UK smart light switches

Obviously I have tinkered with smart light switches, and the like, for a long time.

You only have to look on Amazon to see a lot of different options now, but there was one simple combination that has been lacking. I have been looking for this for ages, and finally they now exists - the Shelly 1. But more on that at the end of this blog post. First a bit of background.

UK lighting circuits

One of the problems is UK lighting circuits have a live and switched live to the light switch from the light fitting. This means that, at the light switch, there is no neutral. The only way to power a "smart switch" is through the light bulb, which is not ideal. Indeed, it is not that reliable as it also depends a lot on the type of light bulb in use. This means that almost all smart light switches need the wiring changed to allow live and neutral to the light switch. In simple partition walls that is not too hard for an electrician to pull through a new cable, but it is not always so easy. The other big issue is that you almost always have to change the back box from a shallow back box to a deep one, and that can mean chiselling out some brick, etc.

Basically, fitting a smart light switch in the UK is a pain, needs an electrician to do properly (and I am not even trying to address the regulatory issues here), and costs a lot more than just the switch itself.

There are now, finally, some UK variety smart switches, e.g. DS-102L. It has a bypass capacitor to fit across the light bulb so as to allow enough in-line power for the switch. This again is fiddly for a non technical person, but saves running new wiring. I am making the huge assumption that this is valid wiring in the UK as well.

Some options

There are a few approaches to smart lights though...

  • A smart switch. But as mentioned, in the UK, this is not always easy.
  • A smart bulb. Simple, but tends to cost more (I'll not go in to these here, but Shelly do one!).
  • A smart in-line power relay in the lighting circuit.

Yet more problems

The other problem is how you control your smart light switch. Obviously some sort of app on your phone, or integration with Alexa or Siri or something. But then what?

We tried - we really did. I got a simple smart light switch, and we decided to try and get it working as intended. I have used these for years, but always re-flashed with new firmware, so trying it as sold was new for me. A (non technical) relative wanted to simply be able to work some lights, from her phone, remotely, so this seemed like a good idea. I also asked my son to try, as a new pair of eyes. No joy!

We even set up a bog standard router with NAT and WiFi (yes, NAT is evil), and still could not get the damn thing to work as intended. They come with an app, which was easy to download, but then we could not get anything to actually work. This did surprise me, to be honest.

We ended up putting a raspberry pi running MQTT (mosquitto) and a tasmota flashed in-line power plug for a lamp.

Using the Internet

The other concern I have is that these things normally use servers somewhere in the Cloud, i.e.on the Internet. No idea where. No contract in place with whoever runs the servers. No recourse if they stop working. No idea if usage patterns are logged or sold somehow. And all this relying on working Internet.

Call me old fashioned, but I like a light switch that does not rely on working Internet and someone else's server in China!

Of course this means having my own "hub" of some sort - in my case a raspberry pi and MQTT server, but this could be some "home hub" or some such.


If you have not encountered Tasmota before, do take a look. It is free open source software that runs on most of these smart switches and devices. It means re-flashing the device, and they vary in complexity from "having a header you can just plug in to with a serial lead", to "soldering bits of wire inside the switch". But once re-flashed they can be re-configured and re-programmed over the air (WiFi). As for actually flashing the code - you just need a simple serial lead and the tasmotizer app, and it is very easy.

The key thing about Tasmota is that it works using a simple standard called MQTT. Having an MQTT server in your home is cheap and easy, and can integrate with various home automation systems. It does not, then, rely on any Internet connection or third party servers. It can work with various home hub / automation systems as well.

Some options

The main three options I would consider are these. All can be flashed with Tasmota.

  • Sonoff basic: This is a neat, very cheap, in-line, 10A switch. It has live/neutral one end, and switched live / neutral the other. It has a tiny button and LED as well, which are not that useful. The main downside I have found is they have a tendency to die after a while.

  • DS-102 light switch: There are a lot of these type of smart light switches. The key thing with this particular model is that it has actual tactile micro switches behind the buttons. There are many that are capacitive, so harder to work in the dark when not looking. Some also have LEDs you cannot control. But the DS-102 seems about the best I have found so far. They come in one, two, and three gang, and as mentioned they have an option for live only, supplied with a capacitor to fit across the light fitting. One big down side is you have to solder wires to re-flash them (though people have made rigs with pogo-pins to do this).

  • Shelly 1 relay: This is what I have been waiting for! It is a relay, like the sonoff basic. It costs more than the sonoff basic, but typically less than one of the smart light switches. See below.

The Shelly 1

I have been after this for a long time - I even considered making one myself - something simple like the Sonoff Basic, but with a proper switch input. The Shelly 1 seems to be ideal for light controls in the UK.

It can go behind the light fitting in the ceiling where the live and neutral are already present, so solving the fact we don't have neutral at our light switches. But it can take the switched live as an input. Obviously it can have a default mode of operation where the switch works the light, so even no Internet or WiFi does not stop it working in the obvious way.

It has a simple header for re-flashing (please do take note of the warnings about these being at live voltages when connected to power!). So loading Tasmota is a doddle.

This means that with no extra wiring, and no changing to a deep back box, and no change of light switch to something cheap and tacky white plastic. It is easy to make a normal light fitting WiFi connected.

It is also 16A not 10A, so much more useful than the Sonoff basic (obviously for things other than lights, which get nowhere near that rating).

I have one coming today :-)

P.S. For those that have not used tasmota, you can have an input as a button or a switch. A button works toggling an output on pressing the button. A switch toggles the output on change of input. So a normal light switch would be connected in switch mode, and turn on/off when changed. If you override via MQTT you simply swap the way it works, much like a normal two-way light switch arrangement, so the switch now works in reverse until you next override.

P.P.S. Smaller than I expected - this is really neat, and can even run off 12V or 24V-60V if you need. This is exactly what I wanted!

P.P.P.S. I had not heard of Shelly before, but they have loads of cool stuff, all looks quite sane, including the simple to re-flash header, and the fact they will do MQTT anyway. Very cool. shellystore.co.uk

(Do always follow local electrical safety regulations, please)


  1. I think LightWave can be used without a Neutral wire.

    1. Still has all the other issues, and may well depend on the type of bulb in use too.

  2. Looks a lot like the Sonoff Mini. I have a couple of those running Tasmota here.

    1. Nice, I had not realised sonoff had done one too. Neat.

  3. Shelly stuff is great. I have about a dozen of them - all working flawlessly without a single issue. The nice thing is that whilst they are cloud capable, they also work entirely locally (or indeed both).

  4. I have sonoff's that have been running for the last 5 years. Not running Tasmota though.

  5. My new(ish) build (11 years) has neutral to all the light switches (thankfully), and back boxes deep enough to take the T1's - not sure if this is common practice nowadays, but it's definitely the original wiring, and no special requests for it were made during construction by Persimmon.

    1. Indeed, I think the 'default' now is to do neutral to the switch in new builds / rewires, for a few reasons:
      1. Smart kit
      2. To avoid the classic problem where a homeowner replaces e.g. a default 'pendant' light fitting with something else, and just connects all the reds/browns together and all the blacks/blues together, and wonders why it goes bang when they flick the switch, as they end up connecting the switch live to neutral and creating a short circuit!
      3. Downlights are far more common now, and running the feed to the switch avoids needing a separate junction box in the ceiling, you just have a single cable that can loop through all the downlights

  6. I asked the sparky who wired my garden office to add neutral to the light switches, he said he does that as standard now as people often want extra things added later, and it really make no difference in a new first fix...

    But it did mean he could install Sonoff T2.

    Used to run Tasmota on all my sonoff kit but moved to ESPHome ... some of the other ESP8266 (magic home LED controllers) kept crashing with Tasmota. ESPHome is great if you use home assistant as it talks directly to the controllers vs MQTT in between so you can always read the actual status of the switch. But yeah, IoT devices all on a separate SSID with no internet connectivity allowed.

    Same on the central heating system, that was carefully selected to be one that doesn't need it's cloud service running to still actually be able to control it!

  7. These are nice, I have a number of the fibaro switches, they run off zwave but they also have a double version.

  8. First, I thing that the "ever" should have been "even" in "(and I am not ever trying to address the regulatory issues here)" in paragraph 4, though either might work.

    BUT, under "Yet more problems" you said "We even set up a bog standard router with NAT and WiFi". What happened to "NAT is Evil"??!! 🙄😜

    Have you looked at https://www.home-assistant.io/ for your Raspberry Pi solution?

  9. I use the Sonoff TH16 for a number of projects. The latest version of the board exposes two GPIO pins to the 2.5 jack with built in pull-up resistors so you can use I2C.

    Also for the wireless AP / router I use a Teltonika RUT950 as it comes with a built in MQTT broker (mosquitto) keeping it simple.

    You can use rules with Tasmota to send commands directly to another Tasmota device using HTTP.

    Home Asistant will automatically detect Tasmota devices and is very useful for bridging diffrent home automation protocols

  10. Possibly a little overkill for what your after however have a look at wireless DALI

  11. A very interesting option for simple switching. I through money at Philips Hue for the rooms where I wanted 'smart' control - Dimming of each lamp in the living room is great and I've used motion sensors to the hall stairs and landing to auto switch as needed. I'll look at the Shelly 1 if I expand to simple switching elsewhere.

    There's a typo in the last paragraph of the 'UK Lighting Circuits' section by the way - Should be 'it has a capacitor' not 'it has a capacity'

    1. Typo now corrected I see :)

      I'm *fairly* sure that a bypass capacitor is OK in the UK - I had a dawn to dusk Smiths Timeguard security lightswitch around 20 years ago that needed a capacitor fitted when I swapped to a CFL bulb.


    2. There's a typo in your reply Peter. "I through money" should be "I threw money" ;)

  12. I have used Quinetic products & their app. throughout my C17 home



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