Non-contact interrupter of the electronic ignition system. Scheme, description

Free technical library

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

Non-contact interrupter of the electronic ignition system. Encyclopedia of radio electronics and electrical engineering

Free technical library

Encyclopedia of radio electronics and electrical engineering /Automobile. Ignition

Comments on the article

Motorists who have installed an electronic ignition system on their car have probably already appreciated its advantages. The contact breaker continues to cause trouble as before. Erosion, oxidation, contamination of contacts force the motorist to periodically carry out work to maintain their working condition. You can get rid of these worries if you supplement the electronic ignition system with a pulse shaper with a non-contact sensor.

There are several types of sensors that can work in non-contact ignition systems - photoelectric, galvanomagnetic, parametric. Parametric sensors include those sensors whose operation is based on the transformation of a change in the measured value into a change in a parameter - capacitance, inductance, resistance, magnetic resistance. The most accessible for manufacturing in amateur conditions is a parametric electromagnetic sensor. Its work is based on the property of the magnetic circuit of a coil in which an alternating electric current flows, to change its magnetic resistance when a ferromagnet with a low specific magnetic resistance is introduced into the gap of the magnetic circuit.

Parametric sensors for a non-contact ignition system have been repeatedly described in the literature, for example [1,2,3]. In these designs, the sensor coil, wound on a W-shaped ferrite magnetic core, is part of the blocking oscillator. Such a solution has many disadvantages - the complexity of manufacturing the magnetic circuit of the sensor in amateur conditions, too small a gap between the magnetic circuit and the switching disk, a significant current consumption.

The design of a contactless interrupter with an electromagnetic sensor, free from these disadvantages, is described below. The contactless interrupter can work in conjunction with all modifications of electronic ignition systems of industrial production ("Electronics", "Iskra", "PAZ"), as well as with amateur designs described in [1.4,5].

These electronic ignition systems are designed to connect a contact breaker, so their input node is designed in such a way as to provide a current through the closed breaker contacts of 70 ... 180 mA. Such a significant current is chosen to reduce the sensitivity of the system to the state of the breaker contacts. Mandatory for the electronic ignition system is the contact bounce suppression unit. The use of a non-contact interrupter makes it possible to exclude the contact bounce suppression unit from the system, to select a much lower current of the input unit and thus make it more reliable and economical. Within the framework of this article, it is simply impossible to give recommendations on the modernization of ready-made ignition systems, since there are many circuit solutions, both industrial and amateur.

Schematic diagram of the contactless interrupter is shown in Fig.1. The sensor is a coil 11, which, together with the capacitor C3, is part of the generator, made on transistors VT1.1, VT1.2 microassembly VT1. When a disc tooth enters the gap of the coil magnetic circuit, the generator oscillations are disrupted, since the energy of the electromagnetic field of the coil is spent on the formation of an eddy current in the tooth.

(click to enlarge)

At this moment, the collector current of transistor VT1.1 decreases, causing an increase in the collector voltage. The Schmitt trigger, made on transistors VT2, VT3, generates a signal with a steep rise and fall. Transistor VT4 operates in switching mode.

The entry of the tooth of the switching disk into the gap of the sensor corresponds to the moment of closing the contacts of the breaker. The equivalent angle of the closed state of the contacts is determined mainly by the angular width of the disc tooth; this angle is chosen to be 50°. A small error in determining the angle of the closed state of the contacts is due to the hysteresis of the Schmitt trigger.

The temperature stabilization of the generator is provided by negative DC feedback through the resistor R2, included in the emitter circuit of the transistor VT1.1, diode thermal compensation (diode switching on the transistor VT1.2) and the use of a matched pair of transistors placed on the same chip. The current through the emitter junction of the transistor VT1.2 is chosen small, about 1,5 mA. Thanks to these measures, the stability of the generator mode is maintained in the temperature range -48...+90°C.

Proximity interrupter of the electronic ignition system

The supply voltage of the generator and the Schmitt trigger is fixed by the zener diode VD1, which eliminates the dependence of the ignition moment on the voltage of the car's on-board network. The HL1 LED is used to set the ignition timing and visual control of the breaker operation.

Coil L1 is wound on an annular magnetic circuit of size 1 (7x4x2 made of ferrite 2000NM. A through groove 3 mm wide is propylene in the magnetic circuit, and the winding is placed on the side opposite to the groove. The winding consists of 37 + 50 turns of wire PEV-2 0,12. Winding width - 3,5 ... 4 mm The magnetic circuit at the place of winding must be wrapped with one layer of varnished cloth or covered with several layers of varnish.

Leads 200 mm long from the MGTF wire are soldered to the winding, the soldering points are isolated and the coil is inserted into a shielding box with a slot in front. The position of the magnetic circuit 5 in the box 2 and its placement on the mounting flange 1 is illustrated in Fig.2. The box can be made of sheet brass or copper (but not steel) with a thickness of 0,2 ... 0,4 mm. The magnetic circuit is fixed relative to the slot by inserting a porous rubber insert wrapped in polyethylene film into it, after which the box is filled with epoxy resin.

After the resin hardens, the box is soldered to flange 1, made of foil fiberglass, brass or steel. The terminal harness 3 is fixed on the flange with a clamp 4, fixed by soldering.

In the electronic unit, MLT resistors, capacitors K1-7 (C1 - C3), K53-14 (C4, C5) are used. It is extremely undesirable to replace the KR159NT1B transistor assembly with individual transistors, since the stability of the generator will deteriorate, especially in the region of negative temperatures.

All parts of the shaper, except for the coil L1, are placed on a printed circuit board made of foil fiberglass with a thickness of 1 mm. The drawing of the board is shown in Fig.3. The board, installed in a strong, tight-fitting box, should be mounted as close as possible to the breaker-distributor of the car.

Establishing the shaper is reduced to the selection of the resistor R3. By connecting a voltmeter to the collector of the transistor VT1.1, this resistor is selected according to the minimum reading of the voltmeter - the voltage should be 2 ... 3 V. Then a steel plate is inserted into the sensor slot. In this case, the voltmeter readings should increase to 6 ... 6,5 V.

The design of a toothed disk designed for installation on a four-cylinder engine is shown in Fig. 4. The disc can be made from any low carbon mild steel. It is fixed with locking screws on the breaker cam.

Proximity interrupter of the electronic ignition system

Installing the coil in the breaker has features that depend on the type of ignition breaker-distributor. Below we consider the option of its installation in the R-118 breaker-distributor of the Moskvich-412 car. To do this, you need to sequentially remove the distributor, "slider" and the vacuum regulator. Then, unscrewing the screws securing the fixed plate to the bottom of the breaker, remove it, separate the movable and fixed plates. Remove the complete contacts from the movable plate and saw off the brass axle of the contact post flush with the plate. Drill out the aluminum rivet securing the cam lubrication filter post and remove the filter.

On the movable plate, drill two holes in accordance with Fig. 5 with a drill with a diameter of 2,1 mm and cut an M2,5 thread for mounting the sensor coil. Restore the connection of the plates and fix the flange with the sensor on the movable plate with two M2,5 screws. Put the plates in place, put the toothed disk on the cam, adjust the position of its tooth in the sensor groove so that the gaps at the top and bottom are the same and fix the disk with two locking screws M2.

After making all the electrical connections, turn on the ignition and, turning the crankshaft of the engine with the start handle, make sure that the contactless breaker is activated by igniting and turning off the LED. Then you can start setting the ignition timing. The procedure for this process is well described in the vehicle's instruction manual. The moment of ignition corresponds to the inclusion of the LED.

The driver board can be built into the housing of the electronic ignition system.

Literature

1. V. Stakhanov. Transistor ignition systems. - Radio, 1991. 1989, pp. 26-29.
2. A.Kh. Sinelnikov. Electronic devices for cars. - M.: Energoatomizdat, 1986.
3. V. Gorkin, A. Fedorov. Contactless ignition system. - Sat. "To help the radio amateur." issue 73. - M.: DOSAAF, 1981.
4. Yu. Sverchkov. Stabilized multi-spark ignition unit. - Radio, 1982, No. 5, pp. 27-30.
5. G. Karasev. Stabilized electronic ignition unit. - Radio, 1988, No. 9, p.17,18.

Author: A. Kolotov, Berdsk; Publication: N. Bolshakov, rf.atnn.ru

See other articles Section Automobile. Ignition.

Read and write useful comments on this article.

<< Back

Latest news of science and technology, new electronics:

Air trap for insects 01.05.2024

Agriculture is one of the key sectors of the economy, and pest control is an integral part of this process. A team of scientists from the Indian Council of Agricultural Research-Central Potato Research Institute (ICAR-CPRI), Shimla, has come up with an innovative solution to this problem - a wind-powered insect air trap. This device addresses the shortcomings of traditional pest control methods by providing real-time insect population data. The trap is powered entirely by wind energy, making it an environmentally friendly solution that requires no power. Its unique design allows monitoring of both harmful and beneficial insects, providing a complete overview of the population in any agricultural area. “By assessing target pests at the right time, we can take necessary measures to control both pests and diseases,” says Kapil ... >>

The threat of space debris to the Earth's magnetic field 01.05.2024

More and more often we hear about an increase in the amount of space debris surrounding our planet. However, it is not only active satellites and spacecraft that contribute to this problem, but also debris from old missions. The growing number of satellites launched by companies like SpaceX creates not only opportunities for the development of the Internet, but also serious threats to space security. Experts are now turning their attention to the potential implications for the Earth's magnetic field. Dr. Jonathan McDowell of the Harvard-Smithsonian Center for Astrophysics emphasizes that companies are rapidly deploying satellite constellations, and the number of satellites could grow to 100 in the next decade. The rapid development of these cosmic armadas of satellites can lead to contamination of the Earth's plasma environment with dangerous debris and a threat to the stability of the magnetosphere. Metal debris from used rockets can disrupt the ionosphere and magnetosphere. Both of these systems play a key role in protecting the atmosphere and maintaining ... >>

Solidification of bulk substances 30.04.2024

There are quite a few mysteries in the world of science, and one of them is the strange behavior of bulk materials. They may behave like a solid but suddenly turn into a flowing liquid. This phenomenon has attracted the attention of many researchers, and we may finally be getting closer to solving this mystery. Imagine sand in an hourglass. It usually flows freely, but in some cases its particles begin to get stuck, turning from a liquid to a solid. This transition has important implications for many areas, from drug production to construction. Researchers from the USA have attempted to describe this phenomenon and come closer to understanding it. In the study, the scientists conducted simulations in the laboratory using data from bags of polystyrene beads. They found that the vibrations within these sets had specific frequencies, meaning that only certain types of vibrations could travel through the material. Received ... >>

Random news from the Archive

Scientists brought together identically charged particles 21.02.2023

It is likely that the charged particles are reluctant to react with each other because they are repelled electrostatically. However, scientists have discovered how to bring them closer. The new method can speed up the reaction by up to 5 million times, according to the Institute of Physical Chemistry of the Polish Academy of Sciences.

Thanks to the research of an international group with the participation of Poles, the rate of chemical reactions in aqueous solutions can be controlled in a new way. It is enough to add particles of opposite charge to the solution, which will force the previously disgusting reagents to approach each other. The use of molecules with a high charge density can speed up the reaction up to 5 million times.

The synthesis of new compounds or the production of materials is extremely complex at the molecular level.

Two molecules with the same charge repel each other, so they rarely react with each other. This reaction may take days, weeks, or even longer. However, this time can be greatly reduced by using the right conditions or by adding different chemicals. Examples include natural catalysts such as enzymes or synthetic nanozymes that mimic natural or metal based catalysts commonly used in industry. Regardless of the type of catalyst, each of them accelerates only selected chemical reactions.

The study concerned the reaction between negatively charged molecules of coenzyme A in the aquatic environment. These particles repel each other.

Although coenzyme A molecules interact with each other, their interaction is much slower in water than in organic solvents. The scientists investigated the effect of adding compounds with opposite charges to speed up the reaction.

The influence of molecules of different sizes and charge values, such as ions, amphiphilic molecules, monomers, oligomers, polymers, and even micelles, was also tested.

When the corresponding positively charged micelles were introduced into the system, the reaction rate increased by a factor of 5 million. Monomers, oligomers and polymers speed up the reaction by 103-105 times, while ions or amphiphilic molecules "only" about a thousand times.

The action of coenzyme A (CoA) or methylmaleimide-substituted coenzyme A (CoA-M) on compounds with opposite charges disrupts the repulsion between negatively charged CoA and CoA-M molecules. Under certain conditions, the convergence of negatively charged particles of a certain concentration occurs. The added compound shields the repulsive forces of the molecules, making this process a special case of catalysis.

The scientists also tested this phenomenon with DNA hybridization, which is an ion-sensitive process. This process was chosen to determine if the proposed effect works for more complex reactions. It turned out that here, too, positively charged compounds significantly accelerate the rate of hybridization.