Hi i'm new need help please with: unitary, modualr and rack PLC sytems.

johnrh89

Member
Join Date
Oct 2006
Location
london
Posts
6
Hi, i am new to Electronics and PLC systems and this website i have been searching for hours to find an answer to a couple of questions from college but can not find anything useful. Could someone please help to direct me to the answer or answer it themselves? Question 1) Explain the difference between Unitary, Modular and Rack PLC sytstems, include diagrams to aid your explanations.

Question 2) Explain which of the three types of PLC is best suited to the following apllications:
a)washing machine controler
b)traffic junction controller which can be used on many different traffic junction layouts. and..
c)Controller for a factory manufacturing a product that is assembled gradually as each part is produced. the production lines producing the parts are located in different parts of a large building.

Question 3)Obtain the manufaturers data sheet for one output device that could be used by a PLC in a control application Explain how each device operates and what it could be used for.

I know it's alot but if you can help with anything it would be MUCH appreciated! Thanks John
 
You couldn't possibly have done an exhaustive search. This question gets asked several times a year.

Question 1
Here are some hints:
1. Unitary, base word is Uni- which means one.

2. Modular, made up of modules. More or less the opposite of one wouldn't you say?

3. Rack, picture a rack, same as a rack mounted computer, with a PLC in it. What do you suppose sits in the rack (Its related to question 3)?


Question 2 you can do once you answer question 1.

Question 3 can be answered by going to a PLC manufacturer's site and browsing for a while in their downloads or manual section.
 
thanks for the replys i have solved the 1st question using the site from Tom Jenkins(cheers!) for my second question would i be right in saying that you use unitary for a modular for b and rack for c?
 
Hi johnrh89.

Questions to you:
How did you find this website ?
Did someone suggest you to ask your question here ?

Why I am asking:
The exact same question pops up every now and then here.
I am beginning to think that it is a joke, that someone gets a kick out of seeing a lot of people getting started on the same question again and again.
 
Q1, Only your school classes PLCs as Unitary, modular or rack mounted. no one else does. That is why it is difficult to find any information on this.

Q2
(a) Washing machine controller, small washing machines can use small PLCs, big industrial washing machines (which I worked on as an operator as a part time job during university) require larger, more capable, PLCs. So, depending on the complexity of you washing machine, the answer can be any of the above PLCs.
(b) Traffic Lights, these are not controlled by PLCs anyway, but if they were, then you could probably find a PLC of any of the unitary, modular or rack mounted variety to do the job.
(c) again, for a factory, any of the type could, in theory, do the job. Some people are good at using lots of smaller PLCs to do this job, others prefer a smaller number of big PLCs.

For Q3,
try looking up Automation Direct, or Omron (registration required, but is free), or Modicon. Don't try Siemens, because the web site will drive you mad.
 
Hi thanks everyone no i am not joking sorry. i am a new college student in my secind week and the work is very hard at the moment for me. thanks evryone:) oh and i found this site searching through google for a long time
 

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