My awning has an angle which is too shallow; rain doesn't run off the awning but pools on the awning and stretches the fabric. To prevent this, the awning has to be retracted when it begins to rain, but this is not possible when I'm not home. The rain sensor described here automatically retracts the awning when it begins to rain.

My motorized awning is radio controlled by Somfy. What I needed was a rain sensor that is radio controlled too, in order to avoid additional wiring. Also, the awning must automatically roll up when it gets dark since I do forget this frequently. Such a radio controlled rain sensor does not exist, therefore I have built one myself. 

Capacitive rain sensor from Radiocontrolli

Resistive rain sensors are susceptible to corrosion and contamination. Capacitive rain sensors don't suffer from these disadvantages. The used sensor is from Radiocontrolli. The capacitance is 100pF in dry condition and increases in wet condition.

Code 

You can download the code at GitHub here: https://github.com/avandalen/Rain-sensor-for-Somfy-motorized-awning.

There are two versions:

• The version from me is the one that I use and it works with the board described here.
• The version from Alessandro Damiani has an improved heating control but uses another board and other pins.