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Sonoff smart relay - no neutral?


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Anyone have any experience with the Sonoff smart relays? I've got one to test and it requires the neutral and it works great. But I've just seen you can get some that DON'T need a neutral. How does that work then? The information is pretty sketchy but my brain can't work out how it runs with no neutral as it will surely be unpowered while the light is off.

 

Any sparkies here have an idea?

 

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I think there's a capacitor in there that stays charged when the light is "off". Also some clever circuitry that lets pulsed power through to keep it charged but not enough to put the light on. 

 

Or something like that!

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  • 2 months later...

Yes, I have used these. Very easy to install and they work faultlessly. The only downside is that without a Neutral they do not act as a "router", i.e. end point only, so they do not help to strengthen the Zigbee mesh.

Using the S1/S2 terminals wired to a normal switch causes the switch to flip the state of the relay, so everything works just as normal. The only difference is that you get a double tick sound, one from the normal switch and one from the relay, almost but not quite simultaneously.

Edited by Norbert
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20 hours ago, Norbert said:

Yes, I have used these. Very easy to install and they work faultlessly. The only downside is that without a Neutral they do not act as a "router", i.e. end point only, so they do not help to strengthen the Zigbee mesh.

Using the S1/S2 terminals wired to a normal switch causes the switch to flip the state of the relay, so everything works just as normal. The only difference is that you get a double tick sound, one from the normal switch and one from the relay, almost but not quite simultaneously.


how do you connect them? L-in live, L-out switched live. S1 to the live side of the switch and S2 the returned switched live? All my new switches have a neutral as i made it that way but my old part of the house doesnt, so these might be interesting. 

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Just connect S1 and S2 to the switch, either way around, it makes no difference. The relay just detects change of state of the switch. I imagine that there is not 230V going via the switch, something more subtle.

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