Connecting smoke detectors to house alarm



  • Hello,

    I have posted below reply to https://forum.mysensors.org/topic/1686/video-how-to-monitor-your-smoke-carbon-monoxide-alarm but never got a response so hoping somebody can help me with this.
    First of all I am a basic diy person so not much experience with electronics other than basic relays, some soldering and basic use of multi-meter.
    I have a brk smoke detectors throughout house and would like to trigger house alarm as it is connected to service that notifies me over the phone. I have looked online for information and stumbled on your video that looked similar to my needs but more so with Edward Cheung. Please advise where best to post this message as I think it may not be appropriate on mysensors.org.
    Initially I was thinking of using brk relay but it is rated for 120V AC, I am based in europe with 240V AC, I do not need to power anything with AC and I want it to work when the power is down as both smoke detectors and house alarm operate on batteries.
    I purchased the breadboard, 1k and 330 ohm resistors and 2 x PC817 4pin optocouplers without checking if my alarm is supporting normally open zones, it has normally closed options 4k7 resistor end of line and 2k2 resistor end of line and basic normally closed (breaking the circuit triggers alarm).
    Alarm zone is a 5 v DC circuit.
    hkc.png
    Question:
    Any advice on how to get output pins to stay constantly closed and change state when alarm is triggered, should I buy some other optocoupler with 6 pins that has ability to change output contacts when energized or any other approach?
    Thank you,
    Oleg



  • @vecnar so you have a smoke sensor with a normally open relay contact, and the contact closes when smoke detection is triggered. As I understand the contact is dry ( potential free).
    Your alarm system requires normally closed circuit and triggers on open circuit. (ignoring the resistor and tamper for now).
    You what to connect the two together, no mysensors stuff in between.
    Did I understand correctly?



  • Thank you for your reply, please see my comments below.

    @alexelite said in Connecting smoke detectors to house alarm:

    @vecnar so you have a smoke sensor with a normally open relay contact, and the contact closes when smoke detection is triggered. As I understand the contact is dry ( potential free).

    Smoke sensors have an interconnect wire that is used to communicate with other sensors (no voltage on it during normal operation), it uses itself and negative ac wire. There is 9 volt dc only when there is alarm (between interconnect wire and negative ac wire). So i assume what you wrote is correct.

    Your alarm system requires normally closed circuit and triggers on open circuit. (ignoring the resistor and tamper for now).

    Correct. I will use zone only for this purpose and it will only operate when alarm is set. I will not need any resistors or tamper on this zone.

    You what to connect the two together, no mysensors stuff in between.

    Correct, just some type of relay/board that wouldn't rely on ac power as both smoke sensors and alarm have battery backup, smoke sensors 9v DC and alarm has 12v DC.

    Did I understand correctly?

    Yes. Just not sure if i correctly answered your first question regarding dry contact.
    I am trying to achieve the same thing as Edward Cheung the only difference is my alarm zone is normally closed where his is normally opened and not exactly sure about zone current that can be used from alarm panel, below is a spec sheet of my house alarm.
    d6aba88a-20ac-4a2f-9363-1041ff564689-image.png


  • Hero Member

    In the United States BRK makes a relay that, if installed, is triggered when the hardwired 120v BRK smoke detectors start to alarm: https://www.brkelectronics.com/product/RM4
    Because it comes with instructions, it takes the guesswork out of it. This allows one to simply connect the relay's dry contacts to your home alarm, if that's your objective. Not sure whether BRK makes anything equivalent for the European or 240v market. Maybe contact BRK to inquire?

    I don't recall whether this solution would work if there's no AC power during a fire though. The interconnected alarms should still all sound from their built-in battery backup power, but I'm doubtful the relay would energize during an alarm if the AC had failed for some reason. If that would be a problem, you might have to consider some other solution. At least on the fact of it, the Edward Cheung solution that you linked to sounds like a good idea. What's harder to evaluate is whether it can be considered truly fault tolerant or not. You certainly wouldn't want it failing for any reason either before or during an alarm event or to in any way (including all possible failure modes) interfere with the proper operation of the interconnected smoke alarms.

    Good luck!



  • Thank you for your suggestions, please see my comments below.
    @NeverDie said in Connecting smoke detectors to house alarm:

    In the United States BRK makes a relay that, if installed, is triggered when the hardwired 120v BRK smoke detectors start to alarm: https://www.brkelectronics.com/product/RM4
    Because it comes with instructions, it takes the guesswork out of it. This allows one to simply connect the relay's dry contacts to your home alarm, if that's your objective. Not sure whether BRK makes anything equivalent for the European or 240v market. Maybe contact BRK to inquire?

    I have contacted BRK a few months ago and they are going away from European market and advised that there is no relay for 240v. I was reading about this relay before and it only operates if there is AC power available.

    I don't recall whether this solution would work if there's no AC power during a fire though. The interconnected alarms should still all sound from their built-in battery backup power, but I'm doubtful the relay would energize during an alarm if the AC had failed for some reason. If that would be a problem, you might have to consider some other solution.

    I would prefer not to rely on AC but if not possible, working on AC is better than not having any notification as power outages are rare here.

    At least on the fact of it, the Edward Cheung solution that you linked to sounds like a good idea. What's harder to evaluate is whether it can be considered truly fault tolerant or not. You certainly wouldn't want it failing for any reason either before or during an alarm event or to in any way (including all possible failure modes) interfere with the proper operation of the interconnected smoke alarms.

    Good luck!

    Thank you! I thought i will be able to use some type of relay and be done but not sure if i can operate 120v realy with 240 volt. I will not be powering anything with relay just nead to break the circuit.


  • Hero Member

    @vecnar The BRK smoke detectors are cheap. Therefore, maybe buy an extra one, wire it into the circuit just as if it were yet another BRK regular smoke alarm, but perhaps put a voltage detecting circuit across the siren leads. In this way, a voltage detection could be what triggers your home alarm system.. I know this sounds kludgy, but the motivation would be that presumably BRK already designed their circuitry to be fault tolerant. Just an idea. Obviously do your own due diligence.



  • @NeverDie
    Thank you for your suggestion, i have one smoke detector just next to alarm panel so may just as well use it for this purpose, providing voltage detect circuit just disables siren and not affect sensor itself. If I do it this way I will rely on functioning interconnect wire to hear alarm detected by that sensor through sirens of other sensors close by. Something to be aware off but as you suggested adding another one just for this purpose would be a more reliable way.
    I will test voltage used across the siren and how accessible connections are in coming days and update the post. Is there a ready made voltage detect circuit that could break 5v dc circuit of house alarm zone, i assume it will depend on voltage and current over siren?
    Thank you for helping me with this!


  • Hero Member

    @vecnar said in Connecting smoke detectors to house alarm:

    @NeverDie
    Thank you for your suggestion, i have one smoke detector just next to alarm panel so may just as well use it for this purpose, providing voltage detect circuit just disables siren and not affect sensor itself. If I do it this way I will rely on functioning interconnect wire to hear alarm detected by that sensor through sirens of other sensors close by. Something to be aware off but as you suggested adding another one just for this purpose would be a more reliable way.
    I will test voltage used across the siren and how accessible connections are in coming days and update the post. Is there a ready made voltage detect circuit that could break 5v dc circuit of house alarm zone, i assume it will depend on voltage and current over siren?
    Thank you for helping me with this!

    My first thought would be to either use a dedicated voltage detection chip or else an arduino (or equivalent) with a watchdog. Or maybe use both so as to have redundancy and avoid a single point of failure? For something related to life-safety, you don't want to take any risks at all if you can avoid it, so what might be fine for a hobbyist solution might not be the best answer for this type of application. Maybe for inspiration look into what kind of reliability testing standards apply to life-safety circuitry.

    The problem with a DIY one-off solution is: how can you ever really be sure? Perhaps through regular testing, just as with regular smoke alarms? At least with a commercial product a lot of eyes have presumably looked over both the design and the final manufactured product during a review, so any reliabiliity or quality errors are more likely to get caught rather than overlooked. For instance, how well might it cope with power surges, brownouts, and/or lightning strikes? You have to consider the worst possible case operating environment and hopefully design the circuit in such a way that if it fails, it fails into a mode that triggers the home alarm that you have monitoring it. Ideally, you'd also make the circuit in such a way that it could be monitored and perhaps even automatically tested.

    Anyhow, please do post whatever it is that you come up with. That's yet another way to get more eyes on the design to possibly reveal whether the design has any flaws or not.

    [Edit: maybe use the siren voltage to drive an opto-isolator (or similar) circuit? As a first step, that might be a very easy way to do it, plus you get the added benefits of the isolation. ]



  • @NeverDie
    Thank you for your insight into this.
    If you feel that I shouldn't proceed with this please let me know. I just hate going away and not knowing if any of smoke detectors are set off due to fire or annoying neighbors if sensor is faulty. I can check cameras remotely or ask people close by to check.
    I think one voltage detection chip is enough as I am testing smoke sensors on monthly basis (ac input and interconnect functionality) so may as well set alarm while doing one and see if it gets triggered. If it triggers house alarm during power outage it is not a problem as i can disarm/disable zone remotely if false alarm.
    I have disassembled one unit that I had laying around that was causing problems with false alarm previously and tested voltage between red and black wires connecting to siren while it was running of 9v battery and pressing test button. Voltage was jumping and the highest my multimeter showed was 4.6v DC, i cut one wire and connected multimeter in line in order to measure DC current but it wouldn't show me anything not sure if i didn't set it properly or current is just so small. Also when i was measuring voltage siren volume was 80% quieter if that makes any sense.

    I think Edward Cheung was using opto-isolator circuit with normally open zone/circuit but i need to use it with normally closed zone/circuit. So not sure how to proceed with this.


  • Hero Member

    I've heard of alarm interfaces that are more or less a microphone circuit, where the microphone is located near the smoke alarm, such that when a smoke alarm triggers, the siren goes off and then the microhone picks up the siren, which then serves as a detection which could, in your case, be connected to your alarm system panel.

    In the past I always regarded that approach as incredibly kludgy and therefore something to avoid. I still tend to think that, but it does manage to create an air gap between your alarm panel and the interconnected BRK smoke alarms.

    Anyhow I have no idea whether anything we've talked about is something you should actually do or not. For one thing, different countries may have different rules and regulations as to what is permissible.



  • @NeverDie
    Thank you for your time and all the help with this.
    I was actually thinking of using some type of relay with microphone after sending my reply yesterday but due to smoke detector location in the room with UPS and NAS that can beep it could create more false positives so need to disable those.

    I just used 2 spare smoke detectors recently due to failures and thought to buy a few extra just in case but no more for sale anywhere in europe. I started looking for new types but majority are going for RF interlink capabilities or provide RF Gateway and no simple way to trigger/interlink with house alarm.
    So microphone /sound triggered relay circuit is my only option, size is not a problem as I can place it on the top of alarm panel and power it from it just microphone cable will have to be ~1 meter to reach smoke sensor but i would prefer to leave the board with microphone on top of the panel and adjust sound levels, just not sure how effective that will be.
    https://www.aliexpress.com/item/4001010170294.html?spm=a2g0o.productlist.0.0.398e1225nICgnl&algo_pvid=493ca447-0a34-4eda-a77d-dd8a8f529791&algo_exp_id=493ca447-0a34-4eda-a77d-dd8a8f529791-2

    https://quasarelectronics.co.uk/Item/cebek-pm-14-vox-controlled-relay-switch-module-with-microphone
    Would you advice on adding a fuse between house alarm panel + power aux output and this board, like 100mA to prevent any damage to house alarm panel?

    Another option would be to install a microphone and connect it to my NAS and use some docker to monitor the sound levels and send email. The problem with this approach is time that email clients on mobile phone check for emails and if no internet connection no notification whereas my house alarm panel uses gsm network to delivery messages.


  • Hero Member

    If I'm not mistaken, an LED on the smoke alarm will illuminate when there is an alarm event. Perhaps you could just glue a photodetector over it to detect when an alarm event occurs? In essence, you'd be making a kind of optoisolator, but without making any changes to any of the smoke alarm elecctronics.



  • @NeverDie said in Connecting smoke detectors to house alarm:

    If I'm not mistaken, an LED on the smoke alarm will illuminate when there is an alarm event. Perhaps you could just glue a photodetector over it to detect when an alarm event occurs? In essence, you'd be making a kind of optoisolator, but without making any changes to any of the smoke alarm elecctronics.

    I think it is not achievable due to 2 leds side by side and their behavior. Green is on when AC is live and Red one flashes once every 45 seconds when all is ok and constantly flashes when it is the sensor that triggered sirens very fast and if i remember correctly others flash slower like once a second.
    ae3cafaf-11ac-44f6-a289-cf197140173e-image.png

    I think trying sound detector would be best as it is placed in utility room where doors are normally closed and it is in the center of the house so no external noise should trigger it (apart from fans on poe switch) if i set it correctly. Just need to order one and wait for it to arrive. Do you think below would be suitable for me, I would just extend microphone cable?
    https://www.ebay.ie/itm/122050147713?_trkparms=ispr%3D1&hash=item1c6ac17581:g:e2QAAOSwFfhXjeFN&amdata=enc%3AAQAGAAACoPYe5NmHp%2B2JMhMi7yxGiTJkPrKr5t53CooMSQt2orsSxXDXcCydCuSj2Tq2S%2F3GnlFoJ%2F%2Fg4j6zPtqbaczZyjxYp6hnurvYmPrjeWDDx9Hj6YC7SEXHV9Y3yT0WWwQ3Kcc8Ak79fTVrvlzB4r5TStd6WfP6r5HYdmzKyo49hRC49lv5vpBpNC7TkTpyE8jbQivSkO3T85XUBnAQOBoTRC7tkLe8So%2BQoL0pS7W5SP6geJL%2FlaY0g6qIAhD76dHnnU%2BlIqQM%2FYXr4Wrsqvf4y6Y8fFMpBMqItyDAQj8nYRpAQsndywQZgHO1v30u%2FG1WU7F2Mmv0D%2FqDb84U%2BKNe1VPNpTL6QJP6ioD1z%2FQjnlo4C%2BdRWai66H140EkemOQ39qelshu01nHodtanaT1Ig7as39NbxZqFs9JuDIeghLNMv11L0oOXGnfGtoJEZoNMQ9EYt0L8TGQOas4ZvOUY2Ce94WnXUKoM5NcWkrc%2B89l1Z%2Fll6Gnzl3ms%2FDqwXfIXQzf93IPHW4NmUpzv6OdFoL4UQ%2FefjUzmW7Wg3o2QvGWiOJJ6MVIlF7u3h9jm1FEfRThZjL4BhfCRKK6NRFMwVvHsNhHod5TO382s1biOIVhPyGaLToToGUDebTMSBriCJ%2FuT6Qa%2FmkZY5O1FgmWrQJneypF2I3k6GARyXVaCWwAQK4ff%2FQPFRtvdfwOMcdE5JJUDxGoDDFxvdH%2B59KZ3CtVugsx9LzNW3ec55gxOK2lkkyz23G7EtVzNv%2BJpAawhoZTRpqr17A71Q9UBZOQ7utVUKI2ba%2F4OlXzNb0ej0GXp3Iuh%2FUh2zFSxt355ekfmqu7Ahb8FPJmMhT%2FrIsAZYlZ4h29y7Gs11KvhI6PSu9eaD%2FtPLTF2NPX6NNx2dEZhHQ%3D%3D|ampid%3APL_CLK|clp%3A2334524


  • Hero Member

    That one looks very different from the model BRK sells in the US.

    Also, BRK in the US sells a model with an "escape light" that might be adapted to be an opto-isolator, like I described above, without changing any of its circuitry.

    Really though, at the end of the day, whatever works for you and your building codes, in whatever jurisdiction you're in.

    Good luck!


  • Hero Member

    By the way, I get the impression that BRK and First Alert products are the same, but just branded differently. Of course, you would want to confirm that with the manufacturer, but if true, then perhaps knowing that would expand the range of products that you can choose from:
    https://support.firstalert.com/s/article/First-Alert-and-BRK-Brands#:~:text=The same parent company (Newell,under%20the%20First%20Alert%20brand.

    I'm probably going to be upgrading my smoke detectors to the talking kind, because my experience with the cheap units is that it's very hard to quickly identify and disarm the one which triggered when you have a dozen interconnected sirens all blaring at the same time. I would have been happy with a bright blue LED or something to do that quick identification, but nooooooo, that would have made too much sense. The one question I'm not sure about is: is it even possible to hear what the alarm is saying when it's simultaneously blasting its siren at 85db? So, something I need to look into.



  • @NeverDie
    Thank you for your information about First alert. I looked online and they are selling off their stock in Europe and not manufacturing anything new. Also I didn't find one that is smoke detector only, only a mix of co and smoke detectors. I think i will have to wait and replace all of them when it is time but in the mean time I just would like to setup notification through sound detect circuit. I ordered one to try from china but it will take a while, many items I ordered previously haven't arrived so fingers crossed.

    I think manufacturers focus only on having alarm panel that they report to in enterprise and think that house owners do not mind checking all sensors.
    I read a bit on "First Alert SA511CN2-3ST Interconnected Wireless Smoke Alarm with Voice & Location" and they list within features "When one detector sounds, the other alarms sound as well, alerting you to a fire in the basement even if you are in the attic."
    Most likely all sirens beep and sound out of sync so it is a matter of distance between sensors and playback volume of the location. I saw one old video on youtube about setting up one and defining zone of the sensor, they do not play siren noise and voice of location at the same time, 3 beeps, pause, 3 beeps and zone location.
    I was reading on some forums in the past that frequent false alarms are caused by bad location and/or wrong sensor type.


  • Hero Member

    From one of the amazon reviews, 'Only the one initiating the alarm speaks the programmed room name. The other interconnected units do not announce the room name; they only sound the alarm. It seems dumb, but I replaced 11 old units in my house with this design, and when one goes off, I have to run around the house listening for the unit speaking its room name to find the one that initiated the alarm.
    By Green Gofer on November 28, 2020"
    Well, if that's the case, it doesn't seem like a great design at all. A bright LED on the triggered alarm would seem to work just as well for identifying the triggered alarm if what the reviewer says about the voice located alarms is true.

    Anyhow, I just noticed that you can buy adapter cables which allow Kiddie alarms to be plugged into a BRK sytem: https://www.firstalertstore.com/store/products/brk-kidde-smoke-alarm-adapter-plug-adk-12.htm
    I may look into this, because in general I like the Kiddie alarms slightly better than the BRK alarms.



  • @NeverDie
    Could it be that person on amazon didn't sync/link all devices together as part of the setup process? One step is to define the zone but the other is to link them together as per video on their website start at 1:16
    One Link smoke alarm installation – 02:28
    — Mayfield Village

    Thank you for finding adapters, I will have it documented in case one sensor goes down and not wanting to replace all BRK sensors.


  • Hero Member

    Good point. If the hardwired variant works the way the amazon reviewer says it does, then it would make no sense it would be rather silly. I'll look into it. What' clear is that the wireless voice location alarms do report the source of the problem:
    Interconnecting First Alert Wireless Smoke and CO2 detectors – 03:18
    — Larry Hayes


  • Hero Member

    I contacted First Alert technical support regarding SC7010BV, which is the hardwired voice location alarm, and to my surprise, they confirmed that the location is only announced on the initiating alarm, not on all the ones connected to it. This despite the fact that their actual product literature seems to imply otherwise. In fact, I read quite a few more amazon reviews for the SC7010BV-6, which is the six pack of the same version, and many of those reviews expressed great disappointment over this particular gotcha.

    This is confirmed by yet another amazon review: "I jut talked to First Alert. Although their advertisement clearly tells me that the location of the fire or CO is announced at each location of a unit: "you are alerted of the danger and where it originates throughout your house" and "tells you where … the threat is among up to 11 pre-programmed locations in your home", Fist Alert says it only announces location at the originating unit. The manual is even clearer stating that "all other installed" units give location. Very, very disappointed and feeling misled. see less
    By Kindle Customer on January 9, 2020"

    I share the disappointment, because I was nearly ready to buy some. It' surprisingly hard to find a consumer friendly hardwired smoke alarm at a reasonable price!



  • @NeverDie
    That is very disappointing and very good that you didn't buy it. Why did they even add this feature, additional setup step with no advantage.
    So wireless is better option than wired but if you have wires in your house interlinking the units why not use them, wired connection is more reliable than wireless, at least it used to be back in the days with wifi networks. But i am not an engineer and there could be some reasons why they did it.


  • Hero Member

    I have to check local code, but I may switch to wireless. You can get wireless smoke alarms with a 10 year battery life, which is the recommended life of an alarm sensor, so I think the requirement for AC power may be effectively obsolete because of technical innovation. Also, I kinda like this type of device:
    https://www.amazon.com/X-Sense-Controller-RC01-Replaceable-Interconnected/dp/B08MSQWC3B/ref=sr_1_5?dchild=1&keywords=interconnected+x-sense&qid=1631226641&s=hi&sr=1-5

    You press it once to turn off all of the alarms except for the initiating alarm. That way you can more quickly identify the initiating alarm. Then you can press it again to "snooze" the initiating alarm. No need to get on a ladder.

    The BRK alarms are fine.... until they go off. We've had numerous false alarms. I think I'm ready to switch to something better.



  • @NeverDie
    Everything is now being driven by batteries, unfortunately lithium batteries is just another thing that can create fire, that is just my association with lithium batteries after watching too many liveleak videos.
    I think the X-Sense comes with "3 V CR123A lithium battery" and they say should last for 5 years. Below is example of worst case scenario and doesn't look too bad compared to phone batteries.
    https://www.youtube.com/watch?v=fG_UuPmLO1c
    Having smoke detector on battery for 5-10 years is good way of doing it as it allows you to place sensor anywhere you want and not to depend on AC wiring.
    The only thing to check if it is possible to link more than 1 remote control, 1 for each floor/location. Possibly as you would need to get to remote first before going to check originating sensor.
    According to below website it is best to use a combination of ionization and photoelectric sensors but not sure if any have 2, I looked on a few and only photoelectric was listed.
    https://www.nfpa.org/Public-Education/Staying-safe/Safety-equipment/Smoke-alarms/Ionization-vs-photoelectric
    X-sense also has smart wifi smoke detector, I assume it still operates internally between other smoke sensors over RF 868 or 915MHZ and uses 2.4GHZ wifi network and internet connection to get to their servers and notify you on the phone. If it would depend on wifi alone power loss to Access Point would cause communication breakdown between the sensors.
    Let me know which one you will go for and your findings.


  • Hero Member

    Unfortunately, it appears that the x-sense smokes I referenced may not be adequately tested:
    https://www.firemarshals.org/resources/Documents/NASFM Documents/NASFM News Release on Non UL 217 Listed Alarms 6 8 2016.pdf

    There don't seem to be many good choices available. It might be best to wait a few years and see if anything better comes onto the market.



  • @NeverDie
    That is unfortunate. Lets wait and see.


  • Hero Member

    @vecnar said in Connecting smoke detectors to house alarm:

    @NeverDie
    Everything is now being driven by batteries, unfortunately lithium batteries is just another thing that can create fire, that is just my association with lithium batteries after watching too many liveleak videos.
    I think the X-Sense comes with "3 V CR123A lithium battery" and they say should last for 5 years. Below is example of worst case scenario and doesn't look too bad compared to phone batteries.
    CR123A Lithium Battery Fire – 00:30
    — HabboX

    Interesting find. I haven't heard of any actual non-abused lithium primary cells doing that in real life though. Have you? It has me wondering now. There's no dendrites that I know of like there are with rechargeable lithium batteries, which is the main culprit in those disasters.

    Having smoke detector on battery for 5-10 years is good way of doing it as it allows you to place sensor anywhere you want and not to depend on AC wiring.
    The only thing to check if it is possible to link more than 1 remote control, 1 for each floor/location. Possibly as you would need to get to remote first before going to check originating sensor.
    According to below website it is best to use a combination of ionization and photoelectric sensors but not sure if any have 2, I looked on a few and only photoelectric was listed.
    https://www.nfpa.org/Public-Education/Staying-safe/Safety-equipment/Smoke-alarms/Ionization-vs-photoelectric
    X-sense also has smart wifi smoke detector, I assume it still operates internally between other smoke sensors over RF 868 or 915MHZ and uses 2.4GHZ wifi network and internet connection to get to their servers and notify you on the phone. If it would depend on wifi alone power loss to Access Point would cause communication breakdown between the sensors.
    Let me know which one you will go for and your findings.

    I suppose the argument in favor of hardwired smoke alarms is that people are lazy and may not replace batteries, or might remove the batteries altogether if they were battery powered to avoid the chirping but then remount the smoke alarm (for aesthetic reasons) and then forget about it. However, as long as one doesn't do that, I think an argument can be made that battery powered smokes are actually safer because they're immune to power surges that might damage them if they were wired to mains. If that were to occur, when would it be discovered? During a weekly test? Well, if laziness is a concern, I don't think doing a weekly test is very likely. In fact, I doubt if more than a tiny minority of people do a weekly smoke alarm test, and I'm not at all sure how thorough those tests really are in terms of discovering failure modes.

    So, out of the battery powered smoke alarms, the BRK battery powered wireless interconnected smoke alarm with voice location does seem to work as expected, even if the hardwired ones don't. The Nest Protect looks even better, but the price is more than 2x as much. If I could convince myself that the Nest Protect actually did a good job of self testing itself (as it claims to), then I probably would pay up for that. So far, though, all the reviews I've seen have been far too superficial to address that question other than to say something like "It tests itself 400 times a day" or some such. Yeah, but what does that really mean? How thorough is the test, and is it really good enough? It might just be marketing puffery.

    Neither of them work with a relay that I'm aware of. However, there is a Ring Listener that listens for a smoke alarm going off. It has the virtue of being rather inexpensive:

    https://www.amazon.com/Ring-Alarm-Smoke-CO-Listener/dp/B07M93Z1NT/ref=sr_1_5?dchild=1&keywords=ring+listener&qid=1631294313&s=hi&sr=1-5

    I'm not sure if there are other listeners available. I suspect so, but I haven't looked. It might save the bother of DIYing a custom solution. Alternatively, the Nest probably sends a text to your phone in the event of a smoke detection, and that could perhaps be used to activate a separate home alarm through ITTT or similar. Maybe it can trigger something less indirect in the event of a smoke detection? If so, if it could avoid needing to DIY a solution, perhaps that might tilt the decision in favor of a Nest. However, I'd rather a solution didn't blithely assume that internet connectivity is working. Something more direct would certainly be preferable.

    P.S. BRK has OneLink, but the reviews on amazon, including nearly all recent reviews, have made it look like a terrible choice--far worse than I would have imagined, especially given its high price. For that reason, I wouldn't consider a OneLink until well after the issues raised are known to be fixed. For the price, people should be getting top quality, and it doesn't read like they are. Nearly all the most recent reviews are pretty consistently extremely negative and in stark contrast to the amazon reviews of the second generation Nest Protect, which has been on the market for quite some time now.

    P.P.S. This article refers to a number of other alarm listeners:https://www.cnet.com/home/smart-home/devices-to-help-your-smart-home-guard-against-fire/ The article is from 2016, though, and I haven't confirmed whether all of those products are still on the market or not. I did check on Halo, and they went out of business in 2018. In contrast, the Roost Battery thing actually sounds kind of interesting: https://getroost.com/sensors/ [But is it even still available? Their webstore says it's sold out] Some ebay sellers have it, but at a much higher price. And if it hinges on using a special battery.....I don't know that I'd want to be chained to that except as maybe a short-term stopgap. ]

    There's probably somethig out there that I haven't seen that might do the job. Overall, it seems like a strangely stagnant market filled with products that aren't user friendly. I presume the stranglehold that BRK and Kidde have on the American market has probably stifled innovation, at least as far as what's available here that has regulatory approval. I'd be surprised if Europe doesn't have better options than we do here in the US.


  • Hero Member

    Also, as you would expect, there are quite a few arduino alarm listening projects out there on the internet, such as:
    Simple Smoke Alarm Listening Circuit for Arduino – 11:13
    — Kevin Darrah

    I suppose the one thing to be sure about is that it triggers on the frequency of your smoke/CO alarm and not something else, like a car alarm or leak detector. If mounted nearby to the alarm siren on an interconnected system, then I'm guessing you might also want to include audio loudness as a discriminator.

    I see that you already found the mysensors opto-isolator project:
    How To - Smoke Alarm Monitoring with Arduino and MySensors – 11:01
    — Pete B

    Lastly, this is Nest Protect's argument for why they think their wireless interconnect is better than wired interconnection: https://support.google.com/googlenest/answer/9231654?hl=en

    So, though I haven't yet checked, it occurs to me that the following might work: have a single hardwired smoke alarm with wireless interconnect (BRK does make these), and maybe replace all the other smoke alarms with with battery powered wireles interconnect (BRK also makes those). Then, the question is: would the wirelessly interconnected smoke alarms trigger a BRK relay that's connected to the one hardwired smoke alarm that is also wirelessly interconnected? I'm pretty sure the answer to that would be "Yes". One possible gotcha (?) from that is that perhaps the one hardwired BRK that includes wireless interconection maybe wouldn't relay its location to the other smoke alarms if it were triggered, but, if so, maybe you could utilize that information to identify it as the triggering alarm since it would be the one occasion when the other alarms might not be able to verbally identify the source. Obviously, this is speculative and would need to be confirmed. It would be a shame if BRK disabled all the location information just because there was a single hardwired (but wirelessly interconnected) smoke detector in the mix.


  • Hero Member

    Much to my surprise, Cosumer Reports gave its highest rating of 93 to the First Alert SCO501CN, whereas it scored the Nest Protect at merely 62, because it did not perform well on either carbon monoxide or fast flame spread detection. The SCO501CN is the battery powered, wirelessly interconnected smoke and carbon monoxide detector with Voice location that I had referenced above. I think if the trade-off is between better sensors (First Alert) or better firmware (Nest Protect), I'd lean toward the better sensors, because that is more mission critical.

    Except... Gotcha. The SCO501CN it warranteed for only 7 years, and the listing says it should be replaced every 5 years to ensure an effective CO sensor: https://www.firstalertstore.com/store/products/sco501cn-3st-onelink-wireless-talking-battery-operated-smoke-and-co-alarm.htm
    which means buying two SCO501CN over a 10 year period instead one Nest Protect.



  • @NeverDie
    Wow, lots of interesting information. It took me more than a day to process it.
    My requirements/needs are a bit different and majority of the proposed solutions do not apply in my case but thank you for your time and effort sharing them with me:

    • Do not want to rely on internet connectivity or AC power. I already have alarm that can send text without internet being live or electricity being present, it is a service i pay yearly for and i had to buy mobile add-on card. So ring and nest do not apply.
    • Thanks to your advice I looked at house regulations and my house has to have wired interconnected smoke sensors, so wireless sensor is not an option for me.
    • I think arduino project is too complex for my abilities and needs as I only want to operate a relay to break the circuit when high volume is heard. But i do think filter of some type for microphone may be needed to be included to prevent false triggers with low frequency noise.

    My plan for now is

    1. I couldn't find a listener with relay, majority are wireless and for specific alarm panel, will look more into it.
    2. Test the sound/light relay switch, if it arrives
    3. If not successful try arduino alarm listening project
    4. If not successful change my requirements and look for other solutions.

    I think of programming as a layer on top of hardware and every single layer on top of hardware is just another layer where the error may occur. So because of that It is nice to have more functionality with smart devices but they should be separated, this is just my personal view on things and that is why I wouldn't like to go for nest unless somebody with knowledge in electronics does a review and says that they are independent devices inside. But on the other hand there are many functionalities that may outweigh single broken sensor failure.


  • Hero Member

    No problem. I had to look into this for my own situation anyway.

    I'm not sure what to think of the Consumer Reports test results. It may be true that some detectors detect certain kinds of fires faster than others, but if the price of that turned out to be enduring a high number of false alarms.... is that something that you'd really want? For instance, ionization smoke detectors are known to be much better at detecting fast developing fires, but they are also known to be much more prone to false alarms. AFAIK, Consumer Reports doesn't test the propensity of different smoke detectors to have false alarms. From what I've read, Nest Protect's 2nd generation smoke detector was designed to avoid some of the frequent causes of false alarms (such as insects and shower steam) that other smoke alarms may falsely trigger on, and that's something that the Consumer Reports rating doesn't factor into its numeric rating. i think I like the nest approach of giving a gentle "heads up" when it first starts to detect low levels of smoke rather than doing what most other smoke detectors do, which is doing nothing at all until a higher threshold is reached and then going straight to emergency alarm mode with sirens blaring.



  • @NeverDie
    False alarm is a big annoyance and people start to ignore it/not take it seriously. I was lucky or just strange coincidence that no neighbors reported to me when nobody was in the house and windows were closed (no draft) even with ionization smoke sensors. So based on my personal experience I do not expect too many false alarms when away from the house but i do expect them when i am around be it wife with hairdryer triggering it or steam from bathroom or shower (on rare occasions).
    It is hard to choose modes when you think of fire in confined space and time you will be alerted to either extinguish it or run away so if nest notifies at the same sensitivity as ionization sensors then I think it is good balance but it all depends on how fast someone will see/act on it.
    Lets hope none of us will have sensors triggered by fire or fail to notify us of fire.


  • Hero Member

    Seems like only way to be sure is to test it with canned smoke or similar. If there's a way for a smoke detector to automatically test itself without that, then that would be awesome. The Nest Protect says it tests itself 400 times a day, but as I wrote earlier: what does that really mean? For instance, only just that it can communicate with the sensor? If so, that would be a pretty weak test. Ideally you'd like to know that the sensor is actually working as intended and able to detect smoke in accordance with its specs. Maybe by detecting dust particles in the air it would have some insight into whether it's functioning or not? So, maybe a particle detector would make a superior smoke detector? It probably would have to run off of mains power though.



  • @NeverDie
    Please note that below is just my simple view on sensors of any type.
    I think any sensor exposed to environment will need some type or form of maintenance/cleaning or replacement. I also do not think that sensor can test itself unless there is other sensor of different type/technology monitoring other sensor.
    As you mentioned previously true way to test sensors is using smoke can from time to time as dust particles/moisture/grease may affect sensors of different types.



  • @NeverDie
    Received sound relay switch and connected to my alarm aux power in parallel with pir to supply power, added 100mA fuse on positive dc cable to prevent module making any problems with alarm panel but not sure if i was supposed to do it on negative dc wire.
    0901e07d-720d-441f-a3bc-e5c62450fc81-image.png
    Connected Normally Closed circuit to relay Com and NC contacts and adjusted sensitivity of microphone and time. Microphone is sensitive to claps but in my case it has to be a loud hand clap to trigger it. It has status led that shows when relay is activated so I can see if it is working on my monthly sensor checks.
    Looking at my original intentions I am not 100% there as I am relying on single smoke sensor and its speaker. I think I will wait a few years and maybe something will come up that has relay (not relying on internet) but in the meantime I am happy to have something working and have some peace when I am away knowing that something is monitoring it (ordered same relay module for backup).
    4db79479-aeaa-4836-9a0c-931eb612848e-image.png

    Have a good weekend


  • Hero Member

    @vecnar If I'm understanding right, your device listens for a loud sound and then triggers on that and only that. So, then the tradeoffs are you want to set the threshold low enough that it triggers whenever the alarm siren sounds, but high enough that it doesn't trigger on false events, like a car honking in the distance or possibly someone dropping something on the floor or a baby crying. Well, I imagine that would work, though you might get occasional false positives. If your device could be dialed in to only trigger on sustained loud noise, rather than bursty noise, it might cut-out the false positive of someone dropping a vase on the floor, or the like. One thing to possibly be wary of is whether there's drift in the sound threshold over time or temperature of the components in your detection device.

    Depending on how your alarm sounds, you could maybe improve on that. For instance, if it has some kind of repeating on-off-on-off pattern to the siren, then you could program an arduino to listen for that pattern specifically, instead of just purely level of loudness. I'd wager that would be quite accurate at triggering if and only if your smoke alarm sounds. Otherwise, there are projects out there where you can allegedly "teach" a sensor to identify your particular alarm's sounds.using classifiers. I happened to notice such a project was published just a few days ago: https://www.hackster.io/news/sandeep-mistry-walks-through-tinyml-audio-classification-using-tensorflow-lite-raspberry-pi-rp2040-f4065b654565



  • @NeverDie It is located in the center of the house in the room with with the doors and microphone positioned close to smoke alarm to detect noise. It is very unlikely to be triggered by anything from outside or by neighbors and it doesn't pickup low frequency noise. It only activates alarm if we set it, so nobody is at home at that time and at night time i excluded alarm zone that is connected to sound detector.
    I positioned ip camera to monitor status led and it hasn't set itself while we were inside either. So I am happy with its accuracy but as per your advice I will monitor its accuracy at different temperature ranges.
    Thank you for suggesting Arduino project to try, hopefully someone will benefit from them but in my view this just adds unnecessary layer of complexity and doesn't benefit my setup.


  • Hero Member

    @vecnar 👍 Nice job! I think that I too will mostly stick with my current smoke alarm setup until either prices on the Nest drop to parity levels or something better comes along. Kinda the "if it isn't broken, don't fix it" philosophy. If it turns out that de-dusting my smoke alarms on a regular basis provides 100% anti-false alarm protection, then I may never feel the need to upgrade at all. Meanwhile, I think I will replace my ionizing smoke alarms with photoelectric ones, since photoelectric smokes alarms are thought to have many fewer false alarms.


  • Hero Member

    @vecnar Epilog: I just now had to replace a couple of the BRK carbon monoxide / smoke alarms because they began their 7-year end-of-life chirp (5 very loud beeps that sound for every frickin minute that passes, I guess just to be sure you drop whatever you're doing and attend to it immediately 🤣 ). Anyhow, two nice surprises: 1. the replacements now cost less than the originals did, and 2. the replacement CO sensors are upgraded to last 10 years instead of only 7. So, considering BRK could have us over a barrel because of vendor lock-in, those were pleasant surprises. 😃


  • Hero Member

    Anyhow, I would say that probably everyone should watch the following youtube video, because in all likelihood, your CO detector isn't working the way you might think or imagine or hope that it is. Also, it turns out there's a strong argument for supplementing the kind of CO detectors in your house that are demanded by building code with at least one additional low-level CO detector (all of which, it turns out, will not be UL listed, because of somewhat peculiar government rules that are in play) :
    Testing UL Listed Carbon Monoxide Alarms vs. Defender Low Level Upgrade – 12:33
    — Home Performance

    i.e. when it comes to carbon monoxide detectors, being UL listed probably doesn't mean what you think it would, or should, mean. i.e. the very meaning of "UL Listed" for carbon monoxide detectors is different than what it typically is with other electrical or electronic devices.



  • @NeverDie
    I am sure it wasn't a pleasant experience and i hope it wasn't at night. Great that they do have better and cheaper replacement and no need to move to different manufacturer. It is not the case for me as BRK left Europe but i hope to start looking in a few years hopefully, if they last.
    Thank you for sharing video about carbon monoxide. I will pass it on to my friends that have gas boilers/fireplaces. I personally do not have any and all is electrical but I may get one in case surrounding houses produce too much and it gets inside our house.
    I am sure you will get at least one low level co for your house, let me know which one will you go for and your findings. I did a quick search to see if any available in europe and one has digital meter "Fireangle CO-9d" and Product Manual
    I think this if the information that may be important but to me it looks like to meet some standards but it has display which shows levels and has past 4 weeks worst level also, or so i understood.

    Between 60 and 90 minutes when
    exposed to a minimum of 50ppm of CO.
    •	 Between 10 and 40 minutes when
    exposed to a minimum of 100ppm of CO.
    •	 Within 3 minutes when exposed to a
    minimum of 300ppm of CO.
    
    

  • Hero Member

    Well, since you ask, I've been using this model as a low-level CO detector for around 20 years: https://www.kidde.com/home-safety/en/us/products/fire-safety/co-alarms/kn-copp-3/
    That because, at least at the beginning, it was one of the few that had a digital display showing the CO level. These days, there are more models which have that. It would be interesting to make a low-level mysensor CO detector/sensor.


  • Hero Member

    @NeverDie Just to clarify: not the same sensor (obviously, since they degrade with age), but the same model sensor. It's sensitive enough to detect CO in a garage and show a reading after a car starts its engine. I can't say how accurate it is, but it does manage to detect, and it displays a steady declining CO measurement after the car has left the garage.



  • @NeverDie Thank you for sharing the device you use. I am based in eu and 240 V ac and I think i will just pick one with lcd that can show the highest range even without sounding alarm. Just to check if it is of any concern to me.
    My wife got candy canes, 7 sets 2xAA battery operated modules containing 40 leds each and i am trying to find a way to power them and wire them to one power source. Reading online it looks to be over complicated with so many things to calculate. This is just a side not not relevant to this post and the reason i didn't reply to your posts.


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