How to detect Line Voltage

[Ioannis]

Anand: I have to make an extended research for the opto coupler that need the less current.

Henrik: unfortunately it will not be isolated. The voltage divider would be a good option in that case.

The other idea would be to use a small(?) relay with coil directly made for line voltage. But regarding the wasted power, it would be not so good one.

Ioannis

[dhouston]

Here is a schematic.

[Dave]

I would use a single led opto rather than a dual and put a 1N4004 diode and appropriate resistor in series with it.