HomeMaster DIO-430-R1 — Modbus Relay Module, 3x16A, 4 Digital Inputs

Relay Outputs

The DIO-430-R1 provides 3 SPDT mechanical relays (HF115F-005-1ZS3) for switching AC or DC loads. Each relay provides SPDT switching contacts (NO / NC / COM) available on the relay output terminals and is driven via optocoupler-isolated control circuitry.

Rating: 3 A MAX continuous per output (board/system limit) is the only usable output rating. Loads above 3 A must use an external contactor or power relay. The relay component may be rated higher, but this does not change the 3 A system limit.

⚠️ External protection required: Every relay output MUST be protected by an external fuse or circuit breaker (≤ 3 A per channel). Relay output circuits are not internally fused. External overcurrent protection is mandatory for safe operation.

Relay Specifications

Relay Wiring Examples

Example wiring using Normally Open (NO) and Normally Closed (NC) relay contacts.

• Each relay has COM / NO / NC terminals
• Use NO for default OFF loads
• Use NC for default ON loads
• ⚡ Loads may carry hazardous voltage
• Supports AC and DC switching (DC and inductive loads require derating)

⚠️ Common protection warning: If a single common fuse or circuit breaker is used to protect multiple relay outputs, the protective device shall NOT be sized by summing relay outputs. The rating of the common protective device shall not exceed 3 A MAX per output (board/system limit).

For inductive or DC loads (contactors, solenoids, motors), use appropriate suppression (RC snubbers, MOVs, or flyback diodes). Loads exceeding the recommended PCB current limit shall be switched using external contactors or wiring methods that bypass PCB copper paths.

Communication & Protocols

• Modbus RTU (RS-485) – UART-based communication for expansion modules and field devices

RS-485 Communication

Uses MAX485 RS-485 transceiver.

RS-485 Wiring

Connect A, B, and COM to the bus.

Termination & Biasing

• Terminate with 120 Ω only at the two ends of the line.
• Do not terminate intermediate devices.
• Fail-safe biasing is already provided inside the DIO-430-R1.

COM / Reference Ground

• Connect COM between all RS-485 nodes.
• This limits common-mode voltage and prevents communication faults.

A common 0V reference prevents RS-485 common-mode voltage errors and communication faults.

USB-C Interface

Cable Recommendations & Shield Grounding

General Routing Rules

• Route signal wiring (DI, RS-485) separately from relay load wiring and mains bundles
• Avoid parallel runs with contactor/motor/VFD cables; cross at 90° if needed
• Keep cable runs as short as practical; use cable ducts for segregation
• Label cables and provide strain relief at terminals

Digital Inputs (DI) Cable

• Use 2-core twisted pair per DI channel (INx + GNDx)
• Recommended wire size: 0.2–0.75 mm² (AWG 24–18) (compatible with 5.08 mm terminals)
• For long runs/noisy environments: shielded twisted pair
• Keep DI runs away from relay outputs/contactors; avoid long parallel routing with high-current wiring
• Inputs intended for dry contact (voltage-free) only. Do not apply external voltage.

RS-485 (Modbus) Cable

• Use twisted pair for A/B
• Prefer shielded twisted pair in industrial/noisy panels
• Use a daisy-chain bus (no stubs)
• Use 120 Ω termination at both physical ends
• Run COM/GND reference alongside A/B (same cable or adjacent pair) where required

Shield Grounding

• Terminate cable shield at ONE END ONLY (typically PLC/controller cabinet end) to prevent ground loops
• Bond shield to PE/EMC grounding via grounding bar or EMC clamp (short, low-impedance connection)
• Do not connect shields to signal terminals (A/B/COM, INx/GNDx)
• Keep shield terminations short (avoid long pigtails)
• Maintain separation from relay/mains wiring to reduce EMI coupling