PLC Programming

Welcome to our humble abode. The members here can answer an amazing array of questions and enjoy a variety of challenges, but you'll find one game they/we don't like is '20 Questions'. In other words, please try to keep your request concise. For example, for your post, it would be helpful to know if you are looking for general programming training (for which you may get recommended links) or assistance with a specific problem on a specific PLC (for which you may well receive a specific answer).

Being an ME, I have only tinkered with PLC's, but if you are just beginning here's a couple of links:
http://www.plcs.net/ claims to be 'Your Personal PLC Tutor Site'
http://www.tri-plc.com/products.htm has a free Ladder-Logic Editor and Off-Line Simulator

Any specific PLC, or just in general?

ABB CODESYS

· PLC Configuration

· Design the program(CFC (Main Program) and LD)

· Log in

· Run and Simulate

Resource to Concern

· AC500 PM571 V1.2

· DC522 Digital Unit

· Ax521 Analogue Unit

MAIN PROGRAM (CFC)

On chemical plant two tanks (T­_1 and T_2) exist that flows into third tank (T_3).The level of Tank (T_1 and T_2) is monitored by level sensors connected to the first and second analogue inputs of the PLC Modules. The sensor gives a signal of 0V for the LoLo value and a 10v for the HiHi value>the following condition will need to activate a different alarm condition:

· T_1 Level <T_2Lvel active condition on the first output of the DC522

· T_1 Level >T_2Lvel active condition on the Second output of the DC522

· T_1 Level =T_2Lvel active condition on the Third output of the DC522

A PUMP connected to the system (fourth output of the DC522) consisting of T_1 ,T_2 and T_3 is used to pump chemical from T_1 and T_2 to T_3.This pump will stop after 5 seconds if an alarm condition is triggered. The PUMP can only start when it is manually activated with START_1 xor START-2 N/O push release buttons buttons ( First and second input of the DC522 ) after a 3 second delay.

SECOND PROGRAM

If all three he alarm condition are triggered a fifth output on the DC522 must be set and can only be manually reset with a third RESET _1 N/O INPUT ON THE DC522.

From the data you supplied it appears to be a home work question. If this is so, have you instructor ask us the same question. We then might be able to help. Also in case your wondering, I get $150.00 per hour do do this on a contracted basis.

Now to help you some. Take a piece of paper and draw out the ladder logic for this on it. This helps you to understand the principals to writing in a system and in turn you then understand how to do same.

I would advise some sort of PLC course, a quick internet and ABB website search for PLC programming resources or outsourcing the design and programming to a PLC programming company or individual.

This really looks like a homework question. What have you got so far (apart from a basic design)? Do you have any PLC training?

Just searching Yahoo for "ABB Codesys" got screen of references including ABB website, which will have instruction manuals and Youtube how-to videos.

You will have to munch your way down these until you find the ABB way of doing things.

The actual control programme looks as if a "ladder diagram" (relay) type logic ("LD" in the ABB world"??) with IF comparison rungs between the analog level inputs and constant values controlling output "coils" will do the job. Look up "PLC"& ladder in "Wikipedia" website.

I did not like the idea of a "Level 1" = "Level 2" comparison. In arithmetic this is likely to be true only if they are equal to within the minimum resolution of the analog input and equivalent to say 8773 = 8773. Real world levels in tanks could pass through 8773 just between analog samples, so equality was "unseen" by the program. An X +/- Y band is much safer in real applications in which pressures and levels wobble about and have "noise" levels.

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In a business context, it would benefit both the individual and the employer to for the individual to embark upon a training course. Make enquiries locally.

Outside chance he is stuck in the middle of a mess. I have been caught in a situation like this where our customer specified a certain PLC for a plant process installation, and we assumed (yeah - bad word) they would supply the programming since we stated on our quote we could not handle programming that particular PLC. Guess what the customer did not notice in our quote until a week from start-up? Guess who they expected to correct this problem? Ever try to find a programmer on less than a weeks notice at a reeasonable labor rate?

Yeah - probably not the scenario here - but hey, you never know for sure.

Hi Guys I thought the aim of this website was for helping each other and not for commercial purpose .

whether this is a home work or not a home work but the fact remain that I need assistant . If you can't help me please do not comment at all .

only people who have a good heart of helping should comment .

• What sort of help is needed?
• Are the digital inputs de-bounced?
• What is the range of each analog?
• Is there an I/O Schedule to hand?
• Is there an Alarm Schedule to hand?
• What sort of human/machine interface is to hand?
• Was that the approved-for-construction Control Philosophy above? Is it complete?
• The help - is it PLC-type-specific or is it programming in general?

Do help the forum to provide the assistance required by being more specific with the problem to hand and the assistance needed.

It looks as though there are three DIs, two DOs, three AIs and zero AOs. There is nothing in the Control Philosophy to indicate what the ranges of the alarm levels are and how they are determined, nor what happens to the pump when the single alarm is reset. Worryingly, there is no description on the topic of overfill protection for the tanks, nor anything about what happens to the pump when any number of tanks runs dry. Is there to be a check-sum on the levels to check that there are no detectable leaks (rhetorical question - NNTR)?

Until the Control Philosophy is more comprehensive than that at current, it would be pointless to start programming. Further, it is the role of the Control System Designer to write a Functional Design Specification and obtain approval for it before the system is fully assembled, otherwise the Client runs the risk of not getting what is wanted. So get the Process Engineer to update the Control Philosophy and issue it "for construction" before the work starts. Ideally, this plant should be the topic of a HazOp Study before work begins.

This is a college assignment it is not a really industrial situation .The aim of this assignment is to make student design a basic ladder plc as well make them to program a plc which will meet the conditions like the one in the assignment in question . so please do make it it complicated just keep it simply basic plc.

In an industrial context, the arrangements are more involved as there are value-of-time considerations and contractual relationships to consider. These are absent in academia. Assistance will come from the course tutors, then, for such simple applications.

_{<defers to local academics and unsubscribes>}

I think the main trick is programing the "if"conditions

From the CR4 "FAQ" page:

Do your own homework. CR4 is not a homework cheat site. While some here might relish the opportunity to sharpen up old rusty skills by working the homework problem, consider the following and consider it well. If you cheat on your homework by using someone else's answers, you are only cheating yourself, because the purpose of any homework or other academic assignments is to help you learn - by practice, repetition, and self-discovery.

As you said yourself, "the aim of this assignment is to make student design a basic ladder plc" If we tell you how to program the PLC, it would be us doing the design and not you.

Probably your best resource here are the documents supplied by the manufacturer of the PLC. Check ABB's website for user's manuals and programming references. You might even call ABB on the telephone to request "Quick Start" guides and other literature if their website does not provide that directly. Such documents usually give examples of how various instructions (including conditional instructions) are supposed to be used.