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Old December 25th, 2017, 12:58 PM   #1
rcwalls
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Plc 5

I am starting out with programming (beginner) PLC 5. I understand ladder logic, but struggling with the details of PLC. Trying to program 3 motors to turn on at certain times of the day in sequence. 1st motor at midnight to run for an hour then 1st motor shuts down with second motor coming on for an hour then the third motor. The start button is HOA and will run in A. Struggling with timers to turn motors on automatically and then rest to run the next day at midnight and so forth. 3 phase 480 volt motors so as you can tell, a big sprinkler system. Any help is appreciated. Thanks
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Old December 25th, 2017, 01:36 PM   #2
rupej
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Welcome to the forum! RSLogix 5 is a good program to learn on. Post your code so far and we can help you out with what you're having trouble with.
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Old December 25th, 2017, 02:39 PM   #3
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Thank you so much. Now trying to figure out how to upload the code. LOL! I will work on it. I do learn something each day that I work on it. Starting a program from scratch will force the learning for sure.
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Old December 25th, 2017, 05:48 PM   #4
Ron Beaufort
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Quote:
Now trying to figure out how to upload the code
save the file (it will end with .RSP extension) ... then ZIP the file (forum rule) ... click the "Attach Files" button near the end of the forum's "Reply" feature ...

it will end up as an attachment to your post - right in the thread ...
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Old December 26th, 2017, 01:21 AM   #5
rcwalls
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Plc

I think this circuit is now attached.
The intent of this circuit as stated before will be to start 3 motors. Each motor to come on at different times and run for 1 hour each. 1st motor to come on at midnight, run for an hour then shut off. Then the second motor comes on and runs for an hour then shuts off. Finally the third motor comes on and runs for an hour then shuts off. This will occur every night of the year beginning at midnight.
The start/stop is currently a switch (not momentary). I do think the manager will want to install a HOA so they can turn the system off or place in manual whenever performing maintenance on the system.
Thanks for any help provided. Let me know if you do not see the attachment
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File Type: zip Logic circuit.zip (9.6 KB, 8 views)
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Old December 26th, 2017, 07:46 AM   #6
Ron Beaufort
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the code that you've posted is for an SLC-5/03 system - which is programmed with RSLogix500 software ...

it's not for the PLC-5 system that you mentioned in your earlier post - which would be programmed with RSLogix5 software ...

so which system do you really have? ...

either way, the project that you outlined would probably be easier to handle by using the processor's internal real-time features - if they're present (some systems don't have a real-time clock) ...

good luck with your project ...

PS Edit:

here's a PDF copy of the OP's code in case someone has time to help - but doesn't have the appropriate software available ...
.
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File Type: pdf logic circuit.pdf (11.5 KB, 41 views)
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Last edited by Ron Beaufort; December 26th, 2017 at 08:22 AM.
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Old December 26th, 2017, 10:27 AM   #7
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If I've correctly unserstood your intent, your rung to run the timers is, shall we say, unusual. The operator would have to press both 'start' and 'stop' at the same time, continuously to get cr_1 energized.

The conventional way is a 'seal in' circuit - schematically identical to its relay logic equivalent. A thorough understanding of this simple arrangement will stand you in good stead in the future.
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File Type: png start stop.PNG (13.0 KB, 74 views)
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Old December 26th, 2017, 11:55 AM   #8
rcwalls
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Thank you all so much for the help.

It is the SLC 5/03. Sorry for the confusion.
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Old December 26th, 2017, 12:11 PM   #9
Steve Bailey
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Quote:
The operator would have to press both 'start' and 'stop' at the same time, continuously to get cr_1 energized.
Only if both the Start and Stop buttons were wired to the PLC input through normally open contacts. It is not unusual to find that all contacts on Stop buttons are normally closed.
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Old December 26th, 2017, 12:56 PM   #10
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True. I will have to go back to the field and recheck the start/stop selector switch, but I think when I checked when the selector switch was placed in start the stop was wired N.C.. When I typically hardwired momentary push buttons from a ladder logic diagram, I would use the seal in circuits.
However, I am not confident at all with the PLC programming and may have the the switches organized incorrectly or XIC when they should be XIO. Working through the basics.

thanks again for all of the feedback.
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Old December 26th, 2017, 01:05 PM   #11
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Also Its good practice to have only one instance of output in your program (O:3/0)
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Old December 26th, 2017, 01:16 PM   #12
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Very good. Thank you. You will have to teach me how you moved this to a PDF file. This would be handy to have the hard copy stored away in case the MCC and PLC gets washed away by another hurricane Harvey. We are starting this system from scratch since this storm and no records of the old system so the volunteers here will be making numerous backups of the entire system and attempting to hurricane proof them if that is possible.
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Old December 26th, 2017, 01:19 PM   #13
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Thanks tarik1978. good catch there. I will correct.
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Old December 26th, 2017, 01:24 PM   #14
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just a word of CAUTION! ...

there is a port on the front of your SLC-5/03 which certainly "looks like" an Ethernet port ...

it is NOT for Ethernet ...

it is for Data Highway 485 instead ...

do NOT (I repeat do NOT) plug an Ethernet connection into that port ... damage to your computer' mother board will probably occur ...

ask if you need help on this ...
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Old December 26th, 2017, 02:00 PM   #15
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The biggest secret to success for cases like this is to separate your sequence control from your motor control.

The motor control as you wrote it, as Doug-P pointed out, requires that the START button be held continuously for the pump to run. It also currently has no "hooks" to tie in any sort of timing sequence.

You need to step back and better define your processes. There are so many questions that I have about it, that it's very difficult to help you. It's probably because you are rushing into trying to code the thing that you haven't asked them yourself, which is why you are having difficulty helping you.
  • You talk about HOA -- Hand-Off-Auto. Where does that "live"? Is there an HOA switch next to each motor, or do you have an HMI that performs that function?
  • If the former, does the PLC know about the position of the HOA switch?
  • If the latter, then typically one would hard-wire the <START> & <STOP> pushbuttons to the motor starter relay and the Hand contacts of the HOA switch (and exercise for the reader what that circuit diagram looks like)
  • You have <START> & <STOP> buttons to control each pump. But what Starts & Stops your SEQUENCE? My GUESS (and it's only a guess and I shouldn't have to guess) is that, if all the pumps are in Auto, and if Midnight rolls around, then the sequence starts.
  • What actions do the Pressure Switches and "PM" (?) perform/prevent?

Like I said, the key is to separate your sequence code from your device control code. You device control code might look something like this:



AUTOx OFFx MOTORx
----+----| |---- { here } ----+-----|/|-------( )
| { be } |
| { dragons } |
| |
| |
| HANDx STARTx STOPx |
+----| |---+---| |---+---|?|----+
| |
| MOTORx |
+---| |---+




The -|?|- contact for the STOP buttons depend, as Doug-P and Steve Bailey discussed, on how the Stop button is wired. Normally closed (so that pressing the button interrupts the current flow) is usually best.

The "dragons" section is likely to be a single contact from your sequencer. It's probably a single contact ("Run Pump x"). There are, of course, even more questions to be asked about the sequencer:
  • Does it always start with the same pump?
  • Do all the pumps have to be in AUTO for the sequencer to work?
  • If not, how does the sequencer handle cases where a pump is on HAND or OFF? Does it not run anything for 5 minutes? Does it skip to the "Next"?

And so on. Again, the reason that you're stuck is that you're trying to write code before you've fully described what you are trying to accomplish. You don't know what "success" looks like, so you cannot succeed. This is a common problem in programming and in business.

Last edited by Aardwizz; December 26th, 2017 at 02:11 PM.
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