with KY-038 will not work as you expect. Any loud noise,like something fall off will trigger the alarm. or other alarm fires and you thing its fire. i have one working on my visonic alarm for domoticz notify me, but its powered by mains power supply. I never used battery arduino for that because batteries just end in a few months and you think you are safe and you are not.

how much volts is the smoke sensor powered?3v from 2 AA bateries?

my bet for not drain bateries from smoke sensor itself its use a 3.3v arduino with wireless card(esp,nrf24 or rfm69,depends what you use on gateway) and make the alarm power the arduino itself. It means each time you get an smoke alarm ,the arduino is powered ,boot up and send an signal to gateway or what ever receive it. like this there are no power waste on arduino during months. you can use a transistor to power the arduino from smoke sensor bateries for exemple

Nice work. I did someting like this but much simplified. Only one temperature sensor,one soil moisture that i never used , and a 24v AC controlled by 5v DC.
Do you know that this 24v valved(our european ones )work better with low voltage dc, because don't heat up, but need a start up kick from 9v or so and then decrease it to 5v and at that voltage they hold open position and don't get hot .
Domoticz have a timer for every day on summer,and on winter is off. Soil moisture will help in case of rain but i never finish the integration of this one. Next spring i have to finish this
Thank you for sharing your project.

I changed all my radios to rfm68 exactly because poor range.probably you are on middle of a 2.4ghz signal war. Take a look on your wifi neighborhood.probably there's a lot of 2.4 signal already ,masking you small nrf24 signal.... And then all ebay ones are fake... Just make a try with 2 rfm69w and you never touch an nrf24 again.

My advise if you want upgrade and improve your domotics in your house is what i done. Domoticz,serial gateway, rfm69h and rfm69hw instead of nrf24 that i used before and replace all cards. Nrf24 have many range problems for me and the the chinise clone that are unknown quality in each order.all diferents each time i order...

My bet will be the power supply as well. i had one HC-SR501 running from battery for a few months .False triggers? every time sun comes out from a cloud! for outdoor they are crap.

Just for you know about power supplies , last project that i build a k type thermometer(for high temperatures) on my fireplace, i feed it with a HLK-PM01 and while I didn't connect negative terminal to the fireplace steel chassis(ground) , it fluctuate a lot during readings, like 20c then 45c,25 etc.. not even with a capacitor.

HUM.. nice to advise us then ..and make sense because my windwos 10 have driver updates off(and main updates off aswell…
that explains why i don't have my fake ftdi driver broken on my win 10,because i never update nothing that works,,, grrrr , i hate that Windows update and run policy…

by the way ,rollback to previews drivers and lock them from update. how to do?

if that is not enough create a rule on outgoing firewall trafic that block Windows update service and sihclient.exe from runing.

Yes ,try in other computer to be sure. I already had one windows that ftdi driver was broken(i did it trying revive an almel 34u2) and another time an Windows update (Windows 7 i think) brick all my ebay red and fake ftdi. I had to unbrick them... Nowadays i think Microsoft already don't do that.

I don 't know if it helps but i tell you my story. I had all network using nrf24l01(7or8 nodes) and i had some lost data ,random,depend day time etc... So i change all radios to rfm69 and 69hw and never had a lost packet again. Happy end

Now i have an arduino pro mini 3.3v@ 8mhz connected to raspberry by serial (usb ftdi original) managed by domoticz. Rocksolid solution until now. Its there for months (6 maybe). One of the nodes its 50 m outside,on main gate. And same node controls lights,gate open,door bell and a fence perimeter alarm(fence cutted) .Never miss a notification.

This is my solution to not have issues with radios modules
.

Erik .if you dont have a gateway or mysensors implemented in your house yet,you should do someting simple.that schetch its crazy for a new start person.
Some relays that fire by time its enouf. Wifi part that you want provably its realy Wi-Fi,not mysensors conection that its an wireless protocol,(not wifi). We are deep in summer,its not time to make a new irrigation controller from 0 and tryit