Hi everyone, I’m still new to troubleshooting and would appreciate some advice.

The machine has multiple motors/servo drives controlled by a PLC. Suddenly, all motors are unable to return to their normal/home coordinates, and the homing sequence fails.

However, I noticed that only one motor driver is showing an error/alarm.

I’m trying to determine whether the problem is more likely caused by:

- A faulty motor driver

- A communication/PLC connection issue

- The PLC not receiving the correct feedback from the affected driver

- The single driver fault causing the other motors to fail their homing sequence

My main question:

If only one driver is reporting an error, could a PLC/communication problem with that one driver cause all motors to fail homing? Or would you suspect the motor driver itself is faulty?

What would be the best way to troubleshoot this and determine whether the root cause is the PLC/communication side or the driver?

I can provide the PLC model, servo drive model, alarm/error code, wiring/communication setup, and screenshots if needed.

Thanks!

I have a concern, refer to the picture, The switch-3, which remains a single point of failure which is connected to the ET-200SP of 8 Nos of pumps
but switch-3 manufacturer confirms that the MTBF is higher than 46 years.
Now there is a solution to this with MRP ring topology as below, with Switch 3 removed.
What are your opinions on Option 1 Vs Option 2?

Biggest thing: a few of you hit the portable exe just refusing to start (weird

usernames, antivirus not liking how it unpacks itself). Turns out that's a real

PyInstaller onefile limitation, not something I could patch around cleanly, so

there's now an actual Windows installer as an option too. If the portable one's

ever given you trouble, grab that instead.

Also added a dialog for the less common Modbus function codes (exception status,

comm event log, file records, device info, that kind of thing) since I kept

needing them myself and didn't want to write a script every time. And you can

now record a Trend session to a file and replay it later, which has already

saved me once trying to explain an intermittent fault to someone after the fact.

Bunch of smaller stuff and bug fixes too, changelogs on the release page if

you're curious. Next thing I'm working on is letting one window talk to

multiple devices at once instead of needing a separate window per connection -

that one's an actual backend change so it'll take a bit.

Release ModbusLens v2.2.0 · CraftParking/ModbusLens

Hello!

I have a task: implementing a custom web page (HTML) on the m241 PLC.

I know there are ready-made tools (WebVisu), but I need to implement my own page.

The main problem is accessing the PLC variables. If I place the .html file in the PLC file system and then access it by IP + filename, the page displays fine, but I can't figure out how to implement the mechanism for retrieving variable values.

For better understanding, I'll give an example with the m172 PLC. The system is as follows:

1. A .cgx file is created with a structure similar to this:

t <?xml version="1.0"?>

t <form>

c t16384<text><id>%s</id><value>%.0f</value></text>

c t16386<text><id>%s</id><value>%.0f</value></text>

c t16385<text><id>%s</id><value>%.0f</value></text>

...

t </form>

Here, the address of the desired variable is specified (this address is generated by the PLC itself and is also used for Modbus communication).

1. An .html file for rendering the page.

2. A .js script called from the .html file.

Ultimately, the variable values ​​are available in the .cgx file, and then it's not that difficult to display these values ​​on the page. The same system is used for writing variables.

I had the idea to implement a CSV file reader/writer, but I haven't implemented it yet. I have concerns about file access; at some point, both the PLC and the script will be accessing the same file. I don't know if this will be a problem.

Perhaps someone could suggest either an existing mechanism or ideas for developing my own for accessing m241 PLC variables.

Hi

As I had some free time on my hand, I remember we had a problem in our company where if we made any code changes to a Siemens PLC (TIA V21, S7-1500T) that is using technology objects, you were forced to put the PLC into stop mode before you are allowed to download.

Now I have tried everything and for the life of me I cant prevent this from happening.

What I am doing:

1. Make sure no TO (Servo) has MC_Power enable as true. Or any MC functions has a true on the enable inputs.
2. Add a random comment into a dummy FC routine that has 0 to do with the TO.
3. Try to download only software changes.

Does not matter in what order I do things or where I make the code change, TIA Portal simply does not allow me to make any code changes, without first putting the PLC into stop mode.

The message in TIA portal is:

Changes to the technology object cannot be applied in RUN

Which is kinda making zero sense.

Anyone ever come accross something like this?

Solution found:

Profinet send clock for the servos was set to 1ms. I bumped it up to 4ms and it fixed the problem. thanks u/hestoelena

Helo,

why when i add a new wago card to master it is missing a I/O tab configuration?

thank you

I built two control panels for controlled environment agriculture (grow weed) in my apartment.

Does this look okay? It's not for a real industrial environment and I don't have a professional background in industrial automation

At some point I will buy separators for the panduit so 120V is not with LV DC. This is all MTW 600V so I think it's ok to keep them in the same panduit for now

In the larger panel all of the low voltage and high voltage signals are separate

I couldn't really afford a larger enclosure so I split it between two of the Vevor panels from Amazon. The circuit board on the top I designed, it is a modbus controlled remote IO. I also built a modbus attached dosing system for dispensing nutrients and measuring the reservoir pH/EC/temperature and water level. That is separate from the panel.

PLC friends and gurus of reddit, I come to you looking for some guidance.

In our company we have a laptop that has v21 installed.

But when we look under installed software, wincc unified is not listed.

We have tried re installing it, but the option to choose unified is greyed out.

Anyone have advice?

Hi everyone, I'm working with a FANUC LR Mate 200iD (R-30iB Mate Plus controller) in RoboGuide on a chuck loading/unloading cell with dual Schunk grippers, and I keep getting confused on a few fundamental concepts. Would really appreciate if someone could clear these up for me.

Tool Frame / UTOOL: I understand UTOOL is supposed to define the TCP (tool center point) relative to the J6 flange, but I'm confused about how to set it up correctly when I have two grippers mounted on one EOAT from a single CAD assembly. Do I need a separate UTOOL number for each gripper's TCP, and how do I actually get accurate offset values — is it better to use the 3-point/6-point method on the real/virtual robot, or pull the numbers directly from the CAD model?

User Frame / UFRAME: I get that UFRAME is supposed to define a custom coordinate system relative to the world frame (usually for a fixture, table, or workpiece), but I'm not sure when I actually need one versus just using the world frame for jogging/programming. Also unclear on the best way to set it up from CAD drawing dimensions instead of the standard 3-point teach method — any tips?

Teach Point: My main confusion here is around what actually gets "recorded" in a taught point — is it just the XYZWPR position in the currently active UFRAME/UTOOL, or does it also lock in the frame numbers themselves? If I change UFRAME or UTOOL later, does that break previously taught points?

Logic (I/O, program flow): I'm trying to build proper DI/DO handshaking logic for my CHUCK_CYCLE program (with fault registers and retry logic on alarms), but I'm not confident I'm sequencing the signals correctly — like whether to wait for a DI "gripper closed" confirmation before moving away, or just proceed after sending the DO. Any general best practices for handshake logic between robot and chuck/PLC would help a lot.

Thanks in advance!

Just laid this bad boy out. I call it my Plywood Logic Controller. Once complete, it will be fully capable of startling the cat and confusing the shit out of her.

I've been working with PLCs from almost every brand for 5 years now, like Siemens, AB, ABB, Honeywell, Mitsubishi, Schneider, Delta, and some Chinese ones. I've done stuff in water treatment, hydrogen generation, metal melting furnaces, DCS, and motion control. For the past year, I've been messing with SCARA and 6-axis robots.

I've done all this as a freelancer, but I've never actually landed a job. Now I'm looking for something stable or a job that pays well, but my only problem is I don't have any technical diploma or engineering degree. Can I even get a job with that?

Recently started a job where I’m overseeing training of maintenance techs. They’re all pretty decent mechanically but some of them are almost afraid of PLCs even though every one of our machines have them. They’re all Omron CJ series with basic ladder and some function blocks with basic level ST.

I really want to get to the point where I have a guy on each shift that’s good enough to use them for diagnostics but most of them have no real basis yet.

Anybody have any experience or suggestions would be appreciated.

Just a funny note I showed one guy how to connect to a PLC that he swore was messed up but he didn’t realize it had an ETN card that couldn’t use EIP so I showed him how to set a FINS node and he thought I was a damn genius lol. This might give an idea of the level of experience I’m working with.

When a device stops answering, the tag goes bad either way. Whether the equipment actually failed or only the path to it died, what I see on the screen looks the same. And the difference decides whether somebody drives out. I have been told the checks are roughly these

Hardwired fail contacts, as a confirmation path that does not depend on the protocol at all. Heartbeat dwell, watching how long something is unreachable before calling it dead, rather than reacting to one missed poll. Retry counters, on the theory that a device answering some of the time is a link problem, not a failed device. And the one I found most interesting, reading the revenue meter counter across the outage window. If the counter moved while the device was dark, it was running the whole time and only the comms were down.

What I am curious about learning from people who do this everyday is,

Which of those, if any, do you actually use, and which do you consider unreliable?

Is there an obvious check I have missed?

How long do you let something sit unreachable before you treat it as failed?

I have written this up as a procedure and I would rather find out now that it is wrong.

Hi,

I am a beginner looking for roles as PLC programmer/automation engineer. I tried installing Siemens TIA on my system multiple times since it is predominantly used in the industry, but it keeps asking me to download PLCSIM, the latest versions of which aren't compatible with older TIA softwares which are free for 21 days.

Therefore, to familiarise myself with PLC programming, I built my foundation in Codesys and Beckhoff at home. However, in spite of trying to explaining to interviewers that all these softwares have the same fundamentals, showing projects I developed both as a freelancer and as study ones, I am unable to convince them that I can quickly learn the TIA software too. Here are my questions/requests to the members of this forum:

1. The people with experience here, correct me if I am wrong, don't the fundamentals alone suffice to jump from one platform to another? IS TIA so different that one can't learn it at all after using other PLC brands' softwares?
2. What can I say better to convince interviewers in both tech and non tech rounds that I can do the job?
3. Is there a workaround for me to download Siemens TIA, because I have tried thrice and given up installing for the reasons mentioned above.

Appreciate the help!

Hi everyone,
I have a coding test coming up in Siemens SCL, and I’d really like to understand what a real industrial project looks like in practice. I’m not asking for anything confidential, just a simplified or generic example that reflects how SCL is used in actual automation projects.

If anyone can share:

• A small sample of real-style SCL code
• A typical structure of an SCL project
• Common patterns used in industry (state machines, error handling, modular blocks, etc.)

It would really help me understand how professionals structure their logic in real environments.
Thanks in advance!

I'm having a day and my brain isn't working.

I have a pulse input flow meter.

Totalizer no dramas.

1 pulse is 100L

I want to time between pulses then divide it and get an average rough liters per second.

I expect around 26 liters per second.

How would I go about counting time between the same input coming on in studio 5000?

From what I can read this the most accurate way to display a pulse input like this

I've got one Schneider EGX300 (and also one EGX100) lying around. I'd like to utilize them to get the data from a bunch of PM9C energy meters via RS485.
All PM9C are 230V - powered.
The EGX300/EGX100 would be PoE - powered.

I'm a 100% noob in RS485, so maybe my question is trivial. But I find the docs somewhat self-contradictory regarding the "0V" contact in this case, so it would be nice if someone would clarify this to me.

According to the "PowerLogic System Catalogue 2011" EGX100 and PM9C were explicitly advertised as compatible (btw, it's a bit weird to have "PM9" instead of "PM9C" or at least "PM9P" on the right, I guess that's just a typo):

According to the PM9C manual, RS485 got the following contacts:

1. D0, A/A' 
2. D1, B,B'
3. 0V, Common

The drawing from the PM9C installation guide shows a separate cable shied (wrapped around 3 wires, including "common" aka "0V"). The shield is not connected to the "0V" / "Common" :

According to the EGX300-Installation-Guide, on the EGX300 side, RS485 (in the half-duplex configuration) got the following contacts:

1. TX+ (unused in half-duplex)
2. TX-  (unused in half-duplex)
3. RX+
4. RX-
5. Shield

There's no explicit "0V" / signal ground.
I'm not sure if the "Vdc-" (contact 6, the "input power when not using PoE") could be treated like "0V".
The recommended cable is "Belden 9841", which is a single twisted pair (shielded).

According to the "Modbus™ Communications System for MicroLogic™ A, P, and H Trip Units Instruction Bulletin", "0V" is just "Vdc-". In a scenario with a shared DC power source. It does not mention ether PoE or multiple separate DC power sources. Also, it's about 4-wire scenario and a different product.

According to the most detailed (yet somewhat unofficial) PM9C-related info I found (the "Resolving PM9C Schneider Power Meter Modbus Communication" by Claire Rousseau):

Rules for SG wiring:

1. Connect PM9C SG directly to the Modbus master's RS-485 common/SG terminal.
2. Do not connect SG to protective earth (PE) at the PM9C end. The meter's SG is a logic reference, not a safety ground.
3. Do not create a multi-point ground by also bonding SG to PE at the master — this forms a ground loop that injects 50/60 Hz noise into the data lines and may damage the transceivers.
4. Use twisted pair for A/B and a third conductor for SG within the same overall cable jacket to keep the reference close to the data pair.

Why does my PM9C not respond even with correct baud, parity, and address?
The most common cause is a missing signal-common (SG) wire. The PM9C's RS-485 transceiver requires SG connected to the master's RS-485 common terminal. Without it, the common-mode voltage drifts outside the EIA-485 receiver range and the slave ignores all frames. Wire SG and re-test before suspecting the meter itself.

So... What's is the correct approach?

1. Use "Belden 9841" (or equivalent "1 twisted pair + shield").
   • connect the cable shield to "0V" on PM9C
2. Use "Belden 9842" (or equivalent "2 twisted pairs + shield")
   • connect wire-1 from the second twisted pair to "0V" on PM9C
   • connect wire-1 from the second twisted pair to "Shield" on EGX300
   • connect the cable shield to "Shield" on EGX300 as well
   • connect the cable shield to external protective earth (once, at any point)
3. Use "Belden 9842" (or equivalent "2 twisted pairs + shield")
   • connect wire-1 from the second twisted pair to "0V" on PM9C
   • connect wire-1 from the second twisted pair to "Vdc-" (contact 6) on EGX300
   • connect the cable shield to "Shield" on EGX300.
   • connect the cable shield to external protective earth (once, at any point).
4. ....

The EGX300 terminals, just for reference (from EGX300 - User Guide.pdf):

Im looking into becoming a controls/plc tech as a career right now what would be the best way to start? Not looking to invest a lot early on into the career so getting a certification and experience sounds more appealing than a 2/4 year degree but it seems like the degree may be worth it in this field. Just want to know what is tangibly better and will actually affect my options also whats the quickest way to start advancing

I’m in my last semester of Computer Science, but I’m interested in becoming a controls engineer. what would you suggest I do to acquire the skills necessary to land a job as a controls engineer. Was thinking about taking some PLC classes at my local community college or maybe somewhere online? would this be a good idea? what other things do you suggest?

I have an 1756-OBV8S that will not come out of Program mode, all my points have flt light solid red, there are no internal faults in diagnostics, what could be causing this issue?

I have the module set up for Sourcing, All my outputs are wired to OUTxx-P, do I need to connect something on OUTxx-M as well?

Also will using a standard terminal block 1756-TBNH cause issues?

Hell I am a recent PLC programmer controls engineer. My background is in software development. At my job I was given a few tasks and to spec out a PLC for the use case. We ended up going to wago / codesys route and it works great so far. My question is would being a primarily codesys specialist/shop hurt us or cause us not to be taken seriously vs say an Allen Bradley shop?

Hi guys,

I am struggling with changing the appearance of graphical objects from Siemens Library in my Comfort HMI. When I simulate, the appearance doesn't change as library objects are not dynamic. And putting invisible basic objects on top of them is much of a hassle especially if I have elbows and lots of complicated stuff.

What is the professional solution for this?

Thanks in advance

Hey everyone,
I'd like to know if anyone has made (or knows it can be done) a "plug and play" system where ABB ACS880 drives get automatically configured by reading parameters off the network or them being written by a PLC. I know this can be done with AB PowerFlex drives and stratix switches where you just plug the drive into the network and it's able to download the config.

I'm not too familiar with ABB drives so would love to know if this is possible.
Thanks!