Cheap solution for Alarm Sirens with battery backup

Alarm Siren Setup

So ever since discovering I could have home assistant work double duty as a home alarm system, I’ve been looking for the best solution for a siren system.

This was my criteria:

  • Indoor and outdoor siren
  • Must have a backup battery system
  • Must not rely on wifi (as then the router would need a backup battery too)
  • Must be loud.

So I took a little punt on some products I’d been eyeing for a while and its paid off!

So here is the Kerui Wireless Alarm system components I bought:

  • J008 Outdoor Wireless Siren/strobe
  • J009 Indoor Wireless Siren/strobe
  • F8 Transmitter
  • RC531 Remote

These units operate on 433mhz.

Effectively what I have done is wired the F8 transmitter directly to the GPIO pins of my RPi. I’ve added a GPIO switch inside home assistant that triggers the transmitter. The transmitter, being paired with both the indoor and outdoor siren, then triggers the sirens based on my automations.

Both sirens have internal backup batteries too. So when they have power, the batteries are charging. If the power drops out (or is cut by burglars), they use their internal batteries. My RPi runs off a UPS so there will always be a backup system to trigger the alarm.

Kerui also make an outdoor siren with solar power, which eliminates the need for a power supply to the outdoor siren.

The cherry on the cake is the little remote, which sends different commands to the sirens (Arm, Disarm, Volume and Panic). I have taught my Broadlink RM pro these commands, so I can trigger audible tones when I am arming or disarming the alarm system. I can also choose to mute these at certain times if I wish to do so via the automations. I have also set it to “beep” as a warning for entry delay times.


  • So far distance is very good.
  • The indoor siren is not super loud even at max volume (though it does have volume control all the way down to silent).
  • The outdoor siren is super loud!
  • The outdoor siren does not have a tamper switch, however, there is a header on the board that when shorted triggers the siren directly. So I may add my own tamper switch.
  • The transmitter can also be replicated with any RF sender, or could be wired into an ESP8266 if you’re not running a RPi.


Let me know what you think, or if you have any ideas how I can improve this system.
Also happy to answer any questions anyone may have




Thanks for those who have checked out my work.

Just thought I’d post an update, as I went ahead and added the tamper switch.

I picked up a limit switch from my local electronics store and this fits without any modifications to the case (as many of these types of sirens use these as tamper switches).
I found the traces on the board that can trigger the siren and soldered two wires from there to the switch (Normally Open).

Extremely happy with the results!


Can you share your config and connection details on the transmitter to the pi?
What kind of scripts are you using, etc?
Are you using an alarm panel as well?

Very nice project.


can you also couple a co/smoke/gas sensor with your unit?
one of these ?

neo coolcam zwave siren, is an oiption too

So I’m using RP Gpio Switch to control the transmitter.


###### Alarm Siren #######

- platform: rpi_gpio
    18: Siren

I am not using an scripts, but I am using @gazoscalvertos “Yet another take on an alarm system” to frontend my alarm on my iPhone and iPad.

To trigger the sirens and notifications, I am using Node-Red automations.

In regards to the co/smoke/gas sensor - I’m pretty sure you can pair them directly to the siren, but you might need an RF receiver to directly integrate into Home Assistant (Sonoff RF bridge or RF link for example).

Let me know if you have any other questions.

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I did find these, however they are non-rechargeable, not rated for outdoor use, and only rated for ~90db. Volume wise, its like a loud speaker, rather than a piezo siren.

The Kerui gear is rated at ~110-125db, plugs into mains (as well as battery backup) and I paid about $60aud for all the Kerui gear.

Where did you get it

Banggood or AliExpress.

I got cheated by Aliexpress 2 times so I swore never buy from them for the next 40 years.
Tried Banggood and Gearbest but no luck, will search further. Thanks

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Siren and transmitter.

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Hi, thanks for doing this project.
I would like to know, if it’s possible to enable/disabled the siren battery using homeassistant.

So, I would like to buy only the transmitter and siren, and connect to GPIO of my raspberry pi, and I want to trigger the siren remotely using homeassistant.

There is a small switch on the back of the siren that disables the backup battery. You could connect an ESP8266 to it to be able to switch this on/off.

I’m interested as to why you would want the ability to do this?

After adding the transmitter to the GPIO pins of the RPi, you have a switch that can be controlled in the front end of HA. Either you can toggle this manually, or you can assign it within an automation.

It was a typo, I want only enable/disabled the siren using homeassistant.

Can you give an example of a switch calling the GPIO? Thanks

Do you know if this 433 transmitter, can be in conflit with others 433 devices?


If you refer to post #5:
Cheap solution for Alarm Sirens with battery backup

You’ll see what I use to create the gpio switch. You can then add this to your frontend via groups or Lovelace, etc.

I haven’t had any issues with the 433mhz. Though, I have been able to learn the signal using my Broadlink RM Pro, so I can actually use that instead of the transmitter to trigger the siren.
The benefit of using the transmitter, is if I lose power to the house, my RPi runs off a UPS, so the alarm can still be triggered.

hi, thanks to share your project.
I’d like to build a similar project.
I have a Xiaomi Gateway and three door/windows switches and i’d like to add a outdoor siren.
there is something in your project i don’t understand: in your case what is you trigger? do you have a door/windows sensor? in Which cases your siren switches on?
what does The remote control switch in home assistant?
how can i connect the siren transmitter to raspberry?
Sorry for my poor english…

Hi there, I hope I can answer your questions.

in your case what is you trigger? do you have a door/windows sensor? in Which cases your siren switches on?

I have a multitude of things, including Zwave PIR sensors, and xiaomi door triggers and PIRs.

what does The remote control switch in home assistant?

The remote control came with the siren. It connects to the siren directly. But it operates on 433mhz, so if you have a device that can learn RF signals (Broadlink, RFLink), you can use these device to learn the remote codes and trigger the siren that way. (So you won’t need the alarm transmitter).

how can i connect the siren transmitter to raspberry?

I have showed this in my post. I have it directly connected to the GPIO ports of the raspberry pi. Then I created a switch that turns on that GPIO pin and that triggers the transmitter.

I hope that answers your questions. :slight_smile:

Disarming the alarm with a 433MHx isn’t dangerous (possible sniffers around)?

I would normally be with you, but if your thieves are so that technically clever and waiting outside your house for you to go away, they’re obviously dead set on getting into your house. No amount of alarms and bells will stop them.


Well in any case I got the SOS remote from Neo Coolcam at 18 euros., and is Zwave so safer.

It has 4 keys, although I managed to get work only one as binary_sensor (the other 3 have to figure out what they trigger when pressed