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How HomeMaster 
Works

Smart Home Automation System with RS-485 and Local Logic

HomeMaster is a DIN-rail smart home automation system built on RS-485 Modbus. Every module executes its own logic on the device, the controller runs the logic that spans several modules, and the server adds visualisation and remote access — so the system keeps operating without internet or controller connectivity.

RS-485 Modbus architecture. Deterministic polling, module-level logic, DIN-rail format.

  • Works without controller or internet 
  • Deterministic communication (Modbus RTU) 
  • Automation runs locally on every module
HomeMaster smart home system in a house: a DIN-rail panel of wired modules linked to Home Assistant

System Architecture (Controller, Modules, Devices)

HomeMaster is a distributed automation system — not a centralized smart home hub.
Each module operates independently with local logic, ensuring system operation even during failures.

The system consists of four layers: 

Where a rule lives is decided by how critical it is: a shutter interlock or a leak valve belongs on the module, a rule that reads one module and drives another belongs on the controller, and dashboards, notifications and scheduling belong on the server. How to wire a house so that choice stays open.

02 RS-485 MODULES

Expansion I/O 

  • Modbus RTU Slaves
  • Relay, analog, PWM, RTD, I/O
  • Local Logic & Autonomy
  • DIN-rail mounted


HomeMaster RS-485 expansion modules mounted on a DIN rail

 

04 SERVER

Home Automation Server

  • Dashboards
  • Automation
  • Remote Access

Home automation server running dashboards, automations and remote access

 

03 CONTROLLERS

MiniPLC/MicroPLC

  • ESP32 + ESPHome
  • Modbus RTU Master
  • Central automation logic

MiniPLC and MicroPLC controllers on a DIN rail, acting as Modbus masters

 

01 FIELD DEVICES

Sensors & Actuators

Field devices: sensors and actuators wired back to the panel

 

Automation Data Flow (Local, Controller, Remote)

Three ways the system can operate:

LOCAL OPERATION

No controller required  

Modules execute logic locally

Local operation: a module executing its own logic with no controller involved

Example: Leak detected➡WLD module➡Valve OFF 

WITH HOME ASSISTANT

Visualization, automation,  remote access

Home Assistant providing visualisation, automation and remote access

Example: Monitor, automate, control remotely 

CONTROLLER-ASSISTED

Controller processes system logic  

Modules act as distributed I/O

Controller-assisted operation: the controller runs logic spanning several modules over Modbus

Example: ΔT detected → MiniPLC → Pumps ON 

 

1

LOCAL LOGIC & AUTONOMY 

Each module operates independently.

If controller or network fails:
  • Lighting continues working 
  • Pumps continue running 
  • Leak protection remains active 

System does not stop — automation continues locally.

Which rules run on the module, which run on the controller, and what a Home Assistant outage actually takes away.

2

COMMUNICATION 

RS-485 Modbus RTU
  • Industrial communication standard  
  • Noise-resistant over long distances  
  • Deterministic real-time behavior  

Implementation:

  • Controller = Modbus master
  • Modules = Modbus slaves

Bus topology, termination and the faults behind intermittent timeouts.

 

3

CONFIGURATION 

Two configuration layers

1. Module-level (WebConfig)

  • Modbus address 
  • I/O types 
  • Logic behavior

Configuration is done over USB-C in the browser and stored on the module itself, so it survives a power cycle and does not depend on the controller.

2. Controller-level (ESPHome YAML)

  • System logic
  • Automation rules
  • Integration

 

4

BUILT FOR RELIABILITY

Engineered for real world installations.

✔ DIN-rail modules

✔ Open firmware and schematics

✔ Surge & isolation

✔ OTA updates on the ESPHome controllers 

REAL SYSTEM EXAMPLE 

Wood-fired chimney installation with pumps and valves driven by a MicroPLC

Chimney System 

  • Multi-sensor monitoring 
  • Energy calculation 
  • Pump & valve control 

Works even during outages

→ Read the build guide → Discussion on Reddit

Heating system with delta-T pump control and PT100 temperature sensors

Smart Heating Systems 

  • ΔT-based pump control 
  • PT100 / DS18B20 
  • Flow monitoring 

Fully automatic operation

→ Read the build guide → Discussion on Reddit

RGB and CCT LED lighting controlled over Modbus from Home Assistant

Smart Lighting 

  • RGB+CCT control 
  • 5-channel PWM 
  • Scenes & dimming 

Controlled via Home Assistant 

→ View solution

EXPLORE THE  ECOSYSTEM

Controllers, RS-485 modules, documentation, and ready-to-use ESPHome configurations — all open source.

Product:

Development:

Community:

WHAT MAKES THIS DIFFERENT

Feature

Typical Smart Home

HomeMaster

Communication

Wi-Fi

RS-485 (wired)

Logic location

Cloud / server

Distributed

Failure behavior

Stops working

Local logic continues

Determinism

Best effort

Scheduled polling

Scalability

One device at a time

Modules on one pair