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DOMIX is a real open-source hardware and software project for centralized, DIN-rail home automation. It is built around an ESP32-S3 controller, modular cabinet I/O boards, wired Ethernet, RS485 room sensors, optional Zigbee, and ESPHome firmware.
For a new build or major renovation, DOMIX can be an interesting way to create a low-voltage, serviceable control cabinet. It is not, however, a certified plug-and-play product, a replacement for a mains distribution board, or a turnkey alternative to KNX or industrial PLC equipment. It is best suited to technically capable builders who are comfortable fabricating electronics, maintaining firmware, and involving qualified electricians where required.
What problem is DOMIX trying to solve?
Many DIY smart homes consist of numerous Wi-Fi devices distributed throughout a property. That approach is quick to install, but it can create a fragmented system of power supplies, wireless dependencies, proprietary hardware and difficult-to-maintain devices.
DOMIX takes the opposite approach. Its design brings much of the control logic and input/output hardware into a dedicated cabinet. Wall switches, door contacts, sensors, relays, valves and other field devices can be wired back to a central location. The intended benefits are clearer organization, easier cabinet-level servicing and straightforward expansion.
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The trade-off is substantial: centralization must be planned before walls and ceilings are closed. It requires cable routes, cabinet space, labeling, low-voltage distribution and careful separation from mains wiring. DOMIX is therefore much easier to justify in a new-build or major renovation than in a finished home.
The project describes itself as a research and educational platform. Its documentation warns that it is not certified for production use and that electrical work and compliance with local regulations remain the builder’s responsibility. See the DOMIX repository for the project’s current documentation.
What DOMIX is—and is not
DOMIX is
- An open-source modular hardware ecosystem.
- A DIN-rail cabinet architecture for low-voltage control and monitoring.
- A collection of custom PCBs, expansion modules and firmware targets.
- An ESPHome-based system that can integrate with Home Assistant, MQTT, Node-RED and OpenHAB.
- A platform for combining conventional switches, sensors, relays, irrigation and energy monitoring.
DOMIX is not
- A finished consumer product with a normal retail supply chain.
- A replacement for the property’s mains electrical distribution panel.
- A certified safety-control system.
- A turnkey KNX installation or industrial PLC.
- Permission to switch mains loads without suitable protection, enclosures, wiring design and qualified installation.
The DOMIX cabinet is intended to be separate from the electrical power panel. Even where a module’s documentation states a relay rating such as 10 A at 250 VAC, that number is not installation approval and does not prove suitability for every appliance or jurisdiction.
How the architecture works
Wall switches / contacts / actuators
│
Central control cabinet
│
M1 ESP32-S3 controller
├── I2C M-series modules
├── RS485 room sensors
├── Ethernet / MQTT
└── optional Zigbee
│
Home Assistant / Node-RED / OpenHABDOMIX is not simply “wired instead of wireless.” It combines several communication layers:
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- Ethernet: the primary network connection for the cabinet controller.
- I2C: short internal connections between the central controller and cabinet expansion modules.
- RS485/Modbus RTU: a wired field link for S-series room sensor nodes.
- Zigbee: an optional radio path for compatible devices.
- MQTT or the ESPHome/Home Assistant API: integration with higher-level automation software.
The M1 core and gateway
The M1 is the central controller. The project documentation lists an ESP32-S3-WROOM-1-N8R2 microcontroller, a W5500 10/100 Mbps Ethernet controller, a CC2652-based Zigbee module, RS485 using a MAX13487E transceiver with transient protection, and a 9–12 V DC power input.
Internally, the board provides 5 V and 3.3 V rails. It has two I2C buses, with expansion to as many as eight through an I2C multiplexer. An optional 1.3-inch, 128×64 SH1106 OLED can provide local status information and controls.
These are project design specifications, not a production datasheet or certification guarantee. Hardware revisions and component availability should be checked in the current repository before a build is committed.
M-series cabinet modules
The M-series modules provide the cabinet’s inputs, outputs and specialist functions:
| Module | Main purpose | Project-documented capability |
|---|---|---|
| M1 | Core and gateway | ESP32-S3, Ethernet, Zigbee, RS485 and I2C |
| M2 | General-purpose I/O | Eight inputs and eight outputs |
| M3 | Door and window contacts | Sixteen-channel analog contact input design |
| M4 | Relay output | Six relays, documented as 10 A at 250 VAC |
| M5 | Relay output | Twelve relays, documented as 10 A at 250 VAC |
| M6 | Energy monitoring | Ten-channel current-clamp meter |
| M7 | Digital output | Sixteen outputs |
| M8 | Digital input | Sixteen inputs |
| M9 | Irrigation | Eight-zone sprinkler controller with 24 VAC output |
| S1/S2 | Room sensing | Presence, temperature, humidity, CO2, VOC, light, display and IR options |
The capacities above come from DOMIX project documentation. They should not be treated as independently verified safety ratings. Relay suitability depends on the load, inrush current, protection, wiring, enclosure, clearances and local regulations.
S-series room sensors
S1 and S2 are separate room-node designs based on an RP2040. They can combine environmental and presence sensing with options such as temperature, humidity, CO2, VOC, light, a display and infrared control. The nodes communicate with an M controller over RS485/Modbus RTU rather than relying on whole-home Wi-Fi.
Wiring, addressing and installation planning
Internal module connections use eight-pin IDC flat cables and communicate over I2C. The project documentation identifies address regions including:
0x20–0x27for certain PCA9554A/PCA9535 devices;0x38–0x3Ffor PCA9554A, PCF8574 and PCA9535 devices;0x48–0x4Bfor ADS1115 ADC devices.
An example allocation is:
M1: Core, no address
M2 #1: 0x20
M2 #2: 0x21
M4: 0x38
M3: 0x39 + ADS1115 at 0x48Duplicate addresses can prevent modules from operating correctly, so the address plan should be agreed before assembly. I2C is convenient inside a cabinet, but it is not a substitute for a properly engineered long-distance field bus. Excessive cable length, incorrect pull-ups, noise and poor grounding can all cause intermittent faults.
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RS485 also needs engineering rather than simply two wires connected together. Check polarity, unique Modbus addresses, termination, biasing, shielding and grounding strategy. Keep communications cabling away from noisy power wiring where practical, and plan how the system will report or recover when a room node disappears.
ESPHome software workflow
DOMIX uses separate ESPHome firmware targets for the cabinet controller and S-series room nodes. The documented workflow is:
- Edit
hardware/data.yamlto set the device name, network settings, MQTT credentials, I2C addresses and Modbus address. - Edit
main.yaml. - Comment out hardware modules and sensors that are not physically installed.
- Compile and flash through USB-C.
- Use OTA updates for the M controller after its initial USB-C flash.
- Reprogram S nodes through USB-C when required.
The repository gives these example commands:
esphome run M/main.yaml
esphome run S/main.yaml“Minimal configuration” does not mean beginner-friendly. The builder still needs to select the correct modules, assign addresses, distribute power correctly, verify firmware compatibility and test the electrical behavior safely.
Zigbee and ESPHome versions
The project documentation contains a specific compatibility warning: its external Zigbee component is reported as incompatible with ESPHome 2026. The project recommends using an ESPHome version from the 2025 branch for the Zigbee-enabled configuration, citing 2025.7.5 as the author’s tested version.
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What it takes to build
A practical DOMIX build requires more than downloading firmware. The project identifies the need for basic electronics knowledge, soldering, PCB fabrication and component sourcing, 3D printing, an ESPHome development environment, a 12 V DC power supply, DIN-rail cabinet space and careful low-voltage wiring.
The repository supplies design files such as schematics, Gerbers, bills of materials, software and 3D-print files. It does not provide a manufacturing service, certified enclosure, production testing, installation service, warranty or guaranteed long-term replacement inventory.
Cabinet and electrical design
Allow space for the modules, terminals, power supplies, cable bends, ventilation, labeling and future expansion. Use separately fused power distribution where appropriate, and keep low-voltage circuits properly separated from mains circuits. A qualified electrician should design or inspect any mains connection, relay circuit or interface with fixed building services.
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Clear out junk files and repair common Windows errorsFree Scan →Scan for outdated or missing drivers - takes under a minuteDriver Scan →Design for commissioning as well as normal operation. Every cable should be labeled at both ends. Provide accessible isolation, documented terminal layouts and a way to replace a module without dismantling unrelated circuits.
Cost: the €420 figure needs context
Hackster coverage reports an approximately €420 full-system bill of materials. That is a project-reported estimate, not an independently audited current purchase price or a guaranteed complete installation cost.
A real build budget may also include:
- PCB fabrication or assembly;
- components that are unavailable or must be substituted;
- DIN-rail enclosures, terminals, fuses and cable management;
- 12 V power supplies and distribution hardware;
- 3D-printing equipment, materials or outsourced printing;
- programming and rework tools;
- shipping, taxes, minimum order quantities and spare parts;
- failed boards, redesigns and commissioning time;
- structured cabling and electrician labor.
DOMIX may reduce the cost of custom hardware compared with a professional building-automation system, but it does not eliminate the cost of design, installation or ongoing maintenance.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Reliability and failure planning
Centralization can make troubleshooting easier, but it can also concentrate failure. A 12 V supply failure or M1 fault may affect many rooms simultaneously. Consider separately protected power branches, supply monitoring, surge and transient protection, spare modules and manual fallback circuits where the building function requires them.
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Relay and load limitations
A documented “10 A at 250 VAC” relay figure does not mean that any 10-amp appliance can safely be connected. Resistive heaters, motors, pumps, valves, LED drivers and other inductive or high-inrush loads behave differently. Some applications may require contactors, snubbers, dedicated protection or specialist control equipment. Mains work should be reviewed and completed by a qualified electrician under the applicable local code.
Manual operation and safety
Before installation, answer these questions:
- Can essential lights operate if the ESP32 fails?
- Can irrigation be disabled manually?
- Can heating or ventilation operate during a network or Home Assistant outage?
- Is there a local wall switch independent of software?
- Are safety interlocks implemented in hardware where necessary?
DOMIX is a control platform, not automatically a fail-safe building-control design. Critical functions should not depend on an untested automation rule or a single networked controller.
DOMIX compared with alternatives
Home Assistant and off-the-shelf devices
Home Assistant with commercially available devices is easier to start and offers a broader ecosystem and community. It is often the better choice for an existing home or a small installation. The compromise is more fragmented hardware and less purpose-built centralized I/O.
Home Assistant is free and open source, and it can run on owner-supplied hardware or supported appliances.
Home Assistant Green
Home Assistant Green is an official plug-and-play Home Assistant appliance. Its official page lists an MSRP of $199 / €179, subject to regional and retailer variation. It provides the automation host, not DOMIX’s custom relay boards, field inputs or centralized room wiring.
ESPHome without DOMIX
Individual ESPHome devices provide a lower-barrier route to local, customizable automation. They work well for room-by-room upgrades and incremental projects, but do not automatically deliver DOMIX’s cabinet architecture, centralized wiring or module inventory. See the ESPHome project catalog for examples.
KNX
KNX is the more established choice where formal interoperability, installer support, certification and a mature professional ecosystem matter. DOMIX is more transparent and customizable for a capable DIY builder, but places substantially more responsibility for design, testing, support and replacement parts on the owner.
PLC and industrial control systems
PLCs generally offer stronger industrial tooling, known hardware lifecycles and formal engineering practices, but typically cost more and are less hobbyist-oriented. DOMIX is more accessible to makers and integrates naturally with consumer automation platforms. Neither system is automatically safe for every building-control application without proper engineering.
License and long-term support
The repository identifies a CC BY-NC-SA 4.0 license. It permits sharing and adaptation under its terms but restricts commercial use. That matters if a company intends to sell DOMIX-derived kits, install derivative hardware for profit or create a commercial product. Separate permission may be required.
Open hardware also does not guarantee permanent availability. Builders remain dependent on selected chips, PCB suppliers, ESPHome, third-party integrations and the project’s maintenance activity. Keep schematics, Gerbers, bills of materials, firmware versions and configuration backups with the installation.
Who should build DOMIX?
DOMIX is a strong candidate when:
- the property is being built or substantially renovated;
- centralized wiring and conduits can be installed;
- reliability and serviceability matter more than quick deployment;
- the builder can fabricate or source PCBs and printed parts;
- local control and reduced dependence on cloud services are priorities;
- the owner wants to inspect and modify the hardware and firmware;
- the project is an experiment, learning platform or custom installation.
It is a poor fit when:
- plug-and-play operation is required;
- the finished home has no practical route for new centralized cabling;
- the installer lacks electronics, firmware or electrical experience;
- certification, formal support, warranty and guaranteed replacement stock are mandatory;
- only a few lights, switches or sensors are needed;
- the owner is uncomfortable maintaining a custom software stack.
Bottom line
DOMIX is most compelling as an open design for an advanced, centralized, low-voltage automation cabinet in a new build or major renovation. It offers a thoughtful combination of ESPHome, Ethernet, RS485, I2C, Zigbee and modular DIN-rail hardware, while allowing integration with Home Assistant and related platforms.
It should be approached as a fabrication and engineering project—not as a certified product that can be installed unchanged in an occupied home. If you want a ready-made controller, Home Assistant Green or off-the-shelf ESPHome hardware will be easier. If you need established professional certification and installer support, KNX or a properly engineered PLC system may be more appropriate.
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