Rain Sensor for alarm

There are car rain sensors but it mainly for wipers like someone posted earlier ..

Such as http://www.raintracker.com/

Which use some kind of eye to detect the rain hitting the windshield and speed up the wipers as more rain is detect hitting the windshield .. Sensor is actually placed inside the windshield I believe ..

The easiest homemade rain sensor is to take 2 copper and put it close to each other that when a water drop touches it and close a circuit to a relay switch  which in turn could operate your Windows   but remember one thing ..  You will need to made it so the water will still run off the sensor  and not stay on it .. and with raining dripping on the sensor  it will be like pressing remote button repeatly to your power windows module .. now it may not hurt anything but again it may shorten the life of the relays inside the power windows module if it not a soild state modules .. so you would need to add some circuit to disable then reenable the sensor let say oh every 10 minute once it detect a closed circuit  on it ..

I am sure you can find some type of water sensor but those type of water sensor is used to detect a large body of water not water dripping on it .. Automatic sprinkler system use rain sensor however they require 24 volts to operate and is kinda too big in size that it would stick out like a sore thumb on a car ..

But yes you could ideally add a rain sensor to roll up the windows ..

I have all 4 windows up and down which is connect to the ground and the aux channel of my system/remote also I installed a disable switch which disable the windows roll up during arming the sytem feature that I can toggle during the summer when I want to arm my truck but don't want the windows to roll up however I still could roll it up or down  via aux channel on the remote  ..  My Windows module will roll down all the windows 2 inches when it get over 100 degree in the car to vent it out also ..

Bill