Electronic car ignition. Free Technical Library article

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Electronic car ignition

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

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The proposed device will save motorists from many problems, especially in winter. It does not require changes to the vehicle's electrical circuit and, if necessary, allows you to easily return to the standard system. It is also important that when the on-board network supply voltage is reduced (when the starter is turned on, for example), the multi-spark mode is automatically switched on. The device is operational when the battery voltage drops to 6,5 V.

The figures show a "printed" board with the location of parts and an electrical circuit. The basis of the latter is a voltage converter assembled on a transistor VT1 according to the blocking oscillator circuit with a common collector. The reverse pulses on the winding IV of the transformer T1 with a frequency of 2 ... 3 kHz through the rectifier VD3 charge the storage capacitor C2. As C2 charges, the amplitude of the reverse pulses grows and reaches the stabilization voltage of the Zener diode VD6. Capacitor C6 is charged through the zener diode VD1. The discharge time of the capacitor C1 determines the delay in starting the blocking generator. This reduces the oscillation frequency of the generator and the current consumed by the circuit. After the discharge of the capacitor C2 through the ignition coil and the thyristor VS, the process is repeated.

Electronic car ignition. Scheme of the electronic ignition unit

Pic. 1

The voltage across the capacitor C2 depends on the amplitude of the pulses on the feedback winding II of the transformer T1 and the transformation ratio. With the specified parameters, by the time the zener diode VD6 is opened, the voltage across the capacitor C2 reaches 400 V. The amplitude of the pulses on the winding II of the transformer depends on the difference between the stabilization voltage of the zener diode VD6 and the supply voltage U (the amplitude thus increases with decreasing on-board network voltage).

When the supply voltage decreases, the voltage across the capacitor C2 increases. Turning on the VD4 diode increases the duration of the spark, since a full cycle of oscillations occurs in the circuit formed by the ignition coil and capacitor C2.

Diode VD8 shunts the control winding of the pulse transformer when the breaker contacts are closed, which prevents the thyristor VS from opening before they open. The number of turns of the winding III of the transformer T1 is chosen so that the maximum amplitude of the pulses on it is somewhat lower than the battery voltage, and the VD7 diode opens only when the supply voltage drops below 12 V. In this case, the sparking frequency is determined by the charge time of the capacitor C2. A spark discharge occurs every time as soon as the zener diode VD6 opens and the capacitor C2 is discharged through the circuit: windings II and III of the transformer T1 - diode VD7 - winding III of the pulse transformer T2 - zener diode VD6 (subject to open contacts).

Details and design. For the manufacture of transformer T1, you can use any transformer steel. The cross section of an average core is about 1 cm. The transformer is assembled with a gap of 0,2 mm (you can insert a piece of cardboard of suitable thickness into the gap).

When assembling, the gap should not be blocked by iron plates. Winding I contains 50 turns, winding II - 70, winding W -13, winding IV - 450 turns. Winding I is carried out with a PEV wire with a diameter of 0,7 ... 0,8 mm, the remaining windings - with a PEV wire with a diameter of 0,2 ... 0,25 mm.

The pulse transformer T2 is wound on a ferrite ring with a diameter of 12..15 mm, a height of 4 - 5 mm, with a magnetic permeability of 1000 ... 3000. Number of turns: I - 25, II - 150, W - 10. The diameter of the washing of the brand PEV-0,12 ... 0,18 mm.

Winding I is energized at 400 V, so care should be taken to isolate it fundamentally from windings IV and III. It is better to place winding III between windings I and II.

Capacitor - C2-2.0 x 400V (MBGO-2), C1-30,0 x 6V, thyristor VS - any of the KU202N (K, L, M) series, transistor VT - type KT837B (A), diodes VD1-VD2. VD5, VD7-VD9 - D223 (D219. KD504), diodes VD3-VD4 - D226B (KH105).

The VT transistor is best placed on a base made of aluminum about 6 mm thick, which will also act as a heatsink. The dimensions of the base are chosen in accordance with the size of the board, which rests on the bushings. Their height (about 14 mm) is chosen so that the threaded part of the KU202 thyristor does not touch the base. The case made of tin or pieces of foil textolite is mounted on the side surfaces of the radiator.

To check and configure the device, it is desirable to have an adjustable power supply b ... 15 V with an output current of up to 2,5 A. However, you can do without it. For these purposes, a car battery, an ignition coil and 8 elements of type 373 (1,5 V each) are quite suitable.

At the first stage of tuning, we turn off the multi-spark mode. To do this, we solder one of the legs of the VD7 diode (you can turn on the toggle switch in the gap, which creates additional convenience when setting up). We connect an ignition coil to the assembled unit (you can use a 20-30 Ohm resistor), then a 12 V supply. If the blocking generator is working, you will hear a characteristic squeak, otherwise you need to check the correct assembly of the generator and the quality of the elements. The voltage at the output of the operating unit (on contacts C2) should be 380.. .410 V (in case of discrepancy, a VD6 zener diode is selected). With a very low voltage (100 ... 150 V), the terminals of the winding IV of transformer 1 should be swapped.

To check the power of the converter, instead of the ignition coil, a 220 V 15 W light bulb is used as a load. It is connected to the terminals of the capacitor C2. The light bulb should burn at full intensity. In this case, the constant voltage on it will be 180 ... 220V.

Power is regulated by the selection of resistor R1. The current consumed by the circuit when the light bulb is connected varies between 1.5 ... 2A (no load-50-150 mA).

In the presence of an ignition coil, a spark gap of 10 ... 15 mm is provided between the high-voltage wire and the power minus. A short-term short circuit of wire 3 (see diagram), going to the breaker, to the case leads to the fact that a spark jumps in the spark gap. If power adjustment was not carried out, then visually (according to the power of the spark) it is possible to select the resistor R1 with a certain degree of accuracy.

For better noise immunity of the device, the value of the resistor R5 is selected in such a way that a spark occurs only at a power supply voltage of 5 V or more (that is, a spark should not occur if less than 373 XNUMX elements are connected).

Now you can start setting the threshold for switching on the multi-spark mode. It is done in this way. First, we connect the diode VD7. With a decrease in the supply voltage (in the case of using elements 373, this occurs in steps), a moment arises when, even without closing wire 3 to the case, sparking becomes continuous. If the threshold for switching on the multi-spark mode is 12 V and higher, then another diode should be connected in series with VD7.

The assembled electronic ignition unit is installed under the hood of the car near the ignition coil (it is advisable to choose a place with good airflow). Then the ignition distributor capacitor is disconnected from the breaker contacts. The next step is to disconnect the wire connecting the breaker and the ignition coil. If there is an additional resistor (type B115 coils), it should be short-circuited. To do this, you can use a disconnected wire. The remaining connections are made in accordance with the proposed wiring diagram (Fig. 1).

If there is a toggle switch for enabling the multi-spark mode, then after testing the device in the operating mode, you can increase the gap on the candles by 1,5 ... 2 times.

It should be remembered that with a large gap in the contacts of the breaker, there is a possibility that the last sparks (in multi-spark mode) will fall into the next cylinder, which disrupts the operation of the engine. Therefore, the gap must be reduced to a minimum within the gap range recommended by the manufacturer.

PCB layout:

Fig. 2

Author: Sverchkov Yu.N. "Inventor and innovator", No. 7, 1987; Publication: cxem.net

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