3 types of PLC, practical application to a system.

So i have chosen a traffic light.

3 plc units are unitary modular and rack mounted.

i need to identify and describe the 3 type of programme logic controllet and explain their corresponding pratical application to the system, for example in a traffic light system.


and then i need to describe the selection criterian of each of the plc i said above.

I don't want to sound stupid but why do lots of people read the thread and not reply :S

The topic subject is clearly asking a question which I am DESPERATE about, I only understand the coding side/ mathematical i struggle with this stuff. :/

Do a search on the topic - there have been a great many threads on this topic (but mercifully none for a while).

Tom Jenkins said:

Do a search on the topic - there have been a great many threads on this topic (but mercifully none for a while).

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Can you just tell me some similarities between unitary, modular and rack mounted?

I'll try using that to explain the traffic light system, and how they correspond.

This is a phrase straight out of a standard HNC text. We get it every year, and we're tired of re-answering it.

http://lmgtfy.com/?q=unitary+modular+rack+site:plctalk.net

Demandfivehd said:

I don't want to sound stupid but why do lots of people read the thread and not reply :S

The topic subject is clearly asking a question which I am DESPERATE about, I only understand the coding side/ mathematical i struggle with this stuff. :/

Click to expand...

Frankly, it sounds as if you're asking someone to do your homework for you.

Can you just tell me some similarities between unitary, modular and rack mounted?

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Sure. There used to be definite differences about 50 years ago. Now they sort of all blend together. Unitary means "like a unit" or everything in the same one box. Modular means that the parts are separated into modules, usually with some plug-in Input and Output modules. Rack-mounted means there is a box with slots for parts of the PLC (Central Processing Unit, power supply, input modules, output modules, communications modules, and so on to plug into as needed.

Here are 75 previous threads where this topic has been beaten to death. It is an old obsolete question still asked in the beginning textbooks, although very outdated. Modern PLCs often contain attributes of more than one of these 3 types. For example, the modern "unitary" plcs often have add-on modules that make them resemble the modular type. Modular types are often mounted in racks, and rack types are certainly modular. It really was an ambigeous question even when it was first written a lifetime ago.

http://www.plctalk.net/qanda/search.php?searchid=3229890&pp=25

I'll try using that to explain the traffic light system, and how they correspond.

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Really I have never seen a real traffic light run by a PLC (except in classrooms). The old traffic light problem makes a good student project because no Input devices are needed (only a timer and some output lights). You might say that real traffic lights are totally unrelated to the 3 supposed types of PLCs.

Bit_Bucket_07 said:

Frankly, it sounds as if you're asking someone to do your homework for you.

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Not homework, its my life

Im ****ed, everyone is ****ed in my class, we don't even learn ****.

All I am trying to find out is the basic similarities between the 3 PLC ( even if it simple) IM done, this is only one question out of 8 and I can't even google this ****. I found some the other day but I lost the sites as im using another pc. I have 12 hours left. I wont be sleeping till i have the answers.

Can someone just answer at least 1 question I have like 9 other left LOL

1 will make a big difference for the 6 hours I have spent on it :////

Sure, you need to refresh your screen. You have several answers already, but you will have to make an effort to READ them.

I can't believe BTEC are still churning out this ****

Unitary,modular...... i did this 15 years ago

HNC - Has No Clue?

Demandfivehd said:

Not homework, its my life

Im ****ed, everyone is ****ed in my class, we don't even learn ****.

All I am trying to find out is the basic similarities between the 3 PLC ( even if it simple) IM done, this is only one question out of 8 and I can't even google this ****. I found some the other day but I lost the sites as im using another pc. I have 12 hours left. I wont be sleeping till i have the answers.

Click to expand...

You may want to look into a less stressful career path, if you cannot handle or do the research this yourself.

Ken was nice enough to google the question for you. http://lmgtfy.com/?q=unitary+modular...%3Aplctalk.net

And I agree with Lancie's answer that a traffic light is not normally going to be done with a PLC. So the practical application is none. The application to learning is a little different.

As to your application/choice, the main difference is going to be cost, vs expandability and capability. The smaller systems are going to be more limited, but cheaper, where as a larger system can be expanded more easily, and will provide more options for I/O and network capabilities.

Brijm said:

You may want to look into a less stressful career path, if you cannot handle or do the research this yourself.

Ken was nice enough to google the question for you. http://lmgtfy.com/?q=unitary+modular...%3Aplctalk.net

And I agree with Lancie's answer that a traffic light is not normally going to be done with a PLC. So the practical application is none. The application to learning is a little different.

As to your application/choice, the main difference is going to be cost, vs expandability and capability. The smaller systems are going to be more limited, but cheaper, where as a larger system can be expanded more easily, and will provide more options for I/O and network capabilities.

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You are WRONG

question :

identify and describe 3 types of programmable logic controller and explain their corresponding practical application to the system. (e.g traffic lights)

Question 2: describe the selection criteria of each of the identified plc above?

Brijm said:

You may want to look into a less stressful career path, if you cannot handle or do the research this yourself.

Ken was nice enough to google the question for you. http://lmgtfy.com/?q=unitary+modular...%3Aplctalk.net

And I agree with Lancie's answer that a traffic light is not normally going to be done with a PLC. So the practical application is none. The application to learning is a little different.

As to your application/choice, the main difference is going to be cost, vs expandability and capability. The smaller systems are going to be more limited, but cheaper, where as a larger system can be expanded more easily, and will provide more options for I/O and network capabilities.

Click to expand...

I didn't pick this PLC stuff, I choose electronics. I mean who cares about plc advantages and stuff, at the end of the day it is about maths/coding which is easier for everyone.

unlike english literature there is a right and a wrong to every word and letter you use.

Demandfivehd said:

I didn't pick this PLC stuff, I choose electronics. I mean who cares about plc advantages and stuff, at the end of the day it is about maths/coding which is easier for everyone.

unlike english literature there is a right and a wrong to every word and letter you use.

Click to expand...

The PLCs are usually used for automation. And the automation has much more to do with the physics and the real process in the machine or in the plant, than with the mathematics. In most of the cases the PLC is not calculator but the brain of the machine and it has to have the correct instruments to control the machine. The instruments are different tipe of inputs and outputs, responce time, different comunications that are suitable for different tasks, reliability and so on. It would be perfect if one PLC has it all. But as an engineer one day you will probably prepare an offer and the perfect PLC will be much more expensive than the one that is suitable for the task.