I have got a project to design a circuits to control and detect an external electrical circuit. The project should complete these functions as I list below.
1. I cut off external circuit and connect two broken wire terminal to a relay in my board to realize turn off/turn on external circuit. It is not a problem.
2. Detect external circuit loop status (Open/Close)
3. Detect the relay status in my PCB(On/Off)
4. All my controll circuits should be isolated to external circuits.
5. The voltage of external circuit is 24VDC/24VAC
Please review attachement. K1 is a relay of my project. Besides k1, I have to add a detection circuits to detect S1 status(if it is open/close).
All my circuits should be islolated to external circuit. The basic rule is cheap and reliable.