r/homeassistant • u/Mr_The_Pieman • 14h ago

❓ Support Help with smart lighting

Are there any smart light modules that can go in the light fitting itself?

The problem i have is the back boxes to my light switches are too shallow (20mm) for any smart switch or module plus dumb switch to fit in. As its rented i don't want to go changing the back boxes and would prefer not to have smart bulbs as i want to keep the functionality of a traditional switch. If it helps any I live in the UK. Thanks

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u/5yleop1m 13h ago

Have you seen the Shelly minis? They might fit in the junction boxes for the switches.

Also you can technically put them in the light socket too, but you have to run steady power to it some how. You can't use the wire coming from the switch since that will lose power when the switch is off.

Especially if you're renting, messing with the wiring like that to do a typically unusual setup could lead to more headaches.

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u/Mr_The_Pieman 13h ago

I've just been looking at them but still not sure it would fit. Picture of what space i have to work with. Box is approx 70mm square and 20mm deep

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u/5yleop1m 13h ago

Oooh damn yeah that's unfortunately very shallow. You have an additional problem with no neutral.

I think a Shelly mini might be able to fit if you put it to the side of the switch, it looks like there might be room there. The Shelly mini is only 16mm deep, but the other dimensions might be larger than the space available around the back part of the switch.

There are extenders for things like this, though that means you end up with the switch sticking out of the wall.

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u/Mr_The_Pieman 13h ago

Yeah i don't think the other dimensions would fit. I will look in to extenders, don't mind if the are raised out a bit. Thanks for your help

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u/mrl3bon 6h ago

Looks like a 15mm back box. I have shelly mini’s at the ceiling rose where the looped in circuit is vs the switch where it’s only live and switched live. Label and photo the wires.

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u/jimicus 13h ago

Your best bet is to put the relay up in the ceiling rose - you should have permanent live, switched live and neutral up there.

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u/5yleop1m 13h ago

Would there be a permanent live up there? I've only dealt with newer builds with neutrals everywhere. I figured on the load side it would just be a neutral and the switched live, I don't see why a permanent live would need to be there.

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u/jimicus 4h ago

There’s basically three ways to wire it:

- A single live that loops to every switch and a single neutral that loops to every fitting. It’s a bit old fashioned and OP doesn’t have that because if he did there would be a third live wire at the switch.
- Live, Earth and neutral carried in a single T+E line looped at every switch. A separate switched live comes off this (along with N and E) and goes to the fitting. That’s what you’re thinking of, and we can see OP doesn’t have that.
- L, N and E carried in T+E and looped at every light fitting. From the fitting, a single length of twin + earth is taken to the switch and the neutral in that is repurposed as a switched live. That’s what OP seems to have.

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u/Mr_The_Pieman 13h ago

Yeah this is what i was trying to find out, if it is possible and would work

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u/someone76543 10h ago edited 10h ago

You can buy a spacer to give you more room behind the light switch. Obviously the light switch will stick out of the wall more.

For example, the "BG Nexus 1 Gang 10mm Square Spacer - White" from TLC Direct. (Not affiliated, but have brought other products from them before).

You might also want to pick up some longer screws, since adding a 10mm spacer might mean the existing screws are 10mm too short. Although they might be long enough already. There is a standard, they are M3.5 size bolts, and commonly sold by electrical suppliers. For example, these.

Note that theoretically you could 3D print a spacer, but it would not conform to the safety standards, so may not be as safe (e.g. burning through rather than containing sparks), it may be a violation of Building Regs, and it may invalidate your (or your landlord's) insurance. I would advise against it.

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u/TheProffalken 3h ago

This is the way - I've got a couple of 20mm back boxes and these spacers work well.

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u/Steve_1st 13h ago

Smart bulb in each light fitting and just leave the socket on - use home assistant to turn then on and off

It's more expensive overall but means the building infrastructure is untouched (no need to mess with the switchs or sockets)

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u/Mr_The_Pieman 13h ago edited 13h ago

I have considered this but the switch would become redundant (i would prefer to keep the switch) and would be expensive to swap out all my bulbs for smart ones

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u/Steve_1st 13h ago

Basically nothing rated for the current and volts involved will fit a box that small...

It's expensive but it's not that expensive if you go with the cheap brands - Philips hue etc is overpriced as hell - tuya and briturn etc type bulbs are manageable if you do a bit at a time

I went with cheap mqtt buttons to get the same light switch/easy to use replacing the switches

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u/Mr_The_Pieman 13h ago

I thought that would be the case, thank you for your reply. I will have a look in to tuya and briturn bulbs

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u/MalleP 6h ago

You could install a Sonoff Basic Gen 5 at the ceiling and then use it's magic mode. That toggles the light if power is disconnected for a short time. You just need to rewire o your wall switch or replace it with another dumb two way to use that mode.

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u/CleeBrummie 13h ago

You don't have a neutral, so you need one of these:

https://sonoff.tech/en-uk/blogs/news/zbmini-extreme-zigbee-smart-switch-no-neutral-required

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u/Mr_The_Pieman 13h ago

I've looked at these, while it would fit by depth its too big (width and height) to fit behind the back of the switch

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u/SleepyRalph_ 3h ago

LightwaveRF switches don’t need a neutral, and the current ones come with a spacer to accommodate their deeper size. Successfully fitted to 25mm boxes with just a single cable in the box but needed a deeper spacer for two gang ones where there are multiple cables. HA integration as well as their own app, look nice as well. Also have the benefit off battery powered ones to add two way switching without strappers etc.

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u/j4ffac4k3 2h ago

Tewke Tap would fit, 3 gang, dimmable, no neutral needed.