【Prized Discussion】Which will be mainstream in the future: LD ladder logic or ST structured text?
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In current PLC programming, which language is used more often? Ladder diagram or ST structured text? Which do you think will become the mainstream of programming in the future? Let’s first take a look at the responses from some netizens: Netizen A: ST or other high-level languages are like high-quality products available in exclusive shops, while ladder diagrams are like affordable products found in alleyways – it depends on the requirements. Netizen A: Our ancestors said that simplicity is the ultimate goal; the best programming language is one that can be understood by anyone who knows how to write programs, and ladder diagrams have the highest level of readability. Netizen B: ST is more convenient for handling arithmetic operations, while ladder diagrams provide a more intuitive way of representing points. Netizen C: The ladder diagram makes it simple and easy to understand the logic of the process. Once the program is written, it can be handed over to newcomers for debugging; basically, it’s possible to identify the problem just by taking a quick look at which instructions are not working properly. Complex calculations are ST’s strength, and ST can also significantly reduce the workload for encapsulating axes and standard programs. What’s truly practical is to choose the strengths of both and use them in combination. Netizen D: I haven’t written ladder diagrams in years. It’s not my concern whether others can understand them or not, but I use standard English for naming my variables. My programs may not be perfect, but it’s better to prepare for future needs by establishing my own standards! If it becomes standardized by others, you’ll easily lose your job! Netizen E: Ladder diagrams originated from the relay logic control circuit diagrams of the past; they were essentially a compromise made to help engineers of that era transition to program-controlled systems. These days, there are countless undergraduate degrees in engineering, and since everyone knows C language and microcontrollers, advanced text programming will gradually become the norm. What do you all think? Feel free to reply and leave comments for discussion! Participation reward: Users who participate in the discussion will receive 10 wealth points, limited to the top 20 responders!
In current PLC programming languages, ladder diagrams and ST structured text each have their own advantages and application scenarios. Ladder diagrams are highly suitable for implementing control logic due to their intuitiveness and ease of use; they are particularly appropriate for beginners and in situations where high requirements regarding program logic are not necessary. On the other hand, ST structured text is more similar to traditional high-level programming languages; it has inherent advantages in handling complex data operations and function encapsulation, making it suitable for application scenarios that require high levels of modularity and support for complex algorithms. Looking at future trends, as technology advances and the skills of programmers improve, ST structured text is likely to gradually become the standard, especially in the fields of industrial automation and intelligent manufacturing, where there are increasing demands for program complexity and flexibility. However, due to its simplicity and intuitiveness, ladder diagrams will still hold a certain market share in many practical applications. Therefore, the two languages may coexist for a long time and be used complementarily. In practical work, the choice of programming language often depends on the specific requirements of the project, the developer’s experience, as well as the needs for system maintenance and future expansion. .
The ladder diagram, a simple programming language, evolved from electricians’ relay control circuits; it deals with simple boolean values. Mitsubishi PLCs are particularly good at this aspect, and Mitsubishi PLCs are widely used in machinery factories. Its underlying mathematical logic is mathematical logical operations. To become an expert in self-control, you must master the ST language. Siemens also has its own instruction-set language, which is used in the S7-300 and 400 systems; it is similar to assembly language. Whether it’s the instruction set or the ST language, they are both primarily used for writing function blocks, which are then called from ladder diagrams. Of course, these days things are more mixed up as well – while working on a ladder diagram, it’s possible to insert a segment of ST code. ST statements are more advanced and suitable for computational processing; you can create many new variables within them. Beginners use ladder diagrams, and generally they create few intermediate variables; for example, using the M0.0 relay in Siemens S7-200 is an implicit use of intermediate variables. However, there are still very few intermediate variables used in the ladder diagram. There are also pointers and loop statements in the ST language, all of which are essential for growth.
It must be ST; for more complex calculations, ST is definitely used, as using LD requires too much effort. In practice, a mixed approach is often adopted, and due to the limited skills of on-site maintenance personnel, if ST is used exclusively, others won’t be able to understand it
The ST language is more convenient for SFC sequential control programs