With this little tool, id like to make a simple, but efficient monitor to see if all wiring in a power socket is connected right. In general, a single phase power socket and be wired in 2 ways:

1. PHASE/PHASE/EARTH: we get 2 phases; 230V between them. If the earth is connected right, we measure 115V between both phases and earth.

2. PHASE/NEUTRAL/EARTH: we get 1 phase, 1 neutral; 230V between them If the earth is connected right, we measure 230V between phase and earth. Between neutral and earth we measure 0V.

Id like to make a circuit that detects what type of mains connection we get. Also Id like to see if the earth is properly connected. The circuit is made of 3 double coloured led's, 4 zenerdiodes and 3 1N4007 diodes.

Idea is to measure voltages between earth, neutral and phase. I use the red leds with a series resistor of 68K: 3.35mA for each led at 230V

The green led only lights up when the voltage is +211V (2 zeners 51V + 160V): 2.8mA for each led at 230V.

I keep the currents quite low to avoid the earth leak detection trips.... D5 and D6 avoid reverse currents through the leds.

If a "PHASE PHASE EARTH" socket is wired right, leds light up as follows:

L1   GREEN  (115V)
L2   GREEN  (115V)
L3   YELLOW (230V)

If a "PHASE NEUTRAL EARTH" socket is wired right, leds light up as follows:

L1   OFF (0V) or YELLOW (230V)
L2   YELLOW (230V) or OFF (0V)
L3   YELLOW (230V)

>> When earth is not connected, only L3 lights up !

I will post my prototype soon, schematics attached now!

UPDATE: I add a 1N4007 over each led, to avoid reverse (leak) currents.