Sequential Function Chart (SFC) Programming for Beginners

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⌚Timestamps:
00:00 - Intro
00:51 - What is a sequence in SFC?
01:36 - Init step
02:02 - Step or State
02:08 - Transition
03:20 - Action and Qualifiers
04:14 - SFC example
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In this video, we’ll introduce you to a PLC programming language called Sequential Function Chart, or SFC for short. We will also look at an SFC example.
The PLC programming standard IEC 61131-3 includes five programming languages:
- Ladder Diagram
- Function Block Diagram
- Instruction List
- Structured Text
- Sequential Function Chart
The SFC programming language is different compared to the four other languages. The SFC is used to program a sequence directly in the PLC.
An SFC program is composed of graphic symbols. Each graphic symbol represents one step. A step is the same as a state.
- Init step: The first graphic symbol is used for initialization. This is named the init step. This is a square that is double-lined. Inside the square is a step name. When the PLC turns on the program will go into the initialization step and stay there.
- Step or State: A Step is a single-lined square.
- Transition: Each step is connected to the next step by a connection line. And a small horizontal line is added and this is called the transition. At the transition line, there must be a condition.
- Action: An action can be added to a step if required. A line connects the Step to the Action.
- Qualifiers: Inside the action box is a qualifier:
- An N qualifier means that the variable is TRUE only when the step is active. Therefore you don’t need to set the variable to FALSE when leaving the Step action.
- When using S as a qualifier, a TRUE will be stored for the variable inside the memory. This is used to keep the variable TRUE when leaving the step.
- If you need to reset the stored variable value, you can use R as a qualifier.
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[@steyn5511]

Hele toffe video!😁👍🏻

[@realpars]

Dank je wel!

[@davidpalmer963]

How the specific information is presented in these Videos, is very well thought out. IN one paragraph alone, at least 10 key functional points are administered to the viewer. Concise and to the point....That's REAL PARS!

[@realpars]

Thank you very much! We're happy to read that, David.

[@jdgakuba7137]

Thanks a lot Real Pars!

[@realpars]

Our pleasure!

[@davebennett5069]

thank you for expounding upon the specific reasons i don't use this. SFC is simultaneously more complex and less capable than other languages.

[@yssing]

I use that all the time when analyzing any given situation that needs to be translated to ladder or ST.

[@ahmedmaher5247]

Thanks for your efforts ❤️

[@realpars]

You're very welcome!

[@aliabd-alhalim4695]

Well...Its awonderful explanation with u wish u always more success.

[@realpars]

Thank you so much, Ali!

[@deniskalugin7984]

Thank you, RealPars! Always informative and easy-to-understand explanation! P.S. I hope I will be able to focus on studying your offline courses and continue to learn PLC and HMI programming. For thoose, who did not start yet, I highly recommend them.

[@realpars]

Thanks a million for your kind comment and support, Denis! We truly appreciate that. Always feel free to reach out when you have any questions or concerns, we're more than happy to help!

[@PLCTrainingforBeginners]

So many thanks. From Vietnamese with ❤

[@realpars]

You're very welcome!

[@KevinNguyen-tw5ml]

Thank you very much!

[@realpars]

You're welcome!

[@muzamilaltayebkorabika3103]

Hi every one in real pars inspite of the differences of language between us you making mix between fun & learning in the same time you fired the flame of pation on me when i watched a single video in your channel & then i became adicted to learn more & more to became better automation engineer thank's for every one for the great efforts that you made for every single moment of your time that you spent to help us learn & joy & i hope to see you on the top always thank's from the ❤ Real pars.

[@realpars]

Thanks a million for your kind support, Muzamil! We truly appreciate that.

[@AlexandreSantos-gg9il]

RealPars is fantastic! from Brazil thanks.

[@realpars]

Glad you like it, Alexandre!

[@mdnezamuddin6219]

Tnx

[@mynameismootokoita]

good explanation

[@realpars]

Thank you!

[@DemetriusHazardus]

Very nice 👌

[@realpars]

Thank you!

[@hectorenriquesantandermeza5208]

Thank you Real Pars! That was an amazing explanation. In some cases a grup of mathematichal equations are used to make a transition from SFC to Ladder diagram. Im not sure but there is another method used to draw a sequence called "Time Phase Diagrams" in wich the status of two or more inputs and outputs are arranged in a bidimentional graphic fashion with time variable, depending if IO are digital or analog, then you should construct a set of equations and link them by their properties to develop the ladder diagram. I think it will be great if someday you could make a video related to time phase diagrams. Greetings from Ecuador!

[@realpars]

Thanks for comment and feedback! I will happily pass this on to our course developers. Happy learning!

[@neamotullahjoy2268]

Thanks from Bangladesh

[@realpars]

You're very welcome!

[@George-Smith]

Thanks for the video But am in Cameroon and i really love AUTOMATION engineering i don't know the guide on how realpars could help me

[@ducati651]

Thanks enginer

[@realpars]

You're welcome!

[@joelowens6862]

I have printed and studied several PDFs about SFC. It does seem unnecessarily convoluted and the transistions are vague, in my perception. Ladder Diagram seems the most complete, and Instruction List is more like assembly language for PLC. So I think LD and IL are probably the areas where I am going to put more focus.

[@Jzzzzx]

Question. Would it be possible to reset an input like a start button in sfc? Ive tried to reset the input but it doesn’t seem to work. Thanks

[@realpars]

If the Start button is a physical input (an Ix.x address), you will not be able to reset it from an SFC. It could also be that other logic in the PLC keeps the variable in question in the ON state. SFCs do not "override" other logic. Some PLCs have different "rules" about setting variable states within an SFC. Make sure you know what your particular processor allows.

[@davidpalmer963]

tHAT IS BECAUSE REAL PAR'S IS DA BOMB!!

[@realpars]

Thank you very much!

[@bitebonumbere1426]

Realpars, but please can you place the "JOIN" button beside the "SUBSCRIBE" button on your channel so that we can contribute to sustain this (our) channel? Thanks.

[@realpars]

Thanks for your support and your suggestion! I will be happy to forward your feedback to our team. Thanks again and happy learning!

[@alexanderskusnov5119]

LD and FBD are old. Now we use CFC (Continuous Flow Chart). And for text nobody uses IL, only ST.

[@YewrMan]

The standard is around nearly 10 years. It's just an explain.

[@SakeBarSushi]

TPo

[@ranmjj]

SFC... why?

[@TOM8940]

The is one of the programming language in the PLC standard

[@ranmjj]

@@TOM8940 I know... one that we just really don't need. Structured text with opp extensions till something else better will come. It's time we throw away what does not make sense.

[@user-ff7op1bd8i]

@@ranmjj Nonsense. I advise you to read about finite state machines. And it will immediately become clear that SFC is the highest language for programming robots and machine tools today.

[@ranmjj]

There is a reason why no one in the IT world no one uses graphical languages... these should fi ally die. Everything u do graphically can be done textually.

[@user-ff7op1bd8i]

@@ranmjj But we are not in the pure world of IT. It is much easier for maintenance personnel, such as adjusters, to understand the graphical diagram for maintenance than your "text", the more they do not have to be professionals to search for problems and failures.

[@stevenliu6629]

🐵