Model train crossing signals

[LarryD]

@w8wer

What I am curious/concerned about is whether it would be safe to connect the Arduino ground to the track power supply ground (in place of the accessory power supply in the diagram) and a digital pin to the isolated section of track. The alternative would be to use the relay circuit as shown and connect a relay contact to the Arduino.

You do know the Arduino GND is connected to earth ground when you use a PC USB connector ?

Yes you can connect the Arduino GND to the track power supply GND (which is DC).

I suggest you use either an NPN transistor CE switch to the third track OR an optoisolator then to the Arduino input.

Looks like fun !