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Old October 6th, 2014, 06:08 AM   #1
varunmahendran91
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Rs logix 5000

Hi,
i have some doubts regarding downloading my program.

i have 5 panels,in which one is main panel and the remaining 4 are local control panels. what i have to do is to control the sequence(ie lead,lag1,lag2,lag3) of 4 pumps controlled by seperate motors. each of them having its own control panel(4).
I had done the programing section of sequence control in the main panel, out of which most tags are from 4 local control panels.Do i have to download the specified section of program to the corresponding panel? or is there any othe way to access the complete program globally? i mean using tags?

can anyone explain how to do it?
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Old October 6th, 2014, 09:37 AM   #2
recondaddy
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I think we probably need a bit more information about your setup. Do you have separate PLCs in each panel, or do you have a single PLC in the main panel with only motor controls in the local control panels?

If you have a PLC for each panel, then, personally, I would write the program for each motor in its own respective PLC and have the main PLC communicate with them via produced/consumed tags over Ethernet/IP.

If you have a single PLC in the main panel with only motor controls in the local panels, then that sounds like a job for some remote I/O in the local panels that are communicating with the PLC in the main panel.
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Old October 6th, 2014, 10:00 AM   #3
varunmahendran91
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hi recondaddy,
big thanks for ur reply. as you said we have seperate plc in each 4 LCP. each pump is controlled by seperate motor driven by vfd which is actuated by LCP.
will you elaborate the produced/consumed taging method to control via ethernet? also it will be a great help if you provide me a sample program since i am new in programing.
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Old October 6th, 2014, 10:51 AM   #4
recondaddy
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It's been a while since I've had to set up any produced/consumed communications between PLCs, but this publication will give you a great start:

http://literature.rockwellautomation...m011_-en-p.pdf

I don't know how familiar you are with Ethernet/IP, but there are basically two modes of messaging -- implicit and explicit. An explicit message establishes a connection, sends a request, and gets a reply. If you have a relatively infrequent request between PLCs, this is an appropriate method. Explicit messages are handled in your logic using the MSG instruction.

Implicit messaging, however, is what we are talking about, here. Implicit messaging doesn't require any logic in your program. If you've set it up, properly, the two devices will pass their tag data, automatically, at the rate you've specified.

Make sure that you add the devices you wish to communicate with in your I/O tree. In your case, the main PLC will have the 4 local PLCs in its I/O tree, and each of the local PLCs will have the main PLC in their I/O trees. If you wish the local PLCs to communicate with each other, just make sure that you have them listed in each others' I/O trees, as well.

Let's look at a VERY simplified example, using your application:

In your main PLC, let's say that you want to produce one tag to each of the four local PLCs to command the pump motors to run. Your produced tags will be named:

Pump1Start
Pump2Start
Pump3Start
Pump4Start

When you create the tags in your main PLC, simply designate them as produced tags, and in the connection dialog, specify the number of consumers that each tag will have (in your case, each tag will only be consumed by one consumer).

Let's say that you also want to have bits in your main PLC that let you know when each pump is running. So, you'll need four consumed tags in your main PLC named:

Pump1Running
Pump2Running
Pump3Running
Pump4Running

When you create these tags in your main PLC, simply designate them as consumed tags, and in the connection dialog, choose which PLC is producing the tag and what the name of the tag is in the producing PLC.

Now, let's look at your local PLCs.

Each one will need to produce a tag to the main PLC to let it know when its pump is running. You might name that tag, PumpRunning. Just like we did in the main PLC, simply designate this tag as a produced tag and set the number of consumers. If only the main PLC is consuming the tag, then the number of consumers will be '1'. If you want the other local PLCs to also know, then the number of consumers will be '4' (one for the main PLC + three for the other locals).

Each one will also need to consume the start command from the main PLC. Each one will need a tag to hold that value. You might name the tag, PumpStart. When you create the tag, simply designate it as a consumed tag, and in the connection dialog, specify the main PLC as the producer and the Remote Data tag as "Pump1Start", or "Pump2Start", etc., depending on which PLC you're setting the tag up in.

So, here's a summary of the example I just listed:

Main PLC
Produced tags:
  • Pump1Start - Number of Consumers: 1
  • Pump2Start - Number of Consumers: 1
  • Pump3Start - Number of Consumers: 1
  • Pump4Start - Number of Consumers: 1

Consumed tags:
  • Pump1Running - Producer: Pump 1 PLC; Remote Data: PumpRunning
  • Pump2Running - Producer: Pump 2 PLC; Remote Data: PumpRunning
  • Pump3Running - Producer: Pump 3 PLC; Remote Data: PumpRunning
  • Pump4Running - Producer: Pump 4 PLC; Remote Data: PumpRunning

Pump 1 PLC:
Produced tags:
  • PumpRunning - Number of Consumers: 1 (or 4, if you want the others to know)

Consumed tags:
  • PumpStart - Producer: Main PLC; Remote Data: Pump1Start

Pump 2 PLC:
Produced tags:
  • PumpRunning - Number of Consumers: 1 (or 4, if you want the others to know)

Consumed tags:
  • PumpStart - Producer: Main PLC; Remote Data: Pump2Start

Pump 3 PLC:
Produced tags:
  • PumpRunning - Number of Consumers: 1 (or 4, if you want the others to know)

Consumed tags:
  • PumpStart - Producer: Main PLC; Remote Data: Pump3Start

Pump 4 PLC:
Produced tags:
  • PumpRunning - Number of Consumers: 1 (or 4, if you want the others to know)

Consumed tags:
  • PumpStart - Producer: Main PLC; Remote Data: Pump4Start

Hope this gets you started.

Last edited by recondaddy; October 6th, 2014 at 11:00 AM.
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Old October 6th, 2014, 02:26 PM   #5
varunmahendran91
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thank you soo much for your valuable feedback. i got the idea now.hope your valuable advise in future too
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