Modbus-RTU 4 Channel Relay Module RS485

This 4-channel Modbus relay module is based on a stable 8-bit microcontroller and an RS485 communication interface.
It supports the standard Modbus RTU protocol, allowing reliable communication over RS485 networks. The module provides 4 opto-isolated digital inputs and 4 relay outputs, making it suitable for both signal monitoring and control applications.
Typical use cases include remote switching, system automation and integration into industrial or embedded control systems.

⚙️ Specifications

– Microcontroller: onboard 8-bit MCU
– Communication protocol: Modbus RTU (standard)
– Interface: RS485 / TTL UART
– Baud rate: 4800 / 9600 / 19200 bps (default: 9600, stored in memory)

– Device address: 1–255 (default: 255, stored in memory)

– Inputs:
– 4 opto-isolated digital inputs
– Input voltage range: DC 3.3V – 30V
– Note: inputs are for signal detection only (not for direct relay control)

– Outputs:
– 4 relay outputs
– Relay rating: 10A @ 250V AC / 10A @ 30V DC
– Electrical lifetime: approx. 100,000 switching cycles
– Built-in flyback diode protection
– Status LEDs for each relay

– Control modes:
– Manual switching
– Pulse / timed switching
– Delay control (time base: 0.1 seconds)
– Maximum delay time: 6553.5 seconds

– Configuration:
– Device address, baud rate, input status and relay states can be read and configured via Modbus commands

– Power supply:
– DC 7V – 24V
– Supports both DC jack and screw terminal input
– Reverse polarity protection

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