Local DIY Alarm System
Introduction
The alarm system runs 100% locally using Alarmo as the control panel.
It covers the front and garage side with perimeter beam sensors, followed by window sensors and internal occupancy sensors.
The alarm arms automatically when the last person leaves and disarms when someone returns based on phone location thanks to the HA app.
Once triggered, it sends a critical notification to all family members, sounds the external siren, and sounds the internal siren (iPhone 7 dashboard downstairs).
Topology
Two pairs of beam sensors cover the front and the garage part of the house.
Three of them are connected to the same 12V power supply in the garage, and the last one is alone near the bins.
A single modded Zigbee door sensor reads the signal from both beam sensor central units; it is battery-powered so it works even when the power goes down.
The system works in Normally Closed, so if someone cuts the wires, the circuit opens and the door sensor is triggered.
Hardware
Siren
Smallest and cheapest siren on AliExpress, running on 12V with 110dB of sound power.
Zigbee Smart Relay
Connected to the siren, allowing it to be smart-connected via Zigbee to Home Assistant; it sits in a wrapped and waterproofed box.
Beam Sensors
Outdoor ABT-100 Dual Beam Sensors with up to 100m of coverage via radio signal, operating on 12-24V.
They have been placed at 130cm from the ground to make it difficult to pass over or below the covered area.
Using Dual Beam sensors instead of a single beam sensor to avoid false triggers from animals, and instead of triple beam sensors because of price and dimensions.
Zigbee Door Sensor
This has been modified to act as a listener for the beam sensors since those aren't smart.
The reed switch has been removed to avoid interference with magnetic objects, and two 22AWG wires have been welded in its place; when the circuit closes, the sensor updates its state.
Final Result
The space is limited, but everything stays safely inside with no bare wires inside the flush box. The modded door sensor uses the original batteries, providing power even if there is a power outage and creating zero heat problems.