The operation of any gasoline internal combustion engine would be impossible without a special ignition system. It is she who is responsible for igniting the mixture in the cylinders at a strictly defined moment. There are several possible options:
- contact;
- contactless;
- electronic.
The elements of different car ignition systems are the same
An irreplaceable and most in demand is the presence of a rechargeable battery. Even in the absence or failure of the generator, you can use it to continue driving for some time. The generator is also an integral part, without which the normal functioning of any of the systems is impossible. Spark plugs, armored wires, high-voltage and control elements complement any of the systems mentioned. The main difference between them is the type that controls the ignition timing and is responsible for sparking the device.
Contact breaker-ignition distributor
This device initiates the occurrence of a high voltage spark, up to 30,000 V, at the contacts of the spark plugs. To do this, it is connected to a high-voltage coil, due to which high voltage is generated. The signal to the coil is transmitted using wires from a special contact group. When it is opened by the cam mechanism, a spark is formed. The moment of its occurrence must strictly correspond to the required position of the pistons in the cylinders. This is achieved thanks to a clearly calculated mechanism that transmits rotational motion to the breaker-distributor. One of the disadvantages of the device is the influence of mechanical wear on the time of spark occurrence and on its quality. This affects the quality of engine operation, which means it may require frequent interventions in adjusting its operation.
Contactless ignition
This type of device does not directly depend on the opening of contacts. The main role in the moment of spark formation here is played by a transistor switch and a special sensor. The absence of dependence on the cleanliness and quality of the surface of the contact group can guarantee better sparking. However, this type of ignition also uses a distributor interrupter, which is responsible for transmitting current to the right spark plug at the right moment.
Electronic ignition
There are no mechanical moving parts in this mixture ignition system. Thanks to the presence of special sensors and a special control unit, the formation of a spark and the moment of its distribution to the cylinders are carried out much more accurately and reliably than with the above-mentioned systems. This makes it possible to improve engine performance, increase its power and reduce fuel consumption. In addition, the high reliability of devices of this type is also pleasing.
The main stages of the ignition system operation
There are several main stages in the operation of any ignition system:
- accumulation of the necessary charge;
- high voltage conversion;
- distribution;
- sparking on spark plugs;
- combustion of the mixture.
Video about the principle of operation of the ignition system:
All car enthusiasts know that to ignite fuel, a spark is used on the spark plug, which ignites the fuel in the cylinder, and the voltage on the spark plug reaches a level of 20 kV. Old cars use classic ignition systems, which have serious drawbacks. It is about the modernization and refinement of these schemes that we will talk.
The capacitance in this design is charged from the reverse surge of the blocking generator, which is stable in amplitude. The amplitude of this emission is almost independent of the battery voltage and the crankshaft speed, and therefore the spark energy is always sufficient to ignite the fuel.
The ignition circuit produces a potential on the storage capacitor in the range of 270 - 330 Volts when the battery voltage drops to 7 volts. The maximum operating frequency is about 300 pulses per second. Current consumption is about two amperes.
The ignition circuit consists of a standby blocking oscillator on a bipolar transistor, a transformer, a pulse-forming circuit C3R5, a storage capacitor C1, a pulse generator on a thyristor.
At the initial moment of time, when contact S1 is closed, the transistor is locked, and capacitance C3 is discharged. When the contact opens, the capacitor will be charged along the circuit R5, R3.
The charge current pulse starts the blocking generator. The leading edge of the pulse from the secondary winding of the transformer triggers the KU202 thyristor, but since capacitance C1 was not previously charged, there is no spark at the output of the device. Over time, under the influence of the collector current of the transistor, the transformer core is saturated and therefore the blocking generator will again be in standby mode.
In this case, a voltage surge is formed at the collector junction, which is transformed into the third winding and charges capacitance C1 through the diode.
When the breaker is opened again, the same algorithm occurs in the device, with the only difference being that the thyristor, opened by the leading edge of the pulse, will connect the already charged capacitance to the primary winding of the coil. The discharge current of capacitor C1 induces a high-voltage pulse in the secondary winding.
Diode V5 protects the base junction of the transistor. The zener diode protects V6 from breakdown if the unit is turned on without a bobbin or without a spark plug. The design is insensitive to the rattling of the contact plates of breaker S1.
The transformer is made by hand using a magnetic circuit ШЛ16Х25. The primary winding contains 60 turns of PEV-2 1.2 wire, the secondary winding contains 60 turns of PEV-2 0.31, the third winding contains 360 turns of PEV-2 0.31.
The spark power in this design depends on the temperature of the bipolar transistor VT2, which decreases on a hot engine, and vice versa on a cold engine, thereby significantly facilitating starting. At the moment the breaker contacts open and close, the pulse follows through capacitor C1, briefly unlocking both transistors. When VT2 is locked, a spark appears.
Capacitance C2 smoothes out the pulse peak. Resistances R6 and R5 limit the maximum voltage at the collector junction VT2. When the contacts are open, both transistors are closed; when the contacts are closed for a long time, the current flowing through capacitor C1 gradually decreases. The transistors close smoothly, protecting the ignition coil from overheating. The value of resistor R6 is selected for a specific coil (in the diagram it is shown for coil B115), for B116 R6 = 11 kOhm.
As you can see in the picture above, the printed circuit board is installed on top of the radiator. Bipolar transistor VT2 is installed on the radiator through thermal paste and a dielectric gasket.
Contact transistor ignition circuit |
This design allows the formation of a spark with a long duration, so the process of fuel combustion in the car becomes optimal.
The ignition circuit consists of a Schmitt trigger on transistors V1 and V2, decoupling amplifiers V3, V4 and an electronic transistor switch V5, which switches the current in the primary winding of the ignition coil.
The Schmitt trigger generates switching pulses with a steep rise and fall when the breaker contacts are closed or opened. Therefore, in the primary winding of the ignition coil, the current interruption speed increases and the amplitude of the high-voltage voltage at the output of the secondary winding increases.
As a result, the conditions for spark formation in the spark plug are improved, which contributes to the process of improving the starting of a car engine and more complete combustion of the combustible mixture.
Transistors VI, V2, V3 - KT312V, V4 - KT608, V5 - KT809A. Capacity C2 - with an operating voltage of at least 400 V. Coil type B 115, used in passenger cars.
I made the printed circuit board in accordance with the drawing according to.
In this system, the energy spent on sparking is accumulated in the magnetic field of the ignition coil. The system can be mounted on any carburetor engine with a +12 V vehicle on-board power supply. The device consists of a transistor switch built on a powerful germanium transistor, a zener diode, resistors R1 and R2, separate additional resistances R3 and R4, a two-winding ignition coil and breaker contacts.
The powerful germanium transistor T1 operates in switching mode with a load in the collector circuit, which is the primary winding of the ignition coil. When the ignition switch is on and the breaker contacts are open, the transistor is locked, since the current in the base circuit tends to zero.
When the breaker contacts are closed, a current of 0.5-0.7 A begins to flow in the base circuit of the germanium transistor, set by resistance R1, R2. When the transistor is completely unlocked, its internal resistance decreases sharply, and a current flows through the primary circuit of the coil, increasing exponentially. The process of current increase is practically no different from the similar process of a classical ignition system.
The next time the breaker contacts open, the movement of the base current slows down and the transistor closes, which leads to a sharp drop in the current rating through the primary winding. A high voltage U 2max is generated in the secondary winding of the ignition coil, which is supplied to the spark plug through the distributor. Then the process is repeated.
in parallel with the appearance of high voltage on the secondary winding, a self-induction emf is induced in the primary winding of the coil, which is limited by the zener diode.
Resistance R1 prevents the base circuit of the transistor from breaking when the breaker contacts are open. Resistance R4 in the emitter circuit is a current feedback element, reducing switching time and improving the TCS of transistor T1. Resistance R3 (together with R4) limits the current flowing through the primary circuit of the ignition coil.
Greetings, dear fellow radio amateurs. Many have dealt with very simple, and therefore very unreliable ignition systems in motorcycles, mopeds, boat engines and similar products of the last century. I also had a moped. He lost his spark so often and for so many different reasons that it became very annoying. You yourself have probably seen motorcycle enthusiasts constantly meeting on the roads without a spark, 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 of 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 has undergone many years of testing. I was pleased and would like to suggest assembling such a circuit to you who still have engines from the last century. But modern engines can also be equipped with this system if their own has become unusable, and buying a new one is expensive. It won't let you down!
With the new electronic ignition system, the spark increased by an order of magnitude; previously, on a sunny day, you wouldn’t even see it; after that, the spark plug gap was increased from 0.5 to ~1 mm and the spark was white-blue (on a test bench in laboratory conditions, even thin Kip paper was ignited by a spark). Any minor contamination of the spark plug has become unimportant, since the system is thyristor. The moped started starting not only with half a turn, but also with a quarter turn. Many old candles could be taken out of the “trash can” and put back into use.
The decompressor, which was always “spitting” and fouling the radiator, was removed, because you can now turn off the engine with a simple switch or button. The breaker, which always requires maintenance, was turned off - once configured, it does not require any maintenance.
Ignition module diagram
Module wiring diagram
Printed circuit boards for assembly
For low current consumption, a CMOS chip KR561LE5 and an LED stabilizer were chosen. KR561LE5 operates starting at 3 V and with a very low (15 uA) current, which is important for this circuit.
The comparator on the elements: DD1.1, DD1.2, R1, R2 is used to more clearly respond to the level of increasing voltage after the induction sensor and to eliminate the reaction to interference. The trigger pulse shaper on the elements: DD1.3, DD1.4, R3, C1 is needed to form the required pulse duration, for good operation of the pulse transformer, clear unlocking of the thyristor and for the same saving of circuit supply current.
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 generates a good pulse, with steep edges 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 PEV or PEL wire 0.1 - 0.12 mm.
The LED voltage stabilizer was chosen due to the very low initial stabilization current, which also contributes to saving the current consumption of the circuit, but, at the same time, clearly stabilizes the voltage on the chip at 9 V (1.5 V per LED) and also serves as an additional light source indicator of the presence of voltage from the magnets in the circuit.
Zener diodes VD13, VD14 serve to limit the voltage and are activated only at very high engine speeds, when saving power is not very important. It is advisable to wind such coils in a magnet so that these zener diodes are turned on only at the very top, only at the highest possible voltage (in the latest modification, zener diodes were not installed, since the voltage never exceeded 200 V). Two containers: C4 and C5 to increase the spark power; in principle, the circuit can work on one.
Important! The VD10 diode (KD411AM) was selected based on impulse characteristics; others got very hot and did not fully perform their function of protection against reverse surge. In addition, a reverse half-wave of oscillation in the ignition coil passes through it, which almost doubles the duration of the spark.
This circuit also showed undemanding requirements for ignition coils - any that were at hand were installed and they all worked flawlessly (for different voltages, for different ignition systems - intermittent, on a transistor switch).
Resistor R6 is designed to limit the thyristor current and to clearly turn it off. It is selected depending on the thyristor used so that the current through it cannot exceed the maximum for the thyristor and, most importantly, so that the thyristor has time to turn off 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 containers for high-voltage discharge (this solution is also much more economical and efficient than a voltage converter). This solution came because the coils have different inductive reactances and their inductive reactances depend on the rotation speed of the magnets, i.e. and on the shaft rotation speed. These coils must contain a different number of turns, then at low speeds the coil with a large number of turns will work mainly, and at high speeds with a small number, since the increase in induced voltage with increasing speed will fall due to the increasing inductive reactance of the coil with a large number of turns, and at In a coil with a small number of turns, the voltage increases faster than its inductive reactance. In this way, everything compensates for each other and the charging voltage of the containers is stabilized to a certain extent.
The ignition winding in the Verkhovyna-6 moped is rewound as follows:
- First, the voltage on the oscilloscope screen from this winding is measured. An oscilloscope is needed to more accurately determine the maximum amplitude voltage on the winding, since the winding is short-circuited by a breaker close to the maximum voltage and the tester will show a certain underestimated effective voltage value. But the containers will be charged to the maximum amplitude voltage value, and even with a full period (without a breaker).
- After winding the winding, you need to count the number of its turns.
- By dividing the maximum amplitude voltage of the winding by the number of its turns, we get how many volts one turn gives (volts/turn).
- By dividing the voltage required for our circuit by the resulting one (volts/turn), we get the number of turns that will need to be wound for each of the required voltages.
- we wind it and bring it to the terminal block. The lighting winding remains the same.
Parts used in the diagram
Microcircuit KR561LE5 (elements 2 OR NOT); integrated switch on MOS transistor K1014KT1A; thyristor TS112-10-4; rectifier bridges KTs405 (A, B, C, D), KTs407A; pulse diodes KD 522, KD411AM (very good diode, others get hot 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 ELECTRONIC IGNITION UNIT DIAGRAM
Car enthusiasts make electronic ignition units, as a rule, according to the classical scheme, consisting of a high voltage source, a storage capacitor and a thyristor switch. However, such devices have a number of significant disadvantages. The first of them is low efficiency. Since the charge of a storage capacitor can be likened to the charge of a capacitor through a resistor, the efficiency of the charging circuit does not exceed 50%. This means that approximately half of the power consumed by the converter will be released in the form of heat on the transistors. Therefore, they require additional heat sinks.
The second disadvantage is that during the discharge of the capacitor, the thyristor short-circuits the output of the converter and the oscillations it produces are disrupted.
After the storage capacitor is discharged, the thyristor closes, and the capacitor again begins to charge with a smoothly increasing voltage from the Converter, from zero to the maximum value. At high engine speeds, this voltage may not reach the nominal value and the capacitor will not be fully charged. This leads to the fact that as the speed increases, the spark energy decreases.
The next drawback is explained by the lack of stability of the sparking energy when the supply voltage changes. When starting the engine using the starter, the battery voltage can drop significantly (up to 9-8 V). In this case, the ignition unit produces a weak spark or does not work at all.
We offer a description of electronic ignition that does not have these disadvantages. The operation of the device is based on the principle of charging a storage capacitor from a stable amplitude reverse surge of a waiting blocking generator. The magnitude of this emission depends little on the voltage of the vehicle's on-board network and the speed of the engine crankshaft, and, therefore, the spark energy is almost always constant.
The device provides a potential level on the storage capacitor within 300 ± 30 V when the voltage on the battery changes from 7 to 15 V, maintaining operability in the temperature range -15 - +90°. The maximum operating frequency is 300 pulses/s. The current consumption at f = 200 pulses/s does not exceed 2 A.
The schematic diagram of electronic ignition (Fig. 1) consists of a standby blocking generator on transistor V6, transformer T1, a circuit for generating trigger pulses C3R5, storage capacitor C1, and an ignition pulse generator on thyristor V2.
In the initial state, when the contact plates of the breaker S1 are closed, the transistor V6 is closed, and the capacitor C3 is discharged. When the contact opens, it will be charged through the circuit R5, RЗ, base-emitter transition V6. The charging current pulse starts the blocking generator. The leading edge of the pulse from winding II of the transformer (lower terminal in the diagram) triggers thyristor V2, but since capacitor C1 was not previously charged, there will be no spark at the output of the device.
After the transformer core is saturated under the influence of the collector current V6, the blocking generator will return to standby mode. The resulting voltage surge on the collector V6, transforming in winding III, charges capacitor C1 through diode V3.
When the breaker is opened again, the same processes will occur in the device with the only difference that the thyristor V2, opened by the leading edge of the pulse, will connect the now charged capacitor to the primary winding of the ignition coil. The discharge current C1 induces a high-voltage pulse in the secondary winding of the bobbin.
The device is insensitive to the rattling of the contact plates of the breaker. The first time they are opened, transistor V6 will open and remain in this state until the transformer begins to saturate, regardless of the further position of the breaker.
Transformer T1 is made on a magnetic core ШЛ16Х25 with a gap of about 50 μm. Winding I contains 60 turns of wire PEV-2 1.2, II - 60 turns PEV-2 0.31, III - 360 turns PEV-2 0.31. The transformer core can also be made of W-shaped iron. However, due to uneven cutting of the plates, the gap, even without a gasket, may be large. In this case, it is necessary to grind the irregularities at the junction of the magnetic circuit.
The KT805A transistor can be replaced with a KT805B, but due to the higher saturation voltage, slightly more power will be dissipated on it, which can lead to self-starting of the blocking oscillator at high temperatures. Therefore, it is advisable to install the KT805B transistor on an additional heat sink with an area of 20-30 cm 2.
Instead of diodes D226B, you can use KD105B - KD105G, KD202K - KD202N (V1, V3), D223 (V4).
C1 is made up of two parallel-connected MBGO-1 capacitors of 0.5 μF each for a voltage of 500 V. C2 and C3 are MBM.
Thyristor KU202N can be replaced with KU202M or KU201I, KU201L. Since the KU201 direct voltage does not exceed 300 V, the voltage on the storage capacitor is reduced to 210 - 230 V by increasing its capacitance to 2 μF. Moreover, this does not have a noticeable effect on the spark energy.
To set up the device, you need an avometer and a breaker simulator - any electromagnetic relay powered from a sound generator. The relay can be connected via a step-down transformer to the lighting network. The frequency of the triggering pulses will then be equal to 100 pulses/s. With a diode connected in series, the trigger frequency will be 50 pulses/s.
If the parts are in good condition and the transformer leads are connected correctly, the device begins to work immediately. Check that the voltage on capacitor C1 is 300±30 V when the power supply changes within the above limits. The voltage should be measured with a peak voltmeter using the diagram shown in Figure 2.
The device is connected at the connection point of elements C1, V2, VЗ and, by changing the size of the gap in the transformer core, the required voltage value is achieved. If it is too low, the thickness of the gasket is increased. As the gap decreases, the voltage should drop.
When the ambient temperature is low, the spark energy may drop. In this case, it is necessary to reduce the value of the resistor RЗ, since at low supply voltage the thyristor V2 may not open.
The device was mounted using a printed method on a board measuring 95X35 mm, made of foil getinax or fiberglass (Fig. 3). The design of the electronic ignition unit is very different, depending on the available material and the installation location of the device.
V. BAKOMCHEV, Bugulma
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It is well known that ignition of fuel in internal combustion engines occurs due to a spark from a spark plug, the voltage of which can reach 20 kV (if the spark plug is fully operational).
On some engines, for its full operation, energy is sometimes needed significantly more than 20 kW can provide. To solve this problem, a special electronic ignition system was created. Russian domestic cars use conventional ignition systems. But they all have very big disadvantages.
When the car is idling, an arc discharge appears in the breaker between the contacts, which absorbs most of the energy. At sufficiently high speeds, the secondary voltage on the coil decreases due to the chattering of these contacts. As a result, this leads to poor accumulation of energy for the formation of an ignition spark. Because of this, the efficiency of a car engine is significantly reduced, the volume of CO2 in the exhaust system increases, fuel is almost completely not consumed, and the car simply consumes fuel.
The big disadvantage of old ignition systems is the rapid wear of the breaker contacts. The other side of this coin is that these systems are with a multi-spark mechanical distributor, it is also called “Distributor”, simplicity, which is ensured by the 2nd function of the distributor mechanism.
In order to increase the secondary voltage that is generated by such a system, you can use semiconductor-based devices that will work as control keys. It is they who will interrupt the current in the primary winding of the coil. Today, transistors are used as such keys, which generate currents of up to ten Amperes without any damage or sparks. There are examples built on the basis of thyristors, but due to their instability they have not found wide application.
One of the options for modernizing the BSZ is converting it into a contact-transistor ignition system (CTSZ).
The diagram illustrates the KTSZ device.
This device generates a spark with a fairly long duration. And thanks to this, fuel combustion becomes optimal. From the diagram it can be seen that the system is built on the basis of the so-called Schmitt trigger. It is assembled from transistors V1 and V2, amplifier V3, V4 and switch V5. Here the key acts as a current switch on the coil winding.
The trigger is designed to generate pulses with a fairly wide slope and edges when the contacts in the breaker are closed. As a result, the speed of current interruption on the primary winding increases, which in turn greatly increases the voltage amplitude on the secondary winding.
This increases the chances of a more powerful spark, which improves engine starting and overall efficient fuel consumption.
The following were used in the assembly:
Transistors VI, V2, V3 - KT312B, V4 - KT608, V5 - KT809A, C4106.
Capacitor – C2 (from 400 Volts)
Coil B115.
