Modbus RTU Single Relay Module DC7-24V RS232 TTL UART Board
Modbus RTU Single Relay Module DC7-24V RS232 TTL UART Board
Modbus RTU Single Relay Module — DC7-24V | RS232 / TTL UART
Take precise control of your digital and power switching projects with this compact, single-channel Modbus RTU relay module. Built around a mature and stable 8-bit MCU and a MAX3232 level-conversion chip, it communicates over the industry-standard RS232 or TTL UART interface and supports the widely used Modbus RTU protocol — making it an ideal building block for industrial automation, home automation, PLCs, and DIY electronics projects.
Key Specifications
- Power Supply Voltage: DC 7–24V
- Communication Protocol: Standard Modbus RTU
- Communication Interface: RS232 / TTL UART (dual interface)
- Core Chipset: 8-bit MCU + MAX3232 level-conversion chip
- Baud Rate: 4800 / 9600 / 19200 bps (default 9600 bps; power-failure saving supported)
- Optocoupler Input Signal Range: DC 3.3–24V (for digital detection only; not for relay control)
- Relay Output: 1-way, 5V coil — rated 10A/250VAC or 10A/30VDC
- Relay Endurance: Up to 100,000 continuous operations
- Output Modes: Manual, blinking, and blinking-delay modes; delay base = 0.1 s; max delay = 0xFFFF × 0.1 s ≈ 6,553.5 s
- Device Address Range: 1–255 (default 255)
- Protection: Onboard diode for flyback/leakage protection; short response time
- Indicator: Onboard relay-status LED
- Readable Parameters via Software: Baud rate, input signal status, relay status, device address
- EU LVD Compliance: Low voltage — below 50 VAC or 75 VDC
What's in the Box
- 1 × Single-channel Modbus RTU Relay Module
Important Notes
- Actual color may vary slightly from images due to monitor and lighting differences.
- Please allow ±1–10 mm tolerance from manual measurements.
Made in Mainland China.
For best practices on electrical wiring safety and low-voltage equipment, refer to the OSHA Electrical Safety guidelines.
Frequently Asked Questions
Q: What communication protocols does this relay module support?
A: The module supports the standard Modbus RTU protocol over both RS232 and TTL UART interfaces, making it compatible with a wide range of PLCs, microcontrollers (Arduino, Raspberry Pi, etc.), and industrial controllers.
Q: What baud rates are available, and are settings saved after a power cycle?
A: Supported baud rates are 4800, 9600, and 19200 bps. The default is 9600 bps. Both baud rate and device address settings are saved to non-volatile memory, so they are retained even after power is removed.
Q: What is the maximum load the onboard relay can switch?
A: The onboard relay is rated for 10A at 250VAC or 10A at 30VDC, with a mechanical endurance of up to 100,000 operations. It also features built-in diode protection to guard against inductive flyback.
Q: Can this module be used for both digital input detection and relay output simultaneously?
A: Yes. The module supports 1 optocoupler input (DC 3.3–24V) for digital signal detection and 1 relay output independently. Note that the optocoupler input is for detection purposes only and cannot directly trigger the relay — relay control is handled exclusively via Modbus RTU commands.