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This sub is dedicated to discussion and questions about Programmable Logic Controllers (PLCs): "an industrial digital computer that has been ruggedized and adapted for the control of manufacturing processes, such as assembly lines, robotic devices, or any activity that requires high reliability, ease of programming, and process fault diagnosis."


This sub is dedicated to discussion and questions about Programmable Logic Controllers (PLCs): "an industrial digital computer that has been ruggedized and adapted for the control of manufacturing processes, such as assembly lines, robotic devices, or any activity that requires high reliability, ease of programming, and process fault diagnosis."

On topic subjects

  • News and articles about PLCs
  • Questions about PLCs
  • Homework help; but make it clear it's homework
  • PLC internship, employment and education questions

Off topic subjects


  1. Be civil: do not insult; no all-caps, no excessive "!" and "?", please.
  2. Submissions must be on topic
  3. If asking a question, ask the actual question, fully yet concisely, right in the title
  4. No spam; no self-promotion (*); no commercial content. Any ads (offer or wanted) go to the weekly thread
  5. No shit posts (memes - pictures with superimposed text - are OK)

(*) At mods' discretion, certain self-promotion submissions from people who contribute to this sub in other ways may be allowed and tagged with the "Self-promo" flair

Complete rules:/r/plc/about/rules/

Please click "report" on spam

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74,452 Subscribers


What are the most commonly used (or your favorite) drawing software for electrical diagrams of control panels?

Hi, am a control engineering student, am doing my internships right now, and i Just started learning about drawing softwares, the company uses autocad electrical, but i wanted to know what else is used in the industry.

1 Comment
15:22 UTC


Fanuc Robot Stop Suddenly

Hello guys, please someone can help on this issue , lately in our plant we have a robot that for one sequence goes for around 6 positions , and from time to time if the robot was stopped at the last position ( no part to load ) for around more than 30 min the robot starts taking this position as home , and even after move it manually by the teach pendant once switching to automatic and run move to home command the robot moves to the wrong position which is the last one number 6. My robot knowledge still in progress so i fiix that just by loading the backup.

If someone can help i would be grateful🙏🙏.

14:58 UTC


I have 1783-NATR connected between 2 machines which have different IPs. I can communicate from both machines and data transfer is happening between both controllers. Both machines have a computer and I want to share a file between these computers, is it possible?

12:48 UTC


Logo 5 resetting after power loss


I work in an educational institution and recently I've been given a task to teach PLC automation. It's not really my cup of tea to be honest as I prefer text to visual programming and Ladder confuses me when networks become large (and oh do I hate recursion errors), but I did learn enough to teach basics.

In the meantime, our school bell control system malfunctioned, so I figured what was the better way to show the kids how automation is cool other than doing it in front of them. The system works great and in fact, it worked so well, another school asked if I could install the same system in their building.

This is where problems start... The program in Logo relies on its clock. The bell ring intervals are set with clock blocks (sorry for incorrect term) and every time they unplug the PLC (during school break etc.) for the longer time, the clock seems to reset and instead of running the program when being plugged in, the screen is just flashing until someone sets the time again.

I did plan ahead and implement all these events in the program, but no one in my school could be bothered to build a quick three button setup so they could deactivate the bell if needed (or force ring), so the other school didn't get one either.

I assume it's the Logo battery being old and failing too early when the Logo is unplugged. My question is, is it worth replacing battery, is it simple enough and where should I buy one? I've been googling a bit but can't find reliable info on which model goes inside and I've mostly seen chinese batteries which makes me a bit paranoid because I don't really want to replace them in 3 months again and I don't even know if it's the right ones.

Thanks in advance and have a nice day!

10:55 UTC


Modbus convertion weintek??


Being pretty ignorant on the subject, I'm trying to set up a modbus server on a Weintek HMI connected to a Fatek PLC.

I set up a textbox and I'm trying to read/write data on it

At the moment I can browse the register using modbus poll, but the things i write on the PLC textbox does not match what is on modbus poll (example 2024 = 2 registers 12338 and 13362)

How can i solve this? To write 20 on the textbox and get 20 on modbus poll?

09:57 UTC


Backup program TIA portal v17

I have issue with backup program with s7-1500. The error show 'Action cancelled before upload from device'. Anyone have faced the same issue. Please share me how to solve this matter

09:41 UTC


4-20mA input to PLC not working

I have a weight controller connected to a PLC analog current input module.

When power to the indicator is off the value to the PLC is fluctuating between 10 to 30 kg.

When power is on and the weight is 0kg on the controller, the value on the PLC is fluctuating from around 280kg to 320kg. Even when the weight changes the PLC values don't change.

The weight controller is a newly installed one. I replaced the input module. I also checked the shield ground and found no problem with that.

I did settings on both the controller side and PLC module side. What do you think is the problem?

05:28 UTC




I'm looking to apply for visa for USA, and I need to justify that my work is relevant in America as well specifically New York and Newark or area surrounding it.

I have over 5 years of experience with Allen Bradley PLCs (ControlLogix, CompactLogix, MicroLogix) along with Endress Hauser instrument commissioning and MOVs commissioning. Of course I have end to end project lifecycle experience as well along with managing on site teams, stakeholders and making project plans since I'm involved with systems integrator.

Can the control system engineers from America highlight which industries in America will my experience be useful?

04:36 UTC


Sinamics G120X Frequency

I need to show the frequency in hertz however there is only speed option. How can i manage to get frequency from the tia portal? https://imgur.com/a/920lbdS

03:22 UTC


Where can I download COM Profibus

Does anyone know where I can get COM Profibus? I have a very old TI 505 PLC and my understanding is I need COM Profibus to configure the Profibus connection on it.

03:05 UTC


AB trainer for Automation Class

Pretty Cool, I really enjoyed doing this class. The teacher we had was a tech specialist at Allen Bradley for 15 years & was a little difficult to learn from at times, seemed like he moved super fast. Overall, something I definitely would like to dedicate more time too. That being said- Automation guys don’t deserve enough credit. Programming is the backbone to any successful manufacturing facility and often times under appreciated. Idk how y’all do it in a crisis lol

02:28 UTC


Guide for interpreting "Variable" names on DirectLogic 405 Series Ladder Logic?

01:56 UTC


TIA Portal


More AB tech and not much experience with Tia portal. I don't have a Siemens account, and i need to download Tia Portal V16. Is there any way to download it from somewhere else?

01:17 UTC


Old stuff you say?

Very old Tenor drum sequencer for a starch kitchen.

21:08 UTC


Yo I saw we are doing older controls.

20:47 UTC


OPC UA Certificate for VT SCADA


We have an OPC UA server running on our PC and is receiving data via serial port from an Arduino Uno. When we try to connect VT Scada OPC UA Client to the Server, it says the server is not Valid. We have made our own certificates and private key as well as getting a certificate from UA GDS. Nothing worked. Please advise.

02:45 UTC


New to PLCs. Need help with a simple logic

Hello friends,

I want to design an interlock for the following system.

  1. High system pressure detected by the pressure transmitter(4-20mA) must close the gas input solenoid valve 220V AC.

  2. High system temperature detected by the temperature transmitter/controller (4-20mA) must close the gas input solenoid valve 220V AC.

  3. Smoke detector signal(4 -20mA)must close the gas input solenoid valve 220V AC

As you may see from the above , I have 3 inputs and one output.

Q1. What is the most economical way of executing the above logic and what instruments should I be looking to purchase?

Q2. Can the above be executed without PLCs?

Q3. Could someone help me out with the programming?

Any help is appreciated.

22:01 UTC


Point IO Thermistor Measurement

Hi all,

I'm upgrading an obsolete system and ran into an issue with NTC Thermistor (5.02k Ohm T Type) temperature probes. The old system measures these using a resistance input.

Wondering if there's any similar Point IO modules, else if not, is there any pointers on what I could do here?


18:29 UTC


Controls tech to engineer?

Looking into job searching/relocating in the next few months. I have 12 yrs in multicraft maintenance, always as a "controls guy" within the maintenance world. I'm well versed in plc, relay controls, motor controls, drives, instrumentation, etc. But no engineering degree

I want to make a move in my career and a step up. How willing will most companies be to consider me for controls engineer positions without a degree?

Is the market flooded with degrees, or would I still have a chance to be considered?

Looking for honest "from experience" opinions here

17:46 UTC


What do the numbers following the tag mean and how can I replicate it?

On the output he has Alarms.0 Alarms.1 etc. What exactly is the .0 and .1 and how do I do something like that.

On the Timer he has the same thing going AlarmTmr[0], AlarmTmr[1].

Normally, I'd ask my instructor how to do this, but since it's the weekend, I am struggling to find an answer to this, and I'm sure it's a simple answer... I've spent a decent amount of time trying to figure this out already.. Thanks

17:42 UTC


What is the next step in diagnosing this dinosaur?

17:37 UTC


How do I get software for this ?

I have factory talk software, but I don’t believe I can upload from this HMI. I need to add another HMI with same program.

14:29 UTC


Looking for modern HMI designs.

Looking for modern HMI layouts and designs. Anyone willing to share a picture or example of their HMI main screens look like?

12:45 UTC


Help with setting up Cogent Datahub

Hi, we have an OPC-UA that we need aggregated (sampling) values from, and store forward functionality. Then be sent to a MQTT broker.

I'm having a hard time setting this up and find the manual and use cases confusing.Are there any good resources or anyone that can help us do this?

10:02 UTC


FTView SE 13 Question

Is there a way to access the placeholder names from VBA? I datalog to a SQL server and have a custom web page that can plot any tag, I'd like to bring that up from FT View SE 13. I don't know how to read the value of the #1, #2 etc placeholders from VBA. I have a button that can bring up page for a fixed tag that works already.

1 Comment
09:23 UTC


Does anybody know why Rockwell makes you have to install multiple versions of RSLogix/Studio 5000?

It's been everyone's big gripe ever since it came out, I know. But has anyone ever heard why?

Why is it that, if I want to get online with a 38-year-old PLC-5, all I have to do is fire up the latest version of RSLogix 5 and I'm covered? Why is it that if I want to get online with a 28-year-old SLC 5/04, all I need is the latest version of RSLogix 500 and I'm good to go?

But if I want to connect to a 15-year-old Control Logix running version 17....version 17 isn't compatible with Windows 11, so I need to create a Windows XP SP3 virtual machine and install the software there, and while I'm at it install every other version that's compatible with that OS. Oh you need version 27? You'll need Windows 7 for that. Not XP or 10, it's not compatible with those. Only 7 64-bit, not 32-bit. To cover the gamut of all Logix 5000 class processors from release to the current version, I need no less than 2, probably 3, maybe even 4 different virtual machines that can install all the relevant software versions, and I have to install them all in the correct order. If I install version 30 or above before version 29, version 29 won't install because it has a bug where it detects FactoryTalk Linx as a newer version of RSLinx Enterprise and thus won't install anything if that fails. The other versions will just skip over that and install everything else, but not 29!

And after version 20, it's all over the place. Versions 20.06, 24, 28, 30 and up are compatible with Windows 10, but versions 21, 23, 26, 27, and 29 aren't. Obviously they went back and made minor updates to the older versions to make them compatible with the newer version of Windows, but only some of them.

Meanwhile, FactoryTalk view version 14 can save runtime files down to version 5.0, and I only need to install one version! Why can't we just have the latest version of Logix Designer installed, only that version, and have you tell it what the firmware of the PLC is? Why can't it just compile for a specific firmware accordingly? I mean, RSLogix 5 and 500 do it. You choose the series and FRN range of the PLC you're using right there in the setup. You don't have to install RSLogix 500 1.0 in a Windows 95 VM to talk to a SLC processor made in 1998. It's not like PLC architecture has changed that much from release to release. Why isn't the Logix platform that way?

07:04 UTC


Salary expectations in Australia

Hey guys just wanna know what sort of salary should I expect as automation or control system engineer when I graduate it, and like a rough estimation of progression as I gain experience in industries like tech and others. I also wanna know how much of a difference I should expect in my salary if I was to work a fifo job in the mining industry than working somewhere in the cbd.

02:18 UTC


Does any one know this page : plc-direct.com

Does anyone know / has worked with this site ?

It would help me a lot as I am buying several parts and the prices are interesting.

I have run several pages looking for scams but there is not much information.



- scamadviser


23:48 UTC


Farewell Old Friend

You've done so well and worked so hard. Time to enjoy your retirement.

23:26 UTC

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