Rain detecting windshield wipers

Today it rained in Houston, but I had to get about and I discovered something I didn’t know about my car. When the rain started as a sprinkle, I put the wipers on intermittent.

Suddenly the rain picked up, and so did the wipers, to regular speed. When it became intense, the wipers ramped up to match. Then, when I pulled up to a covered ATM, they stopped.

When I pulled out again, into a light drizzle, they started up on intermittent again.


So, how do they work?

Knowing what kind of car you’re driving would help. Ones I’ve made were two closely spaced wires, but I bet most car rain detectors work like this. Check your rear-view mirror for wires.

Apparently, Infra-red light.

I hope I never have to replace my rear-view mirror. Upon inspection, it (BMW) appears to use the infra-red sensor system.

For our non-clickers, from DarrenS’s link above:

Très nifty.

I’m guessing, Nanoda, that your two wire system compares rates of deflection of the (exposed?}wires. Is that even close?