DOMIX — Open Source Modular Home Automation System

The Problem

Most DIY home automation solutions are either too fragile (standalone Wi-Fi devices scattered around the house) or too expensive and complex (KNX, industrial PLCs). I wanted something in between: structured, wired, cabinet-grade — but fully open, hackable, and built by hand.

What is DOMIX?

DOMIX is a modular, DIN-rail home automation system designed for centralized control. All the logic lives inside a dedicated control cabinet. Inputs (buttons, switches, door contacts) and outputs (relays, actuators, valves) all wire back to one single point — one brain, one place to debug, one place to expand.

The system is built around a family of custom PCB modules, all mounted on standard 35mm DIN rail, connected via I2C bus, and programmed with ESPHome.

Hardware Modules

Core:

I/O Expansion:

Relay Modules:

Specialized:

Room Sensors (S family):

Standalone nodes for ceiling or wall-box installation, with mmWave presence radar (LD2410C), CO₂ (SCD41), VOC/NOx (SGP41), temperature/humidity (BME280), ambient light (BH1750), and IR transceiver. They communicate with the M1 over RS485/Modbus RTU.

Firmware

Two independent ESPHome targets:

• M firmware (ESP32-S3) — manages all cabinet I/O, relays, shutters, energy metering, OLED menu
• S firmware (RP2040) — room sensor node, exposes all readings as Modbus RTU slave

Configuration is minimal: edit `data.yaml` with your IP, MQTT credentials and I2C addresses, comment out unused modules in `main.yaml`, flash via USB-C. OTA updates for M after first flash.

Build Cost

Total BOM for a full system (all modules, enclosures, stencils, consumables): ~€420.

PCBs from JLCPCB, components from LCSC, enclosures 3D printed.

Compatibility

Works with Home Assistant (MQTT or native API), Node-RED, OpenHAB, or any MQTT-capable platform. Zigbee coordinator built into M1 — pairs directly with Zigbee2MQTT.

Why Build This?

This is not a product. It's a research platform — built to learn, built to share, built because building things is still fun.

All schematics, firmware, 3D models, and documentation are fully open source under CC BY-NC-SA 4.0.

Links