How to detect when normally closed circuit is opened

[johnwest80]

Fyi, here is the new thread. I created my first circuit diagram to make sure I'm clear :).

How to know if a normally closed switch is opened (switch is part of 24vac circuit)

So I need to know if S2 in the diagram below opens. I know that I don’t really want to wire it up to the photon like this, since that would, I imagine, kill it. But is there a simple way to do what I’m needing? ps. I have googled, but I can’t find an answer, or might not know if I did :). [2019-01-14_12-59-28]