Scheme of electronic ignition on two transistors. Scheme of the electronic ignition unit. Output stage with controlled ignition transformer

A car is an incredibly complex system that includes many components and devices that constantly interact with each other. Without an ignition system, your car will not move. It is worth paying special attention to this aspect, and, in particular, to discuss issues related to electronic ignition.

What is electronic ignition?

An electronic ignition system is an ignition system that uses electronic devices to generate and transmit current. high voltage on the engine cylinders. Also, this system is sometimes called a microprocessor ignition system.

It should be mentioned that both non-contact and contact-transistor systems use electronic mechanisms in their design, but the names of these systems have long been established. Electronic ignition is devoid of any mechanical contacts, so we can say that electronic ignition is contactless. Modern car models are equipped with an electronic ignition system, which is a component of the engine management system. This system controls the combined injection and ignition system, and sometimes other systems (intake, exhaust, cooling).

All systems electronic ignition can be divided into two categories: direct ignition systems And with distributor. The electronic ignition distribution system during operation uses a distributor on the mechanics, which is responsible for transmitting a strong current to the candle. Direct ignition systems transfer current directly to the ignition coils.

The design of the electric ignition system is formed by fairly traditional components - a power source, an ignition coil, candles, a switch, high-voltage wires. The system also includes an igniter (executor device) and input sensors. These same sensors record the performance of the engine at the current moment and convert these indicators into electrical impulses. In its work, electronic ignition uses the readings of the sensors that are present in the engine management system. These devices include sensors:

- engine crankshaft speed;

mass air flow;

Camshaft positions;

detonation;

Coolant temperature, air;

Oxygen sensor and others.

With the help of the engine control unit, the signals of similar sensors are processed and the control action on the igniter is formed. The igniter itself is an electronic board that provides turning the ignition off and on. The igniter is based on a transistor. If the transistor is open, then the current goes to the primary winding of the ignition coil, and if it is closed, then the current goes to the secondary winding. The coil in the ignition system can be one common, individual or dual. When using individual ignition coils, there is no need to use high voltage wires, since such a coil will be attached directly to the candle. Ignition distribution systems use common ignition coils.

For direct ignition systems, the use of dual coils is typical. If the engine has 4 cylinders, then one of the coils falls on the first and fourth cylinders, and the other on the second and third. With the help of coils, a high voltage current is generated, and there are two outputs for the current, therefore the spark passes immediately into both cylinders. In one of them, the fuel-air mixture ignites, and in the other, the spark goes to waste.

The electronic ignition system works according to the following principle. Sensor signals are sent to the electronic control unit. Based on these readings, the most optimal parameters for the operation of the entire system are calculated. Further, the control impulse goes to the igniter, which is responsible for supplying voltage to the ignition coil. After that, the current begins to "run" through the primary winding of the coil.

When the voltage supply is interrupted, then a high voltage current flows through the secondary winding of the ignition coil. This very current is transmitted to the spark plug either directly from the coil, or through high-voltage wires. After the spark plug is energized, a spark is formed, due to which the fuel-air mixture detonates. When the rotation speed changes, then the speed sensor of its rotation, together with the camshaft position sensor, transmit a signal to the ECU, which produces a signal to change the ignition timing. When the engine is under increased load, the ignition timing is controlled by the mass air flow sensor. Other sensors provide additional information.

If you decide to replace the factory ignition with an electronic one, you will no longer experience most ignition problems, and you will also receive a number of advantages, for example, your car will increase dynamism, and it will be easier to start the engine in cold weather.

If you compare factory ignition with electronic, then the latter system uses an output transistor to close and open the circuit. Such a solution leads to the fact that the voltage on the candles of the car increases, and more energy is obtained from the spark. Also, such a design solution does not allow the voltage on the electrodes of the candles to fall even at low temperatures therefore the engine starts more easily even under unfavorable conditions. Although the coils of both factory and electronic ignition have the same set of wires, it is imperative to check whether they are connected correctly, since in the electric ignition system the coil can turn 180 degrees on the bracket.

Installation of electronic ignition

It makes sense to say a few words about what is included in the kit of elements of the electronic ignition system. The whole system is formed by the following 5 elements:

1) Contactless distributor. Acts as a distribution ignition sensor. On machines with different types engines will be installed different distributors.

2) Switch. The switch is responsible for interrupting the electrical current flowing through the ignition coil. This is a reaction to the signals that come from the distribution sensor. Each switch "can" turn off electricity even when the ignition is on or the engine is running.

3) Ignition coil. This element is necessary to convert low-voltage current to high-voltage. Such a procedure is extremely important because of the need to break through the air gap that forms between the contacts of the electrodes of the candles.

4) Set of wires

5) Candles to transfer the spark to the cylinders.

In order to install electronic ignition, you will need:

1) Set of wrenches;

2) Phillips screwdriver;

3) self-tapping screws;

4) Electronic drill and drill, the diameter of which is similar to a self-tapping screw.

You can start the installation of electric ignition only at the end of a full adjustment of the distributor.

The sequence of actions is as follows:

1) From the distributor, you need to remove the cover to which high-voltage electrical wires go;

3) In the starter system, short turns occur, due to which it is necessary to set the resistor line so that it forms a right angle with the engine. After setting the direction of the resistor, it is forbidden to crank the crankshaft until the end of work;

4) On the right side of the distributor housing there are 5 marks that are needed in order for the ignition adjustment to be done correctly. In order to correctly install the new distributor, it is necessary to mark on the motor the place that is located opposite the middle mark of the old distributor;

6) After dismantling the old distributor, it will be possible to install a new one. This is done by placing the part in the motor based on the label that was previously set;

7) After installing and adjusting the new distributor, it will need to be fixed with a nut;

8) After fixing the distributor, it will be possible to return the cover to its place, and after that you can connect the electrical wire to the cover.

9) After manipulating the distributor, it is necessary to replace the coil, since the contact and electronic ignition coils are different from each other;

10) After reinstalling the coil, you need to bring the wires to the ignition. It is important not to forget about the three-pin high-voltage wire connecting the coil to the distributor;

11) After finishing work with the coil, you can proceed to the installation of the switch. The simplest solution is to place the switch in the free area between the washer and the left headlight. In order to fix the element, it will be necessary to make holes according to the size of its “ears”, and the switch itself is fastened with self-tapping screws. After installation, you will need to “throw” the wire from the switch to the ignition system;

12) After completing all the work, you need to check the correct connection of the wires. The reference book for this will be the service book of your car, as well as a circuit that has electronic ignition elements in the kit.

Electronic ignition malfunctions

While using the car, any of its components can fail, including the ignition system. Defects that are typical for any ignition system were identified:

- exit from standing spark plugs of the ignition system;

Coil failure;

The problem with high-voltage and low-voltage wires (presence of a break, oxidized contacts, insufficiently tight connection, etc.).

In the electric ignition system, problems can also occur due to malfunctions of the computer and input sensors.

The ignition system breaks down for the following reasons:

1) The rules for operating the car were violated (low-quality gasoline was poured into the car, the car was not serviced on time, and if diagnostics were carried out, then it could be performed by an unskilled master);

2) Low-quality structural elements were installed in the car (coils, spark plugs, high voltage wires, etc.);

3) The breakdown occurred under the influence of a factor from the outside (atmospheric impact, mechanical damage).

The most common defect in the electronic ignition system is the failure of the candles. Fortunately, today all motorists can purchase these elements, therefore, the elimination of this breakdown will not take much time.

Even external diagnostics will help to indicate a malfunction of the electronic ignition system. The easiest way to notice how the ignition reacts to malfunctions that are in the fuel system and the fuel injection system. Therefore, it is necessary to diagnose the ignition system in conjunction with these systems.

External signs of ignition failure:

1) Increased fuel consumption;

2) Reduced engine power;

3) At idle, the engine is unstable;

4) Starting the engine became more difficult.

In case of electronic ignition system bad job engine, its difficult start is a signal that a breakdown or breakage of high voltage wires has occurred, candles have failed, the computer, the crankshaft speed sensor or the hall sensor are broken. If your car began to “eat up” more fuel, and the engine began to produce less power, then this may indicate that the candle towers, input sensors or ECU are out of order.

Before you go to a specialist, try to independently diagnose the ignition system, as there is a high probability of self-detection of a defect. In this case, you simply replace the candles or the coil, and you will be "on horseback" again. Good luck.

A. SINELNIKOV

At present, thyristor blocks of electronic ignition with a stabilized secondary voltage are widely used. Such blocks are produced by industry and sold in car dealerships (Iskra-1, Iskra-2, Iskra-3, PAZ-2, PAZ-3, etc.). The schemes of these blocks are basically identical, the difference lies only in the design and types of elements used.

Operating experience a large number such blocks showed that in a number of cases, on some vehicles, the necessary stability of operation was not provided, sometimes without any visible reasons misfiring (failures) were observed, causing a characteristic "jerking" of the car while driving. Sometimes there were misfires during the start of the engine by the starter, at the same time, the engine was started from the handle, as they say, with a half turn.

Strictly speaking, the voltage in the car's on-board electrical network cannot be considered a DC voltage, since in reality there are always impulse noise, and their amplitude is not the same for different cars and ranges from 5 to 50 V! These interferences are created as a result of the operation of the generator, starter, voltage regulator, sound signals, turn signal breaker, wiper motor, switching on and off various consumers (especially when switching off electromagnetic relays), etc.

The author took voltage oscillograms in the on-board electrical network of several Zaporozhets cars during starter operation. For most of the vehicles under study, the interference amplitude did not exceed 3-5 V, and the Iskra blocks worked normally.

However, in two cars, the interference amplitude was 18-25 V, and the engine could not be started at all by the starter. During starter operation, chaotic sparking was observed, even with the breaker turned off.

The analysis showed that the reason for the failure of the blocks is the presence of a transistor trigger in them, which switches under the influence of impulse noise and reduces the noise immunity of the device. In addition, the emitters of the trigger transistors are not connected to ground and are “suspended” to the positive power bus, as a result of which it is difficult to introduce any effective low-pass filter into the circuit.

The described electronic ignition unit is free from these disadvantages. Instead of a transistor trigger, a thyristor is used, which works stably under the influence of impulse noise with an amplitude of up to 50 V.

In addition, when developing the block diagram, characteristic failures of the elements that occurred in the Iskra-1 and Iskra-2 blocks during their long-term operation were taken into account, in connection with which a number of elements were replaced with more reliable ones.

The unit is designed to work with four-cylinder four-stroke engines and has the following specifications:

Supply voltage, V ......... from 6.5 to 15
The strength of the consumed current, A....... no more than 2.0
Frequency of rotation of a cranked shaft, rpm:
at a supply voltage of 6.5 V .... no more than 600
at a supply voltage of 15 V .... no more than 6000
The duration of the spark discharge in the candle, ms .... 0.4-0.6
Ambient temperature, °С.... from -40 to +65

Schematic diagram of the block with connection circuits on the car is shown in fig. 1 and contains the following functional units: a voltage converter consisting of a power transistor switch on transistors T4, T5, T6, a transformer Tp1, a rectifier diode D9, a storage capacitor C3, a stabilization circuit on a transistor T3 and a thyristor D5; anti-bounce cascade on transistors T1, T2, switching thyristor D10; discharge diodes D12, D13.

Fig 1. Schematic diagram of the block

The device works as follows. Assume that the contacts of the breaker B1 are open. Then, after turning on the power (t1 in Fig. 2), the ignition switch B2 opens transistor T1, its base current flows through resistors R4, R5, diodes D3, D2, D1 and resistor R2.

Rice. Fig. 2. Timing diagrams of the operation of the ignition system at a supply voltage of 15 V and a sparking frequency of 100 Hz

At the same time, the capacitor C1 begins to charge through the resistor R1. The collector-emitter junction of the open transistor T1 shunts the base of the transistor T2, as a result of which the latter closes. Thyristor D5 is also closed (off) at this time, since its switching voltage is obviously higher than the supply voltage. The transistor T3 of the stabilization device is closed, and there is no positive voltage on the control electrode of the thyristor D5.

The power transistor key is opened by the base current of the transistor T4, flowing through resistors R8, R9, R10, R14 and diodes D6, D7. The collector current of this transistor, flowing through the base-emitter junction of transistor T5, opens it, and then opens transistor T6. Through the winding of the transformer Tp1 and the resistor R22, a linearly increasing current begins to flow. The voltage drop across the resistor R22 increases, and when it reaches a certain value, depending on the ratio of the resistances of the resistors R15, R16, R20, thermistors R17, R18 and the trigger voltage of the transistor T3, the latter opens and connects the control electrode of the thyristor D5 through the resistor R12 to the positive power bus . Thyristor D5 switches (t2 in Fig. 2) and shunts the base current of transistor T4. The power transistor switch opens, transistors T4, T5, T6 close, and the current in the primary winding I of the transformer Tp1 stops.

The energy accumulated in the magnetic field of the transformer creates voltage pulses in its windings. A positive pulse from the end of winding II (the beginnings of the windings in the diagram in Fig. 1 are indicated by dots) passes through diode D9 and charges the storage capacitor C3 to a voltage of approximately 350 V (t3 in Fig. 2).

After the breaker contacts are closed (t4 in Fig. 2), transistors T1 and T2 remain open until the capacitor C1 is discharged. The discharge current of the capacitor C1 flows through the diode D4, resistors R3, R2 and the base-emitter junction of the transistor T1. At time t5, transistor T1 closes and transistor T2 opens. The collector-emitter junction of the open transistor T2 shunts the thyristor D5 and the latter turns off (t5 in Fig. 2).

However, if there were no anti-bounce cascade and the breaker contacts were connected directly to the anode of the D5 thyristor, the latter would turn off at the moment the contacts were closed, and the first bounce pulse would open the power transistor switch. The spark in the candle would not appear at the moment t6, as it should, but at the moment t4, and the normal operation of the system would be disrupted.

At the moment the breaker contacts open (t6 in Fig. 2), transistor T1 opens, and transistor T2 closes. The power transistor switch opens and winding I of the transformer Tp1 is connected to the power supply. Voltage pulses occur in the secondary winding II. A positive pulse from the beginning of winding II through capacitor C4 and diode D11 enters the control electrode of the switching thyristor D10, as a result of which the latter switches and connects the primary winding I of the ignition coil K3 to the storage capacitor C3 charged to a voltage of 350 V. The voltage on the secondary winding II of the ignition coil within a few microseconds reaches the breakdown voltage of the spark gap of the spark plug (8-10 kV), and a spark discharge is ignited between the electrodes of the spark plug (t1 in Fig. 3).

Fig. 3. Timing diagrams of the operation of the ignition system during sparking, at a supply voltage of E \u003d 12 V

The inductance of the primary winding of the ignition coil and the storage capacitor C3, interconnected through a switched thyristor, form an oscillatory circuit in which damped electrical oscillations occur.

As can be seen from fig. 3, the current in the circuit lags the voltage on the primary winding of the ignition coil by 90°. After a quarter of the period (after about 60 μs), the voltage on the primary winding of the ignition coil becomes zero (t2 in Fig. 3) and then changes its sign, the thyristor turns off and the oscillatory circuit "destroys". However, due to the presence of diodes D12, D13, the current in the primary winding of the ignition coil continues to flow in the original direction, and the discharge in the secondary circuit continues until almost all the energy stored in the magnetic field of the ignition coil is used up (t3 in Fig. 3 ).

As a result, a discharge of higher energy and temperature occurs than in conventional capacitor ignition systems, the duration of the discharge increases by almost 3 times. This circumstance has a positive effect on the operation of the engine, reducing the toxicity of exhaust gases and facilitating the start of a hot engine.

Simultaneously with the appearance of a spark in the spark plug at the moment the breaker contacts open (t6 in Fig. 2), a linearly increasing current begins to flow again through the winding of the transformer Tp1, and when it reaches the set value (t7 in Fig. 2), the power transistor switch opens, and the storage capacitor C3 is charged again to a voltage of 350 V, i.e., the processes that took place at the initial moment after the power was turned on are repeated. If we neglect losses and assume that all energy

Stored in the magnetic field of the transformer Tp1, at the moment of opening the contacts of the breaker, it is converted into the energy of the electric field of the storage capacitor

That value of the charge voltage of the storage capacitor Uc can be determined by the formula:

As can be seen from this formula, the charge voltage of the storage capacitor does not depend on the supply voltage and, at constant values ​​of L and C, is determined only by the current strength ip.

The stabilization device used in the block on the transistor T3, resistors R15, R16, R18 and thermistors R17, R18 provides a high constancy of current ip with changes in supply voltage and temperature.

With an increase (decrease) in temperature, the trigger voltage of the transistor T3 decreases (increases), which is compensated by a decrease (increase) in the resistances of thermistors R17, R18. As a result, the current strength ip remains almost constant. With changes in the supply voltage, the trigger voltage of transistor T3 does not change at all.

Resistor R3 limits the current pulse through the diodes D1, D2, D3, D4 at the moment the breaker contacts close. Before the contacts close, the diodes D1, D2, D3 are open and direct current flows through them. They cannot close instantly and at the first moment after the closure they are a conductor. Therefore, a current will flow through the S1D4R3D1D2D3 circuit at the moment of closing the contacts, the strength of which is limited only by the resistance of the resistor R3 (direct for diode D4 and reverse for diodes D1, D2, D3).

Diodes D6, D7 create a clear current switching between the power transistor switch and thyristor D5: the voltage drop in the switched thyristor can be 2 V, therefore, without diodes D6, D7, transistor T4 would remain open, despite the switching of the thyristor.

Resistor R14 limits the base current of transistor T4.

Diode D8 provides active locking of the transistor T6.

As can be seen from the diagram, in the described block, as well as in the Iskra-3 block, series-connected discharge diodes D12, D13 are used. In the Iskra-1 and PAZ blocks, where there was only one diode, the most frequent failures occurred precisely because of the breakdown of this diode. The analysis showed that at high engine crankshaft speeds (at high sparking frequencies), each new sparking cycle begins before the current stops through the discharge diode, which also flows after the end of sparking (see Fig. 3). It is due to the energy of the ignition coil remaining unused during sparking.

Therefore, to an open diode, the internal resistance of which is low at this time, a reverse voltage of 350 V is applied at the moment of switching the thyristor. The diode cannot close instantly, and for several microseconds a current flows through it, the strength of which is limited only by the resistance of the resistor R23 (2 Ohm ) and internal resistances of an open diode and a switched thyristor. The measurements showed that the amplitude of the current pulse in this case can reach 80 A! Its value depends on the individual properties of the discharge diode, and primarily on its speed, or on the time it takes for the reverse resistance to be established.

The series connection of two diodes accelerates the process of current decay in the circuit formed by the primary winding of the ignition coil and discharge diodes, and the above phenomenon does not occur even at the maximum sparking frequency.

Resistors R27, R28 equalize the reverse voltages on the diodes D12, D13.

Resistor R23 eliminates the surge voltage at the time of turning off the thyristor D10.

Capacitors C5, C6 reduce the amplitude of impulse noise coming through the power circuit.

Construction and details. The design of the electronic ignition unit can be very diverse, but it must provide good splash protection of the product. Power transistors T5, T6 and thyristor D10 are installed directly on the block body, which serves as a cooling radiator for them. In this regard, the body must be made of aluminum alloy. Diodes D8, D12 and D13 must also be placed on the body of the block, electrically insulating them from the body with thin lavsan, fluoroplastic or mica gaskets. The rest of the elements are placed on printed circuit board or a board made of textolite (getinaks) with contact petals. When placing parts, it should be borne in mind that resistors R4, R5, R8, R9, R10, R22, R26 and transformer Tp1 heat up during operation of the unit and should not be placed near transistors and thermistors R17, R18. In addition, it is necessary that the emitter of the transistor T3 and the resistors R17, R18, R20 are connected by one individual wire, and it, in turn, must be connected directly to the resistor R22. The same applies to the resistor R16 and capacitors C5, C6. The first must be connected to the resistor R22, and the capacitors to the "+" terminal and ground, as shown in the circuit diagram of fig. 1.

All resistors, except for R22 and R23, are MLT. Resistor R22 is made in the form of a spiral of manganin wire with a diameter of 1.0 mm. Resistor R23 is wound on the body of the MLT - 0.5 resistor with a resistance of at least 20 ohms with a manganin wire of the PESHOM brand with a diameter of 0.25 mm.

The Tp1 transformer has a Ш16x24 core made of E330 or E44 steel with a non-magnetic gap of 0.25 mm.

Winding data are given in table. 1.

The transformer must be well tightened. The non-magnetic gap is set using pressboard or paper of appropriate thickness.

Capacitors C1, C2, C4, C6 - MBM, operating voltage 160 V. Storage capacitor C3 - MBGCH for a voltage of 500 V. Capacitor C5 - electrolytic K50-3, 50 V.

The switching thyristor D10 (KU202N) must be checked for leakage current before installation in the unit. Only those specimens are suitable for which the leakage current at a voltage of 400 V does not exceed 150 μA.

In table. 2 shows a possible replacement of transistors, thyristors and diodes.

In the case of replacing the thyristor D5 with KU101G, the resistor R14 is excluded from the circuit (closed), instead of the resistors R8, R9, R10, one resistor MLT-2 - 200 Ohm is placed, and the value of the resistor R7 is MLT-0.125-2.7 kOhm.

Adjustment and installation on the car. If the unit is assembled correctly from known good parts, then its adjustment consists only in adjusting the voltage on the storage capacitor, which should be in the range of 350-360 V. The adjustment is carried out by selecting the resistor R22: a decrease in its resistance causes an increase in the voltage across the capacitor.

Checking and adjusting the unit is carried out with the ignition coil connected. Instead of interrupter contacts, you can use the contacts of some polarized relay, for example RP4, the winding of which is connected to a sound generator or to an alternating current network of 127 or 220 V, 50 Hz. In the latter case, through a step-down transformer or a quenching resistor. The voltage on the storage capacitor cannot be measured with a conventional voltmeter - you must use a measuring oscilloscope (C1-19, C1-49, etc.) or a special pulse voltmeter. You can read more about this in.

On the car, the unit is installed in the engine compartment and connected according to the diagram in Fig. 1. At the same time, capacitor C may remain at the breaker terminal, since it does not affect the operation of the unit. The block body must be connected with a separate wire with a cross section of at least 0.75 mm2 to the distributor body. The cross section of the wire from the “+” terminal must also be at least 0.75 mm2.

LITERATURE
1. Sinelnikov A. X. Electronics in the car. Moscow: Energy, 1976, p. 127.
2. Sinelnikov A. Kh. What is the difference between the blocks. Behind the wheel, 1977, No. 10, p. 17.
3. Sinelnikov A. Kh., Nemtsev V. F. Electronic ignition.-Behind the wheel, 1973, No. 1, p. 14-18.
4. Sinelnikov A. Kh., Nemtsev V. F. Once again about electronic ignition. - Behind the wheel, 1974, No. 4, p. 10-12.
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Greetings dear fellow radio amateurs. Many have dealt with very simple and therefore very unreliable ignition systems in motorcycles, mopeds, outboard motors and similar products of the last century. I also had a moped. His spark disappeared so often and for so many different reasons that is very annoying. You probably yourself have seen motorists without a spark constantly meeting on the roads, who are trying to start from a running start, from a hill, from a pusher ... In general, I had to come up with my own ignition system. The requirements were:

• should be as simple as possible, but not at the expense of functionality;
• minimum alterations at the installation site;
• battery-free power supply;
• improved reliability and spark power.

All of this, or almost all of it, has been implemented and passed many years of testing. I was satisfied and I want to offer you to assemble such a scheme to you who still have engines from the last century. But modern engines can also be equipped with this system if your own has become unusable, and buying a new one is expensive. Will not let you down!

WITH new system electronic ignition, the spark increased by an order of magnitude, earlier on a sunny day you would not see it, after the gap of the candle was increased from 0.5 to ~ 1 mm and the spark was white-blue (on the test bench under laboratory conditions, even thin Kipov paper was ignited with a spark). Any small pollution of the candle became insignificant, since the system is thyristor. The moped began to start, not like the floor - a quarter of a turn. Many old candles could again be pulled out of the "garbage bin" and put into work.

The decompressor, which was always “spitting” and polluting the radiator, was removed, because now you can turn off the engine with a simple switch or button. The interrupter, which always requires maintenance, was turned off - once set, it does not require any maintenance.

Scheme of the ignition module

Module wiring diagram

PCBs for assembly

For low current consumption, a CMOS chip KR561LE5 and a LED stabilizer were chosen. KR561LE5 works starting from 3 V and with a very small (15 uA) current, which is important for this circuit.

The comparator on the elements: DD1.1, DD1.2, R1, R2 serves to more clearly respond to the level of increasing voltage after the inductive sensor and to eliminate the response to interference. The trigger pulse shaper on the elements: DD1.3, DD1.4, R3, C1 is needed to generate the desired pulse duration, for good operation of the pulse transformer, for clear triggering of the thyristor and for all the same saving of the circuit supply current.

The pulse transformer T1 also serves to isolate from the high-voltage part of the circuit. The key is made on the K1014KT1A transistor assembly - it forms a good pulse, with steep fronts and sufficient current in the primary winding of the pulse transformer, which, in turn, ensures reliable unlocking of the thyristor. The pulse transformer is made on a ferrite ring 2000NM / K 10 * 6 * 5 with windings of 60-80 turns of wire PEV or PEL 0.1 - 0.12 mm.

The voltage regulator on the LEDs was chosen because of the very low initial stabilization current, which still contributes to saving the current consumption of the circuit, but at the same time, it clearly stabilizes the voltage on the microcircuit at 9 V (1.5 V one LED) and also serves as an additional light an indicator of the presence of voltage from the magnets, in the circuit.

The zener diodes VD13, VD14 serve to limit the voltage and are switched on only at very high engine speeds, when power savings are not very important. It is advisable to wind such coils in a magnet so that these zener diodes turn on only at the very top, only at the highest possible voltage (in the latest modification, zener diodes were not installed, because the voltage never exceeded 200 V). Two tanks: C4 and C5 to increase the power of the spark, in principle, the circuit can work on one.

Important! Diode VD10 (KD411AM) was selected according to impulse responses, others got very hot, did not fully fulfill their function of protection against reverse surge. In addition, a reverse half-wave of oscillation in the ignition coil goes through it, which almost doubles the duration of the spark.

This scheme also showed undemanding to ignition coils - any that were at hand were installed and everything worked flawlessly (on different voltages, under different systems ignition - interrupted, on a transistor key).

Resistor R6 is designed to limit the current of the thyristor and to clearly lock it. It is selected depending on the thyristor used so that the current through it cannot exceed the maximum for the thyristor and, most importantly, that the thyristor has time to lock up after the discharge of capacitors C4, C5.

Bridges VD11, VD12 are selected according to the maximum voltage from the magnet coils.

There are two coils charging capacitors for high-voltage discharge (this solution is also much more economical and efficient than a voltage converter). This decision came because the coils have different inductive reactance and their inductive reactances depend on the frequency of rotation of the magnets, i.e. and the speed of the shaft. These coils must contain different amount turns, then at low speeds the coil with a large number of turns will work, and at high speeds with a small one, since the increase in the induced voltage with increasing speed will fall on the increasing inductive resistance of the coil with a large number of turns, and on the coil with a small number of turns, the voltage grows faster than its inductive reactance. Thus, everything compensates for each other and the charge voltage of the capacitors is stabilized to a certain extent.

The ignition winding in the Verkhovyna-6 moped is rewound as follows:

1. first, the voltage on the oscilloscope screen from this winding is measured. An oscilloscope is needed for more exact definition the maximum amplitude voltage on the winding, since the winding close to the maximum voltage is short-circuited by the breaker and the tester will show a certain underestimated voltage value. But the containers will be charged to the maximum amplitude value of the voltage, and even with a full (without interrupter) period.
2. after winding the winding, it is necessary to count the number of its turns.
3. dividing the maximum amplitude voltage of the winding by the number of its turns, we get how many volts one turn gives (volt / turn).
4. dividing the voltages necessary for our circuit by the received (volt / turn) we get the number of turns that will need to be wound for each of the required voltages.
5. we wind and bring to the terminal block. Lighting winding remains the same.

Parts used in the scheme

Chip KR561LE5 (elements 2 OR NOT); integral key on the MOSFET K1014KT1A; thyristor TS112-10-4; rectifier bridges KTs405 (A, B, C, G), KTs407A; pulse diodes KD 522, KD411AM (a very good diode, others heat up or work much worse); LEDs AL307 or others; capacitors C4, C5 - K73-17 / 250-400V, the rest of any type; MLT resistors. The project files are located here. Scheme and description - PNP.

Discuss the article SCHEME OF THE ELECTRONIC IGNITION UNIT

The benefits of electronic ignition in internal combustion engines are well known. At the same time, the electronic ignition systems that are currently widespread do not yet fully meet the set of design and operational requirements. Systems with pulsed energy storage are complex, not always reliable and practically inaccessible to most motorists. Simple systems with continuous energy storage do not provide stabilization of the stored energy [3], and when stabilization is achieved, they are almost as complex as impulse systems.

It is not surprising, therefore, that the article by Y. Sverchkov, published in the Radio magazine, aroused great interest among readers. A well-thought-out, extremely simple stabilized ignition unit can, without any exaggeration, serve as a good example of an optimal solution in the design of such devices.

The results of the operation of the unit according to the scheme of Yu. Sverchkov showed that, with a generally sufficiently high quality of its operation and high reliability, it also has significant shortcomings. The main one is the short duration of the spark (no more than 280 μs) and, accordingly, its low energy (no more than 5 mJ).

This disadvantage, inherent in all capacitor ignition systems with one period of oscillation in the coil, leads to unstable operation of a cold engine, incomplete combustion of an enriched mixture during warm-up, and difficult starting of a hot engine. In addition, the voltage stability on the primary winding of the ignition coil in the Yu. Sverchkov unit is somewhat lower than in the best pulse systems. When the supply voltage changes from 6 to 15 V, the primary voltage changes from 330 to 390 V (±8%), while in complex pulse systems this change does not exceed ±2%.

With an increase in the frequency of sparking, the voltage on the primary winding of the ignition coil decreases. So, when the frequency changes from 20 to 200 Hz (the crankshaft speed is 600 and 6000 min -1, respectively), the voltage changes from 390 to 325 V, which is also somewhat worse than in impulse blocks. However, this shortcoming can

practically ignored, since at a frequency of 200 Hz the breakdown voltage of the spark gap of the candles (due to residual ionization and other factors) is almost halved.

The author of these lines, who has been experimenting with various electronic ignition systems for more than 10 years, set the task of improving the energy characteristics of the Yu. Sverchkov block, while maintaining the simplicity of the design. It turned out to be possible to solve it thanks to the internal reserves of the block, since the energy of the storage device was used in it only by half.

This goal was achieved by introducing a mode of multi-period oscillatory discharge of the storage capacitor to the ignition coil, which leads to its almost complete discharge. The very idea of ​​such a solution is not new, but rarely used. As a result, an improved electronic ignition unit has been developed with characteristics that not all impulse designs have.

At a sparking frequency of 20...200 Hz, the unit provides a spark duration of at least 900 µs. The spark energy released in the spark plug with a gap of 0.9 ... 1 mm is not less than 12 mJ. The accuracy of maintaining energy in the storage capacitor when the supply voltage changes from 5.5 to 15 V and the sparking frequency is 20 Hz is no worse than ± 5%. Other characteristics of the block have not changed.

It is significant that the increase in the duration of the spark discharge was achieved precisely by a long oscillatory process of discharging the storage capacitor. The spark in this case is a series of 7-9 independent discharges. Such an alternating spark discharge (frequency about 3.5 kHz) contributes to the efficient combustion of the working mixture with minimal spark plug erosion, which distinguishes it favorably from a simple lengthening of the aperiodic discharge of the drive.

The block converter circuit (Fig. 1) has not changed much. Only the transistor has been replaced to slightly increase the power of the converter and facilitate the thermal regime. Elements that ensured an uncontrolled multi-spark operation were excluded. The energy switching circuits and the control circuits for the discharge of the storage capacitor SZ have been significantly changed. It is now discharged for three (and at a frequency below 20 Hz - or more) periods of natural oscillations of the circuit, consisting of the primary winding of the ignition coil and capacitor C3. Elements C2, R3, R4, VD6 provide this mode.

Considering that the operation of the converter is described in detail in, we will consider only the process of oscillatory discharge of the capacitor C3. When the breaker contacts open, capacitor C4, discharging through the control transition of the trinistor VS1, diode VD8 and resistors R7, R8, opens the trinistor, which connects the charged capacitor C3 to the primary winding of the ignition coil. The gradually increasing current through the winding at the end of the first quarter of the period has a maximum value, and the voltage on the capacitor C3 at this moment becomes equal to zero (Fig. 2).

All the energy of the capacitor (minus heat losses) is converted into the magnetic field of the ignition coil, which, trying to maintain the value and direction of the current, begins to recharge the C3 capacitor through an open trinistor. As a result, at the end of the second quarter of the period, the current and the magnetic field of the ignition coil are equal to zero, the capacitor C3 is charged to 0.85 of the initial (in voltage) level in the opposite polarity. With the termination of the current and the change of polarity on the capacitor C3, the trinistor VS1 closes, but the diode VDS opens. The next process of discharging the capacitor C3 begins through the primary winding of the ignition coil, the direction of the current through which changes to the opposite. At the end of the oscillation period (i.e., after approximately 280 μs), the capacitor C3 is charged in the original polarity to a voltage equal to 0.7 of the initial one. This voltage closes the VDS diode, breaking the discharge circuit.

In the considered time interval, the low resistance of the alternately opening elements VD5 and VS1 shunts the R3R4C2 circuit connected in parallel to them, as a result of which the voltage at its ends is close to zero. At the end of the period, when the trinistor and the diode are closed, the voltage of the capacitor C3 (about 250 V) is applied to this circuit through the ignition coil. The voltage pulse taken from the resistor R3, passing through the diode VD6, reopens the trinistor VS1, and all the processes described above are repeated.

This is followed by the third, and sometimes (at start-up) and the fourth discharge cycle. The process continues until the capacitor C3, which loses about 50% of energy with each cycle, is almost completely discharged. As a result, the duration of the spark increases to 900...1200 µs, and its energy - up to 12...16 mJ,

On fig. 2 shows an approximate view of the voltage waveform on the primary winding of the ignition coil. For comparison, the dashed line shows the same oscillogram of Yu. Sverchkov's block (the first periods of oscillations on both oscillograms coincide),

To increase the protection against bounce of the contacts of the breaker, the starting node had to be somewhat changed. The time constant of the charging circuit of the capacitor C4 by selecting the appropriate resistor R6 is increased to 4 ms; the discharge current of the capacitor (i.e., the start-up current of the trinistor), determined by the resistance of the circuit of resistors R7, R8, is also increased.

The electronic ignition unit has been tested for three years on a Zhiguli car and has proven itself very well. The stability of the engine after start-up has sharply increased. Even in winter at a temperature of about -30 ° C, starting the engine was easy, it was possible to start moving after warming up for 5 minutes. Interruptions in engine operation during the first minutes of movement, observed when using the Yu. Sverchkov block, stopped, acceleration dynamics improved.

In the transformer T1, the magnetic circuit SHL16X8 is used. A gap of 0.25 mm is provided by three press-span gaskets. Winding I contains 50 turns of wire PEV-2 0.55; II - 70 turns of PEV-2 0.25; III - 450 turns of PEV-2 0.14. In the last winding, one gasket of capacitor paper should be laid between all layers, and the entire winding should be separated from the rest by one or two layers of cable paper,

The finished transformer is coated 2-3 times with epoxy resin or filled with resin completely in a plastic or metal box. An E-shaped magnetic circuit should not be used, since, as experience shows, it is difficult to maintain a given gap over the entire thickness of the set, and also to avoid shorting the outer plates. Both of these factors, especially the second one, sharply reduce the power of the charging pulse generator.

When establishing the generator part of the block, you can use the recommendations of Yu. Sverchkov in.

Due to the high reliability, the unit can be connected without the X1 connector (disconnection of the capacitor Csp of the interrupter is mandatory), which is intended for a possible emergency transition to battery ignition, but the initial setting of the ignition moment will be much more difficult. While maintaining the X1 connector, the transition to battery ignition is very simple - instead of the block block, a contact block is inserted into the female part of the X1 connector, in which contacts 2, 3 and 4 are connected.

G.KARASEV, Leningrad

LITERATURE:
1. A. Sinelnikov. How do the blocks differ - Behind the wheel. 1977, No. 10. p. 17,
2. A. Sinelnikov. High reliability electronic ignition unit. Sat. “To help the radio amateur”, vol. 73.-- M.: DOSAAF USSR, p. 38.
3. A. Sinelnikov. Electronics in the car. - M.: Energy, 1976.
4. A. Sinelnikov. Electronics and car. - M .: Radio and communication, 1985.
5. Yu. Sverchkov. Stabilized multi-spark ignition unit. - Radio, 1982, No. 5. p. 27.
6. E. Litke. Capacitor ignition system. Sat. “To help the radio amateur”, issue, 78.- M .: DOSAAF USSR, p. 35.

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