Homemade tachometer and its operating principle

The main function of a tachometer in a car is to determine the correct gear, which has a positive effect on the life of the engine. Most cars have an analog tachometer built into them during assembly. The driver looks at the arrow approaching the red line and knows when to shift into a higher gear. Not all cars have the type of device that satisfies the owner, so you just need to figure out what they have and how to connect the tachometer.

Types of tachometers
How to connect a tachometer via the ECU
Connection diagram for a tachometer on a gasoline engine
How to connect a tachometer to a diesel engine
How to check the tachometer for functionality

Did you know? The term “tachometer” comes from the Greek
τάχος - speed and μέτρον - measure.

Types of tachometers

There are two types of tachometers: digital and analog. The first looks like a small screen on which the driver can see all the data he needs while driving. The second one is simpler and looks like a board with arrows and values.

Remote

A remote tachometer is installed on the front panel of the car. For greater ease of placement, this device has a leg for mounting on the panel. Remote digital tachometers are good for monitoring idle speed. Their readings have fewer errors, so using such a device you can check the operation of a standard tachometer. In addition, their stylish appearance gives the car elegance.

Staff

The standard tachometer is built into the dashboard of the car. This device is more convenient, since it is easier for the driver to perceive the movement of one arrow, rather than several indicators while driving. A standard tachometer is more often used in cars, and manufacturers of electronic devices produce kits for self-equipping cars.

Important! Measuring instruments are produced according to the car brand. The readings from a non-native mechanism will be incorrect.

How to connect a tachometer via the ECU

If your car does not have a carburetor engine and the injector, the tachometer is not connected to the ignition. In this case, you need to connect the engine control unit to the controller. The connection diagram for the tachometer is simple: take the ground to the body (ground), connect the plus from the device to the ignition positive. The tachometer has two inputs: the first goes to the control unit, the second to the crankshaft position sensor. The device connected to the computer will read pulses directly from the control unit controller.

Connection diagram for a tachometer on a gasoline engine

Before installing a tachometer on a carburetor engine, read the instructions included with the device. If it is not there, install according to the following steps:

Secure the mechanism in its place (the location is determined by the type of device).
Connect the black wire to the ground (body) of the car.
Connect the red wire to the ignition switch terminal, which supplies 12 W during operation of the ignition system.
The third wire can be any color. Since the ignition system is contact and non-contact, we will consider where to connect the tachometer in both. With a contact system, the device is connected to the distributor breaker. In the second system - to the voltage switch.

If the car has a display backlight, the tachometer is connected to the terminal provided for this in the ignition switch.

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How to connect a tachometer to a diesel engine

Before connecting, let’s figure out what makes the tachometer on a diesel engine work. The operating principle of an electronic device is to read pulses sent by a terminal located in the generator.

Since the process is labor-intensive, it must be carried out in an inspection pit.

The first point of work is to dismantle the protective casing of the generator, try to avoid getting dirt. The second step is connecting the tachometer to the diesel generator. To do this, find the terminal marked “W” on the generator body and connect the device output to it.

Attention! It is imperative to close the contact coming from the oil pump. If this is not done, the tachometer may “lie”.

It happens that the terminal indicated above cannot be found. In this case, disassemble the generator. Connect one of the wires connecting the winding and the rectifier to the tachometer cable. Insulate the wires and reassemble the generator in reverse order. Installing a measuring device is not very difficult, but without any knowledge of how a diesel engine works, how a tachometer works on a diesel engine, without the slightest idea about car repair, it is better to turn to professionals.

How to check the tachometer for functionality

We figured out how to connect a tachometer to a diesel and carburetor engine. Now let's look at the reasons for device breakdowns. You notice problems in the operation of the measuring device, for example, an arrow jumping in different directions. There may be several reasons for the breakdown. If the engine runs for a long time, vibration will occur, which may damage the display. The next reason may be oxidation of the contact group of the electrical wiring, damage to its insulation or disconnection from the tips. These are all visible causes that need to be eliminated immediately. If the sensor itself is broken, it needs replacement. If self-diagnosis does not reveal the cause, you should contact a car repair shop.

Interesting! The tachometer was designed by American Curtis Widder in 1903.

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How to connect a tachometer to a generator

HomeDriving rulesHow to connect a tachometer to a generator

The tachometer is a device that is actively used on gasoline and diesel cars. This device is used to measure the rotation speed (rpm) of the crankshaft or generator. Most modern vehicles are equipped with a standard tachometer straight from the factory.

The need to independently install a tachometer on a diesel engine may arise for various reasons. It should be noted that the tachometer connection diagram on a diesel engine is somewhat different from a similar solution for gasoline internal combustion engines. When choosing a tachometer for a diesel engine, it is necessary to take this feature into account, since a tachometer for gasoline engines will not fit on a diesel engine.

Where does the tachometer signal come from for a diesel engine?

Today, electronic, digital and analog tachometers are available for sale for diesel engines, the connection diagram of which requires a number of features. The fact is that the connection point for the tachometer for a diesel engine in the vast majority of cases is the generator.

To connect to the generator, you must have the tachometer itself, an insulated wire and accompanying instructions for installing and operating a car tachometer.

Connecting the device

The operating principle of an electronic tachometer is based on reading electrical impulses. In gasoline units, pulses are read and supplied in a certain amount to the ignition coil. As for the diesel engine, reading is carried out from a special terminal located in the generator housing.

To connect the tachometer to a diesel engine, it is advisable to carry out work on a lift or use an inspection pit.

At the initial stage, it is necessary to remove the protection from the generator, avoiding dirt getting inside the device. The next step is a visual inspection of the generator coil, which has several terminals.

The tachometer contact (input wire) should be connected to the terminal that is usually marked with the letter “W”.

Also, in some sources it is recommended to additionally implement the closure of the contact that comes from the oil pump.

It is noted that otherwise, after the engine reaches a certain crankshaft speed, a warning light may falsely light up on the instrument panel, indicating a critically low engine oil pressure in the engine lubrication system.

If the terminal marked “W” is not initially present on the generator, then you will need to independently install a separate contact wire. The pre-prepared wire must be properly insulated.

To facilitate access, the generator must be completely removed, as it will require partial disassembly. After disassembly, the wires (3 pieces) will become visible, going from the generator winding to the rectifier, which is also built into the device.

It is imperative to check that during the assembly process the wire brought out does not come into contact with moving elements in the generator structure. Next, the tachometer wire is connected to the contact brought out from the generator in the same way as when there is a terminal marked “W”.

The remaining contacts of the tachometer are connected in accordance with the diagram contained in the instructions for the specific device.

It is also worth considering that directly connecting the wire to the tachometer will lead to incorrect values. Additionally, you will need a divider board, which will make the speed readings correct.

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Comments 31

The diagnostic connector should have a pin with the letter “T” for scanning (under the tachometer). I installed a dashboard with a tachometer on a gasoline Kaldina (which did not have one from the factory). I connected the wire to the diagnostic connector. It still works, although more than five years have passed. If the engine is diesel, then you need to connect it to the speed sensor in the fuel injection pump.

To the connector? Oh well. There are no brains, no connector, no sensor. Fully mechanical diesel. There are two wires going to it. Spark plugs and fuel shut-off valve. The rest does not affect engine operation.

I wrote that it was on gasoline. There the conclusion comes from the brain. And on a diesel engine, impulses to the tachometer are taken from the speed sensor (on the fuel injection pump). You can also take it from the generator (if there is no sensor in the fuel injection pump). But with the fuel injection pump it shows more accurately.

That's right. But the tidy doesn’t understand directly from the sensor, you need a brain

If it’s just a diesel engine (without an ECU), then it should work. Connect a tachometer (for example, from a VAZ-2106) to the speed sensor (in the fuel injection pump) and check the readings. Will it work or not? I changed the instrument panel on my minibus to a digital one (from Mark-2). I also got tired of connecting it. But then I figured it out. It took a little do some magic with the pinout. Put a divider by two (on the chip). Now everything works. Although initially the instrument panel was from a gasoline brand. But I have a diesel.

There is a different tachometer on the jig. The original instrumentation does not understand because the tachometer was only available on the gasoline version of these cars. What about the Sprinter and the Kaldino that didn’t have a diesel tachometer?

Well then, just install a separate tachometer. Or stuff a tachometer, for example from Zhiga, into the original dashboard.

And their operating principle is different. On a jig, the tachometer comes directly from the ignition coil, and is powered from it. And the fuel injection sensor only counts pulses. Power supply for the device separately

The tachometer on the Zhiga is not powered by the ignition coil. It only takes impulses from the coil. And the tachometer itself is powered by voltage from the instrument panel (its plus and minus). Therefore, it can be easily connected to the speed sensor on the injection pump. There are two wires going to the sensor. One of them is for ground, the second is for the tachometer input terminal. If it doesn’t work with a minus, then you can try giving a plus instead of a minus.

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But, as I understand it, you originally had a tachometer on the microphone? Everything is ready for installation. There's just some tinkering with the electrics and changing the sensor in the tank. And there is nothing here at all. Therefore, only a separate tachometer with its own sensor

Analog and digital tachometers

Car gas tank device and operating principle
A homemade tachometer can be of two types:

Analog.
Digital.

The differences are clear from the names. The first convert the electronic signal and output it to an indication device - voltmeters, ammeters, LEDs. The latter convert the analog signal into a sequence of zeros and ones, which are easily recognized by microcontrollers. The latter work with such complex combinations, ultimately converting the original value into numbers on the display.

Analogue tachometer circuit.

Analog tachometers consist of the following main components:

an electronic microcircuit that acts as an amplifier and analog signal converter;
wiring connecting all elements of the tachometer;
scales with a specific graduation, which is applied by simultaneously measuring the rotation speed with a reference tachometer (instead of a scale, LEDs mounted one behind the other can be used);
an arrow indicating the current value of the desired value;
an electromagnetic coil on which the axis for the arrow is located;
a reading device - a breaker (this is often an inductive sensor).

Digital tachometer circuit.

Digital tachometers perform a similar function, but consist of different components:

ADC having 8 bits;
a central processor that performs the function of converting an analog signal into a sequence of 1s and 0s;
LCD display to display the current value of a certain value;
speed sensor - chopper, must be used either with an amplifier or with shunts, depending on the design;
a special chip that allows you to reset the current values to zero;
in cars, sensors for fluid temperature, cabin temperature, oil pressure, speed, and many others can be connected to the CPU.

In the “heart” of the microcircuit, with the help of a personal computer, a certain algorithm is laid according to which the work takes place. The processor calculates mathematical formulas that depend on what parameter needs to be measured. When monitoring one value, the algorithm will be the simplest.

But a digital tachometer in a car can also be used as a temperature, pressure, and speed recorder. The microcontroller has several inputs and outputs. Reading devices are connected to them via buffer cascades - converters and signal amplifiers. But it is worth noting that when introducing additional equipment into the tachometer design, it is necessary to take this into account in the algorithm and software of the microcontroller.

To make a homemade digital tachometer, you will need knowledge of a personal computer and a programming language. The ability to compose algorithms will also be useful. Therefore, it will be simpler to use conventional microcircuits that will amplify the breaker signal and output it to a strip of LEDs or a dial indicator. If there is a row of LEDs, consisting of 10 pieces for every thousand revolutions, then you can determine the current value with an accuracy of one hundred.

Chinese models

Adjusting the carburetor of a Chinese chainsaw, for example, Carver, is carried out in almost the same way as factory models. There are the same three main adjustment screws L, N, T. Sometimes such models have the ability to adjust the idle speed. But as a rule, employees of specialized services and owners of such saws claim that it is not always possible to set up a high-quality Chinese chainsaw right away.

For classic Chinese models, screw L should be loosened 1.5 turns from the maximum value. Screw H must be loosened one revolution from the maximum. Idle speed is adjusted in the same way.

The popularity of hand chainsaws is quite high, so they are used not only for work in the forest, but also in the household, for example, for pruning trees

They have many advantages, among which it is important to highlight mobility, reliability, and long service life. Although the last point depends not only on the quality of the tool, but also on the nature of its operation

The nature of operation includes not only compliance with the correct sawing technology, but also ensuring the care of the tool. In particular, starting to use a new chainsaw requires a break-in, after which you may need to adjust the carburetor. For such purposes, you will need a tachometer for a chainsaw.

Tachometer for a diesel engine, operating principle, types of video

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Unlike other devices installed on cars, the tachometer for a diesel engine is connected through a generator. The device itself is designed to determine at what frequency the crankshaft rotates. In other words, the tachometer shows the number of revolutions over a certain period of time.

You can see the tachometer readings directly while driving; it is located near the speedometer on the instrument panel. Various types of sensors are used to take readings; depending on this, the measurement method can be non-contact or contact. Tachometers are used not only in cars, but also in other devices where control over rotation speed is required.

However, it is in cars that this device has found its widest application. Not a single modern car can do without this device, which allows you to control the operation of the engine and change gears in a timely manner. All this helps to increase service life, contributes to fuel economy, and ensures traffic safety.

There are many varieties of these devices that are used in certain cases.

The very first tachometer was a centrifugal one, where the energy coming from the mechanism is transmitted through an axle. The impact on the arrow in each case is carried out differently, depending on the design of the device.

Tachometer for a two-stroke engine - applications and selection

An electronic tachometer for a two-stroke engine should be considered separately.

One of the varieties of such a device is a waterproof version, used in motorcycles, scooters, snowmobiles and other vehicles with two-stroke engines.

In practice, this is the same as a tachometer for a single-cylinder engine, which determines its service life, as well as the frequency of maintenance, such as valve adjustment, oil change, spark plugs, etc.

Installing such a device on the mechanism is very simple. There is no need for a separate battery thanks to the built-in rechargeable battery. The connection is made directly to the wire of one of the spark plugs. The resolution of such a device is 0.1 hours, it can count up to a maximum of 10 thousand hours, and then reset.

Tachometer dials vary in size.

When a certain number of revolutions is reached, a special flash lamp is activated, after which the gear shifts into the next gear. Such large tachometers take up a lot of space and partially block the view.

Tachometer scale and its additional features

The design of each tachometer in a car provides for working with a specific number of cylinders. The bulk of these devices work with four-cylinder engines.

In some models it is possible to switch to the required number of cylinders.

Depending on the engine speed, the scale graduation has different meanings and can reach from 8 to 11 thousand revolutions per minute.

Certain types of tachometers equipped with a flash can remember the highest number of engine revolutions. The tachometer may additionally include other devices that display engine operation.

Such devices are called multidevices.

What kind of device is this

First you need to understand what the device is and what its main functions are. A tachometer is a measuring device that determines the engine speed. The unit of measurement is revolutions per minute (rpm). Almost every modern car is equipped with a device, as it helps to correctly use the engine's capabilities. If the basic package does not include a tachometer, you can buy it separately and install it on both a diesel engine and a gasoline engine.

What types of tachometers are there?

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Mostly there are analog (in the form of a dial with an arrow) and electronic (display) tachometers. More exotic ones - made in the form of a running scale on gas-discharge lamps (often found on American-made cars), as well as mechanical ones - a legacy of the very first cars.

Mechanical

The very first tachometers installed on cars in the early and mid-twentieth century were devices connected directly to the engine crankshaft.

The principle of operation was quite simple: there was a gear on the crankshaft that meshed with a cable drive, which transmitted torque to a coil, which was an electromagnet of the device itself. The more revolutions, the greater the magnetic induction that occurs, the more the needle of the device deviates. Everything is very simple. However, the measurement error was quite high and could reach values of up to 500 rpm.

Analog

Further development led to the emergence of analog tachometers using a similar operating principle. The difference is that instead of being constantly driven by the crankshaft, the frequency of power supplied to the ignition coil is used to read the number of revolutions.

What it looks like in action. To create a spark on the spark plug, a short-term low voltage pulse is applied to the coil that converts low (12V) voltage to high (from 12,000 to 24,000V). The same pulse is supplied simultaneously to the electrical circuit of the analog tachometer and the electromagnet winding. The more pulses are supplied to the winding, the greater the induction force appears, and the greater the angle the arrow deflects.

It should be noted that the error of analog tachometers can range from 100 to 500 rpm.

Digital

Since digital electronic tachometers are increasingly replacing their analog counterparts, not to mention mechanical ones, we will dwell on them in more detail.

The basic principle of operation of a digital tachometer is to measure and count the number of pulses arriving at the primary winding of the ignition coil, or measure the time interval corresponding to these intervals and convert the received information into digital values displayed on the display.

Video - digital tachometer with many settings and Shift Light:

In addition to the fact that a digital tachometer operates on all of the above values, to improve measurement accuracy, the device also processes values coming from the idle speed sensor and, sometimes, the crankshaft sensor. The 1xbet working website has a fairly wide line: there are about 35 different sports. The painting is also impressive, and, of course, the largest number of events is associated with football. However, for other directions there is plenty to choose from. You should also pay attention to eSports events, since this area is only gaining popularity: there are more and more games, as well as events related to them. Placing bets with 1xbet is not only fun and comfortable, but also as profitable as possible. All data is summed up, and the resulting average value is practically a true indicator.

Since approximately half of the total number of cars (especially compact or small cars) are not equipped with a standard tachometer, electronics manufacturers offer installation kits for self-installation of an electronic tachometer.

A simple set represents, in fact, the display itself, often liquid crystal with a built-in board for processing incoming information and a set of wires for connecting to the standard terminals of the coil (the first cylinder with a distributed ignition system), as well as power.

More complex ones may contain additional idle speed sensors, as well as an external optocoupler. However, such kits are installed for a specific purpose - to gain complete control over engine speed. A simple kit is sufficient for everyday use.

For clarity, below is a typical wiring diagram for an electronic tachometer that receives information only from the ignition coil.

As described above, the tachometer receives the signal from contact K of the ignition coil, which receives low voltage pulses, power is supplied from terminal B of the ignition coil (constant +12V when the ignition is turned on), minus is the vehicle’s weight.

Another version of the tachometer connection diagram - using information from the controller (the “brains”) of the car is shown below.

In this case, to display the number of engine revolutions, information received from the crankshaft position sensor and processed by the controller is used.

Recommendations

An electronic tachometer is recommended for use by inexperienced drivers
who do not know how to navigate by engine sounds;
When purchasing, pay attention to the back of the package, where it is written for which brands of cars it can be used. Otherwise, the readings will be false or prepare for problems in the electrical circuit (this applies more to injectors);
Install the module itself somewhere in a visible place so that you can always see its readings without any problems. As practice shows, installation is carried out on the central panel of the torpedo. Some people manage to place an oblong module in the instrument panel in place of the “STOP” indicator; this is for models 2108, 2109, 21099
.

Operating principle and types

The tachometer receives the signal from the pulse crankshaft speed sensor and converts them into the corresponding numerical value. When using various methods of calculating the control value (direct, reverse, mixed), the reading error reaches 100–500 rpm.

If we touch on the basic diagram of the devices, then in addition to the mechanical tachometer, which can already be considered a rarity, since it is found only on vintage cars, there are two more types of such devices:

digital;
analog.

You can also classify devices depending on the installation method:

standard ones - as a rule, they are installed on the conveyor in a specially designated place on the dashboard of the car;
remote – mounted outside the dashboard in addition to existing control devices, very often used on sports cars.

Digital tachometer

It is an electronic indicator (screen, display) showing the number of engine revolutions at a given time. It is believed that this representation is most convenient when working with electronic control units or when tuning (tuning) the motor. The device also includes a processor, an analogue to digital signal converter, an idle air valve sensor and another converter that is needed to transform electrical signals into light signals (optocoupler).

Analog tachometer

The appearance of such a device has already been described above. Visually, it is similar to most control and measuring instruments: there is a dial along which an arrow moves, indicating the number of revolutions. The value of the engine crankshaft rotation speed corresponds to the angle of rotation of the arrow relative to the zero value. One of the main elements of such a system is a magnetic coil that accumulates the energy necessary to turn the arrow. The electrical signal from the sensors is supplied through microcircuits to a coil that activates an arrow, which, by its deviation, indicates the value of the control parameter. Sometimes a combined design is used, when in addition to an analog device, a digital one is also installed. However, it is believed that with constant use, the signal from an analog tachometer is perceived by the human brain better than from a digital one.

Connection diagram for carburetor type

We connect the red wire from the ET to the plus terminal of the ignition

, we ring the mass somewhere on the body, it doesn’t matter, but the minus goes directly to the coil. Don't forget that at night we also need to read the readings, so depending on the model there is an additional wire that needs to be connected to the dimensions. When the latter are turned on, the display of our ET will light up.

If you do not want to take part in this process or you do not have enough experience, do not take risks, drive the car to a service center. Where qualified specialists will quickly and efficiently install your device, provide consultations on how to use it safely and other issues.

Tachometer with LCD display on microcontroller

There are two options - buy ready-made, or make it yourself. The second way will be within your power if you understand microcontroller technology and know how to program it. In other cases, it is better to purchase a finished product. Again, it should be noted that the VAZ 2101 wiring diagram will be slightly supplemented. First, you need to connect the tachometer to the positive terminal of the ignition switch. VAZ 2107 Replacing the heater radiator! In this video I will show you how to change the heater radiator on a VAZ 2107 car. Secondly, you will need to ensure that the pulses are read. This can be done in two ways:

Take the signal from the ignition coil.
Install the proximity sensor on the crankshaft.

The second solution will be more difficult, since you will have to upgrade the crankshaft pulley - you need to make a protrusion on it that will act on the contactless sensor. But taking the signal from the low-voltage output of the coil is a simpler solution.

Circuit diagram of a simple microcontroller tachometer

But you need to remember that during one revolution of the crankshaft exactly two flashes occur in the cylinders. Consequently, two signals will appear on the low-voltage terminal per revolution. This will need to be taken into account when making a tachometer for a VAZ 2101 with your own hands. VAZ 2105, VAZ 2106, VAZ and toe on the VAZ 2101 it is vertical as shown in. How to connect a 220 volt electric motor. In particular, at the stage of programming the microcontroller, this is necessarily taken into account in the algorithm. Which controller to choose is up to you. AtMega128, which has become a classic, will also do an excellent job. You can find a great variety of designs on it.

To control the actuator (in our case, an LCD display), it is advisable to use an amplifier - a Darlington assembly. How to connect the State on-board computer to a VAZ 2110. This is a small microcircuit that allows you to amplify the signal to the required value. Its price is insignificant, at least 10 rubles per piece, so there will be no problems with the purchase. With its help, the tachometer on the VAZ 2101 will be able to work as stably as possible, and there will be no chance that the output ports will be damaged. Be sure to connect the voltage divider to the input port. It will reduce the voltage coming from the ignition coil.

The module is powered from the ignition switch. How to replace the clutch cable on a VAZ 2109? The error when using microcontrollers can be either 3 revolutions per minute or 50. Therefore, study the datasheets and reviews of people who have used the devices for their designs. The photo shows an example of a circuit that can be used for a VAZ tachometer 2101

. It works stably, all that remains is to program it and install it in the dashboard of the penny. Due to its small dimensions, this will be much easier to do than in the case of installing a six indicator.

Video on installing a tachometer in a VAZ 2101:

How to connect a car tachometer with your own hands

The main function of the tachometer in a car is to determine the correct gear, which has a positive effect on the life of the engine. Most cars have an analog tachometer built into them during assembly.

The driver looks at the arrow approaching the red line and knows when to shift into a higher gear.

Not all cars have the type of device that satisfies the owner, so you just need to figure out what they have and how to connect the tachometer.

Did you know? The term “tachometer” comes from the Greek τάχος - speed and μέτρον - measure.

Types of tachometers

There are two types of tachometers: digital and analog.

The first looks like a small screen on which the driver can see all the data he needs while driving.

The second one is simpler and looks like a board with arrows and values.

Remote

A remote tachometer is installed on the front panel of the car. For greater ease of placement, this device has a leg for mounting on the panel.

In addition, their stylish appearance gives the car elegance.

Staff

Important! Measuring instruments are produced according to the car brand. Indications from a non-native mechanism will be incorrect

How to connect a tachometer through the computer If your car does not have a carburetor engine, and the injector, the tachometer is not connected to the ignition. In this case, you need to connect the engine control unit to the controller.

The connection diagram for the tachometer is simple: take the ground to the body (ground), connect the plus from the device to the ignition positive. The tachometer has two inputs: the first goes to the control unit, the second to the crankshaft position sensor.

The device connected to the computer will read pulses directly from the control unit controller.

Connection diagram for a tachometer on a gasoline engine

Secure the mechanism in its place (the location is determined by the type of device). Connect the black wire to the ground (body) of the car. Connect the red wire to the ignition switch terminal, which supplies 12 W during operation of the ignition system.

The third wire can be any color. Since the ignition system is contact and non-contact, we will consider where to connect the tachometer in both. With a contact system, the device is connected to the distributor breaker. In the second system - to the voltage switch.

If the car has a display backlight, the tachometer is connected to the terminal provided for this in the ignition switch.

How to connect a tachometer to a diesel engine

Since the process is labor-intensive, it must be carried out in an inspection pit. The first point of work is to dismantle the protective casing of the generator, try to avoid getting dirt. The second step is connecting the tachometer to the diesel generator. To do this, find the terminal marked “W” on the generator body and connect the device output to it.

Attention! It is imperative to close the contact coming from the oil pump. If this is not done, the tachometer may “lie”

It happens that the terminal indicated above cannot be found. In this case, disassemble the generator. Connect one of the wires connecting the winding and the rectifier to the tachometer cable. Insulate the wires and reassemble the generator in reverse order.

How to check the tachometer for functionality

We figured out how to connect a tachometer to a diesel and carburetor engine. Now let's look at the reasons for device breakdowns.

You notice problems in the operation of the measuring device, for example, an arrow jumping in different directions. There may be several reasons for the breakdown. If the engine runs for a long time, vibration will occur, which may damage the display.

The next reason may be oxidation of the contact group of the electrical wiring, damage to its insulation or disconnection from the tips. These are all visible causes that need to be eliminated immediately. If the sensor itself is broken, it needs replacement.

Interesting! The tachometer was designed by the American Curtis Widder in 1903.

Technical solution

Before connecting the tachometer, it is necessary to draw up an electrical connection diagram in order to mentally determine the starting and ending switching points and trace the conductor. Any ignition coil has a terminal (terminal) +15 (ignition on), to which battery voltage is supplied when the key is turned to the first (for some cars, second) position. Under no circumstances should you connect the tachometer to this point; the first time you turn it on, it may fail. High-voltage wires also pose a danger, even to humans. The signal input to which the tachometer should be connected must be precisely determined. In older coils it is designated by the letter "K", it is better to find the exact circuit diagram of the car.

The next, more difficult task is the electrical connection of the nodes. As a conductor, you should take a stranded copper wire with a cross-section of at least 2 sq. mm. with polyvinyl chloride insulation.

The connection points of the wire to the ignition coil are cleaned, mechanically twisted, soldered and carefully insulated. Lay the wire along any electrical harnesses, using plastic clamps, towards the engine compartment bulkhead near the dashboard. You can insert the conductor into the passenger compartment next to any electrical wiring harness. To do this, it is easier to use an elastic string. Finally, connect the conductor to the tachometer signal terminal. In some cars that include modifications with or without a tachometer, you can simply change the dashboard, find the stock wire and connect it to the ignition coil.

Digital index

It's no secret that even expensive cars still use an analog tachometer, which is considered the most comfortable for the eye and the most common for quick reading.

How is this convenient? Firstly, this way you can catch a more suitable moment to change gears. Secondly, such a device is often used by fuel system tuners to achieve optimal engine operating conditions and mixture quality.

Obviously, such technology is more complex, and therefore its use on modern automotive technology is still very limited. The electronic device is based on a liquid crystal display, which is either included in the main analog tachometer or has its own place on the dashboard.

In addition to the display, there is a so-called analog-to-digital converter, which converts pulses from a magnetic coil into a digital signal in binary format. Typically this signal is sent to a digital processor. Its task is to analyze the received data and send it to the display in a form that will be understandable to the end user, the driver. Communication between the devices is carried out by an optocoupler, whose task is to diagnose the idle air valve to compare the received data with the reference data and adjust the output values.

Checking the device's functionality

Having connected the tachometer to the engine, you must check its functionality. If the arrow moves, then everything is connected correctly. But do not forget that the device may fail (the needle begins to “jump”, etc.) for some reason. The most common causes of breakdowns are:

Continuous operation of the engine causing vibration and damage to the display;
Insulation failures, contact disconnection and oxidation.

You can identify and solve these problems on your own. If the reason is the sensor itself, which has failed, then it will need to be replaced. In difficult cases, the right solution would be a trip to the service station.

To summarize, we note that installing a tachometer is not such a difficult task. But you shouldn’t get down to business without the necessary theoretical and practical skills in car repair. If you are not confident in your abilities, it is better to turn to specialists. Share your opinion in the comments!

A car enthusiast who cares about his car should have, among other devices, a tachometer, which helps to operate the car correctly. If there is no standard device, then it should be installed. The article describes their types and gives instructions on how to correctly connect the tachometer to a diesel engine and to a gasoline engine.