Are 'Smart Relays' PLC's

[PeterW]

In another forum, someone asked is a LOGO! a PLC and if not what are the differences.

I disagreed with the replies that a LOGO! is a small PLC, others felt I was wrong and it is a PLC.

Am I wrong?

Have LOGO!'s and other manufacturer's equivalents now progressed so much that they do perform the function of a small PLC so much so, that they can be regarded as PLC's.

I have never used one by the way, the smallest PLC's I have used over the last 10 years has been Momentum's. The smallest Siemens a S7300 but more normally a S7400 and the smallest AB a ControlLogix 63.

So really I have no experience on them.

 

[Ken Moore]

No, smart relays are not PLC's, by today's standards.
IMHO todays smart relays are at about the level plc's were in the early 1980's.

 

[TConnolly]

Technically, PLC refers to a particular model of Allen Bradley Programmable Controllers. The term "PLC" is actually a trademark owned by AB. However, the term has become the "kleenex" of the automation world and AB has obviously not enforced the trademark.

Is a smart relay a programmable controller? Yes, it is. But there are other kinds of programmable controllers as well which are definitely not called PLCs (ranging from lawn sprinker controllers to DCS systems). So you can argue one side or the other until you are blue in the face - and you're not likely to change the minds of those who think a smart relay is a PLC or the minds of those who think a smart relay is not a PLC.

For the record, I'm in the "NOT A PLC" camp.... sort of.

 

[PeterW]

Technically, PLC refers to a particular model of Allen Bradley Programmable Controllers. The term "PLC" is actually a trademark owned by AB. However, the term has become the "kleenex" of the automation world and AB has obviously not enforced the trademark.

I'm sure your correct but I remember the late 70's when we first started getting some PLC's. We had Allen Bradley mini's they were called then (think later re-labelled PLC2-20) and IPC90's.

Both at that time were referred to as PLC's (Programmable Logic Controllers).

Maybe it was for simplicity of labelling them something common at the time.

 

[Stephen Luft]

Actually, until the advent of the personal computer they were primarily known as PCs (programmable controllers). The market place took care of the division in that the consumer market being many times greater than the industrial market, came to identify the term PC with personal computer, rather than programmable controller.

Allen Bradley did register the term PLC as a trade mark, I believe back in 1976 the first time.

http://tess2.uspto.gov/bin/showfield?f=doc&state=d6lqg4.4.130

 

[TConnolly]

I remember that. My first exposure was to TI and GE PCs. Then along came the IBM PC and suddenly no one was sure what I was talking about when I refered to the PC.

Back OT. Omron list their ZEN smart relay under PLCs on their website.

 

[ndzied1]

I believe they are PLC's.

They can be "programmed"
The programs use "Logic"
They control things.

I believe the term "smart relay" was brought about to get the products by site specifications that dictated that all PLC"s must be AB.

These things have timers, counters, math, analog I/O, PWM out, high speed counters, data move, OPC server programs available.

They are definately PLC's in my mind.

 

[Ken M]

In fact, as recent research has just revealed, the origins of PLC usage go all the way back to Elizabethan England in the 16th century. Historians have just discovered an early draft by some Bill Shakeshaft poet guy -

'Tis but its name that is my enemy;
It is itself, though not a PLC.
What's "PLC"? it is nor hand, nor foot,
Nor arm, nor face, nor any other part
Belonging to a control system. O, be some other name!
What's in a name? that which we call a rose
By any other name would smell as sweet;
So LOGO! would, were it not LOGO! call'd,
Retain that dear perfection which it owes
Without that title.

What does it matter what it's called?

Ken

 

[L D[AR2P#0.0]]

What does it matter what it's called?

An OT example:- Cruithne, is this the Earth's second moon ?

 

[Ken M]

That was w-a-y OT! I'd love to have seen some neural map of your processing paths that linked a Shakespeare parody to this!

I had to go and do some research on it. The general consensus would appear to be "no, it isn't".

http://www.orbitsimulator.com/gravity/articles/cruithne.html

Regards

Ken

 

[L D[AR2P#0.0]]

I can only lay my hands on a scan at the moment.

Your paradoy wasn't the direct link, it was more:

What properties does object X have to have in order for it to be classifed as a Y

 

[Ken M]

What properties does object X have to have in order for it to be classifed as a Y?

Did I just hear a bugle call rallying the members of Smoke & Mirrors Inc to a new project kick-off meeting?

Ken

(PS : Why is there no smilie for 'rubs hands with glee'?)