Design and Development of an AVR Microcontroller-Based Industrial Programmable Logic Controller

This script presents the design and implementation of an industrial Programmable Logic Controller (PLC) developed using the AVR ATmega2560 microcontroller and tailored for educational and industrial automation applications. This PLC integrates 15 digital inputs, 10 digital outputs, 10 analogue voltage inputs, 6 current loop analogue inputs (4–20 mA via precision shunt resistors), and 8 analogue voltage outputs generated through a DAC60508 over SPI, scaled for 0 –10 V operation using a precision op-amp circuit, utilising a compact design. Furthermore, the controller supports Modbus RTU communication over RS232, RS485, and USB interfaces, enabling interoperability with SCADA platforms such as ScadaBR. In addition to that, the firmware is developed using OpenPLC runtime, offering IEC 61131-3 compliant programming in ladder logic. Moreso, the system also supports I2C-based EEPROM for data retention, I2C-based expansion, and its real-time performance is validated through sequential process control and SCADA visualisation tests. This low-cost, flexible PLC platform provides an ideal foundation for teaching automation principles, prototyping industrial control logic, and exploring Industry 4.0 integration. In this context, this script aims to design and develop a low-cost, programmable logic controller based on the AVR microcontroller, providing versatile I/O options and multiple communication interfaces