PLC for a beginner

[Blaspark]

From what I see it just does redundancy with a loop. It's like profibus.
You have snmp though so not so bad

 

[Blaspark]

No redundancy features such as slave CPUs etc. Reliability has not been an issue.
They are of course all on a UPS power supply system.

You have redundancy available by creating a loop. Obviously I don't know how to set it up since I'm not familiar with you tech and it might only be available with certain hardware. It's available with cc link though

 

[gnuuser]

Im used to allen bradley but have studies siemans and profibus.
they all have decent features.
with slc racks we used in our machines if a cpu failed it was simple to plug a new one in and upload the program to get production going again.
most of the time troubleshooting was simple as you could see the processes on the ladder program, when a function in the machine was not happening, verifying it in the program allowed you to determine if it was in fact the program or the hardware in question.
knowing how the machinery is wired and what inputs and output numbers lead to the components allowed you to diagnose the machinery without . connecting the pc by observing the led's on the cards.
but thats not always the case with multiple machines depending on the training and whatever documentation is there or if it is missing.
its here (automation)where its important that proper training and documentation are stressed. downtime is costly but not as costly as improper safety.
as to writing the programs the absolute number one rule Make sure it is going to be safe to perform that function!

setting up redundant control systems however is a different animal
requiring master control cpus and redundant slaves this would be a complex situation to implement. (not to mention a very costly setup)
For most industrial situations there is rarely any need for a setup such as that (short of a nuclear reactor) and even so the inerrant weakness is one master control and one master output. these points are the weakest links

 

[Bobster]

You have redundancy available by creating a loop. Obviously I don't know how to set it up since I'm not familiar with you tech and it might only be available with certain hardware. It's available with cc link though

Only with S7-400 CPUs can you have redundancy with Siemens so far, they are still working on the S7-1500 to have that functionality.

You can have a profibus network wired in a ring with a suitable ring manager, but this is not the same as redundancy.

Redundant CPUs is not overly complicated to set up, but the cost is huge for the hardware. An then it is only the CPU that has redundancy. In my experience, as long as they are installed in a decent environment, these hardly ever fail. It's usually the IO.

 

[Bobster]

Just noticed a mistake in my post above, I should have said profinet, not profibus.

Profibus can be made into a ring topology, but needs a fiber optics with converters as a backbone, an to be quite honest I have never seen it done.

Profinet is Ethernet based, where as Profibus is a form of RS485 communication.

 

[gnuuser]

Only with S7-400 CPUs can you have redundancy with Siemens so far, they are still working on the S7-1500 to have that functionality.

You can have a profibus network wired in a ring with a suitable ring manager, but this is not the same as redundancy.

Redundant CPUs is not overly complicated to set up, but the cost is huge for the hardware. An then it is only the CPU that has redundancy. In my experience, as long as they are installed in a decent environment, these hardly ever fail. It's usually the IO.

I agree although triacs can handle the higher loads in some system its highly recommended to use fuses or overcurrent devices between the output and coil.
a fuse is very inexpensive insurance against burning out an output module.

 

[SheffSimon]

Just noticed a mistake in my post above, I should have said profinet, not profibus.

Profibus can be made into a ring topology, but needs a fiber optics with converters as a backbone, an to be quite honest I have never seen it done.

Profinet is Ethernet based, where as Profibus is a form of RS485 communication.

I have, in fact I was the one that did it, on a Siemens PCS 7 system. Redundant processors, redundant fibre ring, with redundant copper Profibus links from fibre converter to redundant remote IO processors. At a non-nuclear power station.

But you're right, it's usually the IO which fails.

 

[Automation ATO]

Have a try, you will know it

 

[Bobster]

Have a try, you will know it

After seeing several nonsense postings from yourself. I'm fairly certain this "user" is an AI bot.

 

[Automation ATO]

After seeing several nonsense postings from yourself. I'm fairly certain this "user" is an AI bot.

hello? I can't understand, who is a robot?

 

[koldwater]

Allen Bradley unit in the old system

The golden rule is to stick with the current brand of PLC used in industrial facilities. [Standardize] Plant maintenance (the true end-user) will already be familiar with it and may already have software for that brand, etc. Why? To reduce the customer's downtime, which usually costs the company way more than purchasing and installing a new brand of PLC.

But I always say, there are exceptions to every rule. Like in the example you gave, if it is not an industrial facility, like just lighting control. Another example exception, which you gave, they currently do not have anyone with experience, and there is a better brand for their application and location.

So, I agree with your thoughts, Dave. Siemens would be a better choice for this particular customer as it is the most supported in that country/region. During the equipment's lifecycle, there will be less downtime for your customer. Secondly, try to encourage the company to get some people trained on the new Siemens PLC.

Another golden rule is to do what is easiest and best for the customer, not for the programmer. Many automation control experts choose the PLC brand and programming language based on what the designer/programmer likes best and what is easiest/quickest for themselves. For example, Structured Text may be the preferred and easier PLC programming language for the programmer. Still, plant electricians may be more proficient in troubleshooting and modifying a PLC with Ladder Logic than a computer programming language like Structured Text. So, the true end-user, the maintenance staff, should always be at the top of everyone's mind.

That's my take Dave.