Smart smoke alarms with dumb smoke alarms (EU/Ireland)

(Because the EU issues and devices are so different from the available US options, I have moved this thread to the UK section of the forum. Hopefully more EU members will join the discussion about possible solutions.)

I just saw @anon36505037 post in another topic, he might also have some ideas. :sunglasses:

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Actually, I was hoping you might say more about why you were using the Nest protects and if you are integrating them into SmartThings at all or not. :wink:

With serious things like fire alerts and security I wouldn’t trust something cobbled together and reliant on smartthings - it’s just not reliable enough.

Pretty sure in the UK smokes have to be hard wired together to pass building control.

Are you having a wired alarm system installed? As another poster suggested you could hook 12v smokes to that.

Otherwise they’ll be mains ones, and if you get ones with relay terminals you might be able to use one of the ESP8266 projects on the forums to pair them to smartthings but still keep the hard wired reliability.

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I never considered non-hardwired detectors. Here is the same thing: They must all talk to oneanother.

Nest uses its own proprietary protocol, “nest weave.” While similar to the open standard weave, which is based on the nest protocol, there are some differences.

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I just did that for about $43 in my house. I’m in the US but they all work the same.

Smoke / CO detectors have 3 wires, neutral and hot for power and a common wire to trigger the other detectors in the house, it’s red in the US.

I used a $13 Kiddie smoke alarm relay like this one

and a z-wave dry contact like this one

On the relay you won’t use the gray and yellow wires for this application.

To one of the smoke detectors (I used my basement unit so I did not care about hiding the relay like I would inside the house), wire the black (hot) wire from the relay with the black of your smoke alarm system, the white from the relay (neutral) to the white of your system and the red from the relay (common trigger) to the red of your system.

Then wire the blue wire from the relay (common) and the orange wire (rather salmon color) (Normally open) to the T1 and T2 connections of the dry contact (or T2 and T1, order does not matter)

In Smartthings create a (or several) custom smartapp within the Smart Home Monitor that will send you an SMS when the smoke alarm is triggered (hopefully you will never receive one). You can add other rules to that trigger, such as turning on all your lights, shutting off your furnace (I do that via the Ecobee DTH), turn on your bathroom fan to pull smoke out, turn on an outside strobe light and siren (I have that using a SmartThings plug), etc… Using the same principle, a relay (I like using the ELK-912 relay) and a dry contact, I have SmartThings triggers on a gate entry detection and a few other things.

It’s nice because it could potentially save your house from a bigger disaster as you can call the fire department right away before someone else realizes your house is engulfed in flames while you are not home.


Brilliant!!! Been waiting for a solution to the lack of integration between brands of detectors. I like the halos but the fact that it won’t trigger other alarms is a huge problem for me.

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Having a smoke alarm at home is a wise decision to make. I have adorned my smart home with the best smoke detector from Nest. It is competent to recognize smoke as well as carbon monoxide. You must check it out once.

It is mandatory in the US and I think it is now in EU as well, more than a wise decision, it is a life saver.

I would not make any assumptions that something that is either possible or legal in the US with regard to either wiring or smoke alarms will also be legal/possible in the UK.

UK does not assume that most electrical work can be done on a DIY basis the way the US does.

There are relay devices With a similar function, but you can’t use the one that was linked to and meet UK safety codes.

Instead, you have to buy smoke sensors which are designed to have the ability to have a relay added, And there will be a relay piece specifically for the purpose of connecting to external systems, and it will generally slot into the smoke sensor itself, not into the mains.

Here is just one typical example:

There are lots of these, so you just have to check the specific brand and model of smoke sensor you are interested in.

Community members from the US should be aware that these kinds of issues come up frequently in the UK discussions, so please only recommend specific devices if you have verified that they meet code in the UK. :sunglasses:

I was born and raised in Europe, everybody does DYI projects to great extent just like in the US. Some bother with code some don’t (most don’t from my personal experience), many hire pros “under the table” to avoid paying taxes, probably more than in the US. Adding a relay to an existing smoke alarm system should not bring any concern, especially this particular relay which is specifically designed to be used within a smoke alarm network normally used to hook up an alarm pull, strobe or sirens. Obviously actual models available in the UK or in Europe generally speaking may differ but the principles are the same.

Do you know if you can use the other leads from the kiddie accessory to a zwave switch to trigger the smoke detectors audio alarm contact to make the smoke alarms siren for instance if there was an intruder.

That would be a cool hack.
These specific fire alarm relays are usually used to manually trigger an alarm, for example using a pull down alarm trigger. I am not sure if they trigger the detectors to sound or if that requires wiring an external alarm to it.
I suggest you find the user manual of the relay, Kiddie or other makes and go through it. I remember there was a wiring diagram on how to wire these external triggers, also you can wire a strobe or external siren but I don’t know about triggering the detectors, If not you could try adding a bypass into the red wire. The red wire is what triggers the detectors and it sends 9 volts I believe. If you could send the 9 volts into the circuit from another trigger, it might work (probably would not be legal however).

Unfortunately , I found this post too late, it appears that the Aeon Labs ZW097 Dry Contact Sensor is not available for sale anywhere. I am looking for an alternative do you think this would work?

They told me back then that it was not a big seller and there was a chance they would discontinue it, I’ve bought a couple in advance. Any dry contact you can find will do or you can also use a door contact and short circuit the magnetic contact… solder a small wire between the two poles.

Bummer! I guess I can try that one , I can’t really find any other dry contact zwave on the market and I am not sure I can short circuit the door contact.

Sure you can.
See on that picture for example the glass part on the right between the two copper wires (on the top, not the LED) is what activates the door contact with the magnet.
So all you have to do is solder a wire on each side bypassing the glass part. You can cut it out or leave it, does not matter.

The rest is identical with the dry contact, the dry contact was just a door contact without the magnetic switch.

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I ordered the other one before seeing the post about dry contacts. Will rig it up and see how it works.

I have to say , I am not on the smarthings platform , I am a Vera user, but you guys have been most helpful! Maybe I should look at switching hubs.

Finally got the items for this project. I am struggling with determining what T1 and T2 is on my dry contact sensor . This is what it looks like.

Just to make sure I understand correctly. I have to power the dry contact using L&N.
I use the blue and orange from the SM120X to connect the 2 slots on the right of dry contact
I also connect the Black , red , white, on the SM12x to the smoke alarm

Does that sound right ?