[mr337]

100% agree with this. IMO there are a few efforts to modernize PLC programming but I feel like they are still stuck in the 1990s software development. Take a look at Codesys, got Git support few years ago and in very bad shape. How do you test your code, in the field or buy another Codesys testing plugin....which is in rough shape.

The issue is as machines get way more complex this issue gets worse. Also there are generations of PLC devs that still want to stick with ladder logic. Huge fragmentation.

[applied_heat]

Ladder is a fine choice for visually animating Boolean logic

The fact is the unmodernized plc platforms deliver working machines and plants. The projects are built, commissioned, and unlike modern software they are finished and left to operate instead of constantly modified With no benefit to the end user

[Kim_Bruning]

... sort of. Past a certain level of complexity you get into trouble with just PLC programmers alone.

Don't get me wrong. <PLC programmers> tend to also have electrical skills and some are pretty good at their jobs, and you can learn a lot from them!

But ... they're not programmer programmers. It's a different skill-set with only so much overlap.

[applied_heat]

The ladder paradigm has its place, as does function block diagrams, as does what the plc vendors call ‘structured text’.

controlling physical processes like oil refineries, power generation, or sawmills is different from most computer programs as are the consequences of bugs or errors so it makes sense that it takes different people with different interests and skills.

[Kim_Bruning]

I can't do the nuances justice here for sure. But to make a long story short:

PLCs replace relay circuits for Industrial Electrical technicians (hence: Ladder). And make no mistake: relay circuits are important, and is something they are very adept at!

However, this doesn't imply that they are automatically able to write or debug regular Python or C code or what have you.

-----

PS. If you let a PLC programmer at any language, they'll find a way to do ladder logic. Illustrative example (combining some features I've seen in textbooks and IRL, formatting included):

  if Tank_Level_Reached == True and EF132121 == False and Ready_To_Start == True and Finished == False and Belt == Not_Ready and Stage == 5 and Position_Left_Arm == Up :
    move_left = True
    move_right = False

   if Tank_Level_Reached == True and EF132121 == False and Ready_To_Start == True and Finished == False and Belt == Not_Ready and Stage == 5 and Position_Left_Arm == Down:
   move_left = False
   move_right = True

   if Tank_Level_Reached == True and EF132121 == False and Ready_To_Start == False and Finished == False and Belt == Not_Ready and Stage == 5 and (Position_Left_Arm == Down or Position_Left_Arm == Up):
    move_left = False
    move_right = False

etc ...

[Log_out_]

Then why is nobody using assembler for modern software projects?