Car wiper automatic controller

As shown in the figure, the wiper control circuit consists of an oscillator and a control circuit. The wiper is controlled to swing for 5 seconds and then pause for 0 to 30 seconds. The pause time is adjusted in time according to the size of the rain outside the car.

555 and R1, RP, C1 and D1, D2 are connected to form an astable multivibrator. The oscillation frequency is determined by the charge and discharge time constants of the 555 circuit. The charging time tcharge = 0.693R1C1, and the discharge time tdischarge = 0.693RPC1. The charging time corresponding to the parameters in the figure is about 5 seconds, and the discharge time depends on the position of the potentiometer sliding arm, which can be adjusted within the range of 0 to 30 seconds. The period of the multivibrator oscillation T = tcharge + tdischarge = 0.693(R1+RP)C1. It can be seen that its period length and duty cycle can be adjusted.

When the power is just turned on, the ② pin is at a low level, which sets the 555, and the ③ pin is at a high level, the relay is energized, the motor M is powered and runs, and the wiper swings. As C1 is charged through R1 and D2, when the potential on Cl is higher than the trigger level of ⑥ pin 2/3VDD, the circuit is reset, the ③ pin is at a low level, the motor stops, and the wiper stops. The time corresponding to C1 charging to 2/3VDD is the working time. C1 is discharged to the internal discharge tube of 555 through D1 and RP, and the time when it is lower than 1/3VDD is the pause time. It repeats itself over and over again.