Assistance With Writing a PLC Program Using RS Logix 5000 Software

PLCHelp

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Join Date
Oct 2011
Location
USA
Posts
2
I am having major issues with writing a PLC program. I am taking an advanced PLC course at the local community college and this course is much different than when I had an introduction PLC class, in 1998. This class was not supposed to be part of the degree, but they eliminated an existing class in favor of this one.

I initially learned programming on the old Allen-Bradley 2/15 PLC's. Although the concepts and ideas are essentially the same, this is a totally different way of doing things in 2011.

I have attached 4 jpeg files with what the program is supposed to do. I am lost when it comes to starting the program as well as which instructions, etc. to put in the program.

This program involves start and stop buttons in order to energize a motor, toggle switches and math formulas. These instruction sheets are very descriptive so I don't know if there's anything else I should say in this posting. If you have any questions, please contact me.

I don't have any type of program file I can even send. My apologies if there is a lack of information.

The basics of the program is to push a green start button and turn on a motor for a certain time period. The red stop button will obviously shut off the motor. Lights and a motor have to be on and off for certain periods of time and must come on and off at different intervals.

Honestly, I am completely lost with this. Any help is much appreciated. Thank you very much.

Sheet1.jpg Sheet2.jpg Sheet3.jpg Sheet4.jpg
 
Start with some basic logic to start/stop the motor contactor. Draw it up as a start/stop circuit you would wire, then look at making it into a ladder (should be very close to the same).

Then work on your speed commands over time, the worry about the lights at the end.

Breaking into smaller projects instead of trying to grasp it all at once will help. Do it piece by piece, adding onto them as you go. Write out detailed basics of each piece so you understand what it's asking you to do.

If you are having serious trouble with use of timing and math instructions, you should look at getting help from your instructor. They can be answered here, but usually (in my opinion) it's nicer to have someone you can sit and talk with if you are having trouble understanding how instructions are working.
 
Thank you very much for your help. The bad thing is, my instructor is only there twice a week and has 3 classes in 1 day. He doesn't have any extra time to spend and it's not his fault. He's not even supposed to be teaching this semester but he pushed back his sabbatical so he could teach so people could graduate this fall.

I'm trying to take things step-by-step and piece-by-piece but it's difficult when things are very new. I'll take your advice though and break it down into simple parts.

Thanks again :)
 
I'm trying to take things step-by-step and piece-by-piece but it's difficult when things are very new. I'll take your advice though and break it down into simple parts.

Thanks again :)

Not so very new .....

I initially learned programming on the old Allen-Bradley 2/15 PLC's. Although the concepts and ideas are essentially the same, this is a totally different way of doing things in 2011
.... you have done basic logic, and Logix5000 supports all and everything the 2/15 did...

IMHO, the only concept you must get a hold of is the Logix tag-based data storage, which is conceptually different to the PLC2's File-based data storage.

If it really helps you to understand, (and I'm not advocating this is a good way to progress into Logix-land), you could create PLC2 data-file style array tags in your Logix system...

eg N7:0 to 19 = Logix array N7[20] (indexes 0 to 19)


Here's a couple of kick-start questions which should help...

Q1. How would you do the Start/Stop logic in a PLC2 ? Do you think it could be done the same in a ControlLogix ?

Q2. You need to make speed setting calculations every 0.01 seconds (Hint: Time Period). Have you seen anything in your classes on Logix5000 that could help here ?

Post back with what you achieve.

PS. I spotted the typo on sheet 2, did you ?
 
Oh, buddy - you're good! I had to reread it 3 times to catch it ;) :geek:

Lol, thanks - It comes from a lifetime of trying to interpret badly, or sparsely written client specs - reading between the lines - filling in the gaps - spotting the "catch 22" situations - spotting the "going nowhere" situations - and all the others I've had to deal with. A functional spec. can appear to be impressive, until you code it and realise just how much was left out....

On one occasion, to fill a tank, the client had written the sequence of operations (he called it a Functional Spec.)....

1. Open Inlet Valve
2. Wait Tank Low-level probe covered (So as not to run the pump "dry")
3. Start Inlet Pump
4.......

Only problem was, it was a positive displacement pump !! And they had designed the system !

I re-wrote the spec. and coded both versions for client simulation. I let them simulate their version first, just to see the reaction on their faces when they realised nothing was going anywhere, and the sequence stuck on step 2.

It was a complete throwaway job, as I switched over to my version, which allowed the tank to fill to the low-level probe via the PD Pump by-pass valve.
 

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