Modbus RTU 4-Channel Relay Module AC220V RS485 TTL UART
Modbus RTU 4-Channel Relay Module AC220V RS485 TTL UART
Modbus RTU 4-Channel Relay Module — AC220V Power Supply with RS485/TTL UART Interface
Take full control of your automation projects with this robust 4-Channel Relay Module. Powered directly from AC220V, it features a stable 8-bit MCU, MAX485 level conversion chip, and supports the widely-used Modbus RTU protocol over RS485 or TTL UART interfaces. Whether you're building an industrial control panel, a smart home automation system, or a prototyping project, this relay board delivers reliable, repeatable performance with power-failure memory preservation built right in.
Key Features
- AC220V Power Supply: Runs directly from mains voltage — no additional power converter needed.
- 4 On-Board Relays: Each relay rated at 10A/250V AC and 10A/30V DC, capable of 100,000+ continuous switching cycles.
- Modbus RTU Protocol: Industry-standard communication for seamless integration with PLCs, HMIs, and microcontrollers.
- Dual Interface Support: Compatible with both RS485 and TTL UART for maximum flexibility.
- Adjustable Baud Rate: Supports 4800, 9600, and 19200 bps (default: 9600 bps) — settings preserved through power cycles.
- Power-Failure Memory Preservation: Device address and baud rate settings are retained even after power loss.
- Multiple Output Modes: Supports manual, flash-closing, and flash-breaking modes. Flash delay base is 0.1s with a maximum configurable time of 6553.5s (0xFFFF × 0.1s).
- Optocoupler Input: Accepts DC 3.3–24V input signals for isolated triggering.
- Visual Indicators: On-board LED indicator lights for each relay channel for quick status monitoring.
- Diode Flyback Protection: Built-in diode protection safeguards against voltage spikes, ensuring long-term circuit reliability.
- Configurable Device Address: Address range 1–255 (default: 255), power-off preserved.
Technical Specifications
| Parameter | Value |
|---|---|
| Power Supply Voltage | AC 220V |
| Number of Relay Channels | 4 |
| Relay Rating | 10A / 250V AC | 10A / 30V DC |
| Communication Protocol | Standard Modbus RTU |
| Communication Interface | RS485 / TTL UART |
| Baud Rate | 4800 / 9600 / 19200 bps (default 9600) |
| Optocoupler Input Range | DC 3.3V – 24V |
| Device Address Range | 1 – 255 (default 255) |
| Relay Lifespan | 100,000+ cycles |
| Country of Origin | Made in China |
What's in the Box
- 1× 4-Channel Relay Module Board
- Or 1× Protective Shell (depending on variant selected)
Safety & Compliance
When working with mains-voltage (AC220V) equipment, always follow proper electrical safety practices. For guidance on safe electrical wiring and handling, refer to OSHA Electrical Safety Standards.
Frequently Asked Questions
Q: What communication protocols does this 4-channel relay module support?
A: This relay board supports the standard Modbus RTU protocol and is compatible with both RS485 and TTL UART interfaces, making it easy to integrate with a wide range of PLCs, microcontrollers (such as Arduino or Raspberry Pi), and industrial HMI systems.
Q: Will the relay module retain its settings after a power outage?
A: Yes. This module features power-failure preservation, meaning the configured baud rate and device address are stored in non-volatile memory and will be retained even after the power is completely cut. No reconfiguration is needed upon restart.
Q: What is the maximum load each relay channel can switch?
A: Each of the four on-board relays is rated at 10A / 250V AC for AC loads and 10A / 30V DC for DC loads, making them suitable for controlling lighting, motors, solenoid valves, and other moderate-power devices.
Q: Can I use the optocoupler input to control the relays directly?
A: No — the optocoupler input (DC 3.3–24V) is intended for isolated signal input and cannot be used directly for relay control. Relay switching is managed via the Modbus RTU commands sent over the RS485 or TTL UART interface.