i have been doing this project...

im doing it using the IR sensing technique...
i.e IR transmits and received beam of light after reflection from windscreen from inside...when there is no water outside windscreen then there is more light received at the receiver end ...when rain occurs some of light is lost resulting in less amount of light enters the receiver hence this triggers the system....


anyone has help on this one...the circuit diagrams etc
any help is much appreciated...

 

It would be faster if you could post up your work so we can see how you are trying to do this. How do you allow for dirt accumulation? What is the critical angle for the sensor?

 

I don't think using a variance in light reflected will work, cause there is a lot of refracted light to deal with as well as the change in lighting continually happening which could throw off the detector, since rain is the key factor try some sort of a moisture detector.
Just my opinion.

 

U just have to place ur senser at the bottom of bonnet (inside ) just below the wiper and when it rains . It will get wet and then will trigger the circuit .