The PLC Programming Languages for Controls and Automation Engineering | LD FBD SFC ST IL

what's up you guys welcome back to Lemaster Tech and in today's video we're going to talk about the IEC 61131 programming languages these are the five standard programming languages you're likely to see as an automation or controls engineer [Music] so in this video we're not going to do a long form code tutorial or any sort of step-by-step DIY process but we are going to talk about something that's pretty near and dear to my heart which is Automation and controls engineering that's what I do and I know a lot of people have found the channel from my video top five things you need to know as a controls and automation engineer so hopefully this video can answer some of the most common questions around what these are what programming languages Automation and controls Engineers need to be ready to see in the field and then also How likely you are to see them and what different applications you might use different ones for and before we get totally into the video thank you guys so much for 4 000 subscribers we hit 4k on the channel this week and that is absolutely unbelievable to me if you want to continue supporting the channel be sure to leave a like on the video subscribe to the channel we make a ton of great content comes out every week a special thank you to Dale T my first patreon supporter if you guys want to become super supporters of the channel as well check out the patreon link below this video super excited to see where we go in the next year but without any further Ado let's dive into the content of this video so I know just the name iec61131 can be a little bit confusing but IEC is just International Electro technical committee they are sort of regulators and moderators of a lot of uh specifics and standards in the world of industrial electronics and controls and automation you don't really have to worry too much about the numbers or the letters you just need to know what these different programming languages are and when you're most likely to encounter them in the field so let's start with my personal favorite and potentially the most common one which is latter so ladder diagram ladder logic or just sometimes abbreviated LD is uh essentially the first PLC programming language that ever came up sort of organically because it looks a lot like electronic relay schematics so in the old days before we had plc's dedicated running automation you would read sort of primitive controls Maps as schematics of different relays so you could for example have a relay that would check to see if a button was pressed and if maybe some some thing in the field like a high pressure switch was met and if those were both true the relay would pull in and then something else would happen Downstream of it and so a standard programmer might think of this as like a series of and or gates to do like binary logic in ladder logic it's almost like you could trace a flow of electricity through your program so this is why ladder logic looks sort of like a ladder when you stare at it it's run after run after rung and the individual modules all sort of spawned from the idea that you had relays so the two most common ones are like examinive close and examinif open which is basically a if or an if not so it's basically if condition is a one or if condition is a zero and that's ninety percent of how you do Boolean checking just series of ifs and if Nots and then to turn on Boolean conditions you really just need to know the difference between like an OTE which is a energized the whole time this rung is true versus like an OTL and an otu pair which is latching and unlatching a binary condition when something is true now obviously processes are a lot more complicated than binary logic in a lot of scenarios so essentially what that means is you also have things like greater than less than limits where you check between values and then you can also move numerical values into a numerical variables so you don't just have binary logic in ladder you have all the sort of standard formats that you'd have in any other programming language if you understand General programming types you'll be able to pick up what these separate variable types mean pretty quickly and pretty easily but ladder logic is extremely common it's also super powerful and it's pretty easy for people who don't have a computer science background but maybe are more familiar with the electronic side or frankly they don't have a programming background at all ladder logic is super logical I really like it almost every major PLC manufacturer supports some form of ladder logic using these same basic building blocks so as it controls an automation engineer you are super likely to need to become pretty familiar with ladder logic now for the one I consider second most common some people might debate with me here but I think the function block diagram it's essentially more free form than like traditional ladder logic you just basically have a blank page of workspace and you drop blocks in there that you want to do different functions and typically you tie their inputs and outputs to different process conditions some of the more common ones for this would be like totalizers a lot of the time a totalizer block that would monitor flow over a period of time and continually add to see how much total flow you had in that time you would maybe have this floating function block diagram for a totalizer you would tie a start command a stop command a reset command as well as potentially like your input signal so your actual raw flow meter signal you could pass it through some sort of like time scale or multiplier but it's just where having all of the conditions that control the totalizer and all of the outputs that you could do using the totalizer in one spot is just super powerful I'm only using totalizer as one example function block diagram its advantages are you can see all of the components that will control a block a complicated block like a totalizer in one location you can also map out common programming things like and Gates or gates xor gates knots whatever Boolean control in these as well the disadvantages are it starts to get very hard to read a logical sequence of things happening if you get too far down and too long into one function block diagram so you need to start partitioning it off and making a separate fbd for each major function that happens but I have seen systems where the entire thing is done in a function block I've seen things where the entire system is done in ladder but it's important to understand what this looks like how you control it what it's used for and also it's an important one to familiarize yourself with the next language sfc or sequential function chart is absolutely the most common language you'll see if you run batch processes so GES like ft batch and Rockwell's batch as well as I think just a lot of batch processes the way you see a recipe is with a sequential function chart and this one's really nice to kind of get an overarching view of your process because typically you'll have layers where you can look at one sfc and you'll see like start phase validate parameters phase manual editions phase mix phase uh automated editions phase sample phase and so you can look at a high level sfc and you can see the overall state of your project really quickly as it relates to your whole process and then if you have questions about what's going on in one phase of that sfc typically most software supports you Drilling in and inside one phase at your high level model you could have a number of phases and inside each of those phases you could have a number of phases in there it's definitely most commonly used in batch most plcs themselves don't support a really robust like sfc without a software that you run and configure on an actual computer so plc's typically host mainly um like ladder and fbd and even some of what we'll talk about now next which is structured text but to do an sfc based control schematic you're usually in like more of a distributed control system like DCS platform and you usually have to put your sfc software recipe editor whatever on a computer other than your PLC again most common place you'll see it is batch applications batch just means that you separate all of your devices at the plant and your series of instructions that control devices into phases phases still typically have to get represented as ladder in your plcs so an sfc is almost always accompanied by some form of ladder logic or structured text inside of a PLC not always I'm trying to generalize and give you guys a quick summary but that's a summary of sfc so the next one structured text is uh probably the one that would look the most familiar to someone coming in with a programming background but not a controls background structured text really is what all all programming languages are I mean it's a certain syntax of words and commands that will execute certain things in your code structured text is typically straightforward like saying set i o Point status to digital output set Boolean command equal to one when condition is met like the actual text I'm not going to spend too much time uh digging into because it varies from manufacturer to manufacturer controller to controller so if I were to tell you a bunch of specific structured text there's a solid chance it wouldn't apply to your specific manufacturer but the documentation for what your manufacturer supports what uh whatever your site standard is if you're doing a lot of structured text then the controls at your plant probably got started by a group of people who are more comfortable with software and programming so in general PLC programmers controls and automation Engineers aren't going to need to see a ton of structured text but it is supported and it is one of the IEC 61131 languages so it's important to know what it is if you see it in an application don't be blindsided by it not super common if it's super common at your site you prove me wrong let me know I was wrong in the comments below but most of the time the three we talked about before are going to show up a lot more in your applications okay and the fifth one is kind of neat here it's instruction list typically abbreviated IL and this one is going to be really familiar for people who have done a lot of work with like six axis robots or if you've done a lot of work with like CNC machines or 3D printers instruction list is not too far off from structured text in that it's really just words uh that kind of have some numbers mixed in to command your variables to different stuff whereas the first three languages we talked about were a lot more visual but instruction list is basically like machine code so for like a robot or a CNC machine it's often called G-Code but it usually is a series of commands that run one after another it's always going to typically happen in a sequence but a lot of the time you can have like oh if this condition then do this and jump to this rung but if other condition do this other thing jump to this other rung so it doesn't have to be linear but typically it's in an order that makes sense that you would typically see it sequentially and the most common applications are for things where you need position control in 3D space so you're controlling three or more axes and you would typically say okay go to certain position all right turn on your tool whether it's cutting or drilling or welding or whatever and then your tools on okay move from point A down to your thing that you're operating on okay now move over to point B with your tool on okay now turn your tool off and lift up okay now go back to your home spot but a conveyor will turn on move the next piece in so it's pretty common on like assembly line where you have a lot of advanced like robotics or motion control it's normal to see instruction list but again this is sort of more common in robotics even than you would see it in controls and automation so it is one of the iec61131 languages that's why we're talking about it the first three languages ladder fbd and F sfc so function block diagram and sequential flowchart those are the three most common ones that you'll see in your day-to-day as a like PLC programmer or controls an automation engineer but if you're more of a mechatronics or robotics hybrid or that's a field you're interested interested in it's definitely worth getting familiar with the other two as well and in general the more well-rounded you are as an engineer the better you're going to do in your field so thank you guys so much for watching I know a lot of the content on the channel is Python and programming and I know not too many of you guys might be Automation and controls Engineers but again I think being a well-rounded engineer is the best thing you can do so I hope you found this useful if there's more stuff you'd like to know about this field let me know about in the comments below if I get enough interest and enough questions on the world of controls and automation I can absolutely make another video on those topics so thank you guys so much for watching thank you again for 4 000 subscribers it's amazing growth on the channel I appreciate all of you guys don't forget to leave a like subscribe to the channel help me out a lot until next time good luck with your jobs good luck with your projects thanks for watching bye