[Arduino] Display error messages of an automaton with arduino

Hi guys, I’m working on a project: it’s about an automaton which already have sensors but when there is 1 of 5 issues, only a LED start winking. So the technician lose a lot of time trying to find the issue.

I thought on a solution: connecting an arduino directly on the inputs of the automaton which are connected to sensors and then connect an LCD who will display an error message.

The thing is, the automaton operates with 24V, and the Arduino Uno allows only 5V. I think that a static relay or even only optocouplers can be enough, what do you think?