Nest Hello - Doorbell Chime With Integrated Transformer UK (220-240V AC - 16V AC)




About: Hope my instructables save you some pain...

I wanted to install a Nest Hello doorbell at home, a gizmo that runs on 16V-24V AC. The standard doorbell chimes with integrated transformers currently available in the UK feed 8V to the doorbell push button, so are no good for Nest Hello.

After searching online in UK and European sites without success, I decided to make my own.

This instructable shows what I used and how I put it together, to help others that want to do the same.

DISCLAIMER: if you decide to follow these instructions, you do this at your own risk! Please be responsible and work with safety in mind!



The Chime:

First thing to find was a wired door chime that works within the same voltage range as the Nest Hello and has enough space in the casing to fit the transformer and the Nest connector.

The only compatible chimes I could find in the UK are from the Friedland range by Honeywell, as they work in the 8V-16V AC range.

From the Friedland range that work with upto 16V~ power input, I chose the Freedland D117 Ding Dong chime by Honeywell (see photo). This can be powered by 4 "C" size batteries (so loads of free space in the case), or by an external transformer with outputs between 8V and 16V, has a modern, minimal and simple design, that would suit most homes, and the cover is flat, so maximises inside space. Funny enough, the inside of the chime looks identical to the one shown on the official Nest Hello installation video, so probably a good choice.

I bought mine on Amazon, that had the lowest price I could find.


The transformer:

As Maplin is no longer around (big loss), the obvious choice was to search online for a 240V AC to 16V AC transformer. After looking for a while, I found a generic plugin one on ebay that seemed to fit the requirements (see second photo) and was posted as compatible with Freedland chimes and Nest Hello (link).

In case the posting is gone when you read this, the ebay seller was tssukcom , their ebay shop is called EZ Security Solutions (link) and the posting title was 16V AC Transformer UK 3 Pin Plug (Nest/Friedland Compatible)


Tools and other stuff:

You will also need:

  • A normal black pencil
  • Some bits of mains wire (I only used one brown and one blue bit about 15 cm long
  • Some small wire connectors (see photos) - the ones I got came on a strip of 12. I only used 3, as I soldered together some of the wire joints (more compact than connectors)
  • Insulating heat-shrink tubing or insulating tape
  • Wire-cutting pliers
  • Screwdrivers (one medium flat one, one small flat one, and one phillips)
  • A dremmel tool with a small cutting disk - ALTERNATIVE: you could also use a stanley knife(harder work)
  • A soldering iron - ALTERNATIVE: more small wire connectors
  • Thin cable ties (I used 3, worth having some more just in case)


Step 3: Getting Rid of the Transformer Case & Extending Wires

For the transformer to fit in the chime case, I had to get rid of the plug-in plastick box it came in. This needs to be done with care, to avoid damaging the internal bits you will use.


The transformer plastic casing is welded shut, so I decided to chop it open. I used the dremmel tool with the slim cutting disk (second photo) and cut through the plastic weld on all 4 corners. I then slipped the medium size flat screwdriver in the gap I just cut and twisted it to split the case open (be gentle). Idid this on all 4 sides.


I then checked which wire was connected to the neutral terminal of the plug, cut it as close to the terminal as possible using the pliers, and marked it as N (as both input wires on the transformer are blue). Then I cut the wire connected to the other terminal and freed the transformer from the case. See third & fourth photos showing the resulting item.

I then soldered the short strip of mains blue wire to the neutral wire in the transformer and soldered the short strip of mains brown mains wire to the other input wire on the transformer . You can use connectors instead of soldering, but be conscious that this will be bulkier and you will be adding more stuff to fit in the (tight) chime casing.

I then insulated the soldered joints with heat shrink tubing (you can use insulating tape instead).

For now, leave the free ends of the blue/brown mains cables with no connectors.

I then cut the transformer output cables (black / black with white line) as close to the plastic piece that prevents the cable from braking when going into the plugin black transformer case.

I then separated them and added an extension using a bit of the same cable, roughly 15cm long. I again soldered the joint and insulated it with heat shrink tubing. Doing that should hopefully give you enough flexibility to connect them to the chime and/or the cables coming from the door bell push button to suit your home's set up. You can chop any excess when connecting the chime for testing.

Step 4: Preparing the Chime Casing

Pull open the chime cover. the second photo shows what you'll see.

ATTENTION: While you work in the chime, try not to mess up the bells (the 2 metal strips on the sides, that make the ding dong noise when hit) or their mountings.

Pull out the battery connectors from both battery compartments, as you won't need them when the transformer is installed (see second and third photos).

Note that the chime is upside down on all pictures.

Place the transformer in the battery compartment of the chime case that has the big round hole, with the cables pointing to the outside edge of the case (see fourth photo).

Make sure that the transformer metal core is inside the 4 slots shown in the second photo and that there is some plastic left between the slots and the metal core.

With the pencil, trace around the metal core of the transformer, drawing it's shape on the chime case.

Step 5: Attaching the Transformer

Using the dremmel tool, cut a hole on the chime case following the pencil line. STAY AWAY FROM THE 4 SLOTS! (see 1st photo)

Test fit the transformer and fine tune the hole if necessary until the metal core fits in it. You may need to trim some plastic protrusions on the case to make the transformer sit flush over the chime case bottom.

Feed the cable tie through one of the slots from the back of the case over the metal core and back into other slot, attach on the back of the case (lot's of space there, not enough in the front).

Repeat on the other side. (see third photo for reference).

Tie the 2cable ties with a third one, to avoid them coming off the sides. Make sure the square joint is above the core, or the cover won't close. This cable tie can be loose (just keeps the others in place). See fourth photo for reference.

Step 6: Test the Chime

Note on first photo that I have fed the mains brown and blue cables to the back of the case through the oval hole. I also attahecd cable connectors on the ends of them (second photo).

Note on the first photo that the transformer output cables run upwards one on each side of the transformer.

Cut the mains power, and replace your previous chime with this one. Connect it to mains using the other end of the cable connectors (brown wire to brown wire and blue wire to blue wire).

Feed the cables coming from the door bell push button from the back to the front of the chime case, using the most convenient hole for your home's cable set up.

Connect the transformer output and the cables from the push button as per the circuit on the third photo (2-cable connection to the F and T connectors on the chime, the circuit diagram is a photo of the back of the chime retail box).

Switch on the mains.

NOTE: If the transformer hums loudly, one of your connections is not tight enough or clean enough. Cut off the mains and check all connections. Repeat until the transformer is quiet when powered.

Test the chime with the push button.

If it works normally (ding dong), you are ready to install your Nest Hello. Follow the isntructions on the Nest Hello app (not the ones in the video), selecting the version for a 2 wire connection.

If after installing and powering the Nest Hello the transformer hums loudly, one of your connections is not tight enough or clean enough. Cut off the mains and check all connections. Repeat until the transformer is quiet when powered (in my case it was the cablesconnected to the Nest Hello that were causing the humming - I had to clip a bit the wires that conecct to the Nest Hello and peel a fresh bit of wire for the connection, to stop the humming).

Hope this is helpful - GOOD LUCK!

Step 7: My Final Photos

The above photos show the working finished product in my home, after installing the Nest Hello.

They are for illustration purposes only, as your home's push button wiring set up may be different from mine.

If you are connecting the chime on it's own (i.e. no Nest components) as per the wiring diagram on the prior step, and works ok when testing it, then install the Nest Hello following the instructions in the Nest app (the ones AFTER the video) for a 2 wire installation.

As you can see, the nest wireless conector (round white bit at the top) fits snuggly in the other battery compartment, and the cover snaps on with no issues, covering everything.

Final set up is all tidily contained in the chime case.

Good louck with yours!




NOTE THAT THE CHIME IS FITTED TO THE WALL UPSIDE DOWN USING THE SLOTTED HOLES (had no choice, as the transformer is on the way of the regular fitting screw holes), AND THE CHIME TERMINALS ARE HENCE ALSO UPSIDE DOWN. I had to trim some plastic on the side of the slotted holes for the screws to fit flush.



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    5 Discussions


    2 months ago

    I would not be encouraging non-professionals to play around with the internals of a transformer - one crossed or un-insulated wire and you could risk electrocution or fire.
    Just keep the transformer external to the doorbell. For my install I drilled a hole through the wall to my garage to so the transformer could be kept out of sight.
    FYI, I first wired my doorbell without the Nest the same as the diagram on the right in this attached picture.

    then followed the Nest App instructions for a two wire install (even though there are three terminals connected). This re-routes the wires on terminals F and T through the supplied Nest adaptor. This seems to be working well for me.


    Question 5 months ago on Step 4

    great instructions

    I used a separate transformer

    not clear on your final picture how you wired

    I followed the instructions that came with the ding dong

    wired the nest hello to 0 and 1

    Transformer to 1 and 3

    all works, slight buzz - checked all connectors

    But if I turn on chime in nest and activate, chime buzzes loudly afterwards and chime connector gets hot

    How did you attach your wires?


    1 answer

    Reply 4 months ago

    There are 2 wiring schematics in the back of the box. I used the 2 wires to chime version ( see photo above), then followed the instructions for a 2 wired connection in the Nest app. The ones AFTER the video...


    Question 4 months ago on Introduction

    Brilliant post, I'm glad I came across it. I have a question for you - after some time using your setup, have you had any issues or concerns with how it all works? For example, have there been any outages? Does the transformer make a humming noise? Does the transformer get hot?

    If you had to do it again, would you use the same approach or do something else?

    I think these answers would really help me, and hopefully others who read your post too.

    1 answer

    Reply 4 months ago

    All still working, no issues. There are no chimes with integrated transformers at that voltage yet, so would probably do the same...