In the lift industry, Ladder Logic has been the traditional programming method for many years. Because it closely resembles electrical relay circuits, it has been widely accepted by electricians and maintenance engineers.
Our company has also relied on Ladder Logic for many of our lift control systems.
However, as projects become more sophisticated and customer requirements continue to increase, we began looking for programming methods that provide greater flexibility and better readability.
Recently, we completed our first elevator PLC program written entirely in Structured Text.
From Electrical Logic to Software Logic
Traditional ladder diagrams work very well for simple applications. But when more functions, safety devices, and operating conditions are added, the program can quickly become large and difficult to maintain.
Structured Text allows us to write control logic in a more concise way.
Complex conditions can be expressed in a single statement, making the control sequence easier to understand.
For engineers who come from both electrical and programming backgrounds, ST provides an excellent bridge between machine control and software development.
Our First Practical Project
Our first Structured Text application was a simple two-floor lift.
The program successfully controls:
Upward movement.
Downward movement.
Safety circuit monitoring.
Safety edge protection.
Upper limit safety.
Basic motor interlocking.
Although this is a small project, it demonstrates that Structured Text can be applied successfully to standard lift applications.
Benefits We Observed
After completing the project, several advantages became clear.
Improved readability
The control logic is easier to follow compared with large ladder diagrams.
Easier troubleshooting
Conditions can be reviewed quickly without tracing numerous ladder rungs.
Better scalability
Future functions can be added without dramatically increasing program complexity.
More flexible development
Structured Text allows engineers to think about control systems in a more structured and software-oriented way.
Looking Ahead
This first program is only the beginning of our Structured Text journey.
Future developments may include:
Multi-floor lift control.
Automatic door systems.
Fault diagnosis functions.
Human-machine interfaces.
Maintenance modes.
Parameter configuration.
Remote monitoring.
As the lift industry continues to evolve, we believe that combining traditional electrical experience with modern programming techniques will create better and more reliable control systems.
You can read the complete article here:
https://beaconindustriesltd.com/blogs/news/from-ladder-logic-to-structured-text-plc-elevator-program
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