Micrologix 1100-Counter Problem

[bfranklin]

Rs Logix 500 Version 8.40
AB Micrologix 1100 B

I have 10 counters C5:0 to C5:9. I have different bits triggering them but each counter increments the same all the time. What could be the problem?

Thanks

 

[TConnolly]

Can you zip and post a copy of your program?

 

[bfranklin]

Attached is the program. File 12 labeled CHEMICAL is where my issues is. I haven't labeled anything yet.
The N7:0 to N7:9 are going to be Set points from an HMI

 

[TConnolly]

There is nothing mysterious happening there. All of your counters have a preset of 1. Each counter counts up when the previous counter is DN and the 30 second strobe bit is true. The first counter reaches its preset on the first strobe and set its DN bit. The DN bit sets the trigger bit for the next counter. So the next counter is triggered as soon as the rung is scanned, so it counts up to 1 and sets it DN bit. That DN bit set the trigger bit for the third counter, and so on all the way down.

This program is doing exactly what it was programmed to do. What is it you were trying to accomplish?


edit:
If it helps you to visualize what is happening and why your counters are all programmed to count together, take a piece of paper and write down the address of your timer/DN bit and the bits you are using to trigger the counters and the counter DN bits. Next to each address draw a little box. This is your bit box. Start when you have the timer DN bit and the first counter trigger bit set. Put a 1 in the bit box for each of those and now go down the ladder rung by rung and when a bit is set put a 1 in its bit box. Don't change that bit until another instruction changes it. Using the bit boxes will help you see what your program is doing. (Bit boxes is a technique used by our distinguished colleague Ron Beaufort to help students visualize what the PLC is doing. Search his name on Youtube for move videos on this technique.)

 

[bfranklin]

This is a chemical injection sequence, after a preset time on one device is reached it goes to the next device and so one.
-What I am doing is: a preset number which represents minutes goes into each counter.pre from the hmi.
-In sequence from counter 0-9 the counter increments to its preset, goes done then moves onto the next counter.
What I am seeing when I test it online is all the counters increment together as soon as the program in enabled and do not go in a sequence one after another. when 0 counter increments, they all increment. When 0 counter is dn., they are all done.

 

[TConnolly]

I'm at home now so I can't open the program, but it does that because that is how your program is built. Its doing exactly what you told it to do. You'll need to rethink the logic there.

One suggestion would be to use just one counter and use compare instructions for each step instead.

 

[blftech]

Increase the presets on all of your counters to a higher value than 1. Everything is happening very quickly and you are not able to see your counters count because of the the low preset. Plug in a preset of say 100 for each counter and that should allow you to test things a little easier.

 

[RKGalone]

you should use bit instead of word.

 

[rdrast]

you should use bit instead of word.

Huh?

 

[TConnolly]

Increasing the presets isn't going to solve the problem. What will happen is a one minute overlap of each step. Right now in this logic the counters will upcount at the beginning of its first minute, instead of at the end of its first minute.

 

[bernie_carlton]

I don't know if this would hopelessly confuse the reading of the logic but I have placed sequences like this in reverse order on the file to force triggering on sequential scans.