S7 connecting to MPI port

Johnny T

Member
Join Date
Jul 2003
Location
Fife, Scotland
Posts
642
Hi,

I'll give you the basics of what I'm trying to achieve first and then I'll give you the question...

I need to connect a Touchscreen PC to several S7 PLC's. I have bought a Perle USB-serial 8 port adaptor that gives me 8 'virtual' serial ports from 1 USB port. The adaptor has 8 d-type 9 pin male connectors on the front. I need to connect my S7 PLC's MPI port into those.

Firstly will this work (ie. anyone done anything similar to this themselves)? Secondly, do I just need a standard RS232 lead female to male? If so does anyone know what the pin-out for such a lead is?

Many thanks as always

JT :)
 
I dont think you will need your Perle serial port adapter.

1. MPI is a network that uses RS485 not the normal RS232, and in addition to that, there is no
PC driver that "speaks MPI" directly on the serial port.
You must specify what software you want to use on the touchscreen. The type of online connection will also limit the possible types of hardware that speaks MPI.

You can use (maybe, depending on the software you are using) a serial-to-MPI converter like Siemens "PC adapter". But the performance is awful.

Alternatively use (maybe, depending on the software you are using) the Siemens "PC adapter USB" that connects via USB in stead of serial. The performance is acceptable, but it must hang directly off the programming port of one of the PLCs.

Or use (maybe, depending on the software you are using) the Siemens "CP5611" card which is a PCI type card. The performance is excellent and it doesnt need to hang directly off the programming port of one of the PLCs. Price is approx 50% higher than the "PC adapters".

2. To connect you touchscreen and 7 PLCs in one MPI network you will have to make a daisychanined connection from Touchscreen to PLC to PLC to etc.
There are connectors for this purpose that allows two cables, or one cable and termination.
Use Profibus cable.

Tell us more and we can help you more.
 
Jesper

Thanks for the info. Here's a description of the full job in case you can give me any more info/help in how to go about it... *deep breath*.. I need to upgrade an existing SCADA system (OCME Albatross - one of their old proprietary systems) to a new SCADA system to make it 'future proof'.

The system talks to 7 S5 PLC's via an off the shelf Specialix Terminal Adaptor which has 8 ports on it. The plugs on the ports go off to 7 RS232 to TTY converters and then on to the PLC's.

Initially I'm just upgrading the SCADA with a new PC that is running the Citect SCADA software.

However, in the future I'm going to have to upgrade all the 7 S5 PLC's to S7 PLC's.

The problem with the PLC upgrade is that it has to be done gradually ie. 1 or 2 PLC's per weekend as they can't afford to have any downtime during the week. This means that the system I put in, initially has to talk to 7 S5 PLC's but be easy to switch over to 6 S5's and 1 S7. Then 5 S5's and 2 S7's etc etc as the upgrade progresses.

The drivers I have available to me for S5 115U's are:
CP5412-A1 board via CP5431FMS
Profi-AT-PCAT board via CP5431FMS
* Serial (Siemens AS 511 protocol) via Programming Port
Serial via CP524 or CP525

I believe that if I use the third option and set up 7 virtual ports in the SCADA for the Perle hub I've bought. Then wire the 7 ports from the hub to the TTY converters then (hopefully) it should talk to the S5's. (Does this sound feasible to you?)

The drivers I've got available for S7 300 series are:
MPI CP5412(A2)/CP5611 card
MPI CP5412(A2)/CP5611 card (for reading PID blocks)
PROFIBUS using CP5412(A2)/CP5613 card
PROFIBUS using CP5412(A2)/CP5613 card (for reading PID blocks)
TCPIP using standard PC network card/CP1613
TCPIP using standard PC network card/CP1613 (reading PID blocks)

I haven't got any S5 PLC's but I do have a couple of S7 PLC's that I was going to test my SCADA on. I wanted to connect it up and get it talking just so that I won't have any major problems when I get to site.

I was told when I bought the SCADA software that I would need SoftNet Lite in order to talk to the S7 PLC's. I haven't installed the SoftNet Lite yet but maybe you can help me on how I go about the connections to both the S5's and the S7's as, to be honest, I've not much experience of this.

Any help will be very very much appreciated.

Thanks

JT :)
 
I believe that if I use the third option and set up 7 virtual ports in the SCADA for the Perle hub I've bought. Then wire the 7 ports from the hub to the TTY converters then (hopefully) it should talk to the S5's. (Does this sound feasible to you?)
Yes, it ought to work.

Go with the CP5611 card. There are probably some users on the forum with experience with CP5611 in combination with Citect. Start a new thread with "Citect" in the header and you should get some responses.
If Citect uses some kind of "direct" connection in combination with Simatic Net software, or it has to be OPC I dont know. If you have to use OPC, then I made a guide in the downloads section under "Siemens".
For the CP5611/MPI combination you will probably need Simatic Softnet Profibus S7 software (never mind that it is called Profibus and not MPI).
You didnt state what kind of S7 PLCs, but I guess that they are S7-300's. If so you shall be warned that their MPI ports limits the total network length to 50 meters, and max baudrate to 187.5k (a lot better then 9600 baud for the S5 TTY ports though).
You can extend the MPI network with repeaters.

An alternative is to use Ethernet in combination with Simatic Softnet Ethernet Lean software ("Lean" is limited to 8 connections, so it is exactly enough for you).
But it will cost you either an Ethernet module per PLC or relatively costly CPUs with onboard Ethernet ports (315-2 PN/DP for ex.).
 
Jesper

Ethernet was an option that was suggested to me. When I upgrade to S7 I will probably go the ethernet route.

Maybe I won't be able to set up an S7 network as a test then (I don't want to get all the ethernet gear in now, I'd rather wait until they decide for definite they are going to upgrade).

I'm happy enough though at the moment that you think my method of connecting to the S5's will work. That's my main concern at the moment.

The S7 upgrades will probably not be for about 6 months so I have enough time to prepare for that.

Many many thanks for your informative response and help mate.

Cheers

JT :)
 

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