Need Help on Batch Mixer Exercise 3

ol435

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Hello. I am having troubles with Batch Mixer Exercise 3. I need help with which PLC controls I need for the following steps. In Silo Lab Exercise 1, there is a loop where when the box is full, it will move, and then another box is moved to be filled until it is full, and so on. In this scenario for Batch Mixer Exercise 3, the mixer has to refill after the fluid empties from the tank. What are the PLC Controls to program the following steps? Attached below are Batch Mixer Exercise 2 and Silo Lab Exercise 1. Rung 11 is the last one with the "End output." I have 1-10 rungs filled. Here are the links for the Batch Mixer and the Silo Lab on thelearningpit.com http://thelearningpit.com/lp/doc/bl/bl-ctr.html

http://thelearningpit.com/lp/doc/sl/sl-rl.html

I am modifying from Batch Mixer Exercise 2: Emptying the Batch Mix Tank.

Exercise 3 Continuous Operation:
Modify your program so that the filling and emptying sequence will repeat continuously once it has been started by the initial pressing of the Start switch.

Ensure that the RUN light is energized when the mixer or either pump is running.

The STANDBY light should light and the process should halt when the Stop button is pressed.

The process should restart where it left off if the Start button is pressed following a stop.

Batch Mixer Exercise 2 Part 1 Screenshot.png Batch Mixer Exercise 2 Part 2 Screenshot.png Silo Lab Exercise 1 Screenshot.png
 
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You are asking for help, but have not said what EXACTLY you need help with.

We have a policy on this site of not doing someones work for them, although if sufficient effort is shown, we will quite gladly explain why something isn't working, and give hints as to how to get it to work.

In looking at your screen shots, I notice that the PLC is in PGM mode, not RUN. Perhaps that's your difficulty.

If not, my Magic 8-Ball says, "Concentrate and ask again." You might want to add some comments to your instructions -- what you think you are counting, timing, etc. You'd be amazed how much that helps.
 
I apologize for the trouble.

I put the program into Run Mode. For Exercise 2, the tank operation fills, and the mixer will run for 80 seconds. After it's full, the tank will empty. As the tank empties, I have to manually reset by pressing the start button. On Rung 10, I have an Input connected to an RES for the system to start again.

My question is how can I get a continuous operation to work? I thought of Using a (RES) but my instructor says that it is not a reset that I'm using for continuous operation. It's more than that. I'm confused with which controls to use for a continuous operation. I'm wondering if I can have a hint at what to do.
 
It's no trouble on our part, at least there's no trouble in posting unhelpful answers.

But for my part (as one who's never done "Batch Mixer Exercise 3", per se, I'm not sure what you're trying to accomplish.

By "continuous operation", do you mean:
(0) Start with an empty tank;
(1) Add stuff (pump 1, pump 2);
(2) Mix for a while;
(3) Pump it out until empty;
(4) Now we're on step 0, unless someone pressed a button during the sequence to end it once everything gets to here.

You also show the "package filling" conveyor line, which is similar but different.

If that's what you're trying to accomplish, well, I don't see any of that in the code snippets you've posted.

One thing you might want to try doing is to separate the sequence from the actions. That is, use some internal bits ("B3"s) to keep track where you are in the sequence.

If B3/1 corresponds to my "step 1" above, then you get to ("energize") B3/1 when B3/0 is on, and you are "running". Like so:
  B3/0    O:2/4    B3/1
---| |-----| |-----( )
READY RUN FILL


I'll let you program the rest of the sequence.

Note that this sequence does NOT drive any outputs. It just keeps track of where things are in the process. But knowing where you are in the process makes it easy to drive the outputs.

For example, when do you run pump 1? You start when the process is on the "FILL" step and end when its on the "MIX" step:
  B3/1    B3/2    O:2/1
---| |-----|/|-----( )
FILL MIX Pump1



And so on.

Later on, you can add bells and whistles, like: "What happens if we hit Hi-Level?" Perhaps you just want to stop the pump, in which case the Hi-Level bit would go on the Pump1 rung. Or perhaps we want to stop the whole sequence, in which case, it might go on the B3/0 rung (which I've deliberately left out, BTW).

Don't be afraid of using extra bits to differentiate between things, or to keep track of stuff. Bits are cheap. And this may be what's tripping you up: you're using outputs as both a thing to control AND a marker of where you are in sequence (since, in this case, your outputs are only on on one step in the sequence).

Good luck.
 
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nHqm5p


I inserted in OSR's, C5:1 and 2, and the B3's. I put it into Run Mode and I have a problem. The problem is, once the batch tank is full, the mixer is not working and the timer is not going off. Plus, the tank will not empty itself and the process won't restart. What can I do to fix my Ladder Logic to meet the following requirements for a continuous operation?
 
If you want to use continuous operation, you probably want some kind of sequencer setup where each step is assigned a value, and certain operations happen when that value is true.
 
<O>nce the batch tank is full, the mixer is not working and the timer is not going off.

At first, I hadn't thought that you had included images of your code, but I see that you tried, but they did not show up, as they were linked with both the <URL> tag and the <IMG> tag. I took a chance and went to an unknown web site to look at what you posted. But in the future, please upload the images to this site from your computer, rather than pasting in a web site URL. There are too many virii, etc., out there, and I connect my laptop to client's systems.

So, the mixer is not working? Look at your code. The mixer coil, O:2/0, is driven by B3:0/0 -- "Tub Full". There is no yellow bar on it, indicating that it its value is 0, not 1.

So then we go to the B3:0/0 coil, and ask, why isn't this energized? It is driven by C5:1.DN AND C5:2.DN. C5:2.DN is done, but C5:1.DN is not. So why isn't the C5:1 timer done?

But where is the C5:1 CTU (or CTD) block? I can't find it. There is a reference to C5:1.PRE on rung 0 (preset = 0), and a RES for it on Rung 2. But the actual counting logic? Missing.

My GUESS is that you intended to create a rung similar to Rung 3 for Flowmeter 1, but somehow forgot, or accidentally deleted it.


Plus, the tank will not empty itself and the process won't restart.

Again, look at your code. What makes pump 3 (O:2/3) run? What condition hasn't been met yet? What is that condition missing? Work backwards from outputs to inputs / internal logic until you find it.

Cheers...
 
Get a system together for controlling your sequence...don't just hack at it until it works...

I've told him. Sparkie told him. Now you've told him. We'll see if he listens.

If he doesn't, he's going to run into trouble when trying to end the continuous cycling when the tank is empty, and not somewhere in the middle when the STOP button is pressed.

But that's how you learn: keep making mistakes until you get good at it.
(I don't think that meant what I meant it to mean.)
 

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