Wiper and washer control unit. Encyclopedia of radio electronics and electrical engineering

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

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As you know, some Zhiguli car models developed many years ago are in many ways inferior to their today's counterparts. However, at low cost, some service indicators of old machines can easily be raised to a completely modern level. This article, in particular, describes a device that allows you to increase the usability of the windshield wiper and glass washer.

The unit is an electronic automatic control of the wiper motor, interchangeable with the PC-154 electromechanical relay available on the car (see the book by Pyatkov K. B., Ignatov A. P. and others. "Cars of the VAZ-2104, VAZ-2105 family: A guide to maintenance and repair - M.: "Behind the wheel", 1999, pp. 146-148). zero) in intermittent mode, but also sets the wiper to multiple double strokes when the washer lever is pressed.

The basis of the device (Fig. 1) is a node assembled on the DA2 timer. The timer is switched on according to a typical generator circuit, the timing characteristics of which are determined by the elements R4, R5, R6, C3 in accordance with the expressions: voltage 3Upis/0,693; trC4 is the discharge time of the capacitor C5 to Ipit / 6 (it is assumed that the variable resistor R3 slider is in some intermediate position, and the contacts of the SF3 switch paired with this resistor are closed).

(click to enlarge)

At the moment the supply voltage is applied to the power supply, the capacitor C3 is discharged, the voltage at the inputs R and S of the timer DA2 is zero, as a result of which its internal trigger sets a high voltage at the output (pin 3). For this reason, the transistors VT1 and VT2 of the power amplifier are closed and the power supply circuit of the wiper motor is open. Capacitor C3 begins to slowly charge through resistors R6, R5, R4. Through time

tзC3 the voltage on it will reach a level equal to 2Upit / 3, the timer DA2 will switch, at the mentioned output the high level will change to low, the transistors will open, the electric motor will turn on and the brushes will begin to move.

From this point on, capacitor C3 will quickly discharge through the open collector output (pin 7) of the timer and resistor R4 until the voltage across it decreases to Upp / c. after which the timer DA2 will switch to its original state, and the transistors will close. The brushes will continue to move until the end of the double stroke (until they return to their original position).

The time tpC3 is chosen less than the time of one double stroke of the brushes - 0,8 ... 1,3 s, but not less than 0,2 s (during this time, the contacts of the limit switch of the wiper mechanism must be reliably closed). With a variable resistor R6, you can change the duration of the pauses between double strokes of the brushes.

The node, assembled on the DA1 timer and representing a single vibrator, controls the operation of the generator on DA2. In the initial state, the voltage at the R and S inputs of the DA1 timer and the capacitor C1 are close to the supply voltage, the timer output is low, so the node does not affect the operation of the generator.

When the washer lever is pressed, the contacts SF1 are closed, the pump is turned on, supplying washer fluid to the glass. Capacitor C1 is almost instantly discharged through diodes VD1 and VD2, the voltage at the R and S inputs of the DA1 timer decreases to almost zero, and the low level changes to high at the output. Through the VD3 diode and the R3 resistor, the capacitor C3 is very quickly charged to the supply voltage, the DA2 timer switches to the zero state and the power amplifier transistors open. While the capacitor C3 remains charged, the self-oscillating mode of the generator on the DA2 timer is not possible.

When the washer lever is released, the contacts SF1 open, the washer fluid supply stops, the capacitor C1 begins to charge through the resistor R2, and at the moment when the voltage at the input R of the timer DA1 reaches 2Upit / 3, the timer will switch - the output will again show a low-level voltage, capacitor C3 will start to discharge and the DA2 timer will return to self-oscillating mode. The charging time of the capacitor C1 is chosen so that after releasing the washer lever, the wiper blades make 1-3 continuous double strokes.

Thus, the assembly assembled on DA1 puts the wiper in continuous mode when the washer fluid is applied to the glass and returns it to intermittent mode after a few double strokes of the brushes after releasing the washer lever. With open SF2 contacts (wiper off), the wiper blades can only be set in motion by pressing the washer lever.

The current consumed by the unit when the wiper motor is not running does not exceed 25 mA. Power is supplied to the unit when the mode switch installed on the machine is moved to the middle position ("Intermittent mode"). In the extreme positions "Off" and "Continuous" the unit is disconnected from the on-board network.

Structurally, the block is mounted on two printed circuit boards 65x30 mm in size made of foil-coated single-sided fiberglass 1,5 mm thick. The board drawing is shown in fig. 2, a and b. The boards are installed in the plastic casing of the old RS-514 relay. To do this, a cover of such dimensions is cut out of foiled fiberglass with a thickness of 1,5 mm so that it can be installed in the grooves of the casing (with the foil inside) and removed. Both boards are soldered to the cover foil, for which purpose a foil strip is provided on each of them, electrically connected to a common wire. Boards on the cover have printed conductors outward; the gap between the boards and the walls of the casing is 10 ... 15 mm.

In order to increase the rigidity of the soldered structure, the free edges of the boards are "tied" with a piece of rigid copper wire with a diameter of 1 ... 1.2 mm, soldered into the holes drilled for this. The nodes mounted on the boards are connected into a single whole by three jumpers made of flexible wire; the connection points are marked with the letters A, B and C. The numbers indicate the mounting pads connected to the connectors X1 and X2.

As the pin part of the X2 connector, a pin block from the RS-514 relay was used, which is included in the corresponding socket block of the on-board network. The diagram shows the colors of the on-board network wires according to the above book. Connector X1 - SG-3, SG-5 or any other suitable size. Diodes KD102A can be replaced by any of the series KD102, KD103, KD106, KD109, and KD105B - ​​KD106, KD209, KD213, 2D215, 2D2997. Instead of KT501E, a KT501 transistor with letter indices D, I, M, K or any of the KT502, KT830 series is suitable, and instead of KT855B, any of the KT835, KT837 series with a static base current transfer coefficient of at least 30. There are no special requirements for other parts .

To establish the unit, instead of an electric motor, a car lamp with a power of 5 ... .21 W is temporarily connected (to pins 2 and 4 of connector X2), and the operation of the washer lever is simulated by closing pin 1 to a common wire. A supply voltage is supplied from a laboratory source - plus to pin 1 of connector X2, minus to pin 4.

By observing the duration of the lamp flashes, the desired time ratios are selected. A selection of resistor R2 sets the desired number of continuous double strokes of the brushes after releasing the washer lever (at the nominal value indicated in the diagram, it is equal to three). Resistors R5 and R6 are selected, respectively, by setting the minimum and maximum pauses between brush strokes in intermittent mode. It is advisable to measure the time of one double stroke of the brushes with a stopwatch before selecting resistors.

Variable resistor R6 is placed under the instrument panel to the right of the steering column. Additional connector X1 allows you to quickly replace the unit with an electromechanical relay and vice versa.

If, after installing the unit on the car, the brushes remain motionless when power is applied, the VT2 transistor should be replaced with another one with a large static base current transfer coefficient.

Author: D. Sauri, Moscow

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