PLC on a PCB with ATmega328P

Step into any modern factory and you’ll see a wide range of automated machinery, making the stuff that ends up in stores and listed online for purchase via a few clicks. Inside these machines’ electrical cabinets, you’ll find an array of devices, typically anchored by a PLC, or programmable logic controller.

While PLCs perform the same sort of function as an Arduino Uno et al. – e.g. turn on output X in response to sensor input Y and Z – there are some major differences in how they are designed and priced. PLCs are hardened industrial devices, meant to function day after day, and (hopefully) year after year, while being exposed to vibration, extreme temperature, and more. They also generally work with 24VDC power by default and often interface with industrial protocols like RS485.

PLCs can carry a hefty price tag as well, especially for more well-known brands (which may be worth it considering the cost of downtime). As seen here, YouTuber Mr Innovative came up with a single-board PLC design based on the ATmega328P of Arduino Uno/Nano fame. It features (6) 24VDC digital input pins, along with (4) 24VDC transistor outputs which could be used for servo or stepper motor control. It’s also DIN rail mountable, which would be very helpful in industrial situations.

The video below shows this in action, using its RS232 capabilities to interface with an HMI, while controlling a motor using a VFD via RS485. Although you might not want to sub this for control of a million dollar-plus assembly cell, it could work very well as a learning and experimental tool for industrial automation.