Classes on PLCs?

Does anyone at DMS teach Progammable Logic Controllers (PLCs)?

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There are Arduino classes. Arduino can do just about anything a PLC can, but a whole lot cheaper. We have Raspberry PI classes sometimes. With the breakouts, they can do a whole lot more.

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PLCs are nothing like arduinos in practice.

PLCs are reliable, durable state machines for critical use.

I actually have a couple and could consider a class or so. They would be more basic units from Velocio

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Understand, but PLC’s are the industry standard. I’m looking at job applications that are asking about experience with PLC’s.

I assumed (incorrectly) that PLC used ubiquitous programming languages like C, C++, Python, whatever. I looked it up out of curiosity and found out they have their own languages that are standardized. Pretty cool.

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Most manufacturers support standard languages, though I don’t know how rigorously they follow the standard. I believe Wago is compliant because they use a third party software (CoDeSys), but other companies like Automation Direct have some variation in their implementation.

For what it’s worth, structured text is as close to psuedocode as I’ve ever seen, very nice for math heavy operations. Ladder is much more common and is easy to read for people more used to seeing schematics than software.

Edit: If you really want to learn, my recommendation would be to pick up something off eBay and do projects with it. A Wago 750-841 is an older model that’s easy to program (Ethernet with free software), though Allen Bradley Micrologix (or the knockoff DL05) is also compact and relatively cheap.

I could easily teach a class or two - have been working with Allen Bradley hardware for the last 25 years… Unfortunately I do not have access to a loaner or spare unit. If someone has access to some machines & programming software I don’t mind helping out. If you have a program that you would like some help with we can get together sometime and go through it.

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Smartest guy in the room…

“PLCs are nothing like Arduinos in practice”

Actually, they have a great deal in common: both are micro controller operated, both have analog input, both can relay or analog control output, both can make real time decisions. To say they have nothing in common is utter balderdash. The difference is that in an Allen Bradley PLC, an analog 8 channel input card costs $1300 used, on an Arduino it is 16 resistors–about $5.

“PLCs are reliable, durable state machines for critical use”–essentially true. To qualify as a durable state machine, there has to be redundancy and error checking. A lot of PLCs are very redundant in their cores, but they still can screw-up and need a reboot. The state machine is only as resilient as it’s code.

The act of learning Arduino, then R PI, then FPGA, is an embrace of the future. Picking-up PLC is an exercise in the past. But the past is prevalent, so by all means, teach history. PLC is not going away, as long as people won’t take the time to actually learn to design electronics.

I know how you feel. I hate the fact that people use these ‘microcontrollers’ instead of just learning to design ICs themselves.

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Designing ICs? Nah, kids these day’s need to do their ladder logic with relays like the good Lord intended.

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Seriously, nobody has to design an IC. But, with the state of tech and microcomputer control that is totally free, having to use a PLC is for the willfully dumb. Everyone is just giving away PLC nowadays.

So I’m going to break this down and try to keep it quick, as I really don’t feel like writing work stuff here.

They both have I/O, that’s about it. Their controller architecture is very different; programming them is very different; their electrical tolerances are very different. The member asked about PLCs, and trying to tell them to learn an arduino instead is like asking someone studying mechanical engineering to learn how to use a kid’s tonka truck instead.

This is a dishonest comparison. Calling the analog modules on a PLC the same as the analog on an arduino, or even it’s GPIO, is an outright misrepresentation. PLCs run very different protocols, very different electrical characteristics, and very different implementations.

The rate of a PLC “screwing up” without some kind of outside interference is extremely low compared to that of an arduino; that’s the reason they cost so much, and are everywhere.

This is actually untrue; PLCs have a different type of memory and bus architecture; the rate of errors in the data itself are much lower than typical RAM and memory in a microcontroller. This is why they are so reliable. Yes, your ladder logic can be borked but assuming that’s not then it will have a lower error rate on a system where errors are less likely to be introduced electrically.

You clearly don’t know what you’re talking about here. Arduinos and RPis are nowhere near stable enough to replace PLCs from an electrical perspective. Even on an RPi they don’t run in real time (you can get that on a Beaglebone black for example with the RTC co-processors, but you have to bank on that being enough and still have electrical characteristics to consider).

I think you still have a lot to learn here, as you seem to not understand why arduinos are not used in critical infrastructure.

My above points stand for this statement.

As someone who tests them regularly for work, and someone who watches them being deployed in things that go boom if something goes wrong, these are people that have done their homework and the PLC reigns king for a very good reason.

EDIT: also for the OP, a Velocio PLC unit starts at about $50. They’re much more light duty use, but they have programming ladder logic and controllers you can start out with.

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The simple fact of the matter is that no matter how old-school you think PLCs are they are still industry standard. Many (most?) companies aren’t embracing arduino/R-pi/equivalent because they’re considered hobby electronics. In industrial design you have to consider things like the ability to pass a certification for safety by an NRTL, and I’m sorry to say it but after 3 years at an NRTL I can say it will probably be 5 to 10 years before the standards are updated enough to catch up with “the future”.

PLCs are more physically robust to the dust and debris that can be found in an industrial manufacturing site, and they come with a fancy pants service contract from the manufacturer that means that the company doesn’t pay to keep service personnel for the one time every couple of years that it breaks.

Besides, OP specifically asked about PLCs. Turning this into a thread arguing about the future of electronics doesn’t answer his question.

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I don’t want to speak for the OP, but I’m guessing, since they asked about PLC classes, they do. Maybe they are wanting to brush up on plant engineering, and were wondering what DMS offered.

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That extra cost for a PLC goes to the following:

  • certifications
  • more robust and stable electrical operation
  • industry integrations
  • etc

The fact you throw that out the window shows you just want to argue.

If the OP has any real question they’re free to ask me and I may dig out hardware for a class However, I’m not going to engage with you fuether since you appear to not be interested in actually debating any sincere technical merits.

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If you try to put a product on a manufacturing floor and tell the owner, ‘oh by the way this is an untested design, you can only buy spare parts from me, and I’m the only one with the documentation to service it’ they won’t by buying anything from you.

But you wouldn’t have to worry, because you’ll be three years behind trying to reinvent the wheel while your competition bought it off the shelf.

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https://training.ti.com/?q=node/1139425

Example of online modules that cover some of these topics.

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Arduino’s and PLC’s are only similar in the fact they both can control things… so can a Raspberry Pi or any other PC…

But there is no way I’m going to bet my job, my company’s run time, and employee safety over putting in an Arduino and clobbering together a bunch of I/O when someone else has put in all the engineering, testing, and assuming the risk! Would I do it to automate my pool equipment - sure, but no way in a manufacturing environment.

Arduino’s are also great for learning electronics and sensors and personal projects.

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There seem to be a few key differences between PLC and microcontrollers. I don’t use PLC but just looking into it out of curiosity. These seem to be the big differences in my opinion.

  • Established mechanisms for creating systems with redundancy
  • More robust hardware (like integrated optoisolation, separation of buses from logic hardware, durable enclosures)
  • Ease of use and labor effectiveness are prioritized
  • Very long support life cycles (decades versus a few years)

I can see use cases for both microcontrollers and PLC depending on the situation. I can definitely see why businesses would want to use PLC and hire people who know how to use them. It would be cool to see a class on this topic.

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