I need to know what is the correct power supply for fallowing light dimmer circuit that operate by 230V/50Hz AC supply.

It should be neutral(N) to MT1 or live(L) to MT1? If can use both, what is the most suitable and what are the reasons for that?

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    \$\begingroup\$ The difference between live and neutral is that (ideally) the neutral would have no voltage on it with respect to ground. This TRIAC circuit has no connection to ground so it cannot and will not notice any difference if you swap live/neutral. It does not matter at all how you connect it. The TRIAC cannot and will not notice any difference. It only cares about the voltage and current between live/neutral and since that is AC, from the TRIAC's perspective, they're the same. \$\endgroup\$ – Bimpelrekkie May 5 '17 at 21:32
  • \$\begingroup\$ @FakeMoustache Thanks for your comment and can you tell me real word application for supply swapping cause to a problem? It may be helpful to understand your comment clearly. \$\endgroup\$ – user_fs10 May 5 '17 at 21:38
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    \$\begingroup\$ Usually the problem with swapping live and neutral is safety. If for example the circuit is connected as shown the variable resistor that is to be operated by someone will always have a fairly low voltage that is current limited by fixed resistor R1. If the insulation of the operating knob should fail and the operator touches the electrical connections it is unlikely to be dangerous. If however the connections are reversed the variable resistor will have times when it is at the AC input voltage. \$\endgroup\$ – Kevin White May 5 '17 at 22:39
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    \$\begingroup\$ Although I agree with Kevin's comment that the difference between live and neutral is mainly safety related, in practice you should not rely on the neutral to be at ground voltage and therefore safe to touch. In many installations the neutral does carry a voltage often due to poor grounding. It is best to assume both neutral and live are unsafe to touch. \$\endgroup\$ – Bimpelrekkie May 6 '17 at 14:02
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    \$\begingroup\$ When build up properly there is no real world application where swapping live/neutral matters to this circuit. As I said, the circuit does not even "know" the difference between live and neutral. So stop worrying about live/neutral, it is irrelevant. \$\endgroup\$ – Bimpelrekkie May 6 '17 at 14:05

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