Power to doorbell / transformer in wall

[2Btoo]

Here's a nice simple job that is turning into a trickier one.

I've bought a video doorbell, which needs to be installed by the front door. It needs some volts to be applied in order to make it work, and there is a light switch immediately behind the place where it will be mounted so running a 240v supply through the wall to the doorbell will be easy. Well, that was the plan; now the thing has arrived it takes a 24v supply, with a wall-wart with it to do the magic. However plugging the thing into a wall-wart is not an option, partially as there are no sockets in the area and partially because I'm not trailing an ugly black wire up the newly-painted wall to make it work.

Here's some photos.

Wall-wart, doorbell and long fly lead.



Light switch behind front door.



Old (dead) doorbell.



The hallway is on a concrete slab so there is no option of running anything from underneath, and the room next door (to the right of the curtain) is a cloakroom so there is no real option for either electricity or mounting in there either.

So .... any bright ideas on how to make this one work?

The best idea I've had thus far is to bury a small transformer in the wall, fed from the lighting circuit on one side (there is a neutral wire) and feeding 24v through the wall out to the doorbell on the other side. This is perhaps not quite as daft as it sounds as there is already a Shelly relay in the wall behind the light switch and making this pocket bigger to take a small transformer is possible (although it will be a fight as the wall is old and made of hard bricks.)

If I do go down this route (and I'm open to other suggestions) then can anyone suggest a small 240v AC - 24v DC relay to use? Has to deliver 0.5a, so 12w. As small as possible, as this will mean minimal digging-out of aforementioned bricks. I could dismantle the wall-wart and see what's in there but that would invalidate the warranty so I'd rather not go that route just yet.

Thanks for all suggestions.

[2Btoo]

Guys,

Thanks for the answers.

Good Q about the old doorbell but it's powered with a CR2032 (which is new - the thing really is duff).

Mr Pointy, thanks for the LED driver links. Those would work but they're chunkier than I'd like and would require a fair old pocket to be dug. However I've looked for something smaller (component-sized) but not with any success.

[2Btoo]

megaphone said:

Could you run a thin wire somewhere, then fit the transformer remotely?

That's an idea, but there's not many places nearby where I could put the transformer.

119 said:

Did similar when I wired my doorbell in years ago and when the electrician came to do his stuff he ripped it out as it was against the regs because it was low voltage near mains or something like that.

I'm not that fussed about the regs to be honest. I'm familiar enough with electronics to know what's safe and what's not. The problem is just geographic - namely where to put things.

Belle427 said:

Sadly i think you just need to get a socket installed nearby if there is no chance of plugging it to an existing one or upstairs and dropping the wire down.

Not a chance; putting a socket in would be more destructive than running a thin wire remotely, and then I'd still have the problem of how to connect from the socket to the doorbell.

Slight update: having dug around in my box-of-bits I found a very promising looking wall-wart from some previous item which offered 12vDC at 2a, and small enough to bury in the wall. However having hooked it up and not having it work I re-read the specs on the doorbell and it requires 12-24vAC or 24vDC. And I don't have anything that will provide that. So, do I rip apart the wall-wart that came with it and install the guts in the wall (thus causing problems if I need to send it back) or do I spend some hours looking for a suitable driver and then wait a day or more for delivery?

[2Btoo]

Cow Corner said:

Wouldn’t it just be easier to buy a battery powered unit?

Yes, but WiFi connected battery powered units are usually unreliable, and eat batteries. And a video doorbell ain't going to be light on power.

CharlesElliott said:

You just need a bell transformer, which is what they are designed to run on. Here's an example but you might need more than 8va.

https://www.screwfix.com/p/british-general-fortres...

Personally, I wouldn't bury anything mains powered in the wall, but that's up to you.

Thanks. I get the point about not wanting mains powered things in the wall but most people have cables and lightswitches in their walls, so it ain't unusual. Plus the wall it's going in is both very old and very thick, and I think the fire risk is negligible.

megaphone said:

The problem with many of these door bells is they are designed for the US market, where they often have existing wired doorbells that run off 18vAC transformers. Often it's a straight swap. That's the reason most of them do not have a PoE input, they are designed to swap out with the older US door bells.

Not so common in the UK where if you do have any older wired door bells they are 8vAC or less.

Interesting point, thanks.

megaphone said:

Do you have cavity walls? Are they filled?

No. Old house, thick old brick walls which are a pain to chisel into. SDS drills are a good thing!

[2Btoo]

megaphone said:

Looks like you'll need to go surface then. Have a look at D Line trunking, it is rounded so can sit above or on skirting boards, doesn't look too out of place.

https://www.d-line-it.com/trunking/

That would hide the cable above the skirting, but there would still be the problem of where to plug the wall-wart in (there are no sockets anywhere near by) and also getting the cable up the wall to the point where it goes into the wall.

A small transformer mounted in a pocket cut in the wall is the best bet, and I have a transformer on order. Let's see how it works.

Thanks for your help.

[2Btoo]

Update: Job now done, with a small 240v-24vDC transformer from Amazon. This one, should anyone be interested:

https://www.amazon.co.uk/dp/B09MKVXC6D?psc=1&r...

The plan was to enlarge the pocket in the wall to accept this as well as the Shelly relay which lives behind the switch. However, while bashing away with a hammer and chisel I discovered to my immense surprise that the wall is indeed a cavity wall, with a gap between the (thick) inner wall and outer wall. This made fitting the transformer in very easy indeed, but also opens up possibilities for insulation, which could be quite good news.

Bonus points to Sheets Tabuer and Mr Pointy for these two suggestions though. Had I been less fussy about keeping the walls clear then I'd be going with one or other of them.

Sheets Tabuer said:

I put one of these on the wall:

https://www.toolstation.com/byron-wired-door-chime...

Get a 240v feed and it will output 24v, all cables hid in the wall.

Mr Pointy said:

Further ferreting has come up with a Ring DIN rail transformer housing:

https://www.amazon.co.uk/Enclosure-Ring-Rail-Trans...

Add on a 24v AC transformer:
https://www.amazon.co.uk/din-rail-transformer-2nd-...

There are lots of cheaper transformers:
https://www.amazon.co.uk/s?k=24v+din+rail+transfor...

[2Btoo]

119 said:

Nicely done sir.

Does using a third party power supply risk any warranty claims if needed in the future?

Dunno. It may, but if something stops working then I'm not planning on giving that sort of detail.

Regbuser said:

Did you tie in the new wi-fi camera to the existing chime?

Nope. The existing doorbell and chime were battery powered and comprehensively napoo. They currently grace the bin.