Electronic wiper relay for Zhiguli. Scheme, description

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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
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Electronic wiper relay for Zhiguli. Encyclopedia of radio electronics and electrical engineering

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

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Until now, Zhiguli cars remain the most common "foreign car" that has been running on our roads for many years. Especially a lot of "old women" models VAZ 2101-2107.

During my 30 years, my "deuce" has changed more than one owner. Many components and parts have been replaced. If this can be understood from the hardware, then the repeated failure of the PC514 wiper relay, the PP380 relay-regulator demanded that they refuse their services.

An analysis of amateur radio literature over the past 20 years has shown a trend to replace the PC514 relay with electronic devices. At first it was transistor multivibrators. An electromagnetic relay or a powerful transistor was used as a load in one of the arms. Then they began to use a thyristor as a key.

The simplest wiper relay circuit [1] contains a KU201 thyristor and one low-power transistor. The duration of the pause in the wiper cycle depends on the discharge time of the timing capacitor, and it can be adjusted. This is good, since such a need appears when the intensity of rain or snow changes. But the fact that this simplest circuit is very critical to the parameters of the thyristor and requires painstaking selection of many elements is certainly bad.

Adding another transistor [2] eliminates the selection of elements.

The proposed electronic wiper relay circuit (Fig. 1) is the most complex for several elements, but has a higher reliability of operation, can provide dynamic braking of the engine. No alterations to the standard scheme of the electrical equipment of the car [3] are required.

The wiper relay circuit itself, highlighted in Fig. 1 by a dash-dotted line, is mounted on a printed circuit board (Figs. 2 and 3) made of foil fiberglass and placed in the case of the RS514 relay to be dismantled. The XR1 plug, together with the connecting wires, is also from the PC514 relay.

(click to enlarge)

Electronic wiper relay for Zhiguli

The device works as follows. Regular dual key switch SB1 wiper operating modes has three positions: "0" - the wiper is off; I - cyclic (with a pause) mode of operation; II - continuous operation of the wiper. In position II, power (+12 V) is supplied directly to the winding of the windshield wiper motor M1 through the int contact of connector XR2. In this case, the limit switch SB2 does not affect the operation of the engine. In position I of the mode switch SB1, +12 V voltages are applied to pin 3 of the electronic relay circuit. This state of SB1 is shown in the drawing.

Since at the initial moment the capacitor C1 is discharged, there is no voltage at the base of the transistor VT1 relative to its emitter, and VT1 is locked. In this case, the transistor VT2 is unlocked by the base current through the resistor R5 and the motor winding M1. Accordingly, the thyristor VS1 is unlocked, receiving a positive potential on the control electrode through the resistor R7. The thyristor instantly goes into a conducting state and "remembers" it. +4 V is applied to the motor winding through terminal 12 of the electronic relay circuit, and the wiper begins to move the brushes.

Limit switch SB2 switches almost simultaneously. In this case, the thyristor VS1 is short-circuited by its contacts "int-C" (connector XR2) and goes into a non-conducting state, but the supply voltage to the motor does not stop. Transistor VT6 is unlocked through resistor R3, providing fast charging to the power supply voltage of capacitor C1 through resistor R4, unlocking transistor VT1 through resistor R3. This in turn leads to the locking of the transistor VT2. After the brushes make a double stroke and return them to their original position, the state of the limit switch SB2 changes, the contacts "int-C" open, and "int-F" close. The motor M1 stops because the thyristor VS1 is in a non-conductive state. VT3 is locked. The formation of a pause in the wiper cycle begins.

Capacitor C1 is discharged through resistors R1, R2, R3 and the base junction of transistor VT1. The discharge (pause) time can be adjusted from 0,5 to 20 with potentiometer R1. A decrease in the charge of C1 leads to the locking of the transistor VT1. Accordingly, the transistor VT2 and the thyristor VS1 are unlocked. The motor is supplied with power through the thyristor VS1, and after a very short period of time, power is supplied by the limit switch SB2. The process of brush movement is repeated.

Capacitor C2 reduces the sparking of contacts SB2 of the limit switch and interference with the operation of the wiper relay in the car. Its value is not critical, it can be reduced by a factor of 10.

Diode VD2 protective. It can be replaced by KD105, KD221, KD208, KD209 and similar ones. As VS1, you can use thyristors KU202 with any letter. The use of KU201 is possible, but the reliability of operation will be lower. The printed circuit board allows the use of thyristors in a plastic housing such as KU202N-1 or T106-10. In this case, the printed circuit board can be shortened by 15 mm. You can increase the maximum pause time if you wish. To do this, it is enough to proportionally increase the resistance of the potentiometer R1 or the capacitance of the capacitor C1. Now a few words about the dynamic braking of the engine. The fact is that the mechanism for driving the wiper blades of Zhiguli cars has small friction losses. If, to stop the engine, use only the de-energization of the engine in the initial extreme position of the brushes, then by inertia the engine rotor will turn a little more, and the brushes will additionally advance by 3-5 mm. In principle, this does not create any particular inconvenience to the driver, but this disadvantage is easy to get rid of. In the standard design with the PC514 relay, the "int-F" contacts of the limit switch were used for this, which, during a pause, shorted the winding of a de-energized motor.

In the proposed circuit of an electronic relay for dynamic braking of the engine, it is enough to install a resistor R9. Its value is non-critical from 4,7 to 10 ohms. In fact, a small power is dissipated on the resistor, since the current through it during normal operation of the relay flows only for a short time, but an emergency condition of the wiper cannot be excluded, for example, "sticking" of the "int-F" contacts of the limit switch. Therefore, it is advisable to use a powerful resistor type PEV-10.

As mentioned earlier, the use of an electronic wiper relay does not require changes in the standard wiring diagram of a Zhiguli car. The failed PC514 relay should be disassembled, a four-wire harness with a connector plug should be unsoldered from it. The colors of the wires and their connection to the plug are shown in Fig.4.

Electronic wiper relay for Zhiguli

If dynamic braking is not used, and this is quite justified to simplify the design, then the end of the unused wire should be insulated.

The wires of the harness are soldered to the electronic relay board, and the board itself is placed in the PC514 case and closed with an insulating bottom cover according to the size of the board. The potentiometer R1 is placed in any place convenient for the driver on the car panel, for example, near the wiper mode switch.

More than five copies of the electronic wiper relay were manufactured and installed on cars. The selection of elements was not carried out. All drivers note a wide range of pause intervals. The operation of the wiper motor has become more stable.

In conclusion, it should be noted that the proposed electronic relay is the simplest technological solution to the problem, therefore, the digital relay circuits found in the literature were not considered as unreasonably complicated, especially since neither the exact value of the pause nor its stability is essential for the driver.

Literature

Bornovolokov E.P., Frolov, V.V. Amateur radio circuits. - K .: Technique, 1979.
Radio, television, electronics. Bulgaria - 1979.- No. 11.
Litvinenko V.V. Electrical equipment of cars "VAZ" // Zarulem. - 1997.- S.108-109.

Author: E.L. Yakovlev, Uzhgorod

See other articles Section Automobile. Electronic devices.

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