Profibus networking with 3 s7 CPU's using DP ports

[emokar]

Hello,

I have been trying to set up a PB network between 3 s7-CPU315-2DP v2.6 , but i couldn't...

Here is the connection:

Slave1: A2----------A1 :Slave2: A2-----------A1 : Master
B2----------B1 B2-----------A2

Distances between nodes are quite long , about 600m. That's why i've chosen 187.5Kbps for baud rate.
I have combined all PLC's in the same Simatic Manager project and did the configuration necessary(at least i think so

Strange problem is; when i disconnect Slave1's PB cable, the CPU indicates a bus fault. When i connect it back, the bus fault is OK. But on the other nodes, there is a permanent bus fault(?).

And another strange point is, when i download HW to Slave1, CPU switches to RUN mode properly, however no output becomes active. I get online to check it out and i see that some outputs are seem to be set in software, but in fact no relay gets energised.

I would really be very happy if someone helped, because i am running out of time

Regards,

 

[JesperMP]

If the wires are connected as you describe it, there is no termination in the last connector. The wires in the last connector must be connected to A1,B1.

edit: And disconnecting a slave in the middle (switching termination ON) will also cause a bus fault with the wires connected as you describe it.

The normal is to follow the "arrows", so that you can disconnect slaves downstream, and allow the master to still control the remaining slaves.

Master.........slave.............slave.............slave.............slave 

A1 <-(green)-> A1,A2 >-(green)-> A1,A2 >-(green)-> A1,A2 >-(green)-> A1

B1 <--(red)--> B1,B2 >--(red)--> B1,B2 >--(red)--> B1,B2 >--(red)--> B1

 

[emokar]

I planned to make the cpu in the middle master, but for some reasons (that plc is in a more critical place and is also working as a slave via its cp card, it is not easy to stop it and download HW) i could not.

So, now the order of PLC's are as follows:

Slave1(term. off) --> Slave2(term. off) --->Master (term on)

And below is the connection:

A1...........................
B1...........................
A2--------->A1...............
B2--------->B1...............
.................A2------------>A1
.................B2------------>B1
.....................................A2
.....................................B2


So, should i change the connection to make master first node of the bus?

Thanks in advance,

 

[krk]

You should really connect your network as Jesper suggests, translated to your reversed sketch:

Slave1: [color=seagreen]A1<-------<A2[/color] :Slave2: [color=seagreen]A1<--------->A1[/color] : Master
	[color=red]B1<-------<B2[/color]		[color=red]B1<-------->B1[/color]
SW=ON			SW=OFF			SW=ON

 

[JesperMP]

If the master is in the middle, then do like this:

 

Slave1.........slave2............Master...........slave3...........slave4 

A1 <-(green)-< A2,A1 <-(green)-> A1,A2 >-(green)-> A1,A2 >-(green)-> A1

B1 <--(red)--< B2,B1 <--(red)--> B1,B2 >--(red)--> B1,B2 >--(red)--> B1

ON.............OFF...............OFF..............OFF..............ON 

Notice that Slave1 and Slave2 will remain connected to the master if the termination at the master is turned ON. Slave3 and slave4 will be disconnected.

 

[emokar]

thank you all for your help, that solved the problem.

 

[emokar]

CPU315-2DP does not energise output while in RUN mode

Hello fellows,

I have a very strange problem and would like to learn your suggestions.

Today, i set up a profibus network with kind help of some guys here. The communication works successfully, i can see all nodes in master's HW config and all nodes are OK.

The network consists of 3 nodes , all including CPU315-2DP v2.6 .
One of the slaves is a demo plc for now, there is nothing wrong with it. The problem is on the other slave. This slave switches to RUN mode, there is no fault on it. HW diagnostics says module is 'available and OK'. However, no output gets energised even i see them energised in online connection to software.
In software the output is '1' but on the output modules, all outputs are '0'.

When i download a configuration that does not include Profibus slave config, the CPU starts to run properly.

I am not very experienced in profibus networking. I don't know how to address info that will be transferred. I think that the problem might be due to a addressing conflict i made while configurating profibus.

What are your opinions?

Regards,