Ok… in revision of this topic…
There are two concerns I have now that I have a working prototype…
• The 240v relay gets quite hot when the coil is energised all the time so can’t go inside a box
(I even tried mounting the relay vertically outside the box to try and reduce the heat but it didn’t really work)
• Mixing 240v a/c and signal wire in the same relay might not be the best thing to do.
So…
Power Monitoring 1.1
• 5v relay to hold N/C connection open when power is present (or Vice Versa)
• 5v PSU (Probably some kind of usb charger)
• Fibaro door sensor connected to relay (used WITHOUT the magnet)
Same app & config as before
Same setup as before but probably a little safer and less prone to interference from the mains supply.