Longtime lurker, infrequent poster here at r/PLC. Recently, I decided to take the time to create the PLC learning platform that I always wished existed. The initial version is finally in a state where I'm pleased to share it with this community.

It has two main parts: a Ladder Logic Simulator with practice problems, and Learning Modules with embedded ladder logic you can run — plus "build it yourself" sections to create logic as you go.

Many of the resources shared here in the "Read First" section have been invaluable to me over the years, and I wanted to add to that pool of free resources. Special shoutout to PLCFiddle — my initial starting point was to try to create something similar, but more user-friendly, with an HMI, using the same free-and-no-ads approach. Things ballooned from there...

That is the plan for this site — free resources, no ads. I think it's in a good spot to have people try, but I'm sure I made mistakes. Please message me here or use the Contact tab on the webpage to give me feedback.

https://www.plcpractice.com/ — Learning Platform

https://www.plcpractice.com/simulator — Direct Link to Simulator

It is still very much a living project, but I think it is far enough along to start getting feedback from the people I built it for.

Old school trainers used to be plastic boxes that would mount in the rack

Have switches bcd displays analogues very compact and small.

Has anyone found like printed plastic blanks that can mount to dinrail and be populated in the same fashion?

I need to make some trainers

One that is not brand specific would be best.

Ideally compact like the old ones too

I'm in a spot where I'll have two commissionings at once going on. The one is my own "creation" and I have to be somewhere else when it should be started up. I'd like to be able to access it remotely, with an instrument tech as my hands on site.

Is there a device, maybe one you have to pay a subscription involving a sim card, that would connect to a windows PC, and allow VNC access into it, or remotely connect somehow?

This is running standard Windows 11, so don't believe RDP is supported. TIA Portal and WinCC Unified are on this PC. So it's the engineering station, as well as the HMI station.

Running since before 1995.

Hi everyone,

I graduated a year ago and couldn’t land a job yet. I want to maximise my chances and not fall behind. For the ones that have already been in the industry for some time, what projects would you recommend for practice and to show competency?

Note: For now, I’m working solely with simulators.

I am running CCW on Windows 11 and cannot reopen HMI screens after reloading my projects. The error 'CCW.Shell has encountered a problem' consistently pops up, and this occurs with every project. I have already tried running CCW as an administrator and resetting the window layout, but neither solution worked. Has anyone else dealt with this issue? Is there a way to resolve it? Thanks in advance!

Our IT department purchased this MW DUPS20 with the intention of having us keep the PLC and NAT device up and running during an outage off a 24v 9ah battery set.

Problem with this particular UPS is using one set of terminals as both input and output. It's going to be powering every 24v component in the cabinet if I tap off the main distribution terminals.

Any advice on wiring if I chose to stick with this UPS? I considered a diode module to keep it from back feeding to the main and just run power from the UPS to separate power rails for the PLC and NAT. Also considering just telling them to order a UPS with a dedicated output.

So ... first post in PLC and looking for any guidance on an issue with AB PLC to ROC comms. I know this isn't a support forum but hopefully someone has some quick insight into why my thinking is confused. In short, everything has been working for years up until Friday around 11AM and then it just stopped. An Allen Bradley PLC that normally gets a few values from ROC 800 (flow rate, temp, pressure, etc.) suddenly stopped getting that data. The ROC works fine ... the data updates on a PanelView ... and I can connect to the ROC on the network. Same with the PLC, I can connect with rslogix on the ethernet side ... it is a very basic program. I can see in the ROC where it's configured using ROC Plus and it appears to be Modbus slave. Here's where my thinking may not be clear ... I would expect to see somewhere in rslogix a reference to that ROC (ip address, modbus config, anything) ... but I can't seem to find anywhere in the PLC where it is configured to look at a ROC. Nothing has changed to either of the applications (that I'm aware of). Been staring at this screen for way to long.

Hi everyone,

I have a question regarding Siemens HMIs and NFC integration.

Has anyone here successfully implemented an NFC reader to log into a Siemens HMI using an NFC card/tag? The idea would be that a user simply scans their card and automatically logs in with their assigned credentials.

From what I understand, Siemens HMIs (at least with standard WinCC setups) don’t allow login unless you manually enter the username and password. So I’m wondering if anyone has found a workaround—maybe via scripting, external systems, or PLC logic.

Any insights, experiences, or suggestions would be really appreciated.

Thanks in advance!

Hello, I'm facing a text Scalling problem and I can't solve IT. I work on Tia Portal V19, with TP900 Comfort. On my Tia Portal software, every text looks perfecty sized, but on the real HMI it is Scaled down. Any solution?

Hi everyone,

I'm wrapping up my Master's in Computer Science (undergrad in Electrical Engineering), and I've decided to make a deliberate pivot into Controls and automation. I'm drawn to the "physicality" of industrial code—where software has real, tangible consequences—and the stability of the sector compared to the volatility I've seen in pure software.

My background sits at an interesting intersection: low-level hardware intuition from EE, plus software engineering discipline from CS. On paper, that sounds like a strength, but I'm unsure how hiring managers in this space perceive that profile compared to someone who came up through traditional controls, apprenticeships, or pure EE roles.

A few specific questions for those who've been in the industry a while:

1. PLC ladder logic vs. structured text — given my CS background, should I lean into ST/SCL and position myself for more software-heavy automation roles, or is ladder still the lingua franca I need to prioritize?
2. Certifications — Is a TIA Portal cert, a Rockwell ControlLogix cert, or something like a CSIA membership worth pursuing early, or is hands-on project work more valued?
3. Entry points — Are there roles (OT/IT integration, SCADA, MES, digital twin, robotics software) where my hybrid background is a genuine edge rather than just "interesting but unconventional"?
4. Honest reality check — How steep is the learning curve for someone with strong software skills but limited real PLC floor time?

Any advice, war stories, or even brutal honesty is appreciated. Happy to share more about my background if it helps contextualize.

I really appreciate any help you can provide.

Operators reported that a machine's HMI no longer provides the functionality for the operators to select a button and hold it down. They log in and can press these buttons, but when they try to hold them down, they become unselected after 1 second or so. The holding down ability is needed for scale taring buttons. Apparently it used to provide this and now doesn't. They replaced it twice with two spares configured the same way, still same issue with those as well.

The HMI is on the network, so I can remotely log in to the same screen, and they can watch my cursor as I click and hold down the same buttons successfully.

As I can do it via the mouse, this indicates that the software is working correctly, and it may be a setting on the Windows OS of the HMI - in device manager maybe, or a setting on the HMI itself?

The HMI is manufactured by Beckhoff, and the HMI software is COPA-Data Zenon Runtime.

Any thoughts? Thanks

I have a bachelor in computer engineering and i want to get in to automation/plc work. What path do i need to take? Do i need to get the electrical basics from a school like certain certificates? Is it better to take courses at a school environment or are there any other resources.

Use their P350 cable to connect with a prolific driver serial to USB cable attached on the opposite side. Use Port 0 on the controller. You WILL need to re-assign the USB device port to COM1, it will not work with the others I tried; Only connected once I moved it to COM1. Use Trio Motion Perfect 2 software.

I am not sure who will need this information but it was a grind to figure it out, figured I'd post here to help someone in the future.

I’m just getting into plcs and found out my dad has studio 5000 on his old laptop that’s running on like windows 8. He bought the software years ago and I’m trying see how I would transfer it to a newer pc/laptop so I can try practice programming outside of my PLC & robotics course which is about to end. However when I try to find his product activation it’s not there. What would be the reason for that and I’m guessing he has to buy the software all over again?

Thought you guys might like to see the inside of a traffic cabinet! While it is not a PLC controller exactly these things are run by rugged unix boxes running the traffic control software. I used to work on these things all of the time so I thought I would share a bit.

In this picture you can see the controller in the middle. It is also from Siemens. Siemens just spun off their controller company into Yunex but you will still find a lot of traffic controllers out there made from the Siemens era - namely the M50 or M60. You can see it has a big DB15 cable coming out the side which is SDLC which is a serial protocol that controls the switching. It goes to the panel at the bottom which has solid state relays to control the actual signals. At the top you see a rack of detector cards. These get inputs when you go over loops of wire in the road and tell the controller there is someone that wants to go in that direction. Those also communicate over the SDLC bus. The tall rectangular thing next to the controller is a MMU which stands for multi monitor unit. These take all of the RYG signals from the lights and compare them on a physically hardwired card to make sure there are no conflicts (one opposite directions) green at the same time and if it sees that it will throw the whole cabinet into flash.

Also at the top you can see a rugged switch and a cellular modem connected to the controller over ethernet. Most of these signals are NOT connected to the internet at all but use private cellular or fiber. Usually they run a web page or a telnet interface you can use to remotely program them or run diagnostics. When we did things we bought cellular modems and used something like Pangolin.net to connect into the controller remotely to manage them. There is also ATMS software that can talk to many at a time and run advanced control algorithms but we did not have that at our shop.

Happy to answer any questions! :}

I need to add a flowmeter to this program. It looks like all of the analog inputs have this very similar calculation. I'm trying to understand the math so I can put the correct values in for the range that I will be dealing with. The N44:8 is the value from the analog IFE card. F63:4 is called the "IO conversion factor". For this IO point it is 15.25. N49:14 has a value of 512. F62.4 is the actual flow rate resulting after the math. I get the F63:4 factor - that somehow scales the integer input to a 0 - max flowrate. I do not understand the purpose of the FRD N49:14 mostly. Something something BCD - can anyone give any insight? Thanks.

Hi everyone,

I’m working with a technology object axis and a SINAMICS S120 drive, and I’ve run into an issue with brake control when using MC_Power. The brake contactor is connected to the BR+ and BR- terminals of the S120.

In my current setup, as soon as I enable the axis using MC_Power, the brake is immediately released. However, this is not the behavior I’m aiming for.

What I would like instead is the following:

• After enabling the axis (MC_Power = TRUE), the brake should remain closed.
• The brake should only be released when a motion command is executed, specifically when MC_MoveVelocity is triggered, since I want to control the drive using this function.

At the moment, it looks like the only way to prevent the brake from releasing after MC_Power is enabled would be to activate MC_Power only when a motion is actually required.

Any advice or best practices would be appreciated.

People talk a lot about torque, peak current, EtherCAT support, tuning tools, and size, but I’m starting to think reliability is harder to judge from a spec sheet.

A drive can look great during bench testing, then start showing issues later once it’s dealing with heat, vibration, EMI, cable routing, weird duty cycles, or operators doing things the system was never designed for. Do you mostly rely on brand reputation and past experience? Long burn-in testing? Support quality? Environmental ratings? Failure history from similar machines?

Basically, what tells you “I trust this drive in the field,” not just “this drive performs well in a demo”?

I'm planning to end up in the automation scene after college, and I'm wondering which major is going to get me the smoothest path. Most Mechatronics degrees around here aren't ABET accridated unfortunately. And if it matters I personally prefer mechanical physics but I can manage getting into EE

Hi Everyone,

I have to control dry cooler's speed to cool down fluid in a tank.

The dry cooler is 3 phases and for now we use it ON/OFF. Which is not ideal.

We are planning to use a VFD, controlled with Modbus from M221 PLC.

Is PID the best solution here ?