Large PLC – Open Source Hardware

The large brick-type open source PLC has 22 digital inputs, 6 analog inputs and 16 transistor outputs. It also features a SD card socket, 2 RS-232 ports, 1 RS-485 port, 1 USB device port and a JTAG port for programming and debugging.

Large Open Source PLC

Large Open Source PLC

All the source files including circuit diagrams for building the large open source PLC are available for download at the above link.

12 thoughts on “Large PLC – Open Source Hardware

  1. Very nice buid!

    Are the analog inputs protected from overvoltage?
    Probably the main thing missing is to be able to program it in Ladder over USB or RS-232.If you manage to do that, plus the ability to monitor ladder variables in real time, you have a commercially viable product.

    • Thanks, Martin.
      There is no overvoltage protection on the analog inputs. The only thing that can be done to protect these inputs is to change the voltage dividers on them to handle a higher voltage, at the expense of losing some resolution.
      Yes, I have considered writing a ladder compiler for the PLC – just need to find the time to do the software development now 🙂

  2. Hi

    I want to know that what is the software running inside the ARM processor of your PLC.

    How does it load the ladder logic of PLC and act accordingly.


    • The reason that I made this PLC was because I wanted a PLC that I could program in the C programming language. There is no ladder logic interpreter for this PLC. Ladder logic is very restrictive and designed for electricians so that they could think in terms of relays and circuits. I can use this PLC in all sorts of niche applications where it is difficult or impossible to program in ladder.

  3. ok dear

    I got that this can be programmed in the C language , so can you please provide me some example source code in C program which you have used to control the peripherals.


    Piyush Pandey

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