Any car owner knows well that his vehicle has an additional window with arrows and numbers - a tachometer. Meanwhile, many car enthusiasts do not attach importance to this and do not even imagine what it is needed for. However, if there was no need for a tachometer, then the designers would not place it on the dashboard. What is the device used for? What is this device and what does it show?
What is this?
A tachometer is a device located on the dashboard of a vehicle. It is installed not only in cars, but also on motorcycles and motor boats. The device was first created in 1903, when an American engineer built a cyclometer. The invention made it possible to calculate bicycle mileage. But what is a tachometer for in a car? The tachometer helps to monitor the operation of the engine, since there is a risk of engine damage when operating at high speeds.
Advantages of the device:
Helps extend the “life” of the engine.
Regulates the amount of fuel consumed.
The driver gets the opportunity to set the correct driving mode.
There is no shock effect on the transmission during gear shifting.
It turns out that the tachometer shows the car owner the best moment when to change gear. If the car has a manual transmission, then the device shows the moment of maximum load (the arrow “approaches” the red zone). The adjustment can be made while driving or at idle speed.
If the driver follows the indications, that is, starts and ends the movement within a given range of rotation of the crankshaft, then the engine resource will increase to the maximum.
In addition, the owner has the opportunity to independently diagnose the functioning of the motor. If the “engine” is working properly, then when it starts, the needle approaches 1000-1200 rpm, and after a couple of seconds drops to 600-800 rpm. A jumping arrow indicates that the motor is not operating properly.
What you need to connect a digital tachometer
Many motorists who truly care about their vehicles prefer to switch from analogue or mechanical devices to more modern devices in order to fully control the operation of the internal combustion engine. In particular, this is possible regardless of the make and model of the car, since there are special kits that can be purchased at many auto parts stores. The standard digital tachometer kit includes a display and a set of wires to make connections to the power supply and the ECU.
Also on sale you can find special kits that already contain crankshaft and idle speed sensors, if for some reason the car is not equipped with these elements from the factory. You can also find a remote optocoupler here, although this device is mainly installed on sports cars. It is noteworthy that the connection will not always be made through the computer, since some versions of digital devices provide for a separate installation of the tachometer without a controller. In this situation, the device will be able to read more accurate readings than when connected to the computer. Of course, it is worth doing the work of installing such a tachometer only in cases where the car enthusiast has the appropriate skills and knowledge. In other circumstances, it is better to entrust the work to specialists.
Varieties
Many drivers are interested not in what the tachometer measures, but in how exactly it does it. The accuracy of determining the speed depends entirely on the sensor. Today, devices are classified according to the method of displaying data or the method of installation. The latter are divided into built-in and contactless. On sports cars, non-contact tachometers are mainly used to determine the speed as accurately as possible and adjust it.
Mechanical, analog and digital tachometers are installed on cars today. They all have their own characteristics and operating principles. For example, the mechanical type has already lost its relevance. It was used in the 20th century, since there were simply no other options for measuring revolutions. Today, such a tachometer can be found on very old cars or motorcycles.
The design of the device includes a cable connected to the crankshaft. The operation of the device was based on the fact that the gear and cable interlocked with each other. Tachometers were successfully installed on old low-speed engines. They had rather low accuracy due to the fact that the cable consisted of wire. The thread was twisted, which led to incorrect calculation of the transmission torque. The error level was 500 rpm.
The analog tachometer was invented later. The mechanism of action has been changed. Its operating principle was similar to a mechanical one, but the revolutions were displayed by an arrow on the dial. The values were read using the energy supplied to the magnetic coil. There was a sensor on the crankshaft that calculated the number of revolutions, after which an electrical signal was created that passed to the coil. She deflected the arrow and showed the result. Compared to a mechanical device, an analog one is more reliable, but still not accurate. Its error is 500 rpm. The advantages of such a tachometer include the absence of a cable and simple installation.
It's no secret that even expensive cars install an analog type of device. It is familiar to the driver’s eyes, and quickly calculates readings. With its help, the car enthusiast will be able to catch the moment to change gears, as well as help the engine achieve optimal operating mode.
Another type of tachometer is digital, it works with a small error (100 rpm). A special sensor counts the revolutions and then redirects them in the form of signals to the instrument panel. The device includes a processor, converter, optocoupler and several other essential elements. The connection method is different, depending on what type of engine the car has. On gasoline engines, installation is carried out through an ignition coil, on diesel engines - using a generator.
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:
Principle of operation
Drivers who do not understand the mechanical components of the engine must know how the tachometer works in a car. This will help them understand what this device is intended for.
The operation of the motor is based on the transformation of movement (from translational to rotational). This is facilitated by gases that expand and “turn on” the pistons. They, in turn, use connecting rods to spin the crankshaft. Its speed is precisely shown by the tachometer.
The driver, by pressing the gas, forces an increased amount of fuel into the combustion chamber. The pressure increases accordingly, thereby increasing the crankshaft speed and instrument readings.
To make it even clearer how the device functions, we will give a simple example. Let's say the information in the engine documentation reads: 135 horsepower at 3500 rpm. These values indicate that the engine will achieve maximum acceleration at a given crankshaft speed. Low rotation rates will reduce efficiency, which means the machine will move more quietly.
Experts say that if the driver monitors the tachometer readings and switches gears in time, he will achieve effective acceleration. But it is still not recommended to carry out such manipulations constantly. If the speed increases, it means that fuel consumption will also begin to increase. In addition, high speeds will lead to rapid wear of parts. It is best not to “crank” the motor to maximum values. This will help save fuel and extend the life of parts and oil fluid.
How to use the information
Having figured out what the tachometer in the car shows, drivers, as a rule, do not know how to proceed further and how to use the information received.
To begin with, it is worth remembering that the device indicates an acceptable time to start driving. This is convenient, especially for those who often travel by car in winter, since the device demonstrates the readiness of the “engine” for a trip. Most vehicles are unable to start moving when the engine is cold, so they start at maximum speed. Car enthusiasts just have to wait until the temperature of the refrigerant becomes normal. This will not happen with a tachometer. The driver is allowed to hit the road if the needle approaches 750-800 rpm.
What malfunctions can there be
A mechanical type tachometer may be faulty if its structural elements are damaged. For example, if deformations occur, the cable breaks, or play appears. As for electronic devices, there may be several causes of failure. Let's look at them in more detail:
Electrical wiring is damaged, incl. signal wire.
The contacts have oxidized, or they have loose contact.
The elements of the measuring unit are damaged (burnout of microcircuits, swelling of resistors).
If the device is connected to a generator, then the generator itself is not working. A problem is indicated by a low battery indicator. It happens that the needle starts jumping without any reason. The driver should carefully inspect the wiring, engine components and the device itself.
If the device indicators do not change even when the accelerator pedal is pressed firmly, then it is necessary to check the integrity of the wiring. The tester will help the driver with this.
How to choose a device for a car?
Today, every driver needs accurate tachometer readings, since outdated instruments do not always show the correct values. In addition, not all cars, especially small ones, are equipped with this device. It is the owners of such cars who most need the device. When purchasing an electronic model, the buyer must study its technical characteristics. It is also worth remembering that the tachometer installation for gasoline and diesel engines is different. The installation method depends on the size and design of the model.
The Helios tachometer is very popular. It has a standard appearance. Intended for cars with carburetor engines, where the number of cylinders varies from 1 to 16. The advantages of the model include cost, many additional options and low error.
The MULTITRONICS model is considered less universal. The DD5 tachometer has many functions, including a timer and clock. All other types of this brand do not have additional options except a voltmeter. The error at high speeds is up to 3%.
Is it possible to determine the speed of movement using the device?
As already mentioned, tachometer values can be displayed in different quantities:
- In time (hours, minutes, seconds);
- In distance (kilometers, meters, centimeters, etc.);
- In units;
- In speed (m/s, km/h).
To determine the speed using the tachometer, you just need to change the way the information is displayed on the display. Note that this is only possible in those models that display different quantities. You can also find out the speed on earlier models by examining the existing device and comparing the units of measurement.
