universal devices that can be used not only for cars, but also for other equipment, as well as stationary objects.
Today there are several types of this mechanism. And it doesn’t matter at all which fuel level sensor (float, electronic, digital, ultrasonic, universal) was chosen, its main function still remains the same - determination. But it is the costs of fuel that are the most constant and most significant for the pocket. Also, the gasoline level sensor will allow you to control such issues as fuel drainage (this function is especially important for enterprises, taxi services, etc.), and, of course, will prevent you from being fooled at the gas station.
For more detailed monitoring of fuel levels, you need to install more sensitive devices with the smallest error on your car.
Operating principle of the device
Basically, the design of the fuel level sensor requires the presence of a float. Most often, it is made of plastic, foam or other lightweight material. The presence of a potentiometer is also important; its role is played by a resistor, on the surface of which metal strips are applied, and its moving contact creates variable resistance to the current that passes through it.
Today, the most popular are tubular or lever-type potentiometric sensors. The principle of operation of the first type of fuel level sensor is that a float placed in a tube moves depending on the position of the liquid and closes the wires located parallel to the guides. In the second case, the movable contact of the potentiometer is connected to the float via a metal lever.
Possible problems with the gasoline level sensor
Problems with the fuel level sensor are of various types. The most common problems are related to the fact that the device shows unreliable data, for example, its arrow indicates that the tank is empty, but in fact there is still plenty of fuel in it. And there are quite a few reasons for this behavior, for example, the panel itself may fail, or it is possible that the arrow is out of order, or the float is jammed.
When the readings of the device fluctuate: for example, at the beginning of the movement it indicates the minimum fuel level, but then this value increases on its own, then this also indicates that the device is not working, but how to check and repair the fuel level sensor in such a situation , we will describe below. If the light on the panel, warning about the minimum amount of fuel in the tank, stops lighting up, or it works, but is faulty, then the whole point is the thermistor, which must be replaced immediately.
We repair the fuel level sensor ourselves
But before you begin direct replacement or repair work, you need to know where the low fuel level sensor is located, how to remove and repair it. It is attached to the gas tank from below, and therefore, in order to remove it, it is advisable to jack up the car and disconnect the contacts. First of all, we pay attention to the condition of the paths, since they are often erased from the impact of the runner. If the defect is small, then you can bend the slider so that it is above the damaged area. If this cannot be done, the entire device should be replaced.
Also, checking the malfunction of the fuel level sensor involves diagnosing the contacts and the “ground” (especially that located under). To get to the contacts, you need to remove the panel and then tighten all the nuts, through which the short circuit is created. If the arrow indicating the fuel level is out of order, then you need to press the daily mileage button and then start the engine.
But besides information on how to repair or replace this device, someone may be interested in how to fool the fuel level indicator sensor. One way to drain gasoline unnoticed is to install a so-called dropper, because this device records only those drains that occur in a very short time interval. But if the liquid drips slowly, then such a scam will not be detected. In general, repairing and replacing a fuel level sensor is a simple operation, so it is not at all necessary to contact specialists for this, but you can do most of the work yourself. It is much more important to choose a truly high-quality device.
I decided to make a digital indicator of the amount of fuel for a truck (bus), using a standard (rather mediocre) fuel level sensor...
Read the entire creation process and what came out of it in the article below.
Initial conditions:
- Truck (bus) with on-board voltage 24v
- Fuel tank for diesel fuel on 220l
- Fuel level sensor DUMP39
- Fuel level indicator EI8057M-3
Need to:
Make a digital fuel level indicator using a standard level sensor.
First, you will have to carefully study what a standard fuel level sensor, called a fuel level sensor, is. Let's dismantle it and examine it carefully.
As you would expect, there is a float, a rod, a variable resistor... wait, more about the variable resistor. As they say, it is better to see once than to hear a hundred times:
The design is both logical and clumsy. It is logical that the slider slides not directly over the variable resistance (which is quite delicate), but along the metal taps from it, but for such an increase in reliability you have to pay for discreteness. The clumsy thing about this design is that, as can be seen in the photo, in the middle position of the float we have a fairly large “dead zone”, due to the very wide central outlet from the resistance. Why this was done, we can only guess, but what we have, we will have to work with.
So, we rummage through the Internet and look for information. Here's what I dug up:
Float movement range - 412mm
Nominal resistance - 800 Ohm (according to another source, the nominal resistance is 761.0 – 193.5 Ohm)
Operating range from -40°С to +60°С
MTBF - 400 thousand. km to 95% wasting resources
Weight 160 gram, analogue - MAZ.
In general, not a lot.
We take the tester and measure it, and in the end we get the following picture:
Connection diagram:
Measured sensor parameters:
Total resistance - 767 Ohm
Additional resistance - 187 Ohm(it provides the minimum sensor resistance).
Left (from the photo) part of the resistance - 203 Ohm (13 taps to the slider), right side Ohm 376(17 taps to the slider).
Two metal sectors above the contact group - the left sector is not used, the right one goes to the fuel reserve lamp.
In general, I am giving such a detailed description only for those who are curious; we need the voltage value that we have at the output contact at different fuel levels. With the extreme left position of the contact at the output, we got 1.57v, at the extreme right position 3.28v, half a tank - 2.44v. At the beginning of the sector of switching on the lamp of the remaining reserve 2.95v.
More for the curious. The general connection diagram for the fuel level sensor looks something like this:
Reels L1A, L1B, L2- this is a deflection system of the fuel level indicator (essentially a milliammeter). The resistor is thermal compensation.
In fact, this is a diagram of a classic electromagnetic automotive device, specifically EI8057M-3- this is something else: there is an electronic circuit inside, the arrow is driven by a stepper motor, and all this is controlled using a microcontroller PIC.
In principle, this is enough to calibrate a digital indicator, if not for a couple of troubles:
1. Specified fuel tank capacity in 220l not true, in fact the tank holds more fuel.
2. In the extreme right position of the movable contact of the sensor, when there is supposedly no more fuel in the tank, in fact the float should already be below the tank level, which is, of course, nonsense (determined by the geometry of the tank and the fuel level sensor.
3. Having measured the geometry of the tank with a tape measure, we are convinced that it is a rectangular parallelepiped with slightly rounded long edges, dimensions 40x112x60 cm. Multiplying the sides accordingly, we get an internal volume of 268 liters, which, you see, is very different from the declared 220 l, and it is very doubtful that the internal partitions, mesh, fuel intake, etc. occupy almost 50 l.
4. As already written above, the resistance of the sensor over the length of its resistance is nonlinear.
What we do:
Fill the tank full and control the voltage at the FLS output. It turns out that after reaching the mark 1.57v The tank still contains a good twenty liters of fuel.
Remove the float and put the sensor in place. Naturally, the draft, devoid of a float, goes to the very bottom of the tank, look at the voltage - it is 3.02v! This is important because in fact, in this position there is no longer any fuel in the tank, and the moving contact has not yet reached the extreme position in 3.28v, while the standard device EI8057M-3 shows what's left in the tank 1/8 volume. (Putting the float in the central position, at standard EI8057M-3 we observe instead of the required ones 1/2 tank as much 5/8 level, with a full tank the standard device goes off scale).
We look at the graph of our fuel level sensor,
Let's take three points - the resistance of the sensor, the first point is its lowest resistance (moving contact on the left) formed by additional resistance in 187 Ohm(in the photo there is a vertical black rectangle), the second point at the middle position of the contact when connected in series 187 Ohm And 203 Ohm, i.e. 390 Ohm, the total resistance will accordingly be 390 + 376 = 766 Ohms.
(horizontally - resistance in Ohms, vertically - conventional units of length)
There is nothing pleasant in this picture; the sensor seems to be linear but has a significant kink.
With such a picture, we will either get accuracy in the middle, or at the ends of the broken line, or something in between by approximating:
Having received the formula with the correction and coefficient, you can, in principle, make something similar to a digital fuel level indicator, coefficient R 2 trend lines in 0,97
Of course it’s not bad, you can, in principle, use anything greater than 0.95.
But you can get your own conversion factor for each line, which will be more accurate:
We immediately measure the ADC value at the points we need so that 5%
The tolerance for the divider resistors at the ADC input did not spoil anything for us and we get it in the range of an empty tank (ADC822) before 1\2
tank (ADC700):
(horizontally the received ADC readings, vertically the volume of fuel in liters)
Ranges from 1\2
tank (ADC700) to full (ADC456):
From the above we have the following:
1. As the amount of fuel increases, the resistance of the sensor decreases and the voltage drop across it decreases.
2. The sensor voltage delta is 1.45v, that at 10 bit ADC will be 56% which is more than enough to scale the ADC result to scale 0....220l and will allow you to simply digitize the result without using OU to adjust to the desired voltage range.
The scheme is incredibly simple:
Microcontroller Mega8, LED indicator on 3
discharge with a common cathode, input divider of two resistors R1, R2. Zener diode (in bourgeois zener "zener" diode :)) to protect the input MK just in case. I didn’t draw the power circuits, they are classic 0.1uF ceramics and some kind of electrolyte 100...1000uF as well as quenching resistors between the MK and the indicator, any in the range will do 80...100Ohm depending on the MK supply voltage and the brightness of the indicator. The voltage on board the car with the engine running was 27.5v.
My board layout:
On the right side of the board I placed a power converter that provides 5v at onboard voltage 10...30v the converter is assembled on MS3406 3 according to the typical diagram from the datasheet. throttle murata 1812. The zener diode indicated in the diagram is 3.3v I screwed up when wiring and soldered on top.
Why did I apply Mega8 when there is a much more convenient one Tiny26 and so on. ? because Mega 8 available 1kB RAM, why so much? The microcontroller not only measures the voltage at the input and displays the recalculated value on the indicator, it constantly records the measured values in one of 256 memory cells, filling them in a vicious circle and after recording each cell, it calculates the average value over all currently available 256 cells.
The indicator is located outside the board on the car's dashboard and is connected to it 11 wire loop. The board is placed in a tiny case (the second one, the one with 4 wire terminals); excess plastic was removed from the case with side cutters.
The board is single-sided, without jumpers:
First, I unsoldered the PWM switch and checked the work, it works. varnished. you can continue building:
P.S. The project was created with the enormous support of Roman Viktorovich, for which many thanks to him, also thanks to the man Johnson from Ukraine for mathematical help and some ideas.