CPU, PLC...? A question of nomenclature...?

Why does AB refer to PLCs, while Siemens refers to CPUs? is this only a matter of terminology, or am I missing something crucial?

AB refers to CPUs, also. Both PLCs have CPUs.

AB is American, Siemens is German.

(and that basically explains it all)

In my opinion,
A PLC is composed by: PS, CPU, DI, DO, AI, AO etc.

Jeebs said:

AB is American, Siemens is German.

(and that basically explains it all)

Click to expand...

Agreed...THere is more I have heard them both referred to as controllers, PLCs, and CPUs. Germans like to call Siemens PLCs CPUs probably for the thinking that it is a computer. But in all honesty a PLC is a CPU.

PLC - From Wikipedia
"The first PLC, designated the 084 because it was Bedford Associates' eighty-fourth project, was the result.[2] Bedford Associates started a new company dedicated to developing, manufacturing, selling, and servicing this new product: Modicon, which stood for MOdular DIgital CONtroller. One of the people who worked on that project was Dick Morley, who is considered to be the "father" of the PLC.[3] The Modicon brand was sold in 1977 to Gould Electronics, and later acquired by German Company AEG and then by French Schneider Electric, the current owner."
I understand that "PLC" could be a registered trade mark,
this is why you will also hear it called PLD (Device)
...
Siemens primarily sell component systems so the CPU is generaly seperate. But as has been said - a PLC is the whole system

I view a PLC as a system. This comprises a power supply, CPU/Processor, I/O modules, and function modules. In today's world it is difficult to have consistent terminology. You may have a PLC that consists of once single module that comprises a power supply, IO Modules, and a CPU all in one package. You may have a system where your PLC CPU is actually a computer and all your IO is distributed field bus units. You may have something like a Unitronics PLC/HMI where it is both touchscreen and PLC in one package. The CPU is shared for both the logic as well as the screen functions.

So it is hard to say now that a PLC is exactly "this". It could be many different things. Using the term CPU may be unclear now. Your PLC processor might just be shared time on a PC's CPU. Then the question is "Is the PLC a software thing or a hardware thing". Just like a virtual machine on your PC.

I expect the lines to continue getting even blurrier as time goes by.

hey Damian eventually the PLC will be replaced by a state of the art Super computer that can only be programmed by master degree engineers.
Then we will have no problems with machinery at all...

iant said:

hey Damian eventually the PLC will be replaced by a state of the art Super computer that can only be programmed by master degree engineers.
Then we will have no problems with machinery at all...

Click to expand...

I'm biding my time for the quark based computers with the instantaneously wireless quantum entangled fieldbus. Or IWQEF for short.

There will only be one of these located on the moon and will serve as a PLC cloud for the entire planet. Verizon will charge us $20USD / megabyte for access.

Since the PLC will be able to see into the future, it will be able to repair problems before they exist, thus eliminating all downtime.

iant said:

hey Damian eventually the PLC will be replaced by a state of the art Super computer that can only be programmed by master degree engineers.
Then we will have no problems with machinery at all...

Click to expand...

That's right: a machine that doesn't run doesn't give us trouble at all

iant said:

PLC - From Wikipedia
"The first PLC, designated the 084 because it was Bedford Associates' eighty-fourth project, was the result.[2] Bedford Associates started a new company dedicated to developing, manufacturing, selling, and servicing this new product: Modicon, which stood for MOdular DIgital CONtroller. One of the people who worked on that project was Dick Morley, who is considered to be the "father" of the PLC.[3] The Modicon brand was sold in 1977 to Gould Electronics, and later acquired by German Company AEG and then by French Schneider Electric, the current owner."
I understand that "PLC" could be a registered trade mark,
this is why you will also hear it called PLD (Device)
...
Siemens primarily sell component systems so the CPU is generaly seperate. But as has been said - a PLC is the whole system

Click to expand...

When first released they were called Programmable Controllers (PC) until IBM introduced their Personal Computer that prompted the PLC to hit the Marketing scene. Today it is frequently called the Programmable Automation Controller (PAC). These generic terms are frequently interchanged throughout the industry.

Actually, Allen-Bradley is moving away from using "PLC" and using "PAC"

Thanks for all your answers

However, I must address a crucial point here:

DamianInRochester said:

There will only be one of these located on the moon and will serve as a PLC cloud for the entire planet. Verizon will charge us $20USD / megabyte for access.

Click to expand...

No, no--definitely not the moon. I'm surprised at you. the obvious location is Mercury, from where energy will be channeled to all control apps, thereby solving the problem of renewable energy sources.

The term Programmable LOGIC Controller is a bit mis-leading. They happily do analogue calculations etc. I think PLC used to be fitting back in the day when all they did was logic instructions (and / or / not etc). Back then, Numerical Controllers (NC's) did analogue stuff...

As has been said, lines are very very blurry nowadays between PLCs and PCs to some extent.

I can understand a new moniker of PAC would be more fitting...

;-)

Logic > Boolean logic

With that in mind, I still find PLC fitting for what it does.

No one however have commented on the use of PC.
For the job we use it, shouldn't it be named IC? Industrial Computer?
When it's controlling a process/machine/system, it's not personal anymore.