Alternating Compressor

New to PLC'S and I'm loosing more hair trying to
make the ladder diagram to alternate compressors.
Can somebody please help for info. Is there a book
I should buy that shows this diagram?
Thanks

What kind of compressors? Air? Ammonia?

What are the criteria for alternating them?
--Minimum Off Time?
--Maximum Run Time?
--Maximum Run hours differential?
--probably more

Will you ever need to run more than one simultaneously?

OkiePC said:

What kind of compressors? Air? Ammonia?

What are the criteria for alternating them?
--Minimum Off Time?
--Maximum Run Time?
--Maximum Run hours differential?
--probably more

Will you ever need to run more than one simultaneously?

Click to expand...

Okie is completely correct. What do you want the machine to do? Come up with those criteria - which by the way is sometimes the hardest part - then you can start designing the controls.

Dan Bentler

Yes, get the spec right in your head (or even better on paper first) then once you have this sit down and write the program.

You will waste loads of time if you try to write first with only half a spec. You will end up re-writing it every time you "remember" something else it had to do. I have been there and done it!

Thanks for the replies,
What I'm doing is the Logic-pro simulator problems with 2 air compressors. The process is one has to reach, lets say 50 psi for example then the next time it turns on we would like to utilize the other air compressor to reach 50 psi for example. Basically
Im trying to write the ladder diagram for Alternating. I know the
schematic for an alternating relay but how would I write it for this.
At times both may have operate to keep up with demand.
Thank again,
Victor

There are several ways.

1) Search the forum for a flip flop.

2) Look at this series of binary numbers
0 = 0000
1 = 0001
2 = 0010
3 = 0011
4 = 0100
5 = 0101

Do you notice a pattern in what the right most bit is doing each time the value increases by one?

are you sure you want to do it like this? Run time will then be equal for both compressors, therefore increasing chance of both failing at same time!

Compressor alternate

LogixPro is pretty easy to work with, try this and see if you can get to where you want to go. This program is written for the two compressor sim in Lp.

Click on link below then scroll down.

http://www.plcs.net/downloads/index...ey&PHPSESSID=046239e74208dd688eec43a5657ca4f9