Sorting Numbers in Numerical Order

Hi there,

I'm really new to PLC programming, but I do have experience with other languages. Currently I'm learning to use on an logix 5562 using RSLogix 5000 language.

What I'm trying to do is take 5 numbers, entered by the user, and sort them into numerical order so I can check them. Is there any simple way of doing this? I've read a little bit about the sequencer, but I don't think that's what's best in this situation.

Any help would be great.

Thanks
Chris

Sort routines aren't hard, but first, what PLC, brand & model, are you using? Also, what programming software, incl. version, are you using?

logix 5562 using RSLogix 5000 language

Click to expand...

With only 5 numbers a bubble sort would be quick and efficent.

See PDF below for the "File Sort" instruction.

Thanks a lot. I've actually been looking around and it looks as though you're right, a bubblesort would be the best idea. I have the option of writing in structured text, so that seems like a reasonable idea.

Thanks again.

Hi I'm back again.

I've given it a shot at writing a bubblesort in structured text, but the syntax is a funny guy so I wanted to throw this up here and see what you guys think of it.

WHILE SWAPPED DO
SWAPPED := 0;
FOR COUNT := 1 TO 4 DO
IF DICE_IN_ORDER[COUNT] > DICE_IN_ORDER[COUNT+1] THEN
TEMP := DICE_IN_ORDER[COUNT];
DICE_IN_ORDER[COUNT] := DICE_IN_ORDER[COUNT+1];
DICE_IN_ORDER[COUNT+1] := TEMP;
SWAPPED := 1;
END_IF;
END_FOR;
END_WHILE;

where dice_in_order is my array of 5 dice numbering from 1-6. I've chosen the count to be from 1 to 4 because dice_in_order[0] is a spare to make things more readable, so my array goes from 1 to 5.

I've given it a shot and it appears to not work. Any ideas.

Thanks
Chris

I think the way the WHILE/END_WHILE works is the input WHILE condition needs to be true in order to pass. If it is not true the code moved to the END_WHILE line and continues.

So you will either need to invert your WHILE and END_WHILE lines (if the plc will let you) or seed SWAPPED with a 1 before you get to the sort routine.

Keith

As long as SWAPPED is true before your code, it works for me. What test data are you using ?

Sorry, you want to use REPEAT...UNTIL. Put REPEAT at the top and put the conditional UNTIL at the bottom.

Keith

Thanks again guys, the repeat..until loop worked perfectly. I just needed to do that. The swapped bit wasn't true before it started and that was the problem.

Thanks
Chris