One panel for 3 PLC's (Siemens S7)

Hi

I have 3 stand alone machines. Each one has a PLC and an MP270.

Somewhere else there is a MP270 that is connected to one machine at this moment. But, they want to be able to control the other 2 machines as well.

So the panel must be connected to 3 CPU's. That's impossible, I need a Master, well, I have an extra CPU that may be used as a Master for the Remote panel. But how do I have to connect the Cpu's, with CP cards ?

connection MPI

The connction right now is MPI btw.

any help pls ?

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In general I do this with a master PLC and slave PLCs as you suggest. Your explanation isn't too clear, but I am assuming all three machines are identical. It looks like you have two choices.

1) you could add a PLC to be the master, or else modifiy one PLC to act as both master for collecting data from the others and to control one machine

2) use a peer to peer comm link for all the HMIs, and let one of the HMIs talk to and collect data from all PLCs

Note that most HMIs are essentially the master and the PLC the slave on a comm protocol that is master/slave. As long as you have a separate port for the local HMI and the remote HMI it would work out OK. For peer to peer it doesn't matter.

Hey

Hey,

Connecting 3 PLC's in the same MPI network with the HMI devices is not possible ? Or is it ?

I never worked with MPI networks, we allways use profibus, and when connecting CPU's, we use CP (communication processors) cards for data exchange between PLC's.

What I have now: 2 MP270 devices on an MPI network wit a 314C-2DP PLC. There is a new machine that needs to integrate in this system, and with one of these 2 MP270's I must be able to change data on this new CPU also. My question is simple: can it work, 2 HMI devices and 2 CPU's in the same network, or should I change it to profibus and use some CP cards ?

kind regards

MPI is, I believe, peer to peer. You can have two HMIs talking to a single CPU. I don't know how multiple CPUs and multiple HMIs will work. Although in theory it should, Siemens is full of surprises when it comes to communictions. I suggest you run it past your local distributor.

I think Profibus is master/slave and I don't think you could have 2 HMIs on a single network.

You should have no problems with your MPI project one HMI and 3 plc's. I would put the HMI master. I did a project where I had 4 HMIs and 5 PLC's on the same MPI with each HMI accessing all the PLCs (kinda I can control the line from anywhere). Comunication time is going to be a problem (slow if you have recipes or a lot of other bullcrap) . At the time I used ProTool. There are tricks to make communications faster but I'm sure you'll find them. In ProTool you had an area where you defined your PLC's tags and other params (like addresses).

Yes, you can certainly have the same panel connected to several PLCs at the same time.
You have 3 PLCs and 2 panels on the same network.
So maybe the performance will be "acceptable" only if you use MPI at 187.5k. This obviously also depends on how many tags and alarms you need to scan.
I recommend that you integrate all PLC and Panels in the same project in STEP7. STEP7 will then take care that there are no conflicts.

Maybe it is not relevant for you, but I will mention it anyway:
There is an interesting new development with Win CC Flexible. It is an option that allows the operator at one panel to "take over" the control of another panel.
Both panels have to be on ethernet though.
It could be the easiest way to achieve what you want - all you need is to use Win CC Flexible and panels with ethernet

I think Profibus is master/slave and I don't think you could have 2 HMIs on a single network.

Click to expand...

Actually Profibus is multiple masters and multiple slaves.
But the most common (and efficient) scenario is one master and several slaves.

If combo does not use the Profibus ports on the PLCs then it could actually be a good idea to connect everything via Profibus in stead of MPI.
If set to 1.5 Mbaud it will be much faster than MPI at the 187.5 kbaud that is the max for MPI on the S7-300.
Also, it can reach longer than the 50 meters that is the max for MPI on the S7-300.

If combo do use the Profibus ports for i/o or VFDs or something, then he can still use it for the panels.
But doing so will mean that the scan rate of the i/o on Profibus will drop by a factor 10 (because the Profibus network will work in multimaster mode in stead of monomaster).
If that is a problem or not for combo is up to him to decide.

MPI is peer to peer, and you can have up to 32 nodes on it if I recall correctly.
I do find it is a bit slow, however, and favour Ethernet for our newer machines. If you were using profibus for this you may have a problem.

If you were using profibus for this you may have a problem.

Click to expand...

I am interested in knowing why.

Mpi

I wouldn't consider MPI Peer to Peer that is the PPI (Point to Point Interface). It stands for Multi Point Interface and it can easily allow for multiple HMI's and PLC's. I concur with trying it at 187.5kB first, then gradually increase your rate until nodes start falling off the network. Use the MPI diagnostics within your PG/PC interface to debug your network.

You would be much better off putting all of your devices in one project as well. ProTool Pro will allow you to setup multiple PLC's it can communicate with.

I currently support a network containing 5 PLC's (200's, 300's, 400's) and 5 HMI's as well as another Profibus network containing 1 PLC and 8 HMI's. It can be done...

If you'd like to share data throughout all the PLC's then setup your global database within your project. To keep from bogging down the network, only share what you must.

I concur with trying it at 187.5kB first, then gradually increase your rate until nodes start falling off the network.

Click to expand...

The max baudrate for the MPI ports on the S7-300's is 187.5 k.
Exception is the newer PLCs like 317-2DP. It has an MPI/DP port as well as an extra DP port. The MPI/DP port works up to 12 Mbaud.
Combo's 314C-2DP has an MPI port and a DP port.

My networks

Hi,

The basic idea is this: on a MP270 X we must be able to change data of machine A or machine B. But, machine A and B can work stand-alone, because they both have a PLC + an MP270 panel lacally.

MP270 X has to be able to change data of both machines. We only work with one machine @ once. So, one machine will be shut down. Let's say that we work with machine B, MP270 X has to be able to change data just like the locally MP270 of machine B.

I will do it like this:

MP270 X connected to a Repeater (segment 1)
Machine A: CPU - MP270 - Repeater (segment 2)
Machine B: CPU - MP270 - Repeater (segment 3)
segment 2 and 3 are sometimes offline.

Will I have problems (communication alarms) on the MP270 X when an other segment on the MPI network is offline.