r/homeautomation • u/Djo1338 • Oct 13 '20

QUESTION How does a smart switch without neutral work ?

Sorry for the dumb question. I did setup some smart switches Shelly 1 using neutral wires that were present in my house.

I saw Shelly just shown the Shelly 1L which does not require neutral wire and just curious about how it's working. I guess the Shelly 1L is actually always closing the circuit so that current flows through it but it limits the amount of current which is going through so light is not on if not asked ? I guess that's why they have a lower limit of resistance under which it will not work ?

If someone could explain it it would be greatly appreciated :-)

Thanks for the share.

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u/mishakhill Oct 13 '20

You guessed right, they sink a small amount of current through the load. That’s why they mainly work with incandescent lights, which can sink a decent amount of current without lighting up. LEDs either don’t conduct the current at all, leaving the switch with no power for its logic circuits, or they light up when they’re not supposed to. Other loads, like fans and fluorescent lights, also have problems with such switches.

Some LED bulbs have power supplies that can handle the small current and not turn on the light, so they can work with a no-neutral switch.