Automobile tachometer. Free Technical Library article

Free technical library

ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
Free library / Schemes of radio-electronic and electrical devices

Car tachometer

Free technical library

Encyclopedia of radio electronics and electrical engineering / Automobile. Electronic devices

Comments on the article

Unfortunately, many domestic and imported cars lack one very important device - a tachometer.

I offer a simple but reliable electronic tachometer that works on my Ford Escort car. The scheme published in [1] was taken as a basis. The device has a two-digit digital indicator showing the number of thousands and hundreds of revolutions per minute. The tachometer is powered by the vehicle's on-board network and consumes a current of 0,45A. The circuit diagram of the device is shown in the figure.

The tachometer consists of a control unit on the IC DD1 and elements DD2.1, DD2.3, DD2.4; two generators on transistors VT1 ... VT4; input pulse shaper - Schmitt trigger VT5, DD2.2; pulse counter on IC DD3, DD4; intermediate memory on ICs DD5, DD6; decoder on IC DD7, DD8 and indicator HI.

The operation of the control node is described in detail in [1]. The multivibrator on VT1, VT2 sets the measurement time, and the multivibrator on VT3, VT4 determines the operating cycle of the device. The input shaper and counter are assembled according to a typical scheme and do not have any special features, so they immediately start working. Intermediate memory on triggers has been introduced into the tachometer circuit to prevent flickering of the indicator digits during counting. The K155TM5 triggers are synchronized with a signal from pin 8 DD1 passing through capacitor C4 and DD9.1 to obtain the desired duration and phase. The operating cycle time is set by selecting the resistor R11, and the measurement time is set by selecting the resistor R7.

For a conventional automotive four-stroke four-cylinder engine, an inductive pickup is used. It consists of 50 ... 70 turns of PEL 1.0 wire wound turn to turn on a high-voltage wire connecting the ignition distributor to the ignition coil.

One end of the sensor coil must be insulated, and the other end must be connected to the input of the tachometer.

Automobile tachometer. Digital tachometer circuit

(click to enlarge)

The frequency of the ignition pulses and the number of revolutions of the engine are interconnected by the formula: f=2n/60 where f is the frequency of the ignition pulses; n is the number of revolutions per minute of the motor shaft.

So, the value of the number of revolutions 3000 corresponds to a pulse frequency of 100 Hz. But since the tachometer indicator should show 3.0 at this time, only 30 out of 100 pulses per second should go to the counter. Therefore, the measurement time in this case is set to 0,3 s. The working cycle time should be 10...20 times longer (3...6 s).

Construction and details. The two-digit Bulgarian-made VQE24 digital indicator can be replaced by two domestic ones - ALS324B or ALS342B. If you replace the KR514ID2 decoders with K514ID1, you can exclude resistors R13 ... R19, R21 ... R27 from the circuit and use ALS324A indicators with a common cathode. All microcircuits of the 155 series can be replaced with the corresponding series 133, 555, 1533. KT315 transistors can be replaced with KTZ 12, and KT361 with KT326. Diodes VD2, VD3 - any silicon: KD510, KD521, KD509. Capacitors C1, C2, C6 - K53-1, K53-14; SZ, S5 - K73-17; the rest - KM5, KM6. IC voltage stabilizer DA1-type KR142EN5A, can be replaced by KR142EN5V.

All parts of the electronic tachometer, except for R1 and a digital indicator, are located on a double-sided printed circuit board measuring 60x115 mm. The board is placed in a polystyrene case measuring 65x145x35mm. DA1 is mounted on a small finned heatsink. About 1 V drops across resistor R5, which greatly facilitates the thermal regime of the stabilizer. If all the parts are in order, the device immediately starts working. The adjustment is as follows: a signal with a frequency of 5 Hz is applied to the VT100 base, and by selecting R7, the indicator readings are set to 3.0, which corresponds to 3000 rpm.

In conclusion, I want to note that according to this scheme, my friends assembled several tachometers that differ only in design, and all of them have been working fine on various cars for several years.

Literature

Shirokov B. Digital tachometer//Radio. - 1983. - N9. - P.28-29.
Biryukov S. Digital devices on integrated circuits. - M.: Radio and communication, 1984.

Publication: cxem.net

See other articles Section Automobile. Electronic devices

Read and write useful comments on this article.

<< Back

Latest news of science and technology, new electronics:

Artificial leather for touch emulation 15.04.2024

In a modern technology world where distance is becoming increasingly commonplace, maintaining connection and a sense of closeness is important. Recent developments in artificial skin by German scientists from Saarland University represent a new era in virtual interactions. German researchers from Saarland University have developed ultra-thin films that can transmit the sensation of touch over a distance. This cutting-edge technology provides new opportunities for virtual communication, especially for those who find themselves far from their loved ones. The ultra-thin films developed by the researchers, just 50 micrometers thick, can be integrated into textiles and worn like a second skin. These films act as sensors that recognize tactile signals from mom or dad, and as actuators that transmit these movements to the baby. Parents' touch to the fabric activates sensors that react to pressure and deform the ultra-thin film. This ... >>

Petgugu Global cat litter 15.04.2024

Taking care of pets can often be a challenge, especially when it comes to keeping your home clean. A new interesting solution from the Petgugu Global startup has been presented, which will make life easier for cat owners and help them keep their home perfectly clean and tidy. Startup Petgugu Global has unveiled a unique cat toilet that can automatically flush feces, keeping your home clean and fresh. This innovative device is equipped with various smart sensors that monitor your pet's toilet activity and activate to automatically clean after use. The device connects to the sewer system and ensures efficient waste removal without the need for intervention from the owner. Additionally, the toilet has a large flushable storage capacity, making it ideal for multi-cat households. The Petgugu cat litter bowl is designed for use with water-soluble litters and offers a range of additional ... >>

The attractiveness of caring men 14.04.2024

The stereotype that women prefer "bad boys" has long been widespread. However, recent research conducted by British scientists from Monash University offers a new perspective on this issue. They looked at how women responded to men's emotional responsibility and willingness to help others. The study's findings could change our understanding of what makes men attractive to women. A study conducted by scientists from Monash University leads to new findings about men's attractiveness to women. In the experiment, women were shown photographs of men with brief stories about their behavior in various situations, including their reaction to an encounter with a homeless person. Some of the men ignored the homeless man, while others helped him, such as buying him food. A study found that men who showed empathy and kindness were more attractive to women compared to men who showed empathy and kindness. ... >>

Random news from the Archive

Severe hereditary diseases protect against infections 12.07.2016

Tobias Lenz, professor at the Max Planck Institute for Evolutionary Biology (Germany) and Shamil Sunyaev, associate professor at Harvard Medical School (USA), found out why harmful hereditary mutations do not disappear from organisms during evolution, but , on the contrary, retain their presence in the genes and even benefit.

Hereditary mutations occur when parts of DNA are damaged and lead to the expected consequences - incurable, painful diseases that threaten health and life. Despite the negative effects, evolution does not get rid of mutations, but, on the contrary, keeps them in the genes and even increases their presence.

Lenz and Sunyaev studied the nature of this paradox and modeled various evolutionary scenarios in which genetic selection causes deleterious mutations to progress. Scientists then checked the results of DNA sequencing of 6,5 thousand patients and came to the conclusion that the main acting factor in this case is the so-called. balancing selection, which regulates the genetic variability of generations, expands the adaptive capabilities of species in a changing environment, and also keeps mutations in the body.

Scientists observed the work of balancing selection in the major histocompatibility complex (MHC), a region of the genome in which genes are concentrated, the products of which perform functions associated with the immune response. It is at this site that multiple harmful mutations are localized, leading to autoimmune disorders, cancer, Alzheimer's disease and schizophrenia.

The results of the study showed that the viability of such mutations in the genome is not accidental - they help the body fight external viruses. A good example is sickle cell anemia, one of these hereditary mutations associated with a violation of the structure of the hemoglobin protein. To the surprise of scientists, patients who inherited the mutated genes from their parents turned out to be more resistant to malaria than ordinary people.

News feed of science and technology, new electronics

We recommend downloading in our Free technical library:

▪ section of the site Basics of safe life (OBZhD)

▪ magazines Repair of electronic equipment (annual archives)

▪ book Inductive-frequency converters of non-electric quantities. Goldman V.S., Sakharov Yu.I., 1968

▪ article Medicine. Big encyclopedia for children and adults

▪ article by Joseph Henry. Biography of a scientist

▪ article Loudspeaker with low-pass filter for a radio receiver or radio station. Encyclopedia of radio electronics and electrical engineering

▪ reference book Foreign microcircuits and transistors. R-series

Leave your comment on this article:

All languages of this page

Home page | Library | Articles | Website map | Site Reviews