Rebuilding the DIY alarm system

Tue, 08 Sep 2026 12:15:41 +0200

I’ve decided to completely rebuild my DIY alarm system.

Mean Well UPS supply instead of C-TEK charger
Bigger battery in dedicated cabinet
Arduino Mega as core, Raspberry Pi only as MQTT relay
End-of-line resistors

The biggest change is undoubtedly moving the alarm state machine and all logic from the Raspberry Pi to an Arduino Mega. There are three main reasons for this move:

It’s fun and I’d like to work more with the Arduino
The Arduino Mega has 16 analog inputs, making it possible to use end-of-line resistors
An alarm system needs to be stable — not crash, hang or get a corrupted SD card

I’ve been thinking about end-of-line resistors since I first got started, but the Raspberry Pi doesn’t have any analog inputs. Initially I thought of using the Arduino Mega as an I/O interface device, but as I got started I figured why not let it do more.

So #RPiSecuritySystem is now #DIYAlarmSystem.

alarm-system on Cavelab

Rebuilding the DIY alarm system