Structured text vs ladder logic is the oldest argument in PLC programming, and this week a CODESYS convert changed sides and said so publicly. I agree with where he landed and not with how he got there.
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https://www.joltek.com/services/service-details-workforce-development-educationThe phrase I want to retire is "use the right tool for the job." It sounds like judgement and it is an evasion, because most IEC 61131-3 languages can accomplish ninety percent of what a control system needs. The same interlock builds in ladder, in structured text, or in a function block diagram, and all three run. That is exactly why the phrase settles nothing.
Ladder still dominates discrete control for a historical reason that has not gone away. It mirrors the electrical schematics machines were already built from, and many of those schematics have not changed. A technician tracing a fault at two in the morning holds the print in one hand and the rung on screen in the other. That correspondence is worth more than elegance. Where continuous process is involved, function block diagrams win for the same reason: a P&ID reads as flow and so does a function block diagram.
Structured text earns its place in data handling, recipe management, and anything algorithmic. It also dominates on CODESYS, and this is the part most people miss. It is not objectively better there. The documentation, the community answers and the examples all lean that way, so you get unstuck faster. Platform documentation quality decides language choice more often than anyone admits, which is why a Rockwell Automation shop and a Siemens shop reach different defaults without either being wrong.
The question nobody asks is the one that matters: what happens to this program after you leave? A control system outlives the engineer who wrote it. If the next person needs a steeper learning curve to change one setpoint, you optimised for the wrong thing.
Four more questions in this one. A spinning yarn machine conversion running Siemens ET 200SP alongside Odot remote I/O came back commissioned, one hundred and sixty eight stations of it, which raises a real point about wire tray sizing and heat in a dusty environment. A drive photographed with water under its bus bars leads into what sanitation does to enclosures in food and beverage. And a customer who demanded 0.75 millimetres squared on every input got a bulky panel, plus a fair question about whether that argument was worth having.
Then the one that deserves a straight answer. A controls engineer laid off after four years, told the plant's control team cost too much, asks how to avoid being first on the list. Controls is badly understood by the people who approve budgets, and engineers here are poor at communicating the value they create. The average controls engineer earns $119,682, up 4.3 percent year over year, while 38 percent of manufacturers name the skilled worker shortage as a top business threat. Both are true at once, so the problem is visibility, not demand.
The episode closes on hiring. A small integrator cannot find juniors who can explain what DHCP does. The degree has never been the signal. Extracurriculars are, and so is showing up on time.
Timestamps
0:00 Intro
1:00 Siemens ET 200SP and Odot remote I/O: a yarn machine conversion update
3:30 Panel review: I/O density, wire tray sizing, and heat
6:00 Why run two flavors of I/O in one panel
7:10 Water inside a VFD: what washdown really does to enclosures
11:10 Structured text vs ladder logic: where ladder actually came from
13:40 Why "the right tool for the job" is the wrong framing
16:00 Platform documentation decides the language more than preference does
17:10 A customer demanded 18 AWG on every input: is the customer always right
21:20 Laid off after four years, and how not to be first on the list
28:40 A strange mix of skills, and which layers command a premium
31:40 Hiring junior engineers: what a degree does not tell you
33:40 The DHCP interview question, and better questions to ask instead
40:00 Lateness, moonlighting, and the habits that end a junior career
48:20 Wrap up
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