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

I found a great instructable  by Ambrose Clarke (http://www.instructables.com/id/House-Alarm-Internet-Dialer-With-Arduino-Reverse-E/)

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 https://github.com/conorwalsh/CastleAritechArduinoRKP.

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

Conor.