WLD-521-R1 Water Meter & Leak Detection Module

Firmware Version: 2025-10 snapshot

WLD-521-R1 — Water Meter & Leak Detection Module

HOMEMASTER – Modular control. Custom logic.

Module Description

The WLD-521-R1 is a configurable smart I/O module designed for leak detection, water flow metering, heat energy monitoring, and local irrigation control.
It includes 5 opto-isolated digital inputs, 2 SPDT relays, and optional 4 buttons and 4 LEDs for manual control and local status indication. Configuration is performed via the WebConfig interface over USB-C (Web Serial).
The module connects over RS-485 (Modbus RTU) to a MicroPLC or MiniPLC, enabling deployment in water management, hydronic heating, garden irrigation, and safety automation systems.

Table of Contents

• 1. Introduction
• 2. Use Cases
• 3. Safety Information
• 4. Installation & Quick Start
• 5. WLD-521-R1 — Technical Specification
• 6. Modbus RTU Communication
• 7. ESPHome Integration Guide (if applicable)
• 8. Programming & Customization
• 9. Maintenance & Troubleshooting
• 10. Open Source & Licensing
• 11. Downloads
• 12. Support

1. Introduction

1.1 Overview of the WLD-521-R1

The WLD-521-R1 is a DIN‑rail smart I/O module 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.

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.
In one line: a resilient water‑safety/flow module with local logic that still plays perfectly with your PLC and Home Assistant stack.

1.2 Features & Architecture

Optional: 1‑Wire bus for DS18B20 sensors (e.g. supply/return temperatures for heat energy monitoring).

1.3 System Role & Communication 💧

The WLD-521-R1 is a smart Modbus RTU slave. It can operate autonomously for leak/flow/irrigation safety logic, while exposing its I/O and sensors to a PLC, ESPHome controller, or SCADA system.

2. Use Cases

The WLD-521-R1 supports a range of real-world applications in leak detection, flow metering, hydronic energy monitoring, and irrigation control. Below are practical scenarios with step-by-step configuration.

💧 1) Basement Leak Alarm + Auto Shut-off

Goal: Detect water leaks and immediately shut off the water supply using a relay-controlled valve.

• Set DI1 as Water sensor
• Enable DI1 and set Action = Toggle
• Set Control target = Relay 1
• Wire a motorized shut-off valve (normally open) to R1
• (Optional) Assign LED1 to blink on DI1 or R1

🌿 2) Garden Irrigation with Flow Supervision

Goal: Automate watering safely with flow monitoring and environmental interlocks.

• Go to Irrigation → Zone 1
• Set Valve relay = Relay 2, Flow DI = DI2
• Enable Use flow supervision
• Configure:
  • Min rate = 0.2 L/min
  • Grace = 8 s
  • Timeout = 1200 s
  • Target liters = 50
• Add interlocks:
  • DI_moist = DI3 (dry = run)
  • DI_rain = DI4 (rain = block)
  • R_pump = Relay 1 (pump ON when watering)
• Enable Window: 06:00–08:00 with Auto-start

📈 3) Water Consumption Metering (Billing)

Goal: Track water usage in liters using pulse flow meters.

• Set DI2 to Water counter
• Enter Pulses per liter = 450 (typical)
• Adjust Rate × / Total × as needed for calibration
• Use Reset total to baseline reading
• Use Calc from external after external validation
• View Live rate (L/min) and Total (L) in WebConfig

🔥 4) Heat Energy Monitoring (Hydronic ΔT Loops)

Goal: Measure heat power and energy from flow and temperature sensors.

• Set DI3 = Water counter
• Enable Heat on DI3
• Assign Sensor A = #1 (supply), Sensor B = #2 (return)
• Set thermal constants:
  • cp = 4186 J/kg·°C
  • ρ = 1.0 kg/L
• Adjust Calibration × if needed
• View TA, TB, ΔT, Power (W), Energy (J/kWh)
• Use Reset energy to zero counters

3. Safety Information

These safety instructions apply to the WLD‑521‑R1 module. Improper handling or wiring can cause equipment damage, system failure, or personal injury.

3.1 General Requirements

3.2 Installation Practices

3.3 I/O & Interface Warnings

🔌 Power

⏸ Inputs & Relays

🔗 Communication & USB

🔘 User Interface

🛡 Shielding & EMC

4. Installation & Quick Start

4.1 What You Need

Status LEDs: • PWR – steady ON when powered • TX/RX – blink on RS‑485 activity • USB – active when connected for WebConfig

4.2 Power

The WLD‑521‑R1 operates from a regulated 24 VDC supply connected to the top terminals labeled V+ and 0V. The power supply should be SELV-rated and appropriately sized.

Power Supply Notes

• Input: 24 VDC, reverse‑protected and fused onboard
• Internal regulation:
  • 5 V logic (buck regulated via AP64501)
  • 3.3 V logic (via AMS1117-3.3)
  • +12 V ISO (for field sensors via B2412S‑2WR3)
  • +5 V ISO (via B2405S‑2WR3)

Power Budget (Estimates)

Recommended PSU: ≥300 mA per module (with 30% headroom).

⚠️ Only use the sensor rails for low-power sensors like leak probes and flow meters. Never power relays, valves, or actuators from the module’s +5 V / +12 V outputs.

4.3 Communication

The WLD‑521‑R1 uses Modbus RTU over RS‑485 for all runtime communication, and USB‑C for setup via browser.

RS‑485 Pinout (Bottom Left Terminals)

• Wire A → A, B → B, COM → COM
• Use twisted‑pair cable and terminate at both ends (120 Ω)
• Avoid star topologies; keep stubs short
• Shielded cable is recommended for EMI immunity

Modbus Settings

WebConfig allows you to set the Modbus address and baudrate via USB‑C before connecting to a PLC or ESPHome controller.

4.4 Installation & Wiring

Use diagrams and explain:

• Inputs
• Relays
• Sensor rails (12/5V)
• RS‑485 terminals
• USB port

4.5 Software & UI Configuration

The WLD‑521‑R1 is configured using WebConfig — a driverless USB‑C interface that runs in Chrome/Edge via Web Serial. All settings apply immediately and are saved to the module's flash.

🔌 WebConfig Setup

1. Connect the module to your PC using a USB-C cable.
2. Open https://www.home-master.eu/configtool-wld-521-r1 in Chrome or Edge.
3. Click “Connect” and select the serial device.
4. The header will show the Active Modbus Configuration (Address, Baudrate).

You can safely reset or update Modbus settings at any time.

🧩 Modbus Address & Baudrate

• Set Address (1–255): each module must have a unique address.
• Set Baudrate: choose between 9600–115200 (default: 19200).
• Confirm the updated settings in the banner and Serial Log.

🔁 Input Configuration (DI1–DI5)

Each DI has:

• Enable / Invert
• Type: Water sensor, Soil moisture, Water counter

For Water sensor / Soil moisture:

• Action: None, Toggle, or Pulse
• Control Target: All, Relay 1, Relay 2, None

For Water counter:

• Pulses per Liter (PPL) (e.g., 450)
• Rate × / Total × calibration
• Live Flow: Rate (L/min), Total (L)
• Reset Total / Reset Pulses
• Calc from External to align totals with an external meter

🔥 Heat Energy Calculation (Optional on Counter DIs)

Enable Heat on a DI to calculate:

• ΔT from 1‑Wire Sensor A – Sensor B
• Power (W) and Energy (J / kWh) using:
  • cp (J/kg·°C), ρ (kg/L), Calibration ×

Formula:
Power = cp × ρ × ΔT × FlowRate
Energy = ∑ Power × Δt

You can view TA, TB, ΔT, Power, Energy and reset energy counters.

⚙️ Relay Logic Configuration (Relay 1 & 2)

• Enable / Invert
• Control Source: Modbus, Local Logic, or None
• Manual Override: ON/OFF, with Latch option

Relays are dry contact. Wire loads to NO / NC / COM.

🔵 LED Mapping (LED1–LED4)

• Mode: Solid or Blink
• Source: DI1–DI5, Relay 1/2, Irrig 1/2, Override R1/R2

🔘 Button Configuration (BTN1–BTN4)

• Relays: Toggle R1/R2, Pulse R1/R2
• Irrigation: Start/Stop Zone 1/2
• Manual Override: R1/R2 Override Toggle

Button Press Behavior: Short press = toggle; Long press (~3s) = enter/exit override (relay ignores Modbus/logic while overridden).

🧪 Testing & Diagnostics

• Serial Log to watch live changes
• Status pills on component cards for DI/relay/button states
• Reset Device for safe module reboot

⏰ Clock & Home Assistant Sync

• Use coil 360 = CMD_TIME_MIDNIGHT to sync at 00:00
• Optionally set Minute of day (HREG 1100) and Day index (HREG 1101)

Ensures irrigation windows behave predictably and counters roll over cleanly.

WebConfig saves changes immediately to flash. Disconnect USB‑C after setup — the device runs autonomously and responds to Modbus polling.

4.6 Getting Started

1. Wiring — Power, RS‑485, Inputs/Relays, sensor rails
2. Configuration — WebConfig: address/baud, inputs/relays/buttons/LEDs, irrigation & heat if used
3. Integration — PLC/ESPHome polling and dashboards

5. WLD‑521‑R1 — Technical Specification

This section consolidates diagrams, I/O, electrical limits, firmware behavior, connector map, mechanics, and compliance for quick reference.

5.1 Diagrams & Pinouts

System Block Diagram	Terminal Map
Field Board Layout	MCU Board Layout

5.2 I/O Summary

5.3 Electrical Specifications

Power & Rails

Digital Inputs (DI1…DI5)

Relay Outputs (R1, R2)

Communications

Environment & Compliance

5.4 Firmware Behavior

Input → Action & Alarm Logic

• DI Types: Water sensor, Soil moisture, Water counter (flow).
• Enable / Invert per channel; debounce configurable.
• Non‑counter actions: None, Toggle, Pulse with Control Target (Relay 1, Relay 2, All, None).
• Counter channels: set PPL, Rate× / Total× calibration; expose Rate (L/min) & Total (L).
• Heat energy (optional): enable on a counter; assign 1‑Wire Sensor A/B; set cp, ρ, Calibration×.
  Power = cp × ρ × ΔT × FlowRate • Energy = ∑ Power × Δt

Relay Ownership & Overrides

• Control Source per relay: Modbus (default), Local Logic (e.g., irrigation), or None.
• Override: immediate ON/OFF with Latch option; override supersedes Modbus and local logic until cleared.
• Safety: relays are dry contact; external loads must be powered from a separate supply.

LEDs & Buttons

• LEDs (4): map to DI, Relays, Irrigation Zones, or Override; Solid or Blink modes.
• Buttons (4): assign Toggle/Pulse R1/R2, Override Toggle R1/R2, Irrigation Zone 1/2 Start/Stop.
  Short press = toggle/pulse; Long press (~3 s) = override mode.

Modbus Defaults & Persistence

• Defaults: Address 3, Baud 19200, 8N1.
• WebConfig: changes apply live and are persisted to flash.
• Daily sync: optional midnight sync (coil 360) for counters/windows with Home Assistant.

5.5 Absolute Electrical Specifications

5.6 Connector / Terminal Map (Field Side)

External terminals are 5.08 mm pitch pluggable blocks (300 V / 20 A, 26–12 AWG, torque 0.5–0.6 Nm).

5.7 Mechanical Details

• Mounting: DIN rail EN 50022, 35 mm
• Enclosure: PC/ABS, V‑0, light gray/black, matte
• Terminals: 5.08 mm pitch; 26–12 AWG (to 2.5 mm²); 0.5–0.6 Nm torque

5.8 Environmental & Compliance

• Operating temperature: 0…40 °C; Humidity: ≤95 % RH (non‑condensing)
• Ingress / Safety class: IP20; Operation Type 1
• Impulse / Altitude / Pollution: 2.5 kV rated impulse (digital output), max altitude 2000 m, Pollution degree 2
• Installation: SELV only; by qualified personnel per local codes

6. Modbus RTU Communication

The WLD‑521‑R1 communicates as a Modbus RTU slave over RS‑485, exposing its digital inputs, counters, flow data, heat metrics, relays, LEDs, irrigation state, and 1‑Wire temperatures.

6.1 Modbus Basics

Address and baudrate are configured via USB‑C using WebConfig.

6.2 Address Map Overview

6.3 Coils (Write – Single/Multiple)

Coils are pulse‑operated (write TRUE, then FALSE). Manual overrides may block Modbus control until cleared.

6.4 Discrete Inputs (Read‑only Flags)

6.5 Holding Registers (Read/Write)

📊 Input / Flow / Energy Registers

Flow Rate & Totals (per DI1–5)

Heat Energy (if enabled)

🌱 Irrigation Zones (Z1 / Z2)

🌡 1‑Wire Temperatures

6.6 Register Use Examples

• Read DI1 flow total — Read HREG 1140/1141 (U32) and divide by 1000 → Liters
• Reset DI3 pulse counter — Write TRUE to coil 343, then FALSE
• Start irrigation on Zone 1 — Pulse coil 370
• Sync module time at midnight — Write 0 to HREG 1100 then pulse coil 360

6.7 Polling Recommendations

6.8 Full Register Summary

Discrete Inputs (FC02)
00001–00005: DI1–DI5 state
00060–00061: Relay 1/2 mirrors
00090–00093: LED1–LED4 mirrors
00100–00103: BTN1–BTN4 pressed

Coils (FC01/05)
00200–00201: Relay ON (R1–R2)
00210–00211: Relay OFF (R1–R2)
00300–00304: Enable DI (1–5)
00320–00324: Disable DI (1–5)
00340–00344: Reset DI counter (1–5)
00360: CMD_TIME_MIDNIGHT
00370–00371: Irrigation START (Z1–Z2)
00380–00381: Irrigation STOP (Z1–Z2)
00390–00391: Irrigation RESET (Z1–Z2)

Holding/Input Registers (FC03/04)
01100–01101: Clock (minute of day / day index)
01120–01129: Flow rates (L/min ×1000)
01140–01149: Flow totals (L ×1000)
01200–01209: Heat power (W)
01220–01229: Heat energy (Wh ×1000)
01240–01249: ΔT (°C ×1000)
01300–01301: Irrigation state
01310–01313: Irrigation liters
01320–01323: Irrigation elapsed (s)
01330–01333: Irrigation flow (×1000)
01340–01343: Window & sensor flags
01500–01519: 1‑Wire temperatures (×1000)

All scaling uses ×1000 for flow, temperature, and energy. Convert to engineering units in your controller/ESPHome.

7. ESPHome Integration Guide

The WLD‑521‑R1 works seamlessly with ESPHome through the HomeMaster MiniPLC/MicroPLC (Modbus master). The module exposes all I/O and telemetry via Modbus RTU, which ESPHome maps into entities for Home Assistant.

7.1 ESPHome YAML Setup

uart:
  id: uart_modbus
  tx_pin: 17
  rx_pin: 16
  baud_rate: 19200
  parity: NONE
  stop_bits: 1

modbus:
  id: modbus_bus
  uart_id: uart_modbus

packages:
  wld1:
    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: "WLD#1"
          wld_id: wld_1
          wld_address: 4     # Match this with WebConfig address
    refresh: 1d

Replace wld_address with your module's actual Modbus ID (default is 3). Add more modules by duplicating the package block with unique IDs.

7.2 Exposed Entities (via ESPHome)

• Binary Sensors: DI1–DI5; Relay mirrors; Buttons; Irrigation flags
• Sensors: Flow rate & total per DI; 1‑Wire temperatures; ΔT, Power, Energy; Irrigation elapsed/time/flow
• Switches: Relay 1/2; (optionally) override toggles; irrigation start/stop helpers

7.3 Home Assistant Tips

• Use an HA automation at 00:00 to pulse coil 360 for daily sync.
• Alert on leak detection; shut‑off via R1 override and notify.
• Stop irrigation if flow drops to 0 while zone is running.

7.4 Troubleshooting

8. Programming & Customization

8.1 Supported Languages

• Arduino
• C++
• MicroPython

8.2 Flashing

1. Connect via USB‑C to a computer using Chrome/Edge browser or a serial flasher.
2. To enter bootloader mode, press and hold Buttons 1+2, then release while connecting power.
3. To trigger a hardware reset, press and hold Buttons 3+4 for 3 seconds.
4. Use PlatformIO or Arduino IDE with appropriate RP2040/RP2350 board profile.

8.3 Arduino / PlatformIO Notes

• Board config: Generic RP2040/RP2350 or RP2 family, QSPI flash
• Flash size: 2 MB Flash (Sketch: 1MB, FS: 1MB)
• Required Libraries:
  • Arduino.h
  • ModbusSerial.h
  • SimpleWebSerial.h
  • Arduino_JSON.h
  • LittleFS.h
  • OneWire.h
  • hardware/watchdog.h
• Pin Mapping aligns with RP2350 definitions; see schematic for GPIO layout.

8.4 Firmware Updates

• Use WebConfig or USB‑C to re‑flash firmware with the appropriate boot/reset combination.
• Configuration is stored in persistent flash (retained across firmware upgrades).
• If a flash fails, enter BOOT mode manually and retry via browser uploader or PlatformIO CLI.
• WebConfig can restore base config with default values if corrupted.

9. Maintenance & Troubleshooting

9.1 Status LED Meanings

9.2 Reset Methods

• Soft reset: WebConfig → Reset Device
• Hard reset: hold Buttons 3 + 4 for ~3 s
• Bootloader: hold Buttons 1 + 2 while powering the device

9.3 Common Issues

10. Open Source & Licensing

• Hardware: CERN‑OHL‑W v2
• Firmware: GPLv3
• Config Tools: MIT

The repository contains design files, firmware, and tools. Contributions are welcome.

11. Downloads

• Firmware binaries — Firmware/default_wld_521_r1/
• ESPHome YAML configs — Firmware/default_wld_521_r1_plc/
• WebConfig Tool — Firmware/ConfigToolPage.html
• Schematics — Schematics/WLD-521-R1-FieldBoard.pdf, Schematics/WLD-521-R1-MCUBoard.pdf
• Images & diagrams — Images/
• Datasheet — Manuals/WLD-521-R1 Datasheet.pdf

12. Support

• Support Portal: https://www.home-master.eu/support
• WebConfig: https://www.home-master.eu/configtool-wld-521-r1
• YouTube: https://youtube.com/@HomeMaster
• Hackster: https://hackster.io/homemaster
• Reddit: https://reddit.com/r/HomeMaster
• Instagram: https://instagram.com/home_master.eu