r/PLC

Have you ever hired someone who did well on the interview, but as soon as they started working, you realized they didn’t have the experience they claimed? What did you do?

How do you try to screen this out during interviews?

I am wondering how common this is in this space, given you can get ppl with such varying backgrounds in controls, and often times there is no formal accreditation required for some roles.

I'm not necessarily in the job market right now, but I've always wondered if making the transition to pharma is worthwhile.

I've got nearly 20 years of experience at various OEMs and panel builders for equipment. I know my way around panel design, programming, servos, HMI work, etc. Even done some vision and robot projects. I know my way around machines pretty well.

Only things I don't have much experience in is SCADA and process industry stuff, which I know is a big disadvantage for pharma.

My current job is at an OEM and it's a pretty easy gig, though occasionally boring. We have technicians so we don't travel but a few times a year. We don't work much over 40 hours/week.

It's pretty good in that respect, but the pay is... uh... not great. But I've convinced myself that I'm taking a lower paycheck in exchange for a job that isn't too tough on me or my family. The work/life balance is great, so I'm hesitant to give it up.

Thing is, my area is surrounded by pharma manufacturing. And it's getting more every year. Like, not even out in the boonies anymore... a lot of it is in the suburbs.

I've always heard that pharma is kind of boring. Regulations require reams of paperwork to do anything. Pays pretty well I hear, but the downside is you're more of a paper pusher than an engineer. No idea how true this is, but it's the image I've gathered over the years.

I know the biggest thing missing on my resume is GMP experience and S-88 experience, as well as Delta V/etc. I presume a lot of that is on-the-job knowledge that is hard to pick up otherwise.

Is pharma something worth getting in to? I'm not necessarily concerned about my future job prospects in my current career trajectory, but with the growth of pharma in my area I feel like it might be a good career move.

edit:

So I should note: I'm a degreed engineer, but I know the pharma space has a lot of MS and PhD level people in it generally, so I don't know if I'd fall under engineer or technician in this space. I know a few people who work in the R&D side at the PhD level (process development and MSAT) and I know that side at least is a very different scale in terms of job title vs. education level.

Hey everyone,

I have a robotic cell running on a 1756-L83ES GuardLogix PLC. We want to do some virtual commissioning using a soft PLC emulator, but the emulation software requires the project to be at v35 or higher. Our actual physical hardware needs to stay on v32.011.

Because of this, I might need to downgrade our v35+ project back down to v32.011.

In the past, I had a nightmare experience trying to downgrade from v32 to v28 due to the massive changes in tag structures and string types between those versions. I’m hoping a v35 to v32 drop isn't quite as brutal since they both share the newer architecture.

Before I jump into this rabbit hole, I wanted to ask:

Has anyone done a downgrade from v35+ to v32 recently?

What specific gotchas or problems did you run into?

Any tips, horror stories, or "don't do it" warnings are highly appreciated.

Thanks!

Every company I've worked in has had a coding standard. Naming conventions, forbidden constructs, "always add an ELSE to a CASE on an enum", "don't change a SAFETY_ constant without sign-off". It was in a Word doc or a PDF, and realistically, few people opened it after their first week. Enforcement was whatever a reviewer happened to catch during a visual scan, which meant it was inconsistent and missed things.

So I built a tool that automatically checks ST. It's called plc-st-review. It's free, MIT licensed, and open source.

What it actually does: it parses your .st files into a real syntax tree (using a tree-sitter grammar for IEC 61131-3 ST) and runs semantic checks on the structure, not regex on the text. 56 checks in this release. A few concrete examples of what it flags:

• A TON.PT that changed from T#2s to T#200ms between commits (10x faster, easy to miss in a diff).
• An FB instance whose .Q you read, but you never actually call the instance, so you're reading stale outputs.
• A literal array index outside the declared bounds, arr[15] when arr is ARRAY [0..9].
• WHILE TRUE with no EXIT in the body.
• A VAR_GLOBAL CONSTANT named SAFETY_TIMEOUT whose value changed (it raises the severity of safety-prefixed names).
• A CASE on an enum that gained a value but has no matching branch and no ELSE.
• Naming convention drift, configurable per declaration kind (prefix/suffix/regex), plus a forbidden_symbols blocklist you define.

Enforcing naming convention

The part that matters if your shop doesn't do pull requests (most don't): you don't need a PR, a server, or even Git. Install it and point the CLI at a folder:

npm install -g plc-st-review
plc-st-review --lint "src/**/*.st"

That runs every single revision check on every file and prints findings to the terminal. That's it. If you do run a GitHub or GitLab workflow, there's an Action and a CI image that posts the findings as inline review comments on the changed lines, but that's optional, not the entry point.

New in this version is a --metrics mode that measures a whole codebase instead of reviewing a diff. Point it at a folder, and it ranks your POUs by cyclomatic complexity and nesting depth, and tells you which function blocks nothing calls anymore:

plc-st-review --metrics src/

Top 5 by complexity:
  FB_ConveyorState  complexity:  10  nesting:  2  LOC:  42
  FB_AxisRamp       complexity:   5  nesting:  1  LOC:  27
  ...
Dead code:
  FB_Legacy    (0 callers)
  FB_Watchdog  (0 callers)

It can also emit the call graph as a Graphviz file or a JSON report for a dashboard. Again, no PR needed; it just reads the files.

There's no LLM in the path. Findings are deterministic; the same code produces the same findings every time. I did that on purpose. I want it to be something you can gate a pipeline on, not a slot machine.

Honest about what it is and isn't, because I know this crowd:

• It parses standard IEC 61131-3 Structured Text. It does not understand vendor dialect extensions (TwinCAT, CODESYS-specific stuff) yet. That's on the roadmap, and right now it stays portable on purpose.
• It reads .st text files. The one real prerequisite is that your ST exists as text at all. If your project lives only inside a proprietary binary project format and you never export it, there's nothing for the parser to read. Most vendor IDEs can export ST to source files; that's what you'd point it at.
• It can't compile your project, and it doesn't try to. It checks structure and semantics from the parse tree, which is exactly why it works in CI, where the vendor compiler isn't available.

Repo (with a live demo PR where every check fires on real ST): https://github.com/HeytalePazguato/plc-st-review

I'd genuinely like to hear from people who program or review ST code for a living: what does your standard enforce that a tool like this should catch and currently doesn't? What's the dumbest bug you've seen slip through a visual review? That feedback is what tells me which checks to build next.

Does anyone here can help me or explain how make a dashboard and found it in the webpage? for example i have a PLC Keyence and I need to show the info like good, bad, etc. this need been watching in monitor (PC), using modbus, OPC UA, and sometimes even the HMI works, So I found some ways to do it, but like this is a job I never done before I would like to know some advices from you. Thank's ! and have a great Day.

Hey r/PLC,

Bit of a nightmare situation here. I need to upload a program from a remote S7-1515F-2 PN before the weekend or my manager will have my head.

The engineer who originally commissioned this system took his laptop home on Wednesday and has been completely unreachable since — not picking up calls, not responding to messages. All the project files and GSDML files for the third-party devices were only on his machine. I don't have the original project file and no physical access to the site, only remote IP connectivity to the PLC.

I managed to get an online connection by creating a new project and adding the CPU manually — took a bit of trial and error to find a hardware/firmware combination that doesn't throw a "Not compatible" error. Once online, I tried to upload via right-click → "Upload from device (software)" but the Upload button in the preview dialog stays greyed out no matter what I do.

The upload preview shows a warning about missing GSDML files for some third-party PROFINET devices connected to the system. I set the action dropdown to "Attempt to upload from device", everything turns green and says "Ready for loading" but the button is still greyed out.

Has anyone run into this before? Is there any way to force the upload without having the GSDML files installed? Any help appreciated, desperate at this point.

I have to develop an automation project with Micrologix 1400 and I installed Rslogix V8.0 but the designer used V12.0 to program. I was trying to install this version but I had problems to install because I'm working on Windows 11, does anyone know how to install without problems?

I tried to change the file reading to Windows 7 but the installation procces stays on 60% with no advance signs and I don't know how to solve it

I am currently working at an OEM as the only controls engineer for my lines (I get called during the off shifts if there are any issues on my lines), but how does it work in a large company that have multiple engineers on different shift.

Like if I want to make a major change right now, I just have to get approval from manager.

What would you say are the biggest differences between working in a smaller company compared to a larger one as a plant controls engineer?

Hi guys…looking for some insight here. We are quoting a line that will use 12 different pumps to dispense product. 2 servo Axes per pump (1 for pump and 1 for rotary cutoff noddle) so 24 servo axes there. There are times that all of these pumps could need to run at the same time. Add in a few more servos for conveyor, traveling head, etc and we are looking at about 30 servo axes.

We’ve had good experience with Kollmorgen with CIP Sync. There will also be (3) different ABB 6-axis robots used along the line to move product around. Various I/O here and there, maybe some IO Link on the EOATs.

Customer has specified Allen Bradley and Kollmorgen as our options. The 5069 L330 or L340 can handle this number of Ethernet nodes per the data sheet (CIP sync doesn’t actually require an -M motion controller)

I’m not the best-versed in Ethernet traffic, RPI, etc…..does this much Ethernet stress a 5069 more than it would a 1756? The pump/cutoff combo will always be cammed together. I would think managed switch would be a must here.

Should I split this out between controllers? It would be 4-5% of the overall cost to add another controller.

Hi everyone I am looking to upgrade the motor on my dust collector in my shop to allow me to adjust the rpm of the motor based on which machine is running. Currently it’s a 2 hp 60hz motor, but is single speed and has a rpm of around 1500. I would like to get a motor that would work in the 3000+ range and work with a vfd. Also is does any one have any recommendations for low cost and easy to learn PLCs?

Edit: I currently have a vfd that I would like to use but it outputs 400hz.

I work on a lot of 90s equipment, and I always find myself struggling to connect to serial ports, there's all the different configurations and speeds and protocols, there must be a way to sniff or brute force the connection I haven't figured out yet, looking through crusty old manuals or guessing is super time consuming. I understand some parts of the connection, but is there a way to use PuTTY or RealTerm or something like that to simply determine the active configuration?

Can someone explain why REAL data type can be used for safety tags in Rockwell Guardlogix and Schneider Modicon M580 safety, but NOT with S7-1500F ?

Is ABB having major financial trouble? Have they ended the Bailey line or effectively they are?

Reason I'm asking is I've been working on a multimillion dollar upgrade for a month now. I've gotten precisely ONE email from the salesman, telling me that their new 810E and other 800 series DCS controllers are unreliable crap. So they want to instead sell the BRCs that are no longer made but aren't supposed to stop support for 5 years. On a $40 million USD project. Which means the project is dead when I cap the ROI at 5 years before we have to replace the DCS again. They also ONLY allow comms through Modbus TCP. And the web site is pure AI generated marketing nonsense devoid of any actual product information, manuals, anything. And it tells me something when they're charging $450/hour for in house support and no SI will touch it.

As it stands my next move is to escalate this crap. I'm done with them anyway. Already asking for buds from Rockwell, Schneider, and Emerson. I'm not jeopardizing this project with a garbage company that has apparently brought GE management on board. Neutron Jack has taken out Bailey.

I am trying to communicate with a "Compass Module" which basically works on an RS-232 protocol. I am using an RS232-Rs485 bidirectional converter and connecting the PLC with RS-485 built in terminal.
Regarding the functionality of converter, I have verified it through Docklight by sending querry command to the compass from RS-232 end and receiving on RS-485 to USB adapter connected with my PC on COM port.
Now It seems like a very simple thing but its not that simple or it looks complex to me.
I have been trying multiple ladder logic codes with RS2 instruction but I am unable to get or receive data.
I have previously worked with MODBUS RTU protocol and controlled 2x wind sensors using ADPRW function and it worked great. This compass module has its own custom protocol and 9600 Baud Rate with 8N1 setting. I am sharing the screenshot of the code I am running.

https://preview.redd.it/b29eenbiim2h1.png?width=1480&format=png&auto=webp&s=e4e7acddfece578c62b06172c1ed8edebcf9cf7d

https://preview.redd.it/dd5icqrqim2h1.png?width=1402&format=png&auto=webp&s=5a3e1d35bd532ab343d8a00c5da6cb42a782ac2c

When I first got interested in PLCs, I assumed most of the job would be writing new logic and building systems.

But the more I learn, the more it seems like experienced engineers spend a huge amount of time diagnosing issues between devices, networks, HMIs, drives, and older equipment.

Feels like understanding the overall system becomes more important over time than just programming alone.

Curious how people already working in the field see it.

I am a ThingWorx Developer since 7 years. Now I feel the market for this is declining. Should I learn something new or stay in this? What all should I consider if I should upskill?

I’m a technician with about seven years of experience in controls and instrumentation. I’ve built a few PLC projects from scratch in that time - just small pump controllers with AD parts.

I just got hired on with a company that has the most generous tuition reimbursement package I’ve ever encountered, and I wI’ll be working second shift for a long time, which frees up my daytime hours. I want to take advantage of this opportunity.

I have a bunch of the math and supporting science that an EE degree requires (need to get through diff eq and take some physics). The way I see it, I would probably take about four years to finish an EE degree from this starting point at a manageable rate.

Is this a worthwhile endeavor at age 36? I’m not really interested in design work and I hear that ageism is rampant among engineering circles. At this rate I will be 40 or 41 at the end.

On the other hand, I figure that completing a difficult degree could help me get into bigger money in the long run, since I still have 30 plus years of working to do.

If I just stay at this job, I cap out at 105k or so straight time, plus none of the BS that comes with managing people (did that for five years and about lost my mind).

Thoughts?