DIM-420-R1 AC Dimmer Module

Overview

The DIM‑420‑R1 is a configurable smart I/O module designed for AC dimming control in building automation, lighting, HVAC, and general control systems. It offers 4 opto‑isolated digital inputs, 2 high‑current AC dimming channels, 4 user buttons, and 4 configurable user LEDs. All I/O channels are individually configurable, allowing flexible logic such as toggle, ramp, manual override, and scene control.

It connects via RS‑485 (Modbus RTU) to a MicroPLC, MiniPLC, or any compatible controller, and can also integrate with Home Assistant (ESPHome) or SCADA/PLC systems. Configuration and diagnostics are performed through a driverless Web Serial interface via USB‑C, using the browser‑based WebConfig Tool. The module supports both master‑controlled and standalone local logic modes.

Getting Started

Quick Setup Process

1. Mount & Wire – Install on 35mm DIN rail, connect 24V DC power, sensors, and relay loads.

2. Configure – Plug in USB-C, open the WebConfig tool in Chrome/Edge, set Modbus address and I/O mapping.

3. Integrate – Connect to your controller via RS-485 and start automation.

What You Need

• DIM‑420‑R1 module

• 24V DC SELV power supply

• AC loads (dimmable lamps, LED drivers)

• RS‑485 cable (twisted pair)

• USB‑C cable for configuration

• Chromium-based browser (Chrome/Edge)

Web Configuration Steps

1. Connect USB-C to module and PC

2. Open https://www.home-master.eu/configtool-dim-420-r1

3. Click "Connect" and select serial port

4. Set Modbus address (default: 3) and baud rate (default: 19200 8N1)

5. Configure input actions, mapping, LED modes, and button functions

6. Settings save automatically to flash

Tech Specs

Documentation

The DIO-430-R1 is open-source hardware! You can build your own board using the following files:

Hardware Design Files

• Field Board Schematic: DIM‑420‑R1‑FieldBoard.pdf
• MCU Board Schematic: DIM‑420‑R1‑MCUBoard.pdf
• MOSFET Board Schematic: DIM‑420‑R1‑MOSFETBoard.pdf

Firmware & Software

• Firmware Source Code: DIM‑420‑R1/Firmware/default_DIM_420_R1
• ESPHome Integration Package: default_dim_420_r1_plc.yaml

All design files and documentation are available in the HomeMaster GitHub repository.

Input and Output

Digital Inputs (4 channels)

• Optically isolated dry-contact inputs

• Configurable press logic: Short, Long, Double, Short‑then‑Long

• Actions: Toggle, Ramp, Preset recall, MAX, Ping‑pong

• PTC + TVS protection on each channel

Dimming Outputs (2 channels)

• Phase‑cut AC outputs (Leading/Trailing edge)

• 110/230 VAC, MOSFET‑based (WMM36N65C4)

• Configurable Lower/Upper thresholds

• Zero‑cross detection and sync

• Internal snubber and EMI suppression

User Interface

• 4 Buttons: Configurable for local override (toggle, ramp, preset)

• 4 LEDs: Configurable steady/blink modes, linked to channel or DI state

• Status LEDs: PWR (power), TX/RX (Modbus activity)

Communication Interfaces

• Protocol: Modbus RTU

• Role: Slave device

• Default Settings: Address 3, 19200 baud, 8 data bits, No parity, 1 stop bit

• Supported Functions: Read Coils (0x01), Read Discrete Inputs (0x02), Read Holding Registers (0x03), Read Input Registers (0x04), Write Single Coil (0x05), Write Single Register (0x06)

Modbus Address Map

Coils (Read/Write) - Function Codes 0x01, 0x05

Discrete Inputs (Read Only) - Function Code 0x02

Holding Registers (Read/Write) - Function Codes 0x03, 0x06

Home Assistant & ESPHome Integration Guide

Overview

The DIM‑420‑R1 integrates seamlessly with Home Assistant via ESPHome using the Modbus RTU protocol. This guide covers both quick integration using our pre‑built package and manual configuration for advanced users.

Prerequisites

Before starting, ensure you have:

1. ESPHome device (HomeMaster MiniPLC/MicroPLC or any ESP32/ESP8266 with RS‑485)

2. RS‑485 connection between ESP device and DIM‑420‑R1

3. 24V power to DIM‑420‑R1 module

4. Home Assistant with ESPHome add‑on installed

RS‑485 Configuration

uart:
  id: uart_modbus
  tx_pin: GPIO17
  rx_pin: GPIO16
  baud_rate: 19200
  parity: NONE
  stop_bits: 1

modbus:
  id: modbus_bus
  uart_id: uart_modbus

Import DIM‑420‑R1 Package

packages:
  dim_430_r1:
    url: https://github.com/isystemsautomation/HOMEMASTER
    ref: main
    files:
      - path: DIM-420-R1/Firmware/default_dim_420_r1_plc/default_dim_420_r1_plc.yaml
        vars:
          dim_prefix: "Living Room" # Custom name for your entities
          dim_id: living_room_module # Unique internal ID
          dim_address: 3 # Must match WebConfig Modbus address
    refresh: 1d

Customize Variables

• dim_prefix: Appears in entity names (e.g., "Living Room CH1 Level")

• dim_id: Internal identifier for the module

• dim_address: Modbus address (must match WebConfig setting)

Multiple Module Example

packages:
  dim_kitchen:
    url: https://github.com/isystemsautomation/HOMEMASTER
    ref: main
    files:
      - path: DIM-420-R1/Firmware/default_dim_420_r1_plc/default_dim_420_r1_plc.yaml
        vars:
          dim_prefix: "Kitchen"
          dim_id: kitchen_module
          dim_address: 4
    refresh: 1d

  dim_bedroom:
    url: https://github.com/isystemsautomation/HOMEMASTER
    ref: main
    files:
      - path: DIM-420-R1/Firmware/default_dim_420_r1_plc/default_dim_420_r1_plc.yaml
        vars:
          dim_prefix: "Bedroom"
          dim_id: bedroom_module
          dim_address: 5
    refresh: 1d

Programming

Supported Development Environments

• Arduino IDE with RP2350 support

• PlatformIO with RP2350 toolchain

• MicroPython (community builds available)

Firmware Flashing

1. Connect USB-C to PC

2. Hold Buttons 3 + 4 to enter BOOT mode

3. Hold Buttons 1 + 2 to RESET the module

4. Upload via:

   • UF2 drag-and-drop to mounted drive, OR

   • PlatformIO/Arduino IDE upload

Pin Mapping (Default Firmware)