Retrofit Wireless Alarm System


I have an “old alarm system” (about 15 years), which has wireless motion sensors and wireless siren… ( - I cannot find an english version of it)…

The brand has now been bought by Hager ( and it has since dismissed…

Nothing wrong with the system, it has a cantral with incorporated siren, keypad, and Phone connectors (I can manage the system via phone too - wired to the home phone line)… all the sensor (including an external siren( are wireless)…

I was wondering if it is possible to retrofit the system and make it “smart/connected” so I can see status/manage the system itself with my mobile…

Any suggestion?

Many thanks


I did this with a similar old system via

Thank for the link… sorry but I am a newbie… the all alarm system in wireless… no wires from sensors/keypad/siren to the central… how can I use the suggested sensor? thanks

You need to find a pin in your central which is going high or low when the system is in alert state. You could then try to use that as an input to the Fibaro, which is a zwave module.

Edit: or maybe the central has an external input for switches or keypads which could be used to arm or disarm the system via relays …

Here is a similar topic regarding pir’s and motion sensors:

Thank you so much! you gave me some ideas!!! hopefully not too much crazy ideas :stuck_out_tongue:

I have founded a schema of my alarm system central unit and I have also took a picture of it (uploaded here)…

I apologies if my questions are silly/basics, but I really am a newbie here :stuck_out_tongue:

Let me rephrase what you have just suggested to me:

  1. I get a “binary sensor” and I connect it to the central
  2. I get a RPi (which version and model?) to rung OpenHab
  3. I make the “binary sensor” talk with the RPi via zwave

in theory I get it… but now lets try in reality :blush:

  1. which sensor/s should I get if I want to capture:
  • Change of status via OpenHab (remotely turn the alarm on/off)
  • Status of alarm (question the alarm status)
  • Alarm intrusion alert (get notification if the alarm goes off)

Do i need three binary sensors or there is something more advance (and cheaper that three sensors)?

  1. I do need a “hub” and I guess that that is done by RPi… which version should I use? ( don’t need to over-engineer this… the easier the better and probably the cheaper -> I want to retrofit, but I do not want to spend as much as I would spend with a ready to use solution)

  2. Woudl the solution works also with Google home? (my alarm system has three zones, therefore, while at home I could set the alarm on in the garage…)

  3. the circuit board of the central unit has also an Rj45 plug… not sure what is that… ides? (i do not think is the LAN connection because the allarm is about 15 year old, therefore I do not thin that there is any webserver in it…)

many thanks for the great help!


It is hard to give you any details without knowing the alarm system and I’m pretty sure you will need a multimeter to find the voltage level of the in- and outputs you are seeing in your alarm central.

In general: if you need more than one I/O the Fibaro Universal Sensor is a bad choice because it only provides an input to the openHAB system, not an output. And it gets pretty expensive if you need to buy several devices :smiley:

I would go for the ESP8266 (easiest to connect is the nodemcu version) or any other microprocessor (read the linked posts for other ideas) to connect your alarm pins to openHAB. It also can drive relays to switch your alarm state ON/OFF.
Communication between your router and the ESP is done via Wifi, the status (In and Out) is established via MQTT. Inputs up to 5V can directly be wired to the ESP pins, outputs can be done via a variety of available relays. If you need a voltage free ouput this can be done without relays.
You need to flash a new firmware to the ESP for this.

A lot of users run their openHAB on an RPi. In my opinion using it as sensor I/O is to expensive. You can have this a lot cheaper with microprocs like the ESP’s.

If you want to run openHAB on it, the latest. Mostly older models are not available anymore.


Either way: you will have to tinker and solder to get this working but I think it can be done.

This was exactly my thought when I realised that I woudl need more than one “sensor”…

this is exciting… let me understand (and sorry for the low level here, I am just a newbie, with no HW experience… only SW… but somewhere we need to start, no? :smile: )

  1. I get a nodemcu (Option1 or Option2 sorry, but do you think that are the same? ore one is better than the other?)

  2. I define the voltage of I/O in the alarm system with a voltmeter

  3. I connect nodemcu to the allarm system pins

  4. I program the nodemcu so that I can get what i need (via ARDUINO IDE)

  5. ???

I am not too sure where I need to put the openHAB (you suggested a ESP, does it need any special feature/setting?)

in case I can connect the system to google home, does it go via openHAB, or the nodemcu can connect directly to google home?

Please have patience with me… I will definitely ask stupid question :stuck_out_tongue:

Shopping list recap:

Thank heaps!


Basically yes, option 1 needs to be soldered, option 2 is ready to use and can be supplied with power via a usb charger.

If you don’t want to flash it with alternative firmware you can go the Arduino IDE way and need to program everything in LUA (including MQTT support).
In my opinion it is easier to reflash with Tasmota (good support in this forum) or ESPEasy (also some support here, and has a nice web interface for configuration).

Nope, it can not be put on an ESP. You need a computer supporting java:

A lot of people are using a RPi as their openHAB server.

Yes. You need to define items for your MQTT setup and with those items and correct tagging you can use Google Home.

Thank You! I will start with running a virtual server on my pc in order to test, then I will probably get a RPi…

Accordingly to your expertise, to try to achieve what I have described, to start my project I just need a nodemcu?

Any other HW requirements? if I use my PC for a virtual machine where I will install OpenHAB…

Many thanks!

I will read up while I will wait the nodemcu to be delivered :stuck_out_tongue_winking_eye:

forgot to mention:

which tools do I need to wire Alarm pins to the nodemcu? what wires do you recommend? what “connectors”?

want just to get all in one go :stuck_out_tongue_winking_eye: (I only have a voltmeter)

Based solely on experience with alarms of this period (i.e. guessing) - the “wired commands interface” is probably a serial RS232 port, which would allow an external system to interrogate and control the alarm. Really useful!

But sadly, unless you can get the manufacturer’s specification for the data protocol used, not much chance of exploiting that. As a security system, that is likely been made deliberately difficult.
One approach might be to find out if there is a PC application around that will talk to the alarm. You could then monitor the data traffic and figure out essential commands and data. Very tedious!

I would guess again, that the RJ45 socket is another way to the same serial port, perhaps an RS485 version. It’s not likely to be a LAN port, that would usually be an add-on option.

I don’t think you’ll be able to remotely set or unset this alarm system without this knowledge. However - if you have the installer’s manual it might describe how to control the alarm from a keyswitch instead of keypad. Such a keyswitch could be simulated by a relay under OpenHAB control.

As sihui says, there are many ways to connect two binary sensors for alarm on/off and alarm normal/ringing indication (and possible relay for alarm enable/disable). You might want to decide how your home system might develop in the future, to help choose a suitable technology here - zwave, KNX, WiFi ESP, blah.

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Good idea.

and a power supply, for example an unused usb charger. And an usb cable to program/flash it.

A piece of wire or better: jumper cables and a breadboard for testing:

Make sure you also get the female to female and female to male ones:

thanks again,

last silly question of the day… the cabel you posted are “one or the other”… right? why the [] has also a little circuit?

feel so dump in this field! sorry

Not really: you need jumper cables with a female end to connect it to the nodemcu. So buying different kinds would make send. Then you are able to connect it to the nodemcu, your alarm central and the breadboard if you need testing.

That is a power supply. If you intend to use a plain ESP chip (not the nodemcu version) you will need to connect 3.3V power to it.
The nodemcu runs on 5V, so you can power it with an usb charger.



I got it (I hope so :slight_smile: ) now time ti study :stuck_out_tongue:

first of all, I need to apologize because I might have doubled posted in the followings:

SO, lets summaries everything here:

As newbie, I’m absolutely “incompetent” in HW (my background is more SW/Solutions) and I would like to validate with this amazing community my shopping list:

  • RPi3 B+ (including Power cable and Case) -> is it better to go for a “fancier” case with fans ?

  • microSD for RPi OS -> which size would you recommend ?

  • noceMCU 1 -> ** does it required a power cable/adapter ? **

Now the fun part :slight_smile: : what else do you think I need? my thoughts says:

  • Jumper Cables (Male/Male, Male/Female, Female/Female)

  • BreadBoard for testing… (any recommendation?)

  • BreadBoard Power Supply… (I have seem lots with a rca jack plug… I probably prefer a USB one :P)

  • Volt-meter… (what specs should it have?)

  • welder (which one) ?

does it make sense to get a “starter kit” something like this:

Many thanks all,


If you live in a very hot climate zone: yes. Otherwise not really needed.

See above or

Not for the nodemcu. it is powered via usb power supply.

A simple one if it is really needed at all. Depends on a good or bad manual for your alarm central.

Around 50W, temperature controlled would be nice.

Depends on your budget. Sometimes there is useless stuff in there.

@sihui, @rossko57, @rlkoshak, @Thedannymullen

Thanks Everyone!

Finalized my shopping list:

I have passed for now multimeter (I have an old one which it should still do the job) and the solder/welder (for test the breadboard should be good enough :slight_smile:

Sorry again to be so annoying :stuck_out_tongue: Am I missing Anything?

Thanks again!

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In my experience, no project requires just one shopping trip. You will discover other stuff you need as you go.

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