5 Common PLC Programming Mistakes and How to Avoid Them

5 Common PLC Programming Mistakes and How to Avoid Them

Blog Article

PLC programming is one of the most sought-after skills among automation engineers. It allows them to communicate with Programmable Logic Controllers (PLCs) and define how these controllers interact with sensors and actuators on the factory floor. To communicate effectively with a PLC, you need to understand its language and how to write proper code.

In this blog, we’ll discuss five common PLC programming mistakes and how to avoid them, helping you feel more confident in your programming and troubleshooting skills.

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Mistake 1: Programming Without Defining Goals

One of the biggest mistakes programmers make is starting a project without clear goals. Without understanding the project’s requirements, programmers may waste time, miss key functionalities, or end up causing costly downtime and changes later.

How to Avoid It:
Before programming, clearly define the purpose of your project. Refer to the Functional Design Specification (FDS) document, which outlines the expected behavior of the process. This will help you break the project into smaller, manageable tasks and ensure your code aligns with the project’s objectives.

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Mistake 2: Poor Naming and Lack of Comments

Using unclear variable names and skipping comments can make PLC programs difficult to read and troubleshoot, especially when the code needs updates or debugging. This creates problems not just for you but for your entire team.

How to Avoid It:

• Use meaningful and descriptive names for variables and functions.


• Add clear comments to explain complex parts of the code, making it easier to understand.
  For example, add prefixes like “in” for hardware inputs and “ou” for outputs to improve clarity. Comments and proper naming ensure that your PLC program is easy to maintain and debug.

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Mistake 3: Overcomplicating Logic

Some programmers overcomplicate their code by adding unnecessary conditions or writing the entire program in a single block. This not only makes the code harder to troubleshoot but also increases errors and system inefficiencies.

How to Avoid It:

• Write simple, step-by-step logic by breaking tasks into smaller parts.


• Use modular programming techniques such as Functions and Function Blocks to improve readability and reduce code repetition.
  For example, if you need to repeatedly convert temperature from Celsius to Fahrenheit, create a function block to handle this task. This makes your program reusable and efficient.

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Mistake 4: Ignoring Proper Testing and Simulation

Skipping the testing phase or relying only on physical testing can lead to critical errors in real-world operations. Testing is crucial to ensure your PLC program works as intended.

How to Avoid It:
Use the simulation tools available in your PLC programming software. For instance, Siemens TIA Portal offers PLCSIM, while Allen-Bradley systems use tools like Studio 5000 Emulator. You can also use 3D simulators like Factory I/O for testing smaller programs. Simulating your code early ensures smoother deployment and reduces the risk of failures in industrial environments.

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Mistake 5: Neglecting Continuous Learning

PLC programming technologies and software evolve rapidly. Programmers who stick to outdated knowledge may find it challenging to work with modern systems, limiting their career growth and opportunities.

How to Avoid It:
Engage in continuous learning through online courses, technical blogs, forums, and PLC-related communities. Keeping up with new tools and features ensures you remain competitive in the industry.

 

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