Turn a dumb switch smart into another location

Ok, so i tried to sum up in the title but this definitely needs more context. I have a kitchen down light (4x GU10) with a dumb switch (UK, two wires - no neutral). I want to move the switch to another location (other side of the wall) - and rather than rewiring it into another back box I’d take the smart approach. Am still looking to use a physical switch - app is nice but there’s wife buy in factor, guests etc.

The question is - what approach would work? I am thinking to install a hidden receiver in the existing switch back box (eg a sonoff basic? or a fibaro dimmer 2?) and action it with an apparent momentary switch on the other wall. Can this be done?

Alternatively I could of course replace the lights and use a smart switch (eg hue) but I don’t need to control the bulbs individually and I’d rather only deal with the switch.

Would appreciate any insights, thanks in advance!


This might interest you. The transmitter requires no batteries. I haven’t tried it


The linked device looks almost perfect … but it needs something the kitchen junction box lacks: “UK, two wires - no neutral:frowning:

The junction box appears to be wired as a ‘switch loop’ (see diagram below). The source-neutral is at the light fixture, not the switch. Most ‘smart’ switches can’t function this way. The few that do, achieve it by (typically) leaking some current through the fixture to keep themselves powered when (ostensibly) they are off. As long as the leakage current is low enough to not illuminate the light, the trick works.

Attribution: Image appeared in this post on Stackexchange.

Switch loop


Ok, how about this http://www.smarthome.com.au/fibaro-z-wave-the-button.html

and this https://www.thesmartesthouse.com/products/fibaro-bypass-2-fgb-002

and this: https://www.thesmartesthouse.com/products/fibaro-z-wave-plus-dimmer-2-fgd-212

If you think the switch is ugly I’m sure it could be disassembled and fitted behind a standard wall plate.

Or just use the button and any of the smart globes.

Is this directly behind the existing switch, on the other side of the wall? You can use z-wave dimmers without a neutral and then either switch them from the switch input that is wired into them, or remotely via either HA or another device which you program HA to control said z-wave dimmer.

Directly behind the existing switch.

I’m a bit confused because apart from Fibaro Dimmer 2 and Aeotec Nano Dimmer I’m not finding any other 2-wire (no neutral) dimmers.

These are a tad expensive, at least in my case as I don’t need dimming (just a regular on/off switch), and the only battery-powered switch I found (on Vesternet) also has multiple functions which I don’t need. To be honest I was hoping this would cost less - the Fibaro Dimmer 2 (£40) + Z-Wave Hank Scene Controller 4 Buttons (£32) is pretty much the same as going all Hue (4x GU10 + a dimmer switch).

Is this the price we’re paying for the bloody missing neutral? :slight_smile:

Is it possible to get a neutral wire installed to that location? It would certainly open up a lot more options, cheaper ones that would offset the cost of installing the neutral wire (vs. having to use something like Hue or Z-Wave).

The way that those Z-Wave (and others) power themselves without a neutral is using the concept similar to what is detailed here. You could go the same route and use this circuit to power a NodeMCU to control the light, but I take no responsibility for your safety etc. playing with power! Basically you would leave the light switch ON so that a small current can leak through the load to power the NodeMCU which then switches the light ON and OFF via a TRIAC (using a button / switch / HA). I’m thinking of doing this myself rather than paying through the nose for more Z-Wave devices.

Another version.

EDIT: thinking about it some more I think I’ll just fork out the cash for z-wave devices and save the hassle if I need more switches…or run neutral wires

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That’s what I’ve done, wherever possible but even “wherever possible” is often a long Saturday (or entire weekend) fishing new wires in the walls. Depending on the OP’s skill set it may require a certified electrician … and the magnitude and cost of the job may be prohibitive (‘the juice not worth the squeeze’).

Referring to the ‘switch loop’ diagram above, what I’ve typically done is run a new cable from the breaker box to the light switch. So now the light switch has a new mains supply. Then (and the critical step) I disconnect the existing mains supply within the light fixture and cap the wires. If one omits this step (aside from proving oneself to be unqualified to carry out this work) it will cross-connect two circuits … and now you’re in for some bad surprises.

Our home is ~ 50 years old and switch loops were a fairly common arrangement at the time. I’ve re-wired 5 circuits and the trickiest was a 3-way light (staircase). In order to learn what was connected to where, I disconnected a whole lot of things to check their continuity. I had a detailed diagram on hand before starting the re-wiring process. I have one more to tackle and it’s the toughest of the lot (requires some ‘open-wall surgery’).

Alternately, the OP should install so-called smart bulbs, tape the light-switch in the on position, and use one or more battery-powered remote-switches to control the bulbs. The cost can’t be more than calling in an electrician to run new wiring …

@123 Have you seen the den light switches? Work the same way as you describe in your earlier post. They charge their capacitor though the leaky current and it takes about a min which has put me off. Check them out at getden.co.uk

Agreed on many points there. Currently I’m in a rental so my option was to leave the light switch ON, install smart globes, and use Xiaomi wireless buttons which are stuck to the light switch wall plate.

For another wired option, you can also disconnect the two switch wires from the light circuit (that go down the wall cavity) and use these as signally wires to a home made smart switch (eg: NodeMCU) which gets installed in the roof above the cavity. You can then run a neutral to power said switch and wire the light to a relay controlled by it, running the neutral in the roof without having to fish it down a cavity.

I haven’t but the “co.uk” suggests to me, a Canuck, the product won’t work too well on this side of the pond with our tall and narrow J-boxes and 120 VAC. :slight_smile:

FWIW, I seem to recall there was a version of SmartLinc X10 switch that used leakage current and that’s how I first learned about the technique. That’s easily over ten years ago.

Thank you everyone for your comments, really appreciated.

@bachoo786 - I have looked at den, but it seemed like a proprietary solution that only works with their app and wouldn’t take an external physical button like in my case. I didn’t notice the charging issue - are you suggesting you end up having to wait between presses? that sounds bad.

@123, @sparkydave #1 - I would consider running a neutral but don’t think I can do it myself as this particular wall is brick (load-bearing); and I can’t fathom the cost/effort of using an electrician (at South-East UK rates!) nowhere near the £70 max I’m willing pay for this one switch. Call me cheap if you want but there’s a cost/value ratio.

@sparkydave #2 - the more I think about it the more I tend to go the smart bulbs route instead, even though multiple GU10’s will quickly eat my budget (just as the long-term cost of replacing them).

  • Would this go well with a xiaomi button (which I incidentally already have)?
  • Or actually (even better?), Tradfri?
  • Any other decen GU10’s? (seeing a lot of dubious stuff on amazon…)

Thanks once again!

Lifx. Not particularly cheap. They go on sale regularly. Last sale was buy 4 get 2 free which was the best price for them I’ve seen.

They are also have excellent performance (speed to turn on) and colour. Can be used with or without their cloud server.

Indeed you have to wait for 60 seconds between presses on your phone. However physically on the switch there is no limitation as you are doing the toggle physically.

yes, I actually use them at the moment in the house I’m renting. I have them set up to provide 3 modes: ON, OFF and AUTO (motion based). They work perfectly.

Definitely consider the design I mentioned about using the existing switch wires in the wall as a signal to a NodeMCU input. This allows you to integrate smart switching for only a few quid.

Here is a rough sketch of how to do it.

I’ve disconnected the power from the light switch and the kitchen light (G9 LED bulbs) is connected to a Sonoff Pow.

Then I connected a light switch to a raspberry pi, which sends an MQTT message to tell the Sonoff to turn on or off.

This is my crude version 1, just testing it in place. It works really well.

And here’s the code https://gist.github.com/juliancheal/09054e0dd9e2baf96860d518c62c2c90

Why use that big and bulky (and expensive) raspberry with ethernet?

All you need is a Wemos D1 mini (or other esp8266 based single board wifi)
A 230v (or 110v) to 5v “brick” to leech power for the wemos
Can be done easy with esphome integration in HA, and bonus no need to do MQTT

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Cool, well as I said it was just a proof of concept, I had all the Pi already. I like the Sonoff Pow as it gives me energy readings.

Hi sparkydave,

I understand the wiring you have shown above, but for some reason cannot picture what the code would look like.
As background, I have 1 D1 mini which has 3 momentaryb switches and a multi relay (3) connected (which controls 3 separate watering solenoids). I can control the solenoid from home assistant, and I can push the switches which also shows on the switch in HA dashboard… I want to be able to press the momentary switch, which would trigger the sprinkler for 20 mins… would I just set this up as an automation to trigger the relay?

Thanks in advance.