16
galena
322d

Welcome to PLC development! Your first thing to do is find out whta these dozen global variables do that are used by several tasks in odd places.

Comments
  • 5
    And don't forget the joys of plowing through the enormous amount of brainfuck documentation provided by Siemens!
  • 0
    Control Logix is nice. You have different options of languages. You can also put equations in contacts. I calculated soft limits this way.
  • 1
    Doesn't sound very programmable to me
  • 0
    @NeatNerdPrime B&R isn't better at all. 700 pages which are basically the same about recycling. And fucking Bezier curves are described in there. Like why is that even relevant?
  • 2
    @galena that is actually something important if you're going to control things that require more then just 3,3 or 5 volts and bigger currents then a few milliamps. E.g. an electrical motor capable of intense torques to lift something up. You would need to programmatically consider the right amount of steering current (which gets directly transformed by the electrical transformer into the higher power energy) to make the lift happen.

    In short: often used when translating a steering current into a mechanical high power outcome.

    There are other use cases though, but I forgot it's like 25 years ago for me.
  • 2
    @NeatNerdPrime you might be able to use it for smoother gain scheduling. Did that once with the phase change of a fluid through a valve. It went from a gas to a liquid (cryogenic). As a result the gains needed to be reduced when a liquid because the flow was a lot higher at that point.
  • 0
    That's indeed another use case :-)
  • 2
    Ah, ladder logic. Aptly named as it manages to make both non programmer electricians as well as experienced programmers want to jump of a ladder
  • 0
    simulate the device in your head. Step through any changes or default values and see how things change. Your brain will do the rest of the work connecting function to form.

    Or take LSD maybe.

    Idk.
  • 1
    @Wisecrack Well, we decided to do an entire new generation of our product instead. And removed basically all global variables and replaced the them with a "variable service".
  • 1
    @galena everything now runs as a microservice.

    Everything is also on fire.

    "This is fine"
Add Comment