WLD-521-R1 Water Meter & Leak

Overview

The WLD‑521‑R1 is a configurable smart I/O module designed for leak detection, pulse water metering, ΔT heat monitoring, and local irrigation control. It exposes 5 opto‑isolated digital inputs, 2 SPDT relays, 4 user buttons, and 4 status LEDs, and is serviced over USB‑C via WebConfig.

It integrates with a MiniPLC/MicroPLC (or other PLC/SCADA/HA controllers) via Modbus RTU over RS‑485. Configuration is done in a browser using the WebConfig tool (Web Serial over USB‑C): set Modbus params, choose per‑input modes (sensor/counter), link 1‑Wire temperature sensors, and enable autonomous irrigation/flow‑safety logic.

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

• WLD‑521‑R1 module

• 24V DC SELV power supply

• RS‑485 cable (twisted pair, shielded)

• 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-wld-521-r1

3. Click "Connect" and select serial port

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

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

6. Settings save automatically to flash

Tech Specs

Documentation

The WLD‑521‑R1 is open‑source hardware! You can build your own board using the following files:

Hardware Design Files

• Field Board Schematic: WLD‑521‑R1‑FieldBoard.pdf

• MCU Board Schematic: WLD‑521‑R1‑MCUBoard.pdf

• System Block Diagram: WLD_SystemBlockDiagram.png

• Field Board Diagram: FieldBoard_Diagram.png

• MCU Board Diagram: MCUBoard_Diagram.png

Firmware & Software

• Firmware Source Code: WLD‑521‑R1/Firmware/

• WebConfig Tool: ConfigToolPage.html

• ESPHome Integration Package: default_wld_521_r1_plc.yaml

Mechanical Files

• Dimensional Drawing: WLD_Dimensions.png

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

Input and Output

Digital Inputs (5 channels)

• Configurable actions: None, Toggle, or Pulse

• Target mapping to individual relays or all relays

• PTC + TVS protection on each channel

Relay Outputs (2 channels)

• SPDT contacts (NO/NC/COM)

• 3A @ 250V AC rating

• Individual enable/invert settings

• Controlled via Modbus coils or local input mapping

• RC/TVS snubbers recommended for inductive loads

User Interface

• 4 Buttons: Configurable for relay override (toggle function)

• 4 LEDs: Configurable steady or blink modes, linked to relay status

• 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

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Function Codes

FC02 - Read Input Status (Discrete Inputs)

FC03 - Read Holding Registers

FC05 - Write Single Coil

FC01 - Read Coils

Input Status (FC02) - Read Only

Coils (FC01/FC05) - Read/Write

Maintained Coils (Switched - ESPHome can set ON/OFF directly)

Pulse Coils (Cleared after use)

Holding Registers (FC03) - Read Only

Status Registers (UINT16: 0 or 1)

Flow Meter Data (UINT32 - 2 registers each, Little Endian)

Heat Energy Data (S32/U32 - 2 registers each, Little Endian)

1-Wire Temperature Data (SINT32 - 2 registers each, Little Endian)

Notes

1. Maintained Coils (200-224): These coils maintain their state. ESPHome can read/write them directly as switches.

2. Pulse Coils (340-344): These coils are automatically cleared after being read. Write 1 to reset the corresponding counter.

3. Holding Registers: All 32-bit values (UINT32/SINT32) are stored as two consecutive 16-bit registers in Little Endian format (low word first).

4. Scaling:

   • Flow Rate: Multiply by 0.001 to get L/min

   • Flow Accumulated: Multiply by 0.001 to get L

   • Heat Energy: Multiply by 0.001 to get Wh

   • Temperatures: Multiply by 0.001 to get °C

5. Total Register Range: 1-173 (continuous address space for FC03)

Example Usage

Read Digital Input 1 State: FC03, Address: 1 → Returns: 0 (OFF) or 1 (ON)

Control Relay 1 ON: FC05, Address: 200, Value: 1 (ON) or 0 (OFF)

Read Flow Rate for DI1: FC03, Addresses: 104-105 → Read as UINT32, divide by 1000 → Result in L/min

Reset Counter for DI1: FC05, Address: 340, Value: 1 (will be auto-cleared by firmware)

Home Assistant & ESPHome Integration Guide

Overview

The WLD‑521‑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 WLD‑521‑R1

3. 24V power to WLD‑521‑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 WLD‑521‑R1 Package

packages:
  wld_521_r1:
    url: https://github.com/isystemsautomation/HOMEMASTER
    ref: main
    files:
      - path: WLD-521-R1/Firmware/default_wld_521_r1_plc/default_wld_521_r1_plc.yaml
        vars:
          wld_prefix: "WaterModule"
          wld_id: water_module
          wld_address: 3
    refresh: 1d

Customize Variables

• wld_prefix: Appears in entity names (e.g., "Staircase Relay 1")

• wld_id: Must be unique if adding multiple DIO modules

• wld_address: Set to match your DIO-430-R1 Modbus address (default: 3)

Multiple WLD Modules

For additional modules, duplicate the package block with unique IDs:

Example: Multiple WLD Modules

packages:
  wld_kitchen:
    url: https://github.com/isystemsautomation/HOMEMASTER
    ref: main
    files:
      - path: WLD-521-R1/Firmware/default_wld_521_r1_plc/default_wld_521_r1_plc.yaml
        vars:
          wld_prefix: "Kitchen"
          wld_id: kitchen_module
          wld_address: 4
    refresh: 1d

  wld_garden:
    url: https://github.com/isystemsautomation/HOMEMASTER
    ref: main
    files:
      - path: WLD-521-R1/Firmware/default_wld_521_r1_plc/default_wld_521_r1_plc.yaml
        vars:
          wld_prefix: "Garden"
          wld_id: garden_module
          wld_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 2 + 3 to enter BOOT mode

3. Upload via:

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

   • PlatformIO/Arduino IDE upload

4. Press Buttons 1 + 3 for hardware reset if needed

Pin Mapping (Default Firmware)