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In our newly-renovated house the Kidde's CO2- and CO-detectors are everywhere. They are also all interconnected, which means there is a wire running throughout the house already. The detectors came straight from Home Depot - you must've seen them.

I'm wondering, what standard/protocol is used for the interconnection? Is there any chance, it is the 1-wire, perhaps? Even if not, can 1-wire devices be attached to it?

I have two immediate applications in mind:

  1. Help myself figure out, which of these bastards thinks, it detected "carbon monoxide" - when one does, it tells the others and they all begin to scream.
  2. Help identify, which one needs its backup-battery replaced - identifying, which one is beeping periodically, is currently a sport...
  3. Add cheap temperature and other sensors to the "bus" provided by the interconnect wire.
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My advice would be to not mess with your smoke/CO2 detector system, your life depends on it working. –  GdD Nov 19 '12 at 15:06
    
A stupid alarm system is worse. When it "cries wolf" too often, you stop trusting it. –  Mikhail T. Nov 19 '12 at 15:10
    
The answer there is to get it fixed, not to mess around with it. Maybe the question you should be asking is how you can stop it going off for the wrong reasons. Try vacuuming them out and replacing all their batteries first would be my advice there. –  GdD Nov 19 '12 at 15:23

2 Answers 2

First, don't use the wiring for anything else. It's a life safety system. Don't mess with things that are this critical.

Second, the signaling is simple: voltage on the line means one of the detectors has detected something.

To address your ideas:

  1. Anything but the cheapest detectors has an indicator light on the front that tells you which one has been tripped. For example, my First Alert smoke detectors have a solid red light on when it detects smoke. The el-cheapo detectors installed by the original builder did not have such and indicator light.
  2. Again, anything but the cheapest detectors has an indicator light on the front that tells you the state of the battery. On my detectors, the green light tells you the state of the battery and the line power with various blinks.
  3. Don't mess with your life safety systems.
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Some home security systems can be wired to accept smoke/CO detector inputs. One install manual says 4-wire smoke detectors. I haven't tried it. The high-end ones like a Honeywell Vista-128BP also have an RS-232 port, which you can then connect to an interface like a GC-100. http://wiki.linuxmce.org/index.php/Example_of_ultra_low-cost_X10_setup

A couple software solutions that work with security systems say they can tell you which detector is going off and what the battery levels are http://www.insteon.com/2982-222-smoke-bridge.html YMMV!

The First Alert smoke detectors with voice alerts advertise the ability to tell whether it is Fire or CO and which location, I don't know how well it works when some of them are wireless ONELINK and some are hardwired, or whether it can successfully interconnect with Kidde hardwired. Consumer Reports says heterogeneous hardwired alarms interoperate, but wireless ones don't - but I suspect interoperability may not extend to location information.

First Alert doesn't have any wireless or hardwired ionization alarms that can be interconnected and Consumer Reports and fire saftey groups recommend having both ionization and photoelectric, as well as CO. Kidde doesn't seem to report location. I'm not sure the best ones are necessarily the ones that interconnect. Some particular models (Kidde p12040 and First Alert SC07CN) seem to be very susceptible to false alarms according to Amazon reviews.

I don't know what you mean by a Carbon Dioxide detector, what models do you have? I'd think a CO2 detector would go off every time you exhale.

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