Structured Text PLC Programming Tutorial with the Arduino Opta

Okay, in uh this chapter we are going to make a new project and we're going to call it first structured structured text. Okay, so we're going to go new project. Make sure you have the opta selected if you're using the same controller as me. And we're going to say okay. It's going to generate a new project. Um now I have previously loaded the firmware onto my uh Arduino. So everything else here should be fine. We'll go to online setup communication mod bus and properties and just make sure COM 10 is still selected. That looks good. And we're going to hit connect just to make sure that connections look good and the uh all PLC Arduino Opta still looks good. All the available interfaces should show green lights. So this is all good. Hopefully uh in a previous video and previous chapter, if you're watching a long form uh tutorial, uh I covered all of this stuff in some greater detail. So, if you haven't gotten to this step and you're not able to get online with your Arduino Opt, I suggest you go back on the channel and you watch the getting set up or getting started with your Arduino PLC video. Um, so, uh, assuming you can get to this step and you have a new project just like I have and if you were to go into the project tab over here on the left and hit main, you just have this default program it gives us that is count equal to count + one. Um, but if you're able to get this far, then we're in the same spot and the rest of this video is going to go so smoothly. So, let's go to resources because for today's video, I'm going to use the uh LEDs that are built into the Arduino Opta. And I'm going to use the user button, which is on the front of the PLC. Uh so, you could see there actually when I was pushing that button, it was doing stuff. That's because I have different code on there as shown by this diff code thing uh in the bottom left of my window right there. Um so, maybe I'll hang out right there so you can see my tab. Um, but right now I'm going to go ahead and just download this empty uh PLC program to it so that there's nothing on my PLC. Uh, and then we'll be in exactly the same spot. So, compiling sketch, please wait. I will wait for you Arduino. Okay. So, once you get source, okay, or you might have had nothing. Um, but in this case now we have PLC that has nothing on it. Uh, pushing the button does nothing. The lights are not there. The green light isn't even on. You would not know anything was working on this. Um, so let's go to the resources and click on the opta. Um, this should still look good, but since we're using the button and the LEDs that are on the opta, we're going to add variables here. So, the name of them is just kind of how you identify what the button is. There's one push button on the front of the Opta uh that is programmable. The other one is the reset button, which is used for like factory resetting. So, there's only one button on the front of the Opta we can use. It's the user push button. So, I'm going to assign it a variable name that is just going to be user all caps like that. Now, I'm going to go to LED outputs and I'm going to do basically the same thing. L1, L2, L3, L4, LR, LG, LB. And so this is my exist, but it's not automatic. That's fine. LR. Okay, it's really unhappy. Oh, mercy. Okay, I'm going to call this red, green, and blue. uh basically you need to assign variable names to these uh hard-coded inputs and outputs so that we can use them in our program. So we have L1 through L4 refers to the four status lights at the bottom of the opta and then red and green show up in the same spot above the reset button and blue shows up right above uh the user button. So we're assigning all those variable names so that when we go to write our program here in Maine, we have user and uh all seven of those lights that we can play around with. So let's write functionally what can be considered uh the hello world the intro to programming for structured text. Let's say green equals true. And a couple important syntax things here is green colon equals is how you set a value equal to true all caps and then a semicolon. So for structured text it's variable that you want to change the value of and then setting a value is colon equals and then the value you want to set it to and then a semicolon. And this should compile and download. So I'll hit this little button for download PLC code. It'll ask me if I want to compile it. Say yes. And now if I hold up the PLC, the green light is on. Okay. So that's my hello world right there. That's the green light is on. I am talking to the PLC and it is listening. Now let's go ahead and go a little bit further. Let's say that red will be equal to false. By default, it'll be off, but um let's go ahead and say blue is equal to user. Okay. So, uh, you'll notice the colon equal sign for all of those and the semicolon at the end for all of those. And all I'm doing is making sure the red light is off. But the blue light, I'm doing something a little more interesting here. I'm saying it's equal to the value of user. And I'm going to do something here. I'm going to add all of these values to watch. Uh, just by right-clicking on the variables that I want to watch. I'm going to add them to watch. And I have this window over here. That's the watch window. And it shows the current value of them. the current value of green is true because my original code was just green equals true. So now if I download and compile this and then hold the PLC up, you'll see green is still true, red is still off, and that's all good. But if I go ahead and push this button, you'll see the blue light turns on. And if you're watching the watch window here, you'll see user and blue change when I push the button. Okay, so uh that's actually it's pretty cool how fast we're able to advance through this uh PLC programming tutorial. We are now controlling the state of an output from an input. So the input being that user push button, blue being the output light. Um but you're not really learning too much structured text with this. We're just directly setting values based on uh other values. So let's go ahead and take a look at an if else if statement. Uh let's say if the user push button is pressed. So if user semicolon actually if user then and no semicolon I get my uh Python my C++ and my structured text syntax is messed up. But here we're checking if a boolean value is true. So, it's just if user, so if the user push button is pressed, then let's go ahead and set L1 equal to true. And let's go ahead and do L2 also equal to true. And let's just make sure that L3 is off when the push button is pressed. And that L4 is off when I push the push button in. Now, I'm going to do else if not user. So this is about the same thing as an else statement. Um but I think it's important to call out that else if in structured text looks a little different than most programming languages. So it's this els if and then not user then and you'll notice if user then and else if user then don't have semicolons but all these command lines do. So, I'll copy these four instructions here, and I'll shift tab. There we go. I'll change L3 and L4 to the ones that should be on and L1 and L2 to the two that should be off. And then, super important in structured text, you need end underscore if and then a semicolon. Okay. So, unless I miss something important, which is perfectly possible, this should make uh the the bottom four status lights flip-flop once it's downloaded. Okay. So, actually good sign. You can see that three and four turn on with the button not pressed. So, I'll go ahead and press the button. And there you go. You can see all four of the status lights on the bottom of the PLC as well as the blue light are changing. Okay. So, that's cool. That's if, an else- if, and an end if statement. Um, but again, it's all pretty uh straight up boolean binary con comparisons. So, let's add one more thing here uh for this introduction to structured text. Let's add a variable and do a little bit of sequencing. Okay. So, let's go into uh project and global variables. Doubleclick. And I'm going to insert two variables here. I'm going to call one last user. And this is going to be a boolean that I'm going to use to track the last state of the user push button. So similarly, if you've done anything in Arduino or other programming languages, sometimes you want a condition that only happens on the rising edge of a value. And to do that, you want some sort of VA variable to track the last state of it. Uh, and then at the end of your routine, you'll set last user equal to user. Uh, and then this second variable I will just call position. And I'm actually going to make this an integer. And I'm going to say initially I want it to be zero. Initially I'll have this be false. False. So those are just initial values. Come on. There we go. Oh, I have caps lock on. Okay. Uh, and I'm going to use position to track where in the sequence we are. And here I'm going to give it an attribute called retain, which means on uh downloads and power cycles, it's going to keep its value. Uh, so that's a useful thing when you have some sort of PLC program that you want to hold values even when you download new iterations of the code, you want it to be set to retain. Okay, so we made a few new global variables that we can use in our code. Let's go back to main. And we're going to scrap most of this, all of this really. And let's go ahead and start by setting L1 through L4 all equal to false here in the beginning. Um, and a little way that structured text programming works is this code is going to go through and set all four of these lights equal to false uh at the beginning of each scan. But it's only going to matter what the value of it is at the end of the scan. So if you had code here that said green equals true and then you added a line here that said green equals false within your code right here, you're changing the value of green to true and then to false. But what's going to happen? The only thing that would actually happen if you ran this code, so let's just do it is Whoops. There we go. Is the green light will be false. all the lights will be false. It doesn't show green turning on and then green turning off because the only thing that executes is the value of the variables at the end of the routine. So by setting L1 through L4 false at the beginning, we have the rest of this code to decide if we want to turn uh L1 through L4 off or on. So what we're going to do is we're going to say if position is equal to one then I want L1 equal to true. Okay. And uh a couple things to call out here. In structured text the comparison is just single equal sign. Most programming languages that you've probably seen before two equal signs is how you check for equality. Um that's definitely how Python works and that's my favorite. So uh then we're going to say else if position is equal to two L2 is equal to true and then we'll say else if position 3 L3 else if position 4 L4 and then we'll say else if one more thing and then I'm going to end if okay so let's just get this all lined up position 3 three position four four and now let's say else if position is greater greater than four. Then what I want to do here, dang. Then what I want to do here is say, okay, position has been has exceeded my max step. So I'm going to set back to zero. I'm going to put back to the beginning. And notice that the if thens don't have semicolons at the end. Uh, but end if does. And all of the action lines in each if condition do have semicolons. Okay, so this is great, but nothing's actually changing the state of position yet. So let's move this down a little bit and let's say if the user button gets pressed and it's a rising edge. So not me holding down the user button. Let me say this is just when user first gets pressed. So if user and not last user then I want position to be equal to position + one and then end my if statement. And I missed a semicolon there. Then at the very end, like we talked about, we're going to say last user set it equal to the value of user. Okay, so this should be all we need. This is setting the initial values of all of our lights. And just to make sure this new program really took let's go ahead and say we actually want red to be on now. And we're going to turn green off. So, when this boots up, if it's working properly, we'll know right away from red being on and green being off. Let's see if we made any errors. Looks good because I'm a professional. And the red light's on. Nothing else is on, which makes sense based on the code that we wrote. And let me try to get this framed properly. I'm going to push the button and the blue light turns on. And position one turns on. Push it again. Position two turns on. three 4 0 1 2 3 4 0 Okay. And you can add position to your watch window. Add to watch as well as last user if you really want to as well as L1 through L4. Um and now as you're cycling through pressing the button, you can see the value of position change every time you push the button as and blue user and last user all change almost exactly together. Um but so that's really fun. That's basic sequencing. Um, a a very common way to write uh controls sequencing is in step one do a series of things and then once you've checked some condition like pressure, flow, temperature, move to step two and then do a series of things in step two. So this sort of sequential move through a position value uh is actually a really great introduction to PLC programming. So that's some basic structured text. I think uh up next we'll sort of recreate this program in ladder logic. So you get to see both of the main sort of two uh PLC programming languages that sort of duke it out for ultimate control. Um but I hope you found this uh introduction to structured text programming useful. The Arduino Opta is a really cool affordable way to get into PLC programming. Thank you to Arduino for providing the hardware for this video. I hope you learned something with this structured text uh tutorial. Let me know what you want to see next on the channel. Thank you for watching and we'll see you next time. Thanks.