The end of PLCs?

I was looking at valves today for a project and one of the options they came with was an ethernet connection. Over my short time as a controls engineer I have noticed just about every instrument I spec out has an ethernet option. This lead me to the thought of what if we just got ethernet connections back to a network rack then had a server running as a PLC. I am sure that exists in some form, maybe not on an industrial level at this point.

But if you could eliminate the need for a 10-15k plc cabinet or series of plc cabinets and just replace it with a server and network rack that may or may not be already existing, I would think that would be more advantageous given the amount of data you could pull over ethernet. With IIOT gaining a lot more traction, this seems to be the direction we are being pulled in.

I was wondering if any of you have seen something like this done in the field today.

Distributed IO has been a thing for at least 20-30 years.
As to a central CPU placement, today you can have a 'traditional' controller, or a software based controller. Some of these software controllers that I know of are running under Windows, but there is a clear trend away from Windows and towards realtime Linux or Open BSD.

edit: There will be no "end to PLCs". But the classical control cabinet with a massive PLC and 1000s of terminals and wires and cables may be the exception. The norm will be that IO (incl. intelligent IO such as drives and instrumentation) will be tied in by a network protocol.

Back in 1988 I started working in the warehouse for A-B in a local sales office while I was going to school at night. In the copy/literature room there was an article posted next to the copier. I think it was from Control Engineering and it was titled "The Death of the PLC". It forecasted that PCs would soon be running everything so there would be no need for dedicated PLCs.

The technology has evolved and will continue to do so. I'm left wondering what else the writer of that article forecasted. He/she managed to look at the PC industry and see it evolving, but couldn't forecast the same for PLCs.

OG

Operaghost said:

Back in 1988 I started working in the warehouse for A-B in a local sales office while I was going to school at night. In the copy/literature room there was an article posted next to the copier. I think it was from Control Engineering and it was titled "The Death of the PLC". It forecasted that PCs would soon be running everything so there would be no need for dedicated PLCs.

OG

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I remember that article, and many others like it. People have been predicting the death of the PLC for decades.

JesperMP said:

Distributed IO has been a thing for at least 20-30 years.

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I had my first experience with DCSs recently as part of a DeltaV system. I only built a panel though. Nothing on the software side of things. Isn't there still a physical controller with that system or am I wrong?

Edit: I guess AB remote IO is the same concept but there is still a controller involved.

I use some Ethernet/IP valve manifold controllers, I still have the PLC controlling them, they just look like an IO drop.

jakeparsons03 said:

I was looking at valves today for a project and one of the options they came with was an ethernet connection. Over my short time as a controls engineer I have noticed just about every instrument I spec out has an ethernet option. This lead me to the thought of what if we just got ethernet connections back to a network rack then had a server running as a PLC. I am sure that exists in some form, maybe not on an industrial level at this point.

But if you could eliminate the need for a 10-15k plc cabinet or series of plc cabinets and just replace it with a server and network rack that may or may not be already existing, I would think that would be more advantageous given the amount of data you could pull over ethernet. With IIOT gaining a lot more traction, this seems to be the direction we are being pulled in.

I was wondering if any of you have seen something like this done in the field today.

Click to expand...

Any PC based system needs to provide the following before it would be considered by most plants, at least in the US: real-time behavior, Ladder logic, live debugging with monitoring.

Realtime behavior is almost impossible in most virtualized environments (and with most operating systems), but is a solvable problem. The others are certainly do-able. You end up with essentially a PLC that runs on different hardware.

PC based automation has been a thing for years. Beckhoff controllers are all PC based, I think. Siemens has had Soft PLCs as an option for a long time. AB has (used to have?) one, I don't think it's been updated in a while though. There are advantages, especially when it comes to interacting with things like databases.

You still need cabinets for all the electrical stuff: circuit breakers, transformers, drives. You still need cabinets for the IO, whether they are remote IO controlled by a PLC, IO local to a PLC rack, or remote IO controlled by a PC. I see many systems where the PLC is sitting by itself in the corner of a cabinet somewhere, with no local IO, or even an IP65 PLC with no cabinet at all.

What changes between your scenario and mine? A server in a closet somewhere vs a PLC in a closet somewhere? You won't be able to replace the performance of a $10k PLC with a $200 PC. Maybe with a $3k PC, but how often do you see a typical PC running for 20-30 years?

And, don't forget about the Windows is updating blue screen when you are trying to run production.

I had one Win10Pro that installed the latest and greatest update last week and it rebooted more times than I could count and took over 12 hours to get back to the login screen. If that PC was supposed to be running production at the time it would have been a bad day for that company.

Plan on Linux for this.

Skynet will make the ultimate decision

I_Automation said:

And, don't forget about the Windows is updating blue screen when you are trying to run production.

I had one Win10Pro that installed the latest and greatest update last week and it rebooted more times than I could count and took over 12 hours to get back to the login screen. If that PC was supposed to be running production at the time it would have been a bad day for that company.

Plan on Linux for this.

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To be fair, the Siemens 1500 software controller currently allow windows to reboot without affecting the PLC, so it is a solvable problem.


Switching to linux has a ton of plusses though, regardless.

mk42 said:

To be fair, the Siemens 1500 software controller currently allow windows to reboot without affecting the PLC, so it is a solvable problem.
Switching to linux has a ton of plusses though, regardless.

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Siemens software controller IS running under Linux.

The trouble with PCs is that they are always changing. Sometimes getting a PC that exactly replaces another PC can be a problem. I know it used to be a problem when PC back planes started changing and the cards I had in the old PC wouldn't work in the new PC.


Manufacturing companies like stability. I know of companies still running old TI-505 PLCs and our very outdated motion controller designed over 32 years ago. Try that with a PC.


I do agree that Ethernet will be a common bus for a long time. However, a lot depends on the Ethernet protocol. If each device requires a connection that will be a problem with CPU power and memory since it takes a lot more CPU and memory to talk over Ethernet than it does to simply input or output something.

Yes, Ethernet will be around - in some form.

ProfiNet is an adaptation based on Ethernet.

The 10/100 standard (which used to be 10 only) is quickly getting replaced with 10/100/1G as standard, and in a few years the new standard may not support 10/100 at all - it would bog down the network, so 1G/10G/100G it may be.

Don't forget, the serial and joystick ports were the standard and now no computer has a joystick port and a serial port is getting hard to find. My new Xidax PC has COM1 listed in Device Manager but has no DB-9 port on it. (I am presuming it is used for all the LED's)

Even new laptops are WiFi only and don't have an Ethernet port.

No standard today can be guaranteed to even be supported in a few years.

Bit_Bucket_07 said:

I remember that article, and many others like it. People have been predicting the death of the PLC for decades.

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The trick is to predict its death every year, then eventually one year, you will be right. Hopefully not soon though.

Peter Nachtwey said:

The trouble with PCs is that they are always changing. Sometimes getting a PC that exactly replaces another PC can be a problem. I know it used to be a problem when PC back planes started changing and the cards I had in the old PC wouldn't work in the new PC.

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+1

I was going to mention this myself.