logix pro dual compressor exercise

hello to all on the forum,I am starting on the comp exercise,here is part 1.Ian

LogixPro dual com[pressor

Hello to all,just trying part 2- sharing the load. Thought that I could have one compressor running for 60 seconds,then have the other running for 60 seconds to bring up to pressure.I decided that that wasnt what was meant by sharing the load, Had a go and ended up with this,thanks to lance1 for the altenator example.hoping to build on this for part 3[had to upload image with the altenatoron its side as it was making the image too wide]

Here's another way to do it.

rung 002 you cant have loads in series only parallel

dtune951 said:

rung 002 you cant have loads in series only parallel

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LogixPro allows you to do that.

And in the real world.

RSLogix5000 for Controllogix, CompactLogix controllers also allows that.

RSLogix5 ( PLC5) RSLogix500 (SLC500/Micrologix) do not.

Really I love Logixpro Simulator!!! Sometimes PLC seems boring but if u sit in front of LOGIXPRO, you will not be bore even if u keep on creating logix for days.Because you see your logic working and controlling a big process.

chrisk_81

It isn't "illegal", but in terms of trying to explain it of what my teacher told me, you can't have two outputs in series like that. Parallel using the bracket branch for one per bracket branch is ok.

Outputs in series can be allowed by the programmers of the software, even though in relay logic it is absolutely a severe error that causes a malfunction.

A bigger issue is putting the Compressor RUN Lights after logic that says only that the system is in RUN mode and the pressure switch is closed. In the real world, this does NOT tell you that the compressor is actually rotating.

For this student problem, with no Zero Speed Switches or rotation sensors or feedback contacts from motor starters, the closest you can come to knowing that the compressors are running is to use contacts from O:2/1 and O:/2 that says "contactor enabled". ChrisK's Rung 002 is short-cut logic that does not do that.

Lancie1 is correct about real world wiring.

May I add that while you can program outputs, move, copy commands, etc in series, you cannot wire it in the real world.

Often times, (at least at the plants I worked at), this type of programming is difficult for maintenance to understand and follow. They are used to programming as if it were wiring.
At my last job, the logic rung was so long and complicated, one of the oem's programmers had to split the logic into several rungs not only to follow, but the rung took 3 different displays to look at.

regards,
james