wow thanks so much for your answers !
the idea of the diode is great, I dont expect to get reverse voltage but better to be save. if i finally use 2 resistors, I guess i can put the diode in also,right? just at after the 2 resistors meet.
So i could just get a 1k and 16k resistor and if the input is 80V I get 5V. I like the idea but...
I might get some voltage surges and would not like to fry my arduino, also its a good oportunity to use them for the first time. Can you help me out on how to choose the appropiate one?
thank you so much for the help, hope to be heading the electronic shop this afternoon to buy the stuff I need. Just need to figure out which optocoupler I could use.
I guess 1N4148 as diode is as good as 1N4001 or 1N4007 which I already have at home?
thanks a lot