Comparing PLCS

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Thread Starter

Farzad Nasehi

Hi All
I would be very grateful if anyone lets me know what parameters must be noticed
when comparing PLCS made by the different companies i.e. How the
PLCS should be compared.

Best Regards
Farzad Nasehi
 
D

David Lawton Mars

> I would be very grateful if let me known what parameters must be noticed
> when comparing the PLCS made by the different companies i.e. How the
> PLCS should be compared.

You need to consider rack vs. shoe box depending on your app, but a few
factors as follows (in no specific order);
1. Processor memory / speed
2. Cost
3. Communication protocols supported (eg do you need to interface to other
kit)
4. Tech support and spares
5. Programming software tools (cost to develop application, diagnostics etc)
6. Types of I/O cards available for special apps (eg auto-tune PID, motion
control etc)

Regards
David
 
D

Daniel Boudreault

Hello Farzad,

Here is what I look at when choosing a PLC for basic usage.
1. I/O required, and type.
How many inputs and outputs are needed, and is it AC, DC, ANALOG, etc?
Also does the I/O meet the voltage and curreny requirements?
What is the I/O response time, and does it meet my needs?
What is the mtbf?
2. Networking and Communications.
Do I need to network my plcs?
What type of networking does the plc support? Master and/or Slave?
Protocol supported? Especially when connecting to other manufacturers
plc.
Is the comms fast enought for my needs?
Number and types of ports available?
Number of nodes supported?
3. Processor.
How big will my program be, and do I need a lot of memory for data?
I.E. Memory.
For large programs, I would need a faster processor speed.
Does the plc do complex math and support all of the functions that I
need?
Does the plc allow online program changes? <- most helpful during debug.
Does it support redundancy?
4. Ease of integrating with operator interface, and other input devices.
Does the manufacturer provide operator interfaces that can be easily
connected to the plc? Also, is the plc supported by other
manufacturers?
Is the plc supported by major hmi/mmi software?
5. The most important: Programmability.
How easy is it to use the programming software?
6. Last but not the least: Cost.
How many am I going to need?
If I only need one, then the higher cost of the plc may actually be cheaper after the programming and installation is done.
Good Luck, Dan B.
 
B

Bradley Timm

Dan B. wrote:
>Hello Farzad,
>
>Here is what I look at when choosing a PLC for basic usage.
> ...<clip>...
>5. The most important: Programmability.
> How easy is it to use the programming software?
,,,<clip>

Under item 5 I would add the ability to be programmed Online. You do not
want to have
to halt the process to make program changes.

Some PLCs allow major online editing and some only minor. Check this out
carefully !

Bradley Timm
Cape Town
 
You need to think what information to compare if you are still stuck email me from the 29 October to the 23 November as I will be on holiday from then.
 
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