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What are the Most Popular PLC Programming Languages?


There are 5 languages that
are all a part of the IEC (International Electrotechnical Commission) Section 61131-3 Standard. This IEC Standard allows
some ground rules that standardize PLC’s
and their languages. Let’s take a deeper look into all
these PLC Programming Languages. Before we get started
on today’s video, if you love our videos, be sure to click the
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notifications of new RealPars videos. This way you never
miss another one! The 5 PLC Programming Languages
are Ladder Diagram (LD), Sequential Function Charts (SFC), Function Block Diagram (FBD), Structured Text (ST), and
Instruction List (IL). Let’s show you a little
bit about each of these. I will start with Ladder Diagram which is a graphical type of
PLC Programming Language. Ladder Diagram was originally
modeled from relay-logic which used physical devices, such as switches and mechanical
relays to control processes. Ladder Diagram utilizes
internal logic to replace all, except the physical devices that need an electrical
signal to activate them. Ladder Diagram is built in
the form of horizontal rungs with two vertical rails that
represent the electrical connection on relay-logic schematics. You can program all the
necessary input conditions to affect the output conditions,
whether logical or physical. The main advantages of the
Ladder Diagram language are that the rungs allow it to
be organized and easy to follow. It also lets you document comments that are readily visible, and it supports
online editing very successfully. The main disadvantage is that
there are some instructions that are not available, which might make it more difficult for
programming such as motion or batching. The next PLC Programming Language that I will talk to you is the
Sequential Function Charts which uses a graphical
type of programming. If you have any experience
with flowcharts, then this PLC Programming language
will feel familiar to you. In Sequential Function Charts, you use steps and transitions
to achieve your end results. Steps act as a major
function in your program. These steps house the actions that occur when you
program them to happen. This decision can
be based on timing, a certain phase of the process, or
a physical state of an equipment. Transitions are the
instructions that you use to move from one step to another step to another step by setting
conditions of true or false. Unlike traditional flowcharts, the Sequential Function Charts
can have multiple paths. You can use branches to initiate
multiple steps at one time. A couple of the advantages of
Sequential Function Charts are: Processes can be broken
into major steps that can make it faster and
easier troubleshooting. You have direct access in the logic to see where a piece
of equipment faulted. It can be faster to design
and write the logic due to the ability to use repeated
executions of individual pieces of logic. Even when you consider the advantages
of the Sequential Function Charts, this PLC Programming Language does
not always fit every application. Now we are on to our third
PLC Programming Language. The Function Block Diagram which is
also a graphical type of language. The Function Block Diagram describes a
function between inputs and outputs that are connected in
blocks by connection lines. Function Blocks were originally
developed to create a system that you could set up
many of the common, repeatable tasks, such as
counters, timers, PID Loops, etc. You program the
blocks onto sheets and then the PLC constantly scans
the sheets in numerical order or is determined by connections
which you program between the blocks. The code can get disorganized using
this PLC Programming Language because you can place the function
blocks anywhere on the sheet. This can also make it more
difficult to troubleshoot. The Function Block Diagram does
work well with motion controls and the visual method is
easier for some users. The biggest advantage of
Function Block Diagram is that you can take many
lines of programming and put it into one or
several function blocks. Our 4th PLC Programming Language that I am
going to review is the Structured Text. This language is a
textual based language. Structured Text is a high-level language
that is like Basic, Pascal and “C”. It is a very powerful tool
that can execute complex tasks utilizing algorithms and mathematical
functions along with repetitive tasks. The code uses statements that
are separated by semicolons and then either inputs, outputs, or variables are changed
by these statements. You must write out
each line of code and it uses functions such as FOR,
WHILE, IF, ELSE, ELSEIF AND CASE. If you have experience
with Basic or C languages, this PLC Programming
Language will come easier than some of the other languages. Some of the advantages
of Structured Text are that is very organized and good at
computing large mathematical calculations. It will also enable you to
cover some instructions that are not available in some other
languages like the Ladder Diagram. The disadvantages are that
the syntax can be difficult, making it hard to debug and it
is difficult to edit online. I will now show you the 5th and
final PLC Programming Language which is Instruction List. The Instruction List is also
a textual based language. The Instruction List language
resembles Assembly Language. When you use this PLC
Programming Language, you will use mnemonic codes such
as LD (Load), AND, OR, etc. The Instruction List contains instructions with each instruction on a new line with any comments you might want to
annotate at the end of each line. This Instruction List language
is valuable for applications that need code that is
compact and time critical. The main disadvantages of
this PLC Programming Language are that there are few
structuring possibilities with the Goto command
being one of them. There can also be many errors that are more difficult to
deal with in comparison to many of the other languages
that I have previously reviewed. So, have you decided which
PLC Programming Language you consider to be the most popular? After reading many reviews and
opinions and with my own experiences, the Ladder Diagram language
is by far the most popular. The main reason for this is that the
Ladder Diagram language naturally followed the
technology advancement from a physical relay logic
to a digital and logical one. This allowed the engineers
and skilled workers to follow and troubleshoot
and make that transition. In summary, there is certainly a place
for all the PLC Programming Languages that I have discussed with you today. Background, experience and the
application you are working with are really going to be the key to which
PLC Programming Language you choose. Want to learn PLC programming
in an easy to understand format and take your career to the next level? Head on over to realpars.com

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