S7 PC Adaptor Replacement RS485 Converter

John Gaunt

Member
Join Date
Nov 2004
Location
Tasmania, Australia
Posts
362
I am trying to use an ADAM 4520 RS232 to RS422/485 Converter
as a replacement for the PC Adaptor from Siemens.
To do so I need to know the pinout details of the MPI port
of my S7-414-2 PLC CPU.
The ADAM Converter has the following terminals at the RS422/485 end:
Data+ (RS485)
Data- (RS485)

TX+ (RS422)
TX- (RS422)
RX+ (RS422)
RX- (RS422)

(R)+Vs 24VDC supply (I believe)
(R)GND 10 supply -ve (I believe)

The ADAM Converter has a DB9 (female) connecter at the RS232 end.
I also need to know what the cable needs to be from this port to
the COM1 port of my PC. (The Siemens PC adaptor cable seems not
to be appropriate).

Any help or advice appreciated
John Gaunt.
 
I am afraid that exchaning the Siemens PC adapter with a regular RS232/RS485 adapter isnt so straightforward (meaning: it cant be done).

The thing is that there is a protocol converting chip inside the Siemens PC adapter. It changes the serial protocol at 38.4k on the PC side to MPI protocol at 187.5k on the MPI side.
 
Thanks Everybody,
It looks like I will have to keep buying these PC Adaptors
from Siemens to give to my customers for the "once in a blue moon"
event when they must start from a virgin CPU.
Once I have a configured PROFIBUS port I use that for all
programming and SCADA interfacing. The PC Adaptor just collects dust.
Is there some way to get PROFIBUS started without the PC Adaptor?
Regards........John Gaunt
 
If all that you are after, is to let the customer have a way to get up and running if he has to replace the CPU, then let him have another MMC card with the same program ON. He can then put that in a CPU out of the box, and it will run.

He could also use the MMC card that is allready in the existing CPU, but then what if THAT one fails ?
 
Thanks JesperMP,
I have done it that way myself. In fact with one particular
S7-400 CPU new out of the box I was unable to communicate with
it with either PROFIBUS or the PC Adaptor (MPI). I plugged in
a Flash Memory Card with an old project that had both PROFIBUS
and MPI ports configured and was able to communicate via
each port. Then after removing the Flash Memory Card I was able
to get MPI working with the PC adaptor as usual.
However for my customers (mainly in India) using the memory card
with S7-400 CPU's seems to be too confusing for them. They end up
with most blocks loaded from the Card but blocks they change being
in the CPU load memory only. I find it impossible to instill in
them any self discipline. Presumably soon the S7-400 CPU's will
use the MMC which I believe is then the only memory in the CPU
thus avoiding the confusion.
Perhaps for now I will leave the customer with a memory card with
only the hardware configuration to use to get a new CPU going.
Regards..............John Gaunt
 
??

looks like you managed to connect a scada thru the siemens MPI/rs232 converter, i'm wondering How thats fitted in the PC, by using an applicom card or OPC? my guess my thoughts are very off track.

Maybe somone that can help a student back on track

Dutch automation student
 
hluijcks,

which SCADA are you talking about ?
If it is a Siemens Protool Pro or WIN CC, then there will be drivers included that supports the PC adapter.
3rd party SCADA suppliers also sometimes work directly with the PC adapter.

It is also possible to use OPC.
Siemens SIMATIC NET does not allow you to use the PC adapter to establish an OPC connection. Minimum requirement with SIMATIC NET is a CP5611.
3rd party OPC servers often support the PC adapter, but not the CP cards (it is the exact opposite of Siemens). Exception is Deltalogic that also supports CP5511, CP5611 and CP5613).

To use an Applicom card will probably mean that you MUST use OPC, and use the OPC server from Applicom.
 
Thanks Jesper,

I am using Citect SCADA. I will have to have another go
at getting some information from Citect about using the PC
Adaptor for COMMS. Last time I contacted them I didn't have
a Citect License still under support. Now I have just got a
new License for commissioning in New Delhi next month so
they should be more helpful now.
Thanks again.......John Gaunt
 
thanks jesper for your advice

I'm using Cimplicity from GE and an siemens whith een MPI-PG-cable.

Cimplicity doesn't support MPI at all but does support OPC, the company Merz has een OPC server for MPI. So i put him in between and its working fine, i'm still suprised by the speed of it.

But thanks anyway

Greetz Hluijcks
 
i'm still suprised by the speed of it
You mean "surprised" as in "disappointed" ?
Well, the serial PC adapter is indeed very slow. Have you set the comm speed between the PC and adapter to 38.4 kBaud ?

If this is a "serious" application, you may want to consider a CP5611 card with either Simatic Softnet Profibus S7, or Deltalogic S7 OPC server.

You may also consider the Applicom card with OPC server you mentioned before.
 
well jesper

my scada has an graphic function and no logging or data analysing, so the speed is not the mayor.
I was positivly suprised by it, while i'm not an expert (yet) i was prepared for the worst

And I know (with some help) there are better solutions, the problem is, ive got no funding for my project.

Im working on my final project, for my bachelor degree in Automation Engineering. So in my report includes al the possibilities including the ones you mentioned.

My product must run for half an hour during my presentation, so een hour demo trail like Merz is no problem.

greetz HLuijcks
 

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