Need help with PLC exercise in textbook

I have a problem exercise in my textbook that I can't figure out. Can anybody help me with this?

A conveyor has 6-,8-, and 12-packs of canned soda entering it. Each size of entering pack has an individual pack quanitity counter feeding a PLC register. To know how many total cans are entering the conveyor, set up a program for multiplying and then adding to give a total can count.

Thanks a lot for any help.

Any brand of plc for this?

I am familiar with GE and use their math function blocks.

I suspect that Allen Bradley's method would not even be close.

regards....kc

It is a mini PLC-2. And it is actually an Allen Bradley method. I have to use GET and CTU'S.

I hope you realize that you're using an old obsolete PLC. While you will gain some insight into how PLCs work and a little of what they're capable of by working on the old-timers, your school isn't doing you any great favor by giving you dinosaurs for lab experiments. When you're through with the course, you'll be at the leading edge of obsolete technology. Currently available PLCs have made math functions a lot easier to use.

If you're trying to learn on your own, then lose the history book and get a copy of Phil's book from this site. It's not based on any particular brand.

If you're specifically interested in learning AB, then download a copy of the LogixPro simulator from thelearningpit.com

A conveyor has 6-,8-, and 12-packs of canned soda entering it. Each size of entering pack has an individual pack quanitity counter feeding a PLC register. To know how many total cans are entering the conveyor, set up a program for multiplying and then adding to give a total can count.

Click to expand...

Technically this should work about the same for any PLC.

CTU1 counts 6 packs
CTU2 counts 8 packs
CTU3 counts 12 packs

Multiply CTU1 count by 6 and put in Integer file 1
Multiply CTU2 count by 8 and put in Integer file 2
Multiply CTU3 count by 12 and put in Integer file 3

Add Integer files 1, 2 and 3 and put in Integer file 4 (total can count).

What model of mini-PLC2 are you working with?
As I recall, only the -LN3 had multiply and divide instructions - the -LN1 and -LN2 only did add and subtract.

The PLC2's only understand 3-digit BCD numbers. To go beyond 999 requires you to write ladder logic to handle carry/borrow, etc. When multiplying two 3-digit numbers you get a 6-digit result in two consecutive words. Adding 6-digit numbers requires several rungs of ladder.

...are you beginning to realise why they're obsolete?

We need more details. What kind of soda is it? And are we sure it's soda or could it be pop?



Sorry, I couldn't help myself.