HomeMaster WLD-521-R1 — Water Leak Detector & Flow Meter, Modbus

Tech Specs

Installation, Environmental & Mechanical

Home Assistant / Modbus / Web Config Integration

The WLD-521-R1 supports:

• HomeMaster MicroPLC and MiniPLC as Modbus masters
• PLC and SCADA via Modbus RTU
• Home Assistant using ESPHome (on the controller) or a Modbus integration
• USB-C setup with WebConfig (Chrome / Edge, Web Serial)

Configuration is saved to flash and restored at power-up.

Quick Setup (USB-C WebConfig)

1. Mount & power — DIN rail; connect 24 V DC to V+ / 0V.
2. USB-C — connect to the PC.
3. Open WebConfig — WebConfig in Chrome or Edge.
4. Connect device — Connect → select the serial port.
5. Modbus — set address (1–247) and baud rate (9600–115200).
6. I/O & logic — inputs (sensor / counter / heat), relays, LEDs, buttons, irrigation zones as required.
7. Save — disconnect USB-C for field operation if desired.

WebConfig highlights

• Per-DI mode: water sensor, soil moisture, water counter (flow)
• Counter: pulses per litre, calibration, totals and live rate
• Optional heat: 1-Wire sensors A/B, cp, ρ, power and energy
• Relay source: Modbus, local logic, override
• LED mapping (solid/blink) and button actions
• Irrigation zones with flow supervision and time windows

Register-level detail: Modbus_Table.md and README.md.

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
  turnaround_time: 100ms
  send_wait_time: 250ms

packages:
  wld1:
    url: https://github.com/isystemsautomation/homemaster-dev
    ref: main
    files:
      - path: WLD-521-R1/Firmware/v0.1.0/default_wld_521_r1_plc/default_wld_521_r1_plc.yaml
        vars:
          wld_prefix: "WLD#1"
          wld_id: wld_1
          wld_address: "4"
    refresh: 1d

Connectors & terminal map

Top row (24Vdc | INPUTS | 1-WIRE)

Bottom row (RS-485 | RELAY OUTPUT | PS 5/12 Vdc)

Ports & service interfaces

Housing notes

• One shared Gnd (GND_ISO) for all five inputs, not one per channel.
• The Gnd on the top-row BUS block is the logic domain. Do not power field sensors from it - use the isolated PS rails.
• Isolated sensor rails 5 Vdc and 12 Vdc, 150 mA total.

Cabling and Wirings

24 V DC supply (V+ / 0V)

Regulated SELV 24 V DC to V+ and 0V; fuse the feed per local rules and the datasheet.

• Use a SELV 24 V DC supply within the rated input range
• Observe polarity; input is reverse-polarity protected
• Size the supply for module + relay coils + modest sensor rail load

Digital inputs (leak / moisture / contacts)

Field sensors and contacts — use GND_ISO as the input return (not logic 0V unless your design explicitly ties domains).

Pulse flow meter (counter mode)

Configure the DI as a water counter in WebConfig; set pulses per litre to match the meter.

1-Wire temperature sensors

1-Wire: +5 V, DATA, GND — keep leads short; follow DS18B20 wiring practices.

Relay outputs (NO / COM / NC)

External protection required: each load shall be protected by a suitable fuse or breaker. Relay contacts are not internally fused. Relay terminals may switch hazardous voltage — install per applicable electrical codes.

Dry contacts only — external load supply and protection are mandatory.

RS-485 / Modbus RTU

Terminal order differs across the HomeMaster range. Always read the silkscreen - do not wire by habit from another module. On this module the order is B-A-COM. Swapping A and B damages nothing but the node will not communicate. COM is required on every node.

All HomeMaster controllers and modules share the same RS-485 front end.

Bus wiring rules — apply to every device on the bus:

• One twisted pair for A/B, 120 Ω characteristic impedance.
• Run COM to every node. Required, not optional: the ports are not isolated, and COM is what bounds the common-mode voltage the transceivers see.
• Prefer one power supply for the whole bus, distributed in star topology. With separate supplies, additionally tie the 0 V references together at a single point.
• Bond the cable shield to cabinet PE at one end only. Never land a shield on A, B or COM.
• Where the bus crosses into a different electrical installation with its own earthing reference — a utility or billing meter, another building, another cabinet's PE system — fit an external galvanic RS-485 isolator at that boundary. The on-board components are transient protection, not isolation, and will not survive a sustained ground-potential difference.

Cable Recommendations & Shield Grounding

Use shielded, twisted constructions and bond shields correctly to reduce EMI and ground-loop issues (per datasheet).

General routing rules

• Route low-level signal cables separately from power and relay load wiring
• If crossing power cables is unavoidable, cross at 90°
• Keep runs short; avoid long parallel routing with high-current conductors
• Label cables and provide strain relief at terminals

Digital inputs & sensor cables

• Twisted pair from each sensor to the corresponding Ix and return
• Wire size compatible with 5.08 mm terminals (e.g. 0.2–2.5 mm²)
• In noisy panels, prefer shielded cable; terminate shields per the shielding section below — not to signal terminals

RS-485 (Modbus) cable

• Twisted pair for A/B; characteristic impedance ~120 Ω recommended
• Shielded cable recommended in industrial environments
• Second conductor or pair for COM reference where required by the network design

Shield grounding

• Bond cable shield(s) to cabinet PE/EMC ground at one end (PLC/controller side typical)
• Do not connect shields directly to A, B, or COM signal terminals
• Keep shield pigtails short and low-inductance

System Architecture & Pinout

System block diagram — MCU, field I/O, relays, comms.

MCU GPIO and major interfaces (reference).

Field board — inputs, 1-Wire, sensor rails.

MCU board layout overview.

Safety and Installation Notes

• SELV on power and signal terminals as defined in the datasheet; relay contacts may switch up to 250 V AC — observe separation, insulation, and local electrical codes
• Installation by qualified personnel only
• Indoor control cabinet; IP20; protect all terminals from accidental touch
• Respect the 3 A / 750 VA / 90 W system limits for relay loads; use contactors for higher currents or demanding inductive loads
• Provide external fuses or breakers for every switched load; snubbers or suppression for inductive DC/AC loads where required
• Do not power valves, pumps, or heavy actuators from +5 V ISO / +12 V ISO — sensors only, within current limits
• Do not exceed 5 V DC on digital inputs (datasheet continuous maximum)
• USB-C is intended for configuration/diagnostics — not a field power input

Compliance & Certifications

The WLD-521-R1 module is CE marked. ISYSTEMS AUTOMATION S.R.L. (HomeMaster® brand) maintains the technical documentation and a signed EU Declaration of Conformity (DoC) available for download in the Documents and Resources section above.

• EMC Directive 2014/30/EU — EN 55032:2015 (Class B emissions), EN 55035:2017 (immunity), tested by Idvorsky Laboratories Ltd. (Job #1648)
• Low Voltage Directive 2014/35/EU — EN 62368-1:2020 + A11:2020, in-house dielectric and isolation testing by ISYSTEMS AUTOMATION compliance laboratory
• RoHS Directive 2011/65/EU — EN IEC 63000 technical documentation
• HomeMaster® — registered EU trademark (EUTM No. 019082911, EUIPO, registered 15 January 2025)