IEC 61131-3 Standard: The Core Foundation of Modern PLC Programming

Folks Automation - Bahasa pemrograman PLC menurut standar IEC 61131-3
Folks Automation - Bahasa pemrograman PLC menurut standar IEC 61131-3

Industrial automation is moving fast. But one thing remains the foundation for every engineer: the ability to program a Programmable Logic Controller (PLC). If you imagine a PLC as the “brain” of a factory, then IEC 61131-3 is the international grammar. It ensures that the brain communicates effectively, structurally, and universally.

At Folks Automation, we often see technical teams struggling to migrate between PLC brands. This usually happens because they rely on only one specific language. This is where the IEC 61131-3 standard comes as the solution. This article will dive deep into why this standard is crucial, the types of languages involved, and its real-world implementation.

What is the IEC 61131-3 Standard and Why Does It Matter?

IEC 61131-3 is part of the international standard for programmable controllers. It defines the software architecture and the set of PLC programming languages according to the IEC 61131-3 standard. Before this, every vendor (like Siemens, Rockwell, or Schneider) had unique ways that were often incompatible with each other.

We see IEC 61131-3 as the “English” of the industrial world. Standardizing your workflow allows for:

  • Code Portability: Easily move program logic from one device to another.
  • Reduced Training Costs: Engineers only need to learn one standard to master various PLC brands.
  • Efficient Debugging: A neat structure makes it easier to track errors.

The 5 PLC Programming Languages According to the IEC 61131-3 Standard

This standard offers five languages divided into two main categories: Graphical and Textual.

1. Ladder Diagram (LD) – The Timeless Classic LD is the most popular language. It uses symbols similar to electrical circuit diagrams (relay logic).

  • Analogy: Imagine a train track. Electricity flows from the left rail to the right rail through “rungs” if all switches (contacts) are closed.
  • Strength: Very easy for electricians to understand due to its similarity to physical wiring schematics.

2. Function Block Diagram (FBD) – Visual Logic Flow FBD represents functions as boxes connected by signal lines.

  • Analogy: Like assembling a puzzle or using patch cables in a music studio. Inputs enter a “Logic” box, and the result flows to the next box.
  • Strength: Highly effective for analog signal processing and complex process control.

3. Sequential Function Chart (SFC) – The Flow Conductor SFC divides large processes into steps and transitions.

  • Analogy: Like a flowchart or a cooking recipe. Step 2 won’t start until Step 1 is finished and certain conditions are met.
  • Strength: Provides a “big picture” of the machine’s work sequence, helping manage complex processes.

4. Structured Text (ST) – The Power of Modern Programming ST is a text-based language very similar to C, Pascal, or Python.

  • Analogy: Like writing detailed instructions: “IF temperature is over 50 degrees, THEN turn on the fan.”
  • Strength: The most powerful for complex mathematical calculations and data manipulation.

5. Instruction List (IL) – The Low-Level Language IL is similar to Assembly language, based on short command lines.

  • Current Status: While still in the standard, IL is rarely used in new projects because it is difficult to read and maintain. However, it is very efficient for small memory usage.

Case Study: Automated Logistics Sorting System

Let’s look at a real project we handled: A package sorting system based on weight and destination. We combined different PLC programming languages according to the IEC 61131-3 standard for maximum efficiency:

  • SFC (Sequential Function Chart): Used as the main structure (Step 1: Entry, Step 2: Weighing, Step 3: Sorting).
  • ST (Structured Text): Used to calculate weight averages and process barcodes. Doing math in Ladder is a headache.
  • LD (Ladder Diagram): Used for safety and simple motor control. If the Emergency Stop is pressed, the Ladder immediately cuts the power.

Why You Should Switch to the IEC 61131-3 Standard Now

  1. Investment Security: Your business logic won’t be locked into one vendor (Vendor Lock-in).
  2. Team Collaboration: An engineer in Jakarta can easily understand code written by an engineer in Germany.
  3. IoT Integration: This standard simplifies data structures, making them ready for modern IT systems and the cloud.

Quick Tips for Success

  • Understand Boolean Logic: Master AND, OR, NOT, and XOR first.
  • Use the Right Tool: Try software like CODESYS to practice all five languages.
  • Documentation is Key: Good code is code that others can read without having to ask the author.

Conclusion The IEC 61131-3 standard brings efficiency, safety, and flexibility to your production floor. Whether you are a student or a plant manager, mastering these languages is a priceless long-term investment.