Aritech Smart Alarm

Aritech Smart Alarm

I took an old Aritech CS350 alarm from 1994 and made it smart using an Arduino.

I found a great instructable  by Ambrose Clarke (

I fitted the alarm as normal to the Garage but I also ran an ethernet cable to the garage.

This project was very easy to complete using an Arduino Uno, ethernet shield and a few stock parts.

The alarm now sends emails when the alarm goes off and the Arduino acts as an online keypad.

The Arduino mimics a keypad and the alarm panel doesn’t know any different.

I have been running it for a few weeks now and it seems to be very reliable and it is very handy to be able to control the alarm remotely. If you are building it I would recommend using a genuine Arduino Uno as I tried it first with a clone and it didn’t work but since I changed to the real one it has worked flawlessly.

I made a custom box with a fan and buck converter and I was able to use just the 4 standard keypad wires and an ethernet. I modified the code slightly to send warning emails for low battery and power failure also. The web interface doesn’t work in Chrome and I was unable to fix this but I mostly use Firefox so this is not an issue for me. Overall it is a very cheap way to make an internet connected alarm especially if you have an old panel lying around.

Panel and Arduino testing:

Closeups of Box:

Box and panel installed in attic of garage:

Online web panel:

Circuit Diagram for the board I modified from the original design:

My version of the code is available on my GitHub at

If you are interested and have any questions the original instructable is excellent and I’d be happy to answer your questions,


6 thoughts on “Aritech Smart Alarm

  1. Hello,

    I have a 25 year old Aritech model 300 IR zone detector…the red LED (lights-up) indicating movement, but the unit may not be sending a signal to the alarm panel. Do you have ANY idea how to troubleshoot it ?

  2. great project, well done!

    I think I’ll try this myself.
    Would this work with an arduino wifi shield? Would the code need to be changed much to work with the wifi shield?



    1. Hi Alan,
      In the long run this project turned out to be a bit flakey and I have since removed it and gone with a different solution.
      I dont think the code that is there would require much change to be used with a Wifi Shield.

  3. Hi, this is a cool topic. I’ve an Aritech CS350 and was searching for ways to make it smarter, so I ran in to this website. My goal would be to turn the alarm on/off remotely. Also an integration with Home Assistant would be nice. I was wondering if the old wall panels where you enter the code keep working as they do now, or does it bite with the web-based panel? Kind regards from the Netherlands, Maurice

    1. Hi Maurice,
      The old wall panels still work with this solution. The alarm sees the Arduino as another keypad.
      But this project turned out to be too flakey for me in the long run the alarm would sometimes get set off as it would lose connection the Arduino and think it was being tampered with so I have since removed it.

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