4-Channel Modbus RTU Relay Module with RS-485 Interface

This 4-channel relay module operates via RS-485 using the Modbus RTU protocol. It features high-current relays rated up to 30A at 250V AC or 28V DC and is built for applications requiring reliable switching and communication. The ABS DIN rail-mount case makes it easy to install in industrial environments.

The module includes multiple protection circuits such as power isolation, ADI magnetic signal isolation, a resettable fuse, and a TVS diode. It also includes optocoupler isolation to guard against interference from high-voltage circuits, as well as reverse-polarity protection. A dedicated relay driver chip with built-in flyback diode protection ensures consistent switching performance.

Power input supports a wide 7–36V DC input range via an onboard voltage regulator. A unibody isolation design provides stable voltage to the isolated terminal without requiring an additional supply. The relay supports flash-on/flash-off operation using command parameters, and each unit can be assigned an address from 1 to 255, allowing multiple devices to share the same RS-485 bus. Three onboard LEDs indicate MCU activity and RS-485 communication status. High-quality screw terminals with covers simplify wiring for high-current loads.

Note: Power adapter not included (12V DC Barrel Jack supply recommended).

⚠️Electrical Safety Precautions⚠️

• This product should be operated and used by professional electricians or technical personnel. During use, please ensure electrical safety and take protective measures such as anti-leakage and insulation.
• Before installing, maintaining, or replacing relay equipment, make sure to turn off the power and unplug the device.
• Do not attempt to dismantle relay equipment to avoid damaging the device or risking electric shock.
• Please properly install and place the relay equipment. Avoid using it in damp, overly hot, or flammable environments to prevent safety accidents due to improper installation or use.

Features

• Configurable device address (1–255); supports cascading on RS-485 bus
• Flash-on/flash-off relay control via command with timing support
• Wide input voltage range: 7V–36V DC
• Integrated power supply isolation; no extra supply needed for isolated terminal
• ADI magnetic isolation for reliable signal transmission and low interference
• Resettable fuse and TVS diode for surge, overcurrent, and electrostatic protection
• Optocoupler isolation to reduce high-voltage interference
• Relay driver chip with flyback diode for stable operation
• Reverse-polarity protection circuit
• Relay contact rating: ≤30A at 250V AC or ≤30A at 28V DC
• DIN rail-mount ABS enclosure
• Three status LEDs for MCU activity and RS-485 communication

Specifications

Power Supply	DC 7~36V
Communication Interface	RS485
Communication Baudrate	4800, 9600, 19200, 38400, 57600, 115200, 128000, 256000
Default Communication Format	9600, N, 8, 1
Relay Channels	4 Channels
Relay Type	High-power relay
Contact Form	1NO 1NC
Contact Load	≤30A 250V AC or ≤30A 28V DC
Modbus Protocol	Standard Modbus RTU protocol
RS-485 Address Setting	1~255
Indicator	STA: MCU indicator, keeps flashing when MCU is working normally TXD: Transmit Data indicator, lights up when transmitting data RXD: Receive Data indicator, lights up when receiving data

Resources

• Product Wiki

Package Contents

• 1x 4-Channel Modbus RTU Relay Module with RS-485 Interface

Power supply not included.