There are five different PLC programming languages, all of which are in accordance with International Standard IEC (International Electrotechnical Commission) 61131-3. These are the five distinct types of PLC programming languages, in accordance with this standard:
- Ladder Diagram(LD)
- Function Block Diagram(FBD)
- Structured Text(ST)
- Instruction List(IL)
- Sequential Function Chart(SFC)
One of two categories—graphical or textual—applies to each of these languages. Textual languages employ strings of text, whereas graphic languages use visual features.
Taking a closer look at each of these languages individually
1. Ladder Diagram(LD)
A graphical PLC programming language based on relay logic’s circuit diagrams is known as Ladder Logic, sometimes refer as Ladder Diagram as well. Two parallel bars are join by a sequence of rungs to form Ladder Logic, which has the appearance of a ladder (hence, the name). These rungs have contacts and coils that stand in for inputs (like a sensor value) and outputs (like an instruction to start a motor), respectively.
Ladder Logic is widely used in North American control system programming, and for good reason. It is adaptable, versatile, troubleshootable, and simple to learn. Nevertheless, one disadvantage is that after a ladder reaches a certain number of rungs, it can become cumbersome and require splitting into several ladders for maintenance.
Some use cases that lend themselves to ladder logic include systems with plenty of Boolean algebra, state machines, and PID control.
Ladder Diagram (LD) Benefits
- Simple to learn, comprehend, and apply
- For the majority of instructions, the visual language Ladder Logic offers status confirmations. In other words, even someone with a limited understanding of a certain process may readily follow the programmed and understand the logic.
- Ladder Logic | Modular Design may easily be modifiy through adding or deleting logic. Each rung stands for a unique condition that may be added or deleted as necessary.
- The user may create a broad variety of functions thanks to the durability and consistency of Ladder Logic. Nevertheless, the language lacks total flexibility and is heavily standardized, producing code that is constant across implementations.
- The discrete logic may be represent in a very practical way.
2. Flowchart of a Function Block (FBD)
Another well-liked graphical PLC programming language is Function Block Diagram (FBD). It is made up of a variety of blocks with inputs and outputs. Variables can be supplied to an output and connected devices can be linked to an input. Blocks can also be connected to one another such that the output of one block can flow into the input of another. These building components specify how a system works.
While needing some training to use, the FBD language is rather easy. It’s a fantastic option for PID loops and safety-related PLCs, as well as when you need to encapsulate, reuse code repeatedly, conceal or protect data, or do analogue input filtering
Function Block Diagram (FBD) benefits include:
- Simpler thanks to a manner of pictorial representation
- Each block has numerous lines of logic, similar to a repetitious activity.
- The ability to reduce several lines of code into one or more function blocks is the main benefit of function block diagrams.
3. Structured Text (ST)
PLC programming is done using the high-level language Structured Text (ST). Those who have studied these kinds of computer programming languages will find it easier to use because it is a textual language with syntax similar to C or C++. In S.
ST is a clear language that runs swiftly and is not too difficult to read. Nevertheless, since the states of the variables aren’t always obvious, troubleshooting it can be a more difficult procedure. This language excels in complex algebra, barcode parsing, looping, data manipulation, bridge to machine code, and data searching.
Merits of Structured Text (ST):
- excellent with mathematical reasoning and sophisticated algorithms.
- Because of the common code format, programming is simple to adapt.
- You’ll be able to discuss a variety of instructions that aren’t available in other languages, including the ladder diagram.
Also check: How Deep Learning Is Applied In The Field Of Stock Market
4. Instruction List (IL)
One of the PLC programming languages that resembles assembly programming is called Instruction List (IL). The language has a number of instruction lists.
It’s unlikely that new PLCs would be programmed with Instruction List because it was deprecated in the IEC standard. Yet, since some modern PLCs could still employ IL, it’s useful to understand what it entails.
IL is similar to assembly language in that it consists of a short list of instructions. “Jump” or “store” are examples of some of the usual instructions you’d utilize in Instruction List. If you’re thinking about utilising IL in new apps, you should choose Structured Text instead because IL has been deprecated.
Benefits of an Instruction List (IL):
- High Speed of Execution
- Reduced memory use than other PLC programming languages.
5. Sequential Function Chart(SFC)
Sequential Function Charts (SFC), a GRAFCET-based graphical PLC programming language that mimics algorithm flowcharts, was developed. SFC comprises of transitions and stages. Steps are the tasks that must be completed, and transitions are the logical requirements that must be satisfied before proceeding to the following step. The operational flow of a programme is controlled by SFC because of the structure of this architecture.
SFC’s ability to deconstruct a complex process into more manageable pieces simplifies it, which is one of its main advantages. In comparison to some of the other languages used here, it may also be simpler to test and troubleshoot. SFC works best for batch production, connected processes, complicated multi-state processes, and activities that need to operate in parallel or sequentially.
Advantages of Sequential Function Chart(SFC)
- Simple to comprehend programme control overall.
- Because of the repeating instructions, logic is simple to build and adapt.
This article is all about the many PLC programming languages that are often used. These programming languages are also usable when creating PLCs based on automation projects.
Use this information if you are unsure about the programming language to learn for a PLC and are confused. With a small PLC or modular PLC, getting started is simple.
