Connected Smoke Alarms

Were you guys able to fit both the relay and the contact sensor into a regular one gang rectangular electrical box?

I hooked up both the smoke and CO relays. The relays are rather large so I took them to Lowes and found a box they would both fit in plus room for Romex wires. The best box was a deep double gang. I chose to use a separate single gang for the contact sensors and used a blank plate and screwed the sensors on to it so I had easy access to change the batteries. I could have screwed them to the double gang blank plate but I will be adding another smoke detector in several months and I wanted to make sure I had room for another Romex and didn’t want to impact the sensors hooked up.

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Awesome. I too went to lowes and ended up getting a double-gang box. This is what my final product looks like!

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I’m using a GoControl Door/Window sensor and none of the existing device handlers posted here worked with Smart Home Monitor. I was able to build a new device handler based on the original “Z-Wave Door/Window Sensor” template. I removed the Contact Sensor capability and added the Smoke Detector capability. I only modified three places in the code, the sensorValueEvent method, the simulator, and the tiles section. I just tested it with SHM and it worked as expected.


When you connect the smoke and CO relays, which I assume are the SM120X and CO120X respectively, do you connect all of the red wires from the CO relay, SM relay, and the detector together? I assume you have the combination smoke/co detector installed. Does it know only to trigger the respective relay depending on whether it’s a smoke or CO event?

Currently I only have smoke detectors, but plan on putting in the combo to replace them all in the near future and want to make sure I can get notified independently for both smoke and CO. Thanks.

Yes that is correct. When I bought my house I only had 1 wired smoke detector in my upstairs hallway. Code in my area has changed and now requires smoke detectors in all bedrooms. When I was renovating my kitchen I didn’t want to get caught up in all of that and have to pay an electrician for something I could do so I installed a wired smoke detector in all bedrooms and connected them to the hallway smoke detector in parallel: hallway to bedroom 4, bedroom 4 to bedroom 3, and so on. Then I found a way to run the wire from the attic to the crawl space below the first floor so I removed my downstairs battery hallway detector and connected it with a wired one. Long story short I knew how it was all wired together and I had easy access to the last run. The bedroom detectors are just smoke and the hallway are combination smoke and CO, all Kiddie brand. I am adding on to the back of the house which will require another smoke detector so I wanted to get this done prior and have room to add another 14-3 Romex into the box.

Since the downstairs hallway detector is at the end of the run, I ran another 14-3 Romex up into that junction box and then down into my crawlspace into 38-cu double gang box:

This particular box was the only one I could find that would fit both relays:

  • The Kiddie relays are quite long and I didn’t want to bend the wires too much
  • I wanted to have room to easily add another 14-3 Romex for my new smoke detectors with my addition
  • The back of the box is flat and requires that you use wire connectors to secure the wires coming into the box.

As mentioned above I took both relays into Lowes and tested each box until I found a fit - of course I had to explain what I was doing to the electrical dept employee since I was on that isle for quite a while. Lowes nor Home Depot carry the Kiddie relays so I just purchased from Amazon. For those of you with First Alert, I believe Home Depot may carry at least the smoke relay.

You will see the black SM120X in the back and the purple CO120X in the front (the CO120X is a little longer than the SM120X). On the right I put a 3/4 wire connector that the Romex wires will run though and into the box. Then on the left I have a 3/8 wire connector that the low voltage relay wires run out of and into a single gang box next to it. I bundled together the Romex red, black, and white wires from the smoke detector with the red, black and white wires from the relays and put a wire cap on them. The ground wire from the smoke detector is not used and is just tucked away in the back.

I have plenty of room to the right of the relays for additional wires. The SM120X does have a 9V DC output to power another device. I am not using that so I just tucked it in behind the relays and the only wires going out into the single gang are the low voltage NC, NO, and Common wires from the relays. The 9V DC output could be used to power an Arduino or something in the future ;).

In the single gang box, I connected the NC and Common wires to a small piece of 24-2 security wire I had laying around. This wire’s diameter is much smaller and easily fit into the Ecolink or Schlage contact sensors without additional drilling or alteration. You can easily use telephone wire or something small. Since I prefer to have the normal state of my contact sensor be “closed” (NC) and when tripped “open”, I just wire capped the NO wires and left them in the box. But if you prefer to have normal state be “open” and “closed” when tripped you can choose to use the NO wire instead but point being is you only need to use the common wire and NC or NO, not both.

I wanted the ability to change the contact sensor battery without having to open a gang box. I purchased a blank wall plate and drilled holes to hold the contact sensor mount and drill extra holes to run the 24-2 security wire through that is connected to the contact sensor. Both the Ecolink and Schlage contact sensors have wire terminals inside. There are reports that the Schlage doesn’t report battery, but my Ecolink appears to, though I am not 100% sure since it is still on 100% - at least I got a value of something so hoping it works.

And finally here is the finished project all closed up:

I added both contact sensors to SmartThings BEFORE installing them under the house to make sure they worked with just the magnet. Once installed I ran a zwave repair since the location changed. I ended up cloning the zwave contact sensor device handler and made my own so I could change the words “open” and “closed” to smoke/no smoke and co/no co and I also changed the image to a smoke detector.

Each time a push the test button on a smoke detector, the smoke relay will trip and report Open, though re-labeled to “Smoke”. When I press the test button on a smoke/CO combination both the smoke AND CO relays trip and reflect an open state.

Something I may consider in the future is wiring the smoke relay into my home security panel since that is also supported too.


This is awesome. Thanks for taking the time to write this!

Hi all,

In the UK we tend to have RF (non z-wave) interconnects. Would some of the ideas discussed in this thread work on a modified RF smoke alarm if I could wire a relay in?



I’m looking at doing the same thing.

I’ve got half a dozen Aico heat/smoke detectors and I intend to add a couple of wireless ones. I can then place a relay in one of them and use that to enable notifications in ST.

That what you’re thinking?

I’ve done some more investigating…

One of my (AICO) detectors has a RadioLINK base:

This enables me to test, silence and isolate using this switch, which I already have:

The rest of the detectors do seem to be hard-wired.

Aico have a RadioLINK Relay Module like this:

So I guess this relay could be connected to a z-wave device as discussed earlier on in this thread.

Make sense everyone?



That’s pretty much my intention but I have a completely hard wired system at the moment.

My installer will be adding 3 more smoke and one more heat. They will be added where I have power but where there is no comms cable present. He will be adding a Radiolink relay to an existing detector which permits the addition of the wireless detectors. He will also add a relay to a current wired detector which I will use to trigger ST.

So to answer your question, yes sounds about right :wink:

Might be better to hook the relay into something like this:

Would that work?

I was planning to use:

Looks to be a simpler solution.

Yep, simpler to setup. However the Universal Sensor can be DC powered and so no need for batteries (as with the door sensor).

Just waiting for confirmation from Vesternet (or wider confirmation on this thread!) that it will all work together and integrate into SmartThings with a little config.


I specifically bought a Fibaro binary sensor to integrate with my Aico smoke alarms. I have three alarms in the house. Building Regulations stipulate that they must be wired together in a signal sense, and power must be mains+battery. Aico are good in that you can daisy chain an additional unit that provides a volt free relay. I have one of these with the though of putting the tiny Fibaro binary sensor in. The Aico relay module (Aico Ei428) takes mains (240v) but does not present any easily accessible DC voltages inside. The fibaro sensor needs 9v and up (36v?). However, when I probe all the pads in the Aico relay box I can easily find 5v and 6v, but this is not enough. I’ve stalled on the project at the moment, but will get back to trying to find a DC supply in the Aico relay board I can tap into. Then I will have a totally enclosed smoke alarm relay board with ZWave enablement.

Again, building regulations (UK) say “Smoke alarms in all areas”, but “Heat alarms in kitchens”, so I have two of these:

AICO Ei Mains Lithium Ei166RC Optical Smoke Fire Alarm + Ei168RC Radiolink Base

and one of these:

AICO Ei Mains Lithium Ei164RC HEAT Fire Alarm Detector + Ei168RC Radiolink Base

I also have used the tiny Fibaro Binary sensors as temperature sensors and strap the heat transistor (DS18B20) to the inlet and outlet of my underfloor heating manifold.

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@DaveStoneHub sounds like you’ve done the hard work for us. Thanks for posting!

I’ve got a heat detector in the garage so I might have the relay in there where I can locate the z-wave sensor near a socket (or just use the battery).

Any easier way may be to use Leeo Smart Alert that listens for your connected smoke alarms, then triggers a virtual smoke alarm in ST via IFTTT instantly. I have this setup and works great.

I’ll be trying again to reverse engineer the circuit board in the Aico this weekend looking for that elusive 9 (or more) volts. I’ll keep the thread posted on results. I just can’t bring myself to wire in another power source into the box, just for the binary sensor. Sadly, the current (approx 10mA) demands of the sensor put it outside the scope of a battery.

Update …

Have probed/traced the Aico relay module (Aico Ei428) circuit board. It looks as though the output from the mains (240v) regulator is 5V so that’s not very helpful for the Fibaro Binary Sensor that wants 9v-30v. Have identified the tapping in points and now ordered a Pololu 9V Step-Up/Step-Down Voltage Regulator S10V3F9 (£3.60) to get the 5V up to 9V.

Getting closer…

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I think Leeo only works in the US? It’s listening for the standardized sound that smoke and co alarms make (in the US). The last several posts have been about a solution in the UK. Not sure if Leeo has a comparable product in the UK.

Success… after a false start. The step-up converter seemed to be presenting too much of a load on the board and was dropping the voltage too much. In desperation, started probing the board again and found either side of a capacitor presenting almost 12v DC. Hooked the Fibaro Universal Binary Sensor straight to this and wham, it fired up. I can now short GND to IN1 and the SmartThings Hub sees it. I’ll wire IN1 to the Normally Open (NO) contact on the relay and GND to Common ©. I’ll use heat-shrink wrap sleeving round the Fibaro UBS when I’m done just to protect it as it’s a bit naked. I’m using Stuart Buchanan’s (fuzzysb) device handler. Here’s another photo of the underside with the wiring. I’ll clean it up at some point.

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