Making an external alarm siren smart

I have a SmartThings network with a number of Fibaro sensors used for home security (window sensors and PIRs). One device I’ve struggled to find is a compatible external siren. I’ve found internal sirens and I know people use a switched mains socket to activate an external siren. But I want to go a little further and have the external sired on all the time, so the LEDs are working.

I’ve bought a Honeywell external siren (HWAG6S) which a needs a 12v supply to work and needs to be continually powered to work (you interrupt the negative supply to activate the alarm), I understand I need a dry contact relay to activate this through SmartThings. Other than the expensive Fortrezz MIMOlite I haven’t found a way of doing this. Well that was until I discovered Fibaro’s FGS-222 relay switch. Whilst I think it’s intended to switch 110v or 220v the switching contacts appear dry contacts (if you don’t feed the ‘IN’ supply with 110v or 220v) -I’ve tested / proved this on the bench with a multi-meter.

So my question to the forum is… would there be any reason why I couldn’t use the Fibaro relay to activate my alarm sounder? I know I’d need to get a project box to install the 220v > 12v transformer and relay in.

This will definitely work for you.

Thanks - logically it certainly looked like it should work. I was slightly concerned about having a 12v connector right next to a 220v one.

One further question, how would I get the Fibaro relay to show as a Siren within SmartThings, is this something I need to configure in the Device Handler?


Normally it would show up as a switch with on/off capabilities. If all you want to do is change the icon, you can do that in the mobile app. If you want it to be found with alarm capabilities so it’s seen as a siren that can be tripped via smartapps like SHM, then you need to create your own DTH based off a zwave switch to add alarm capabilities.

In all honesty, since SHM and other SmartApps can trigger lights and sirens, and other things, just stick with the stock DTH and in SHM turn on the light switch you’ll have set up to actuate the siren. That way it will be local to the hub and not in the cloud.

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Thanks, I didn’t think just to use it as a simple on/off switch.

I’ve noticed the relay is an open circuit when off and a closed circuit when on, is there a way to invert the status (which is what I’d need with the siren as you need continuity on the switched neutral for no siren and you break the circuit on neutral to sound the siren).


That’s a good question, and I’m not sure about the Fibaro relay. Perhaps there’s something in their documentation that enables a parameter that makes it a normally closed relay, or a certain way you’d wire it? I’m not familiar with the Fibaro relay.

I am embarking on a very similar project.

My hope is to have a 24v IP67 Rated 110db siren with flasher alarm if my Zipato RFID is not used to Disarm the system within (Currently) 30 seconds of my Front or Patio door opening. Obviously this will only trigger the siren from an armed Away state. I have decided to go with a Sonoff Basic which is running Tasmota and should work brilliantly…

I have various Tasmota Sonoffs running my Garage door and Garage Lights and even my daughters bedroom light as she requires a flush mount due to her very high bed (and a smart bulb wont fit in the casing)…

if you need a Smartthings configurable relay which for lower voltage stuff you can use to just trigger a conventional 240v relay this is the trick… The beauty of the sonoff is if you need to trigger a 240v appliance it just goes inline and hey presto you have a wifi smart device.

I have done lots and lots of testing with Sonoff so if you need any advice or help give me a shout :smiley:

Sorry, just realised how old this post is! :open_mouth: