WLD-521-R1 Water Meter & Leak

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 — configtool-wld-521-r1 in Chrome or Edge.
4. Connect device — Connect → select the serial port.
5. Modbus — set address (1–255) 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

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"
    refresh: 1d

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 (A / B / COM)

• Daisy-chain topology; keep stubs short
• Match A/B polarity across the bus
• Terminate with 120 Ω at the two physical ends of the segment
• Connect COM between nodes for a stable reference (per installation design)

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 is CE marked and designed to comply with applicable European Union directives. ISYSTEMS AUTOMATION S.R.L. (HomeMaster) maintains technical documentation and a signed EU Declaration of Conformity (DoC).

EU directives

EMC 2014/30/EU · LVD 2014/35/EU · RoHS 2011/65/EU

Standards (datasheet)

Equipment classification

Industrial / commercial control equipment — install only in the intended environment and enclosure class.

Safety notice

Power input and signal-level circuits are SELV. Relay outputs may switch hazardous voltages — qualified installation only. See the datasheet PDF for the full conformity statement and manufacturer contact.