Triggering smoke alarms from the hub

I’m going to finally get around to installing a relay to bridge my hardwired smoke detectors into the hub. It got me thinking, though, has anyone spliced together a circuit to permit you to remotely trigger the alarms by dumping voltage onto the interconnect wire from a battery? According to the diagrams any 9 volt source (+ on red, - on neutral) should trigger all alarms.

I’m thinking I could use the smoke alarms as secondary sirens for the burglar system, as they are VERY loud given the number we have. Plus maybe I’d want to be able to trigger them for other reasons.

In my head at least it would be as easy as wiring a switch in with the relay so when the switch is closed it routes voltage from a 9-volt battery onto the interconnect wire.

You might end-up cheaper to buy an already done solution versus an Arduino or other MCU based solution with a wireless shield.

If your purpose is really DIY, an Arduino, some circuitry and a http POST sent from a device handler to a socket listened by the Arduino would work but I am pretty sure this is more expensive than a Siren.


I wasn’t even going to go that far. I was thinking some sort of ST compatible relay that simply closed the circuit from the battery when triggered.

Check your local city code, in most places in the United States, this would be a fire safety code violation for a residential property, because you are not supposed to use smoke detector alarms for anything except smoke detectors. The fear is that there might be a fire but the alarm wouldn’t sound because the noise was being used for something else. The specific acoustic pattern that a smoke detector makes is limited by law now to just smoke detectors. It’s just a really complicated code issue.

On the other hand, If This is in a warehouse or a farm building or a storefront, you may be able to have a single multipurpose alarm.

But for places where people sleep, a fire alarm is now supposed to be very specifically a fire alarm, which is both warning people inside the house to get out and warning people outside of the house not to go in.

It’s also supposed to help ensure that neighbors will notify the fire department for fires and not notify the fire department for burglars.

But your local city or Township can tell you what applies at your location.

Here’s the national code reference (see, I don’t make this stuff up :wink:)

the system must ensure that fire warnings are audibly distinct from other alarm sounds and take precedence, even if a non-fire warning sounds first [NFPA 72(.07)-];


Yeah, that’s not a bad point. Depending on how fast the alarms react I could make the current pulse so the alarm started and stopped every few seconds, which would still be audibly distinct. True alarms would also take precedence because then the alarms would supply constant voltage. But it’s probably not worth it…this falls into a “is it possible” Project.

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