Tips and tricks for PLC programming

1) Plan in advance

Using the correct system for programming your PLC will allow you to use the full eventuality of both your controller and your system. Creating, editing, and perfecting the PLC functionality can be made significantly easier by following introductory coding techniques. Below, you can find a list of practical tips and tricks for easier PLC programming, allowing you to find further space for enhancements to your design.

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Mentioned tips are generally applicable to any PLC; then, the UniPi programmable sense controllers were used for the show along with the Mervis-UniPi’s functionary supported software platforms offering its users scrutable development interface, HMI editor, SCADA interface, and numerous other useful features.

Thorough preparations and planning both on the tackle and the software position will save you a lot of time during the programming itself, reduce the number of errors, and better the overall inflexibility of your design. We also recommend keeping in mind that in the future you may need to extend your design by adding new features or factors. The more detailed your plan is, the less delicate the accomplishment of your project will be.

2) Choose the right programming approach

Mervis supports a pair of programming approaches- Function Block Diagram (FBD) and Structured Text (ST). Which one to choose? The choice should depend not only on your experience degree but also on the type of your project, as both styles have their own pros and cons and are suitable for different kinds of systems.

A Function Block Diagram is based on so-called function blocks- parts of the pre-defined law made to perform a specific function. By using the FBD you can fluently define the regulator routines, set conditions, produce input/ affair counters, etc. Thanks to their intuitive design function blocks are a good choice for newcomers or lower robotization design. FBD is, still, less suited to complex systems, as the high number of function blocks needed may beget performance drops and longer response times.
The Structured Text system, having a form of textbook law, is, on the other hand, suitable for complex fine functions or for repetitious tentative tasks. The main advantage of the ST is its capability to encompass indeed veritably complex functionality into only many lines of the law. The textbook law is, still, lower stoner-friendly and is suited rather for the more educated druggies.

3) Follow the tried and tested

rendering styles and structural ways
During the PLC programming, try not to produce exorbitantly complex canons, no matter which system you use. For illustration, an unnecessarily high number of function blocks will make harder not only the exposure in the design but also the hunt for any implicit crimes. We, therefore, recommend putrefying the law as much as possible by looking for repeating parts of the law and re-using them in another corridor of the design. A practical illustration if you’re programming an automated heating system in several apartments, you can produce a single law structure using the FBD and also simply bury it for each individual room. By doing that, you’ll save a large quantum of time and the performing law will have a high position of thickness.

4) Make notes, leave commentary

During PLC programming, it’s easy to lose track of the law, especially when working on complex systems containing dozens of function blocks or hundreds of lines of the law. For easier exposure to the law, we recommend writing down notes describing I/ O designations, the functionality of a function block, a short companion for the law, etc. With similar notes, you can fluently acquaint yourself with the law indeed after a longer time period and also make the design accessible to other druggies similar as associates, conservation crews, or guests. When used constantly, a string of commentary can also form a scrutable” homemade” for the design, describing in detail its functionality. In the case of function blocks, you can fit commentary into the Mervis IDE interface. ST druggies also can write their commentary directly into the law.

An illustration of a comment in the Mervis IDE

5) Produce and follow a picking convention

The arbitrary picking of valuables or function blocks, especially in complex systems, can make the work much harder not only for you but also for any other person working on the design. We therefore explosively recommend creating a unified template for names of variables and/ or function blocks and following that template during the entire work on the design. The Mervis IDE allows you to fluently re-name variables, I/ Zilches or regulators-this point is especially precious when searching through dozens of variables, where a unified picking convention can save you a lot of time and stress. The rearmost Mervis release also introduced the Hunt function, allowing you to search for a specific variable and all of its circumstances across the design.

6) Anticipate issues and produce fail-strongboxes

Indeed the stylish system will sooner or latterly witness some kind of error. What will your heating system do if a temperature detector fails? What will be if a counter on a regulator input overflows? Anticipate similar issues in advance during the planning phase, from simple element failure to a serious functionality error caused by unauthorized access, and also produce academic scripts for working on similar problems. With these scripts, you can also fluently apply to fail-strong boxes, fall- tails or exigency modes. For illustration, if a temperature detector fails in a heating system, you can program the regulator to automatically maintain a predefined temperature. You can also use these scripts to help mortal crimes by limiting the access of external druggies to critical system functions.

7) Test and check your law

In any phase of the design, it’s a good practice to regularly check variable values, function blocks, or law parts. By doing that you can help any implicit crimes when starting the system, similar to lighting switches not working due to a defective variable setting, or a failure to switch heating due to a mistake in one of the function blocks. For the purpose of debugging, the Mervis IDE features a devoted Debugging Mode; in this mode, all variable values are displayed in the IDE without the need of checking them collectively, allowing you to snappily look for typos, wrong values, or other types of miscalculations. The system will also automatically punctuate function blocks with incorrect configuration, precluding the system from working as intended. Last but not least, the debugging mode will allow you to display a graph of variable value changes over time.

Mervis IDE with the Debugging Mode enabled, displaying both variable values and variable value change graph.

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Tips and tricks for PLC programming