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.

@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.

@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.

@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.

@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.

@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.

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).

Have a good weekend

@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
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.

@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.

@NeverDie
That is unfortunate. Lets wait and see.

@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.

@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.