Problem using counters and memories with a basic PLC

[juanmdx]

Hello,

I'm working on a project where I have two encoders (which I'm reading through counters).

What happens at the line is that an inspector is checking for marks on a metal sheet that is unwinding.
When the inspector sees a mark, he presses the button for as long as the mark is.
What I need to do is to actuate a pneumatic cilinder a few meters ahead, and the cilinder should stay expanded (it has a marker at the end) for as long as the button was pressed.
A couple of meters ahead, the PLC should trigger an output letting the system know that the mark has reached the end of the line.

The "meters ahead" issue I solved with the 2 encoders I'm using.
I can "read" how many time the button was pressed using another counter, that counts when the encoder sends a signal and when the button is pressed.

The main issue I have is that I can have more marks (as many as 20 or 30) before the first mark reaches the end of the line, so I have to use a memory to keep track of the time (or counts) each mark was pressed and when it was pressed.

I'm using a compac PLC from Schneider (a Twido) and I can only use some PLC features and I can't figure out how to keep a record of the marks, can anyone help me here, the PLC I'm using is very basic and doesn't have a lot of functions.


Thanks and regards.

Juan

 

[sthompson]

I am not familiar with the TWIDO, but this sounds like an application for a FIFO. If it isn't included in the Instruction Set for this PLC, you could build your own. Do a search here on FIFOs, and you will find lots of information on them. The trick will be shifting the Data out at the correct point.

Stu.....

 

[juanmdx]

Ok,
I looked around and tryed to figure out how to use a FIFO register on this problem.
So I think I got it, I writed and commented it.

So now, I attach it here, I really hope someone with experience can review it, I have some doubts on the memories I'm using and the positive pulses and Set and Reset's.

So, I'm really counting on you guys.


Best regards.

Juan

 

[juanmdx]

Ok,
I looked around and tryed to figure out how to use a FIFO register on this problem.
So I think I got it, I writed and commented it.

So now, I attach it here, I really hope someone with experience can review it, I have some doubts on the memories I'm using and the positive pulses and Set and Reset's.

So, I'm really counting on you guys.


Best regards.

Juan

 

[juanmdx]

The program I'm attaching is a *.tif file, I'm compressing it because the site doesn't allow me to upload the *.tif flie, and a *.pdf is too big (more than the 300KB the site allows).

Juan

 

[juanmdx]

Hello,

Does anyone had the time to check my program?

 

[juanmdx]

Hello,

I'm trying to debbug my program, and I made some changes, but I still have a lot of doubts on rungs 6, 11, 13 and 14.

On rung 6 I can't make the Input word of the FIFO register to get the value of the timer, I believe is because I reset the timer to 0 before the FIFO gets the word, so it gest a 0 (that's what I believe). And on the other rungs I have doubts regarding the use of the memories.

(On rung 3, I change a 300 for a 3 just for simluation porpouses).

Hope someone is following me.....


Best regards

Juan

 

[juanmdx]

Hello everyone,

I'been debugging the program I wrote with a simple simulator that comes with the software, so I made a couple of modifications to be able to write the value of the timer on rung 8 to the FIFO register (rung 9), so I added rung 10.

But this isn't helping either,the value of my FIFO register stays in zero.

I hope someone is helping me, and if you guys need more details I'll be glad to answer the questions you may had.


Best regards

Juan