N4ROD08: 8-Channel RS485 Modbus RTU Relay Module for Industrial Automation and Smart Home Control

N4ROD08 is an 8-channel RS485 relay module designed for industrial automation, remote switching, PLC output expansion, and smart home control.

Using the standard Modbus RTU communication protocol, the N4ROD08 allows a PLC, industrial computer, HMI, or compatible automation controller to operate eight independent relay outputs through an RS485 communication bus.

The module supports multiple operating commands, including momentary switching, self-locking, interlocking, timed switching, and all-channel control. These functions make it suitable for applications ranging from industrial equipment control to lighting automation, CCTV systems, and motor-control interfaces.

In addition to its hardware capabilities, the N4ROD08 has been included in a third-party Home Assistant integration on GitHub, demonstrating how the relay channels can be exposed as software-controlled switches in a smart home automation platform.

2. Key Features

Eight Independent Relay Outputs

The N4ROD08 provides eight relay output channels in a compact module.

Each channel can be controlled individually through Modbus commands, allowing users to switch compatible electrical loads without requiring eight separate relay controllers.

This makes the module useful for systems that need to control multiple lights, solenoid valves, auxiliary contactors, alarms, or other switching devices.

Standard RS485 and Modbus RTU Communication

The N4ROD08 communicates through RS485 using Modbus RTU.

This widely used industrial protocol allows the module to connect to compatible PLCs, HMIs, industrial computers, and automation gateways.

Its standard communication interface makes it easier to integrate relay control into existing industrial systems without relying on a proprietary network protocol.

Eight Built-In Control Commands

The module supports eight control commands:

  • Open: Turn on a relay output.

  • Close: Turn off a relay output.

  • Momentary: Activate an output temporarily according to the configured operating behavior.

  • Self-locking: Maintain an output state until another command changes it.

  • Interlock: Allow only the permitted output state or combination according to the configured interlocking behavior.

  • Delay: Apply a timed switching operation.

  • Open All: Turn on all relay channels.

  • Close All: Turn off all relay channels.

The maximum configurable delay is documented as 255 seconds.

These functions reduce the need to implement every basic switching behavior in the host controller, although application-specific sequencing and safety logic may still be required.

Low Power Consumption

The N4ROD08 is designed for low-power operation.

For the documented DC 12V version, the standby current with all relays closed is approximately 6mA. Current consumption increases as more relays are energized, reaching approximately 150mA with all eight relays open.

Actual consumption depends on the supply voltage, relay state, and specific hardware version.

Multiple Modules on One RS485 Bus

The N4ROD08 supports configurable Modbus device addresses, allowing multiple compatible modules to share an RS485 network.

The published specifications indicate support for up to 64 devices in parallel under Modbus control. The practical network configuration depends on the complete bus design, electrical loading, cabling, and any repeaters required.

DIN-Rail Installation

The module is available as a bare circuit board or with a DIN-rail enclosure.

The enclosed version is suitable for installation in electrical cabinets and control panels, while the bare-board version can be used in custom equipment and OEM designs.

3. Technical Specifications

Parameter Specification
Manufacturer Eletechsup
Model N4ROD08
Function 8-channel relay output control
Number of outputs 8
Communication interface RS485
Communication protocol Modbus RTU
Supply voltage DC 12V or DC 24V version
Standby current Approximately 6mA for the DC 12V version
Current with one relay energized Approximately 24mA for the DC 12V version
Current with eight relays energized Approximately 150mA for the DC 12V version
Relay contact rating Up to 3A at 250VAC or 30VDC for resistive loads
Recommended inductive-load limit Within 1A, subject to load and switching conditions
Default baud rate 9600bps
Default serial format 9600, N, 8, 1
Supported baud rates 1200–115200bps
Parity options None, Even, Odd
Supported write function codes 05, 06, 15, 16
Supported read function codes 01, 03
Maximum delay setting 255 seconds
Maximum documented device count Up to 64 devices
Bare-board dimensions 67 × 72 × 14mm
DIN enclosure dimensions 69 × 88 × 38mm
Bare-board weight Approximately 59g
Weight with DIN enclosure Approximately 115g

Specifications are based on the published Eletechsup product information. Confirm the selected voltage version and current product manual before installation.

4. How Does the N4ROD08 Work?

The N4ROD08 receives Modbus RTU commands from a host controller over an RS485 connection and operates the corresponding relay outputs.

A typical installation follows these steps:

  1. Select the DC 12V or DC 24V version appropriate for the installation.

  2. Connect the module to a suitable power supply.

  3. Connect the RS485 A/B communication lines to a PLC, industrial computer, USB-to-RS485 adapter, or compatible gateway.

  4. Configure the Modbus slave address and serial communication parameters.

  5. Send the appropriate Modbus command to operate a relay channel.

  6. Connect the relay contacts to the equipment being controlled, observing the contact ratings and electrical protection requirements.

For example, a PLC can use the module to switch eight independent indicator lights, control relays connected to contactors, or activate auxiliary equipment according to a programmed sequence.

When several N4ROD08 modules share the same bus, each module must have a unique Modbus address.

5. GitHub Application Example: Integrating N4ROD08 with Home Assistant

A practical third-party software reference is the GitHub repository:

DRP Modbus Boards — Home Assistant Custom Integration

Repository: https://github.com/r-renato/drp-modbus-boards

The project explicitly lists eletechsup_n4rod08 as a supported board identifier and describes it as an 8-channel RS485 Modbus RTU relay module.

For this device, the integration exposes eight relay channels through Home Assistant's switch platform, using entity identifiers from channel_00 through channel_07.

This demonstrates how the N4ROD08 can be incorporated into a software-based automation environment rather than being controlled only through a PLC or serial terminal.

How the Integration Works

The general architecture is:

  1. The N4ROD08 is connected to an RS485 network.

  2. An appropriate Modbus gateway provides communication between the network and the Home Assistant host.

  3. The third-party integration defines the board and its Modbus slave address.

  4. Home Assistant exposes the eight relay channels as switch entities.

  5. Users can operate these entities through Home Assistant automations, dashboards, or compatible interfaces.

The repository documents Home Assistant 2024.x or newer and requires an accessible Modbus TCP, RTU-over-TCP, or other supported gateway configuration.

GitHub repository:
https://github.com/r-renato/drp-modbus-boards

Relevant board identifier:
eletechsup_n4rod08

Important: This is a community-developed integration, not official Eletechsup software. Check the repository's current configuration instructions and verify the gateway and Modbus settings for your installation.

6. Typical Applications

Industrial PLC Output Expansion

Use the N4ROD08 to add eight relay outputs to a compatible PLC or industrial controller over RS485.

This is useful when the controller has insufficient onboard relay outputs or when additional switching points are required at a remote location.

Smart Home Automation

Control compatible lighting circuits, auxiliary relays, and other switching equipment through a Modbus-based home automation system.

The third-party Home Assistant integration provides a starting point for developers who want to incorporate the module into a broader automation environment.

CCTV and Security Systems

Use relay outputs to operate compatible auxiliary equipment, such as lighting, alarm interfaces, and supported camera-control circuits.

The exact functionality depends on the controlled equipment and its electrical interface.

Automatic Curtain Control

Operate compatible curtain-control interfaces or external motor-control circuits through relay switching.

For motors requiring forward and reverse operation, use appropriate electrical and software interlocks to prevent conflicting commands.

LED and Lighting Control

Switch compatible lighting circuits or LED power supplies through the relay outputs.

For loads with high inrush current, check the power supply's characteristics and the relay's switching limitations before selecting the module.

Pump and Valve Control

Use relay outputs to operate suitable contactors, solenoid valves, or other control interfaces.

For high-current pumps and other inductive loads, an appropriately rated contactor or intermediate control circuit may be necessary.

Identification and Access-Control Systems

Integrate relay outputs into compatible access-control or identification equipment to trigger switching actions when authorized commands are received.

Security-critical installations should use independent safety mechanisms and appropriate fail-safe design.

7. Why Choose the Eletechsup N4ROD08?

The N4ROD08 combines eight relay outputs, standard RS485 communication, Modbus RTU compatibility, and built-in switching commands in a compact module.

Its low standby current makes it attractive for applications that require continuous availability without keeping all relay coils energized.

Its configurable communication settings and multi-device support also make it suitable for distributed switching systems, where several modules are controlled by a central PLC, computer, or automation gateway.

The availability of a third-party Home Assistant integration provides an additional starting point for developers who want to build smart home or software-based control systems around Modbus relay hardware.

8. Installation and Safety Considerations

Choose the correct supply voltage. The module is available in DC 12V and DC 24V versions. Use the version that matches the intended power supply.

Respect relay contact ratings. The published 3A rating applies to specified resistive loads. Inductive loads, motor starting currents, and capacitive inrush currents can require substantially more conservative ratings.

Use external protection where necessary. Select appropriate fuses, contactors, surge suppression, and isolation based on the connected load and installation requirements.

Design the RS485 network correctly. Use suitable twisted-pair cabling, unique slave addresses, and appropriate termination where required.

Verify command behavior. Test momentary, self-locking, interlocking, and delay functions before using them in a production installation.

Implement independent safety controls. Do not rely solely on a communication module or software automation for emergency stops, personnel protection, or other safety-critical functions.

9. Conclusion

The Eletechsup N4ROD08 8-Channel RS485 Modbus RTU Relay Module is a versatile switching solution for industrial automation, PLC output expansion, security systems, lighting control, and smart home projects.

With eight relay outputs, multiple built-in control commands, configurable Modbus communication, and a compact DIN-rail enclosure option, it provides a practical way to add remotely controlled switching channels to an existing system.

The third-party Home Assistant integration on GitHub further demonstrates how the N4ROD08 can be incorporated into software-based automation platforms.

Official product page:
https://www.eletechsups.com/products/n4rod08-8ch-modbus-rtu-rs485-relay-module-3a-multifunction-din-rail-controller-with-8-commands-for-plc-hmi-smart-home

GitHub Home Assistant integration:
https://github.com/r-renato/drp-modbus-boards

Eletechsup — Practical Electronic Modules for Industrial Control, Remote Switching, and Automation.

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