What are Rain-Sensing Wipers?
As the name suggests, rain-sensing wipers are the windscreen wipers which come into action automatically. They do so when they sense the water on the windscreen of the vehicle.
Initially, only some of the luxury vehicles offered this feature. However, it is now gaining rapid popularity even on the new vehicles. Ford Fiesta is one of the cars which offers the rain-sensing wipers as an optional fitment.
Working of Rain-sensing wipers:
Rain-sensing wipers employ an electronic module fitted near the windscreen. It serves as the brain of this system. The diagram below depicts the parts of this control module:
As seen in the diagram, the control module hosts light emitting diodes (LED) which emit infrared light on the windscreen. When the glass is clear, the light is reflected back from the windscreen and is received by the sensor again. But when the water droplets are present on the glass, the infrared light beam passes through them instead of reflecting. So, the amount of light coming back to the sensor is very low.
This reflected light generates a voltage in the electronic module. When the reflected light is more, it generates more voltage and vice versa. The engineers program the electronic module in such a way that it activates the wiper motor when the generated voltage is less i.e. when it reflects very small light. The speed and time of activation of the wipers depend on the degree of wetness of the windscreen. Some advanced systems are capable of directly measuring the moisture level on the windscreen.
Generally, it is observed that the rain-sensing wipers reduce driver fatigue to some extent.
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See Rain-sensing wipers in action here: