On-board indicator of the deviation of the angle of the ZSK. Encyclopedia of radio electronics and electrical engineering

Encyclopedia of radio electronics and electrical engineering / Automobile. Ignition

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The device described above is intended for use in a garage, when repairing an engine. In the further process of operating the car, there is a gradual increase in backlash in the drive mechanism of the breaker-distributor, wear of its cam and lining of the moving contact, electrical erosion of contacts, etc. And only when a malfunction occurs in the engine, they usually remember the angle of the ZSK.

It is known that the deterioration of the engine performance becomes noticeable when the CSC angle goes beyond ±5...7% of its optimal value. This fact makes it possible to equip the car with a simple indicator that informs the driver in a timely manner about the approach of the moment when the angle of the ZSK goes beyond the established limits.

The indicator scheme is shown in fig. 3.

(click to enlarge)

The device allows you to control the angle of the ZSK in the range from 30 to 60 degrees, which is quite enough for most domestic passenger cars. Specific angle limits are set during the adjustment process. With the ratings of the parts indicated in the diagram, the angle corresponds to a value of 55 ± 3 degrees, (for cars of the VAZ family).

A rectangular pulse shaper is assembled on elements DD1.1-DD1.3, and a two-channel threshold device is assembled on resistors R3-R5 and elements DD2.1-DD2.5. With each opening of the breaker contacts, positive voltage drops are fed to the input of the DD1.1 element, which is turned on by the inverter. The duration of the closed state of the breaker contacts is equal to the duration of the high-level pulse at the output of this element.

After passing through the buffer elements DD1.2 and DD1.3, rectangular pulses are fed to the voltage divider R3-R5, which includes an integrating capacitor C5. Since the elements of the DD1 chip are powered by a stable voltage (9 V), the amplitude of the pulses is constant in any mode of engine operation.

A constant voltage will be formed on the capacitor C5, proportional to the duty cycle of the pulses from the chopper, i.e., proportional to the angle of the ZSK. By choosing the values ​​of the resistors R4, R5, the voltage levels are set corresponding to the controlled angle limits.

The threshold device channel that controls the lower limit is assembled on inverters DD2.1-DD2.3, and the upper one - DD2.4, DD2.5. The outputs of both channels are loaded with a common two-color LED HL1. To expand the range of controlled voltage downwards, the DD2 microcircuit is powered by a five-volt DA2 stabilizer.

Resistors R3-R5 are selected so that in the case when the voltage across the capacitor C5 corresponds to the optimal value of the angle of the ZSK, the input of the inverter DD2.1 was high, and the input of the inverter DD2.4 was low. The outputs of the channels will be low - the LED is off.

When the voltage decreases, the high level at the input of the inverter DD2.1 will change to low, and at the input of the inverter DD2.4 will remain the same. Therefore, the output of the inverter DD2.3 will be level 1, and the output will remain zero - the HL1 indicator will glow green.

It is easy to see that the result of increasing the voltage above the nominal value will be a red glow of the indicator. Correspondence of voltage levels to the input and output codes of the channels and the color of the glow of the indicators is shown in the table.

Consider the procedure for calculating the values ​​​​of resistors R3-R5.

The maximum ZSK angle (theoretical value, since the contacts are constantly closed, there is no sparking) for a four-cylinder engine is 360 degrees: 4 \u90d 9 degrees. Such an angle would correspond to a constant voltage of 1.3 V at the output of the shaper (at the output of element DDXNUMX). The minimum ZSK angle (also theoretical - the contacts are constantly open, there is no sparking) is equal to zero; the voltage at the output of the shaper is close to zero.

This allows you to take the intermediate values ​​​​of the angle equal to the corresponding output voltage multiplied by ten: 9 V - 90 degrees, 5 V - 50 degrees, 1 V - 10 degrees. Let's calculate the resistor values ​​for the control zone 52...58 deg. The voltage values ​​of 5,2 and 5,8 V correspond to the zone boundaries. The threshold voltage Unop for the inverters of the K561LN2 chip is UnfcTT / 2 = 2,5 V.

Let's set the minimum current through the circuit of resistors R3-R5 of the divider Un = 0,01 mA. Then Rtot = R3 + R4 + + R5 = Umin/Imin = 5,2/0,01 = 520 kOhm. Maximum current through the divider lmax = Umax/Rtot = 5,8/520 = 0,0112 mA.

Hence R5 = Unop/lmax = 223 kOhm;

R4 + R5 \u250d Unop / lmax \uXNUMXd XNUMX kOhm;

R4 \u250d 223-27 \uXNUMXd XNUMX kOhm;

R3 \u4d Rtotal - (R5 + R270) \uXNUMXd XNUMX kOhm.

According to the calculated values, the nearest values ​​​​of the divider resistors are selected. In the same way, the resistor values ​​are calculated for other boundaries of the control zone.

The corresponding microcircuits of other series can work in the indicator - K564, K176, KR1561. Instead of Schmitt triggers in the pulse shaper, elements of the K561LA7, K561LE5 microcircuit can be used. Instead of stabilizers 78L09, 78L05, domestic ones are suitable: KR1157EN9A, KR1157EN9B, KR1157EN901A, KR1157EN901B, KR1157EN902A, KR1157EN902B (DA1), KR1157EN5A, KR1157EN5B, KR1157EN501A , KR1157EN501B, KR1157EN502A, KP1157EH502B(DA2).

Capacitor C5 should be selected with a minimum leakage current; it is best to use a tantalum capacitor K52-1, K52-9, etc. Its capacitance is not critical and can be in the range of 5 ... 20 microfarads.

Instead of the KD522B diode, you can use any of the KD521, KD522 series. We will replace the KIPD45A-M LED with KIPD45V-M, KIPD41A-M, KIPD41B-M (red-green), KIPD45AZ-M, KIPD45BZ-M (red-yellow). In extreme cases, you can use any pair of conventional LEDs of different colors of glow, turning them on in parallel in opposite directions.

All parts of the indicator, except for the HL1 LED, are mounted on a printed circuit board made of foil fiberglass with a thickness of 1,5 mm. The drawing of the board is shown in fig. 4.

If the values ​​​​of the resistors R3-R5 are chosen correctly, the adjustment indicator usually does not require. Nevertheless, the accuracy of laying the boundaries of the control zone should be checked. This will require as a model any CG angle meter (either described in the first part of this article, or in journal publications [1-3]). An exemplary device and an indicator are connected to the breaker of a serviceable engine and, gradually changing the width of the gap between the breaker contacts in one direction and the other, the boundaries at which the indicator is triggered are marked. If correction is needed, resistor R3 is selected.

You can check the boundaries of the indicator control zone using a 3H generator capable of generating rectangular pulses with an amplitude of 9 ... 20 V with an adjustable duty cycle.

The finished board should be varnished to protect it from moisture and placed in a metal shielding box. The LED is mounted on the instrument panel in a specially drilled hole, and the box with the board is placed behind the panel.

Author: I.Potachin, Fokino, Bryansk region

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