8-Channel RS485 Modbus RTU Relay Board DC 12V/24V DIN Rail
8-Channel RS485 Modbus RTU Relay Board DC 12V/24V DIN Rail
8-Channel RS485 Modbus RTU Relay PLC Expansion Board | DC 12V/24V | DIN Rail Mount
Take full command of your automation projects with this versatile 8-Input / 8-Output (8I8O) RS485 Modbus RTU Relay Control Board. Designed for industrial and DIY control applications, this board operates on DC 12V or 24V, fits neatly on a DIN35/C45 rail, and communicates via the widely supported Modbus RTU protocol — making it an ideal PLC expansion module for smart switching, sequential control, and multi-device networks.
Key Features
- Dual Voltage Support: Compatible with DC 12V and DC 24V power supplies for flexible installation.
- 8 Isolated Digital Inputs: Photoelectric (optocoupler) isolation on all 8 input ports (NPN, low-level active) for reliable, noise-immune signal detection.
- 8 Relay Outputs: Each relay handles up to 10A @ 250VAC / 30VDC — robust enough for a wide range of loads.
- Modbus RTU Protocol: Supports function codes 03, 06, and 16 for seamless integration with PLCs, HMIs, and SCADA systems.
- 6 Relay Command Modes: Open, Close, Momentary, Self-locking, Interlock, and Delay (up to 255 seconds) — giving you precise control over every output.
- Selectable Baud Rate: Set via jumper: 2400, 4800, 9600 (default), or 19200 BPS.
- Multi-Device Networking: Connect up to 64 devices in parallel on a single RS485 bus.
- Input/Output Association: The input-to-output relationship can be set to associated (default) or non-associated via command.
- DIN Rail Box Included: UM72 flame-retardant V0-grade enclosure fits DIN35 and C45 rails; color: green.
Technical Specifications
| Supply Voltage | DC 12V / DC 24V |
| Standby Current | 12 mA (all relays closed) |
| Current per Open Relay | ~27 mA additional per relay (e.g., 8 relays open = 225 mA) |
| Relay Max Load | 10A / 250VAC, 10A / 125VAC, 10A / 30VDC, 10A / 28VDC, 10A / 12VDC |
| Communication | RS485, Modbus RTU (Function Codes: 03, 06, 16) |
| Baud Rates | 2400 / 4800 / 9600 (default) / 19200 BPS |
| Max Delay | 255 seconds |
| Max Devices on Bus | 64 |
| PCB Size | 136 × 72 × 20 mm |
| With DIN Rail Box | 140 × 88 × 42 mm |
| PCB Weight | 134 g |
| With Box Weight | 223 g |
| Enclosure Model | UM72 | Flame-retardant V0 | DIN35 / C45 rail |
| Input Voltage (EU LVD) | Below 50 VAC or 75 VDC (Low Voltage) |
| Country of Origin | Made in China |
Ideal Applications
- Industrial PLC expansion and relay output control
- Building automation and smart switching panels
- Multi-zone control systems (lighting, HVAC, access control)
- DIY home automation with RS485 networks
- Sequential and interlocked machine control
What's in the Box?
- 1× N4D8B08 Relay Control Board (with DIN Rail Box)
For more information on industrial control and electrical safety standards, visit the OSHA Electrical Safety resource page.
Frequently Asked Questions
Q: What power supply does this RS485 Modbus relay board require?
A: The board runs on DC 12V or DC 24V. Simply connect a suitable regulated DC power supply to the designated terminals. At full load (8 relays open on 24V), current draw reaches approximately 225 mA, so a 500 mA or greater supply is recommended for comfortable headroom.
Q: Can I use this relay board with a Raspberry Pi, Arduino, or industrial PLC?
A: Yes. Any controller with an RS485 interface and support for the Modbus RTU protocol (function codes 03, 06, 16) can communicate with this board. You can also use a USB-to-RS485 adapter and control it via a serial terminal or Modbus Poll software on a PC.
Q: How many boards can I connect on a single RS485 bus?
A: Up to 64 N4D8B08 boards can be connected in parallel on a single RS485 network, each with a unique Modbus device address, allowing large-scale switching control from one master controller.
Q: What relay command modes are available?
A: The board supports six command modes: Open, Close, Momentary, Self-locking, Interlock, and Delay. The Delay mode allows timed switching of up to 255 seconds per channel, configurable via Modbus commands.
Q: Does the DIN rail box provide electrical insulation and protection?
A: Yes. The included UM72 enclosure is made from a flame-retardant V0-grade material, providing a degree of insulation and mechanical protection. It mounts on standard DIN35 and C45 rails for easy panel installation.