Have you seen Audi, Lexus, or Ford automatic rain-sensing wipers and wondered how they work in these vehicles? They are handled by sensors at the center of the windscreen which detect rainwater and turn the wiper motor on. Here is the working of rain-sensitive wipers with a circuit schematic.
The main component of this circuit is a 555 timer IC that works in monostable mode. Two metal sheets fixed at a small distance apart are used as rain detector sensors. From the working of a monostable 555 timer, a negative voltage on the trigger pin will cause a high output.
So when it rains, the trigger pin gets a negative voltage. The output of one-shot 555 (monostable) is connected to a relay through a transistor. The transistor acts as a switch for the relay to turn ON the wiper motor during rain.
Circuit Diagram of Automatic Rain Sensing Wiper
Components Required
- IC 555
- Transistor BC 548
- Resistor (1K,10K,1M,)
- Capacitor(0.1uF)
- Relay (12V,10A)
- Rain sensor (Two metal sheets as figure)
How Do Rain Sensing Wipers Work
The working of this circuit is the same as the working principle of the monostable multivibrator.
- Here the trigger to the second pin is given by rain sensors.
- A small water drop on the rain sensor will connect the negative voltage to the trigger pin of 555 IC.
- This in turn will turn the output pin of 555 high. 555 Output is connected to the base of the transistor through a 1K resistor which forward biases the transistor.
- Thus relay gets negative and it switches ON the wiper motor.
Components Pin Out
Conclusion
To put it simply, the automatic rain-sensing wiper senses the rainwater and actuates the motor through a relay. You can refer to our previous post on how a relay works for a better understanding of relay.
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