help needed on high voltage project

hello everyone I'm just starting out with Arduino one of my other hobbies is model railroading and i want to incorporate Arduino with model railroading by using it for a signal system, long story short i want to use isolated track method as a detector and the track carries 18v what would i need to not fry the Arduino being that in only supports 5v thanks everyone

I'm not familiar with "isolated track", what exactly want you to do?

Hi, Google arduino model railway railroad

You will be surprised at the number of sites concerned with what you are after.

Tom.... :)

Does your model railroad use the conventional DC powering of train motor with the voltage and polarity controlling speed and direction?

Surely you need to detect whether current is flowing in the isolated length of track, not to monitor its voltage.

You may need to consider how to detect a stationary train.