I am an industrial controls engineer. I work with PLC hardware and software.

I am wondering if questions about PLC programming software are on-topic here. For example, I was thinking about asking a question about determining which version of Rockwell Software is required to open a particular .ACD file, which is a project file for Rockwell/Allen-Bradley PLC. (I figured out the answer myself, so I would probably self-answer this question.)

The question isn't about programming, exactly, so I doubt it would be on-topic on Stack Overflow. It is definitely related to Electrical Engineering, although I rarely see any questions of this type on this site. The question certainly isn't hardware-related.

I personally would love to see these types of questions here, but I'm curious how the current users of the site feel about it.

If it would not be a good fit here, would it perhaps be more welcome at Engineering.SE? Does that site handle Electrical Engineering topics that are related to industrial controls?

  • \$\begingroup\$ Take a peek at questions with the PLC tag, and see I you can get a feel. \$\endgroup\$ Apr 26, 2016 at 1:16
  • \$\begingroup\$ @ScottSeidman I've seen the questions with the PLC tag and even answered some of them. They don't seem very well-received, but admittedly, many are low quality. In any case, most of those are hardware related; I'd like to ask software-related questions, but I'm wondering if that would be considered on-topic. \$\endgroup\$
    – Ben Miller
    Apr 26, 2016 at 1:54
  • \$\begingroup\$ I think the biggest issue with PLC questions is we don't really have a core group of PLC experts. \$\endgroup\$
    – Matt Young
    Apr 26, 2016 at 3:52
  • 1
    \$\begingroup\$ I could see some PLC questions being on topic here, but "which version of Rockwell Software is required to open a particular .ACD file" sounds very far removed from electrical engineering as practiced here - it is basically a software usage question and I would probably vote to close it as such. There is the argument that it is a "development tool" but it is a development tool for a system that purposely abstracts out the kind of hardware details that are the main focus of the target audience here and are what make some other "software" questions appropriate for this site. \$\endgroup\$ May 4, 2016 at 3:32
  • 1
    \$\begingroup\$ It would be good if it was on topic for this site, since this site already has regulars, but in case it isn't, there is still a young proposal on Industrial Automation, but I'd follow it. \$\endgroup\$
    – CaptJak
    May 9, 2016 at 17:14

4 Answers 4


I'm inclined to say that PLC software and programming is on-topic. (If you disagree, please feel free to downvote).

Please note, I have very limited experience with PLCs, I welcome concerns and comments from more experienced users.

The standard reasoning that we use for software and programming is that it's on-topic as long as it's not so removed from the hardware or programming environment that it's a better fit on StackOverflow. We allow questions on Quartus, Atmel Studio, and other development environments, and I don't see why we shouldn't allow the same for PLC development.


What W5VO said, but in addition, make sure you specify your environment properly. State what hardware you are using, what language, what compiler or software environment if it matters, etc. We get too many questions here like "How do I set a single register bit without affecting the other bits" without specifying the micro or the language. Those will get closed and downvoted to oblivion for good reason.

The reason you don't see a lot of PLC questions here is because we don't have a lot of PLC users here. I agree this is on-topic as long as there is a hardware-related angle. It's been my observation that in the real world, EEs don't do PLCs as much as "production engineers" or the like. In some sense, the PLC language is designed to appeal to those that would run away screaming if they realized they were programming a computer. It's basically programming for those that don't want to admit they're programming, with doesn't apply to most EEs (and shouldn't apply to any EE).


One thing worth note here is the many similarities between PLCs and PLDs/FPGAs. I don't think anyone would label the latter off-topic here, nor that anyone would label VHDL or Verilog off-topic for this site.

Historically, the first use of PLCs was to replace chains of relay logic. The first use of PLDs was to replace chains of digital logic. Then as the technologies evolved, both PLCs and PLDs got more functionality, more uses, more advanced languages and so on.

Both technologies are supposedly general-purpose, yet they are used in niche markets with specific needs: mainly factory automation in the case of PLCs, mainly telecommunications in the case of PLDs.

With this in mind, I don't quite see how it would make sense to label PLC programming as off-topic, where VHDL or Verilog programming is considered on-topic. They are both forms of niche programming of electronic devices.


I'm very much a n00b but it would seem to me PLCs both hardware and software should be on topic. At least here in the UK, PLCs are very much seen as within the remit of the electrician and electrical engineer rather than say in the "programmers' trade". If you see what I mean.


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