I need determine if a cable is connected to a wall-socket (230V) on the other end with a timer in-between.
Depending on how the timer is plugged in, it can either cut the phase or the neutral. If the timer is "ON", then it's quite simple by just putting a relay on the 2 AC-cables that shorts/closes another circuit. However, if the timer is "OFF", then it can cut either the phase or the neutral.
Brown is phase Blue is neutral Yellow/green is ground
My main problem is how to detect which wire at the end of the cable that is the phase or the neutral. Until that I can not perform a continuity test on the correct wires (neutral and ground) and not a voltage detection on the phase.
My first thought was to rectify the AC voltage and when given DC+ and DC-, I would make a continuity-test between ground and DC-, and a "non-contact voltage detection" on DC+. If one of them is "true", then the cable is connected. If non is "true", then the cable is not connected.
I know how to build a "non-contact voltage detector" and a "continuity-tester", but when I made a simple rectifier-bridge with 4x 1N4004 diodes I measured voltage around 100V between ground and DC- and I don't want to continuity-test on that!
So what am I missing? How can I safely make a continuity test between zero and ground on AC voltage?
Best Regards Niclas Rådström