Making automatic windshield wipers

Automatic control wipers and windshield washer for Niva

The domestic Niva crossover uses the simplest windshield wiper control system. This is a lever for three positions: 0 – off; 1 – intermittent mode of operation; 2 – continuous operation of wipers. And also the button without a fixation including the motor of giving a liquid on nozzles of washer of windshield, activated by pressing the lever on itself. All this is simple, but terribly uncomfortable. It is necessary to switch the lever and press the washer button simultaneously to clean the window while driving. And all this while it is raining and flying mud, limiting visibility, distracting from the road.

I have developed a device which eliminates this disadvantage. The advantage of this scheme is that you do not need to cut and remake the car. The device is connected between the lever and button connection terminals on the steering wheel switch to the circuit of the car and uses the same lever and button for control. The modes of operation of the device are shown in Table 1.

Wiper motor control lever position

1 short press

2 short presses

0 – wipers motor off.

One pass of wipers.

Automatic windshield wiping. Washer motor is switched on for 7 seconds, wipers motor is switched on for 7 seconds after 3.5 seconds.

Washer motor is switched on for 3.5 seconds for as long as the button is pressed, then the wipers are switched on.

1 – Intermittent mode wipers (3 time intervals pause (7, 5 and 3 seconds).

Cyclic reduction of the pause.

Same as mode 0.

Same as mode 0.

2 – Constant mode of the wipers

Washer motor is switched on for 7 seconds.

The washer motor is switched on for 7 seconds.

The illustration shows the diagram


The heart of the device is the ATTiny13 microcontroller. The circuit is powered from the onboard electrical network, the microcontroller is powered via the LM7805 voltage regulator. The resistor R1 and the capacitor C5 in the reset circuit of the MC provides a time delay to start the controller, for a reliable start of the firmware. Input PB0 (5) is connected to the windscreen washer button. Input PB1 (6) to the wipers control lever, in position 1 is pulled up to the ground. To determine the position of the lever input PB2 (7) is connected through a divider and a soliton, limiting the input voltage up to 4.7 volts, to a relay contact U3, in the normal position which in turn connects it to + wiper motor. The logic of determining the position of the wiper lever is as follows: if PB1 is down to ground, the lever in position 1, otherwise in 0 or 2nd position. If PB2 is logic 1, then position 2. You could of course also connect PB2 to the wiper lever. But in this case the relay U3 would have to be kept on for the whole time of the wipers in mode 2. With the connection used, the wiper motor is permanently switched on by the regular contact of the lever and there is no need to apply voltage to the U3 relay.

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The output PB3 controls the wiper motor relay U3 via resistor R4 and transistor Q1. Output PB4 through resistor R5 and transistor Q2 and with the help of relay U4 turns on the washer motor.

The firmware of the controller is based on the RTOS given in the series of articles on the website The fuses are default and it is not necessary to change any fuses on the new MC.

The wiring diagram to the car electrical system:

Wiring diagram

Pin 1 in the wiring diagram is the leftmost pin J1 in the circuit diagram, then in order.

Transistors and diodes in the relay circuits can be replaced with any suitable parameters.

In archive to article: firmware in hex file, assembler source (in file you can set other time intervals, if for some reason preset ones don’t fit, you can compile in AVRStudio), project in Fritzing, printed board in PDF and also models for 3d printing device case and plug housing (I printed everything as is, except for 2 pins plug, I scaled it 1.05 times when printing).

Automatic device for windshield wiper operation

It’s drizzling rain. I turn on the windshield wiper. Two or three cycles of the brushes and the windshield is dry. I turn the wiper off. But after 30 seconds the glass is dirty again. I turn the wiper back on and so on.

This mode of operation is not rational for the front windshield wiper or the rear windshield wiper. The latter often works “dry” in this case, because less rain drops get on the rear window (although this is compensated by more mud). However, intermittent windshield wipers have been known for quite some time. Therefore, the proposed system is of some interest for all vehicles, given its low cost.

Automatic device for windshield wiper operation

In this device a long activation time of the windshield wipers is first of all envisaged. The first time the wiper motor is switched on, the wipers need to be switched on for only 2 seconds in order to keep the glass clean. This time is sufficient to cause the wiper motor to hold itself in place. However, the main importance here is the pauses between successive cycles of the wiper motor. Their duration is adjusted by means of an external trimmer (it is especially important for the rear window of the car) in the range from 5 to 40 seconds (Fig. 1).

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The clock mode of operation of this device is provided by the TCA 335A operational amplifier, since it allows connection of high impedance RC circuits to the circuit due to

Automatic device for windshield wiper operation

the circuit due to very small input currents (less than 20 nA). The output current of the operational amplifier ensures the operation of the relay. However, in this case the motor has to be switched through a normally closed change-over contact.

The first, longest interval of motor switching on is realized by the fact that the electrolytic capacitor C has to be charged only once to the voltage determined by the voltage divider (2,7/3,3 kOhm) and the resistor R1. For the next switching intervals this voltage is determined by the voltage at resistor R1 only. The electrolytic capacitor C is discharged through resistor R3 and the external adjustment potentiometer R3′, which determines the pause duration.

Fig.2. Schematic of an automatic wiper control device used in older vehicles.

Two diodes 1N4148 are used to charge and discharge the electrolytic capacitor. A third diode 1N 4148 prevents voltage peaks at the relay. The diode 1N 4001, connected in parallel to the motor, has a similar function. The somewhat ‘exotic’ diode 1N 5624 prevents the voltage on the motor switch during continuous operation of the circuit that would cause it to become unstable. It should also be mentioned that a standard windshield wiper should have a three position switch as shown in the circuit diagram.

Since there is almost always high humidity in the car, it is advisable to fill the finished circuit with a special mass. At the same time the filling mass should not penetrate into the relay. In addition, the connection terminals should be so strong and the connection wires should be clamped so tightly that they can withstand the vibrations that occur in cars with rigid suspension.

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In older cars equipped with two-stage wiper switches, the relay can not be switched according to the circuit shown in Fig. 1. Therefore, it has to be slightly modified (Fig.2). In this case, a relay with one normally closed contact is used. Here it should be noted that terminals 53 are disconnected from terminal 31e, and the corresponding connection is made through terminals 87 and 87a of the relay. Under certain circumstances, it may be necessary to introduce an additional relay stage.

Automatic device for windshield wiper operation

Fig.3. Printed circuit board(a) and its wiring diagram(b).

This relay is best installed under the windshield wiper motor cover, because this is the most convenient place to connect it. The circuit board of this device (Fig.3) can be mounted, for example, under the dashboard of the car. Instead of a potentiometer, a multi-position stepped switch is sometimes used to provide the windshield wipers with a clock mode. This allows you to set intervals for the blades and you do not have to turn the potentiometer slider for a long time to finally achieve the desired mode of operation.

The step switch is, of course, set in such a way that the driver is comfortable to use it.

In conclusion, let us remind you that when carrying out work related to the electrical equipment of the car, first of all it is necessary to connect the battery terminal, i.e. to disconnect the power supply.

For the circuit assembly besides those mentioned in the circuit diagram, the following elements are additionally needed: ELO 6/85 board; 3 A three position switch; 6 position terminal; V23027-A002 Siemens relay; 66H130 Burklin case.

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