Project Hub /Robotics & Autonomous Systems/Motor Drivers & Motion Control/RS-485 MODBUS Serial Communication using Arduino UNO as Slave

Intermediate

ARDUINO

₹500 – ₹1,500

3 – 6 Hours

Partial Kit

RS-485 MODBUS Serial Communication using Arduino UNO as Slave

Learn how to configure an Arduino UNO as a Modbus Slave using RS-485 communication to control LEDs and a servo motor from a PC.

Originally published on CircuitDigest

View original tutorial

Parts You'll Need

This project is sourced from another site, not written by us — this list is our best match of their components against what we stock, not a verified bill of materials. Always check the original blog (linked above) for the actual parts list before buying.

Arduino UNO R3 Board (Compatible) – ATmega328P Microcontroller with USB Cable Rs. 999.00
USB to UART/ESP8266 Adapter Programmer for ESP-01 WiFi Modules with CH340G Chip Rs. 99.00
10pcs 5mm RED Diffused Light Emitting Diodes - LEDs Set Rs. 39.00
10pcs - 220 ohm 1/4 W Resistor Set Rs. 39.00
TowerPro SG90 Mini Servo – 180 degree Rotation – Standard Quality Rs. 179.00
400 Points Mini Solderless Prototype PCB Breadboard High Quality Rs. 89.00
MB102 Adjustable Breadboard Power Supply Module (3.3V & 5V) for Arduino & Raspberry Pi Rs. 139.00
Jumper Wire 10 Pin Male To Male 20cm Rs. 45.00
Jumper Wire 10 Pin Male To Female 20cm Rs. 45.00

Selected: Rs. 0.00

This list includes a generic resistor set as a placeholder — it is not matched to the exact value or part number this circuit needs. The correct one is specified on the original source page linked above; check it before buying.

We don't carry yet: LCD (generic / unspecified)
Potentiometer / Trimpot

Browse all components

How It Works

This industrial-inspired automation project establishes robust serial communication between a PC and an Arduino Mega 2560 configured as a Modbus slave. The system utilizes the ModbusRtu protocol over a reliable RS-485 physical layer, interfaced through a MAX-485 TTL to RS-485 converter module and a USB to RS-485 converter module on the PC side. When commands are dispatched from the Simply Modbus Master Software running on the computer, the Arduino interprets the incoming differential signals. Depending on the registers addressed, the microcontroller triggers various peripheral actions: it toggles two discrete LEDs protected by 1k-resistors, positions an SG-90 servo motor to a specified angle, and refreshes system status text on a 16x2 LCD display driven by the LiquidCrystal library. Contrast for the 16x2 display is fine-tuned locally using a 10k potentiometer. This master-slave architecture allows reliable multi-device command routing over longer physical distances than standard TTL serial permits, demonstrating how microcontrollers integrate into broader industrial control networks.

Why Build This

Master industrial Modbus protocol implementation and differential serial bus topologies relevant to modern plant automation and PLC integration.

Gain hands-on experience interfacing microcontrollers with heavy-duty communication hardware like MAX-485 transceivers for long-distance data transmission.

Develop practical undergraduate-level systems engineering skills by combining digital actuation, servo control, and human-machine interface feedback over a shared network.

Real-World Application

Used in industrial automation, PLCs, home automation, and sensor networks requiring robust long-distance serial communication.

Skills You'll Learn

RS-485 serial communication

Modbus protocol implementation

industrial network architecture

servo motor control

LCD interface programming

digital output switching

Safety Precautions

No specific precautions noted for this build — always follow general electronics safety practices.

Technology Tags

RS-485

MODBUS

SERIAL COMMUNICATION

ARDUINO

MAX485

SERVO MOTOR

LCD

Frequently Asked Questions

Why is an RS-485 converter used instead of a standard USB cable directly to the Arduino?

Standard USB cables have strict length limitations and are prone to data corruption in electrically noisy environments. RS-485 uses differential signaling over twisted-pair wire, allowing reliable serial communication over much longer distances typical of industrial applications.

What is the role of the Simply Modbus Master Software?

The software runs on your PC to act as the Modbus Master, sending structured read and write commands across the serial bus to request data or control outputs on the Arduino slave device.

Can I use an Arduino UNO instead of the Arduino Mega 2560?

While the project title references an Arduino UNO, the platform parameters specify the Arduino Mega 2560; ensure your code matches the specific hardware serial ports available on your chosen board.

Gallery

This page is part of Kitkraft's Project Hub — a curated collection of electronics & robotics projects gathered from the maker community to help students and hobbyists discover and learn to build. Kitkraft does not claim authorship of the original project, and makes no representation as to the accuracy, completeness or safety of third-party source material. The summary and "How It Works" explanation above are AI-generated, rewritten with reference to the original tutorial — not a reproduction of it. Full credit and a direct link to the original source are provided above. If you're the original creator and have a concern about how your work is represented here, please contact us and we'll address it promptly.

Kitkraft Project Hub — curated from the maker community, credited at the source.

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