Safe I/O for higher voltage?

I use solid state relays for my high voltage outputs ( either AC or DC units).
But, what is good/safe for input readings?
I want to check the voltage on solar panels. This can get up to about 18 volts.
I could use a pair of resistors as a voltage divider, but I am a little gun shy, since last year, I blew a processor when the resistor to ground got disconnected. Any other/safer suggestions?

You may be able to try a sensor such as the one in this instructable. I have never tried this personally, but there seem to be a lot of people using this setup. Check out a Google search for “arduino voltage sensor”. It definitely looks safer than a resistor voltage divider!


Some of the information in this Hackaday forum thread looks promising?

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