Connecting AB SLC 5/03 with Siemens HMI

VoltSmith

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Join Date
Jan 2010
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I'm trying to connect a Siemens HMI (MP277) with an Allen Bradley SLC5/03. I understand that the channel 0 of of the AB CPU is RS232C, and can be used for HMI connection. But I'll need an RS232C-RS422 converter for it, since the MP277 doesn't have an RS232C port.

A more direct connection can be made from ch 1, which is RS485, to the HMI serial port (which is selectable between raw RS485 and Profibus).

Has anyone tried this?

I'm connecting IF1B of the Siemens MP277 to the RJ45 on the SLC5/03. Pinout is as follows

Code: 
RJ45   IF1B   Description
1      3      B
2      8      A
4      5      Gnd
However, the devices are not communicating. I have no experience with AB platform. Is it actually possible, what I'm trying to do?

Regards.
Rahul
 
Last edited:
Electrically you should be fine (I didn't scrutinize your pinout) but they probably can't communicate anyway. The RS232C port on the 5/03 is limited to DF1 protocol or ASCII.

Channel 1 is purely DH485 protocol.

You would be better served with a protocol converter in between them.
 
Thanks much OkiePC. That was a _quick_ response!!!

The Siemens HMI can talk to a LOT of PLCs using a LOT of protocols, including DH485. That's what the configuring software (WinCC Flex) is saying.

I was interested to know, if someone has actually done this before.
 
VoltSmith said:
Thanks much OkiePC. That was a _quick_ response!!!

The Siemens HMI can talk to a LOT of PLCs using a LOT of protocols, including DH485. That's what the configuring software (WinCC Flex) is saying.

I was interested to know, if someone has actually done this before.
Click to expand...

Oops, I saw Siemens and didn't see HMI...my bad...I was locked onto the idea that it was a Siemens PLC. I have no experience with Siemens yet.
 
geniusintraining said:
Depends on the model of 277 you have..
Click to expand...

Thanks much for the link, Genius. MP 277 doesn't have that many varieties, and all of them support DH485. My challenge is on the AB side, which I know very little about.

I have not yet seen any HMI connectiopn from channel 1 of SLC5/03. Admittedly my exposure to AB based systems is very limited. I just want to know if it is possible or not.

Thanks.
 
VoltSmith said:
OkiePC, have you done any HMI connection from an SLC5/03 through channel 1?
Click to expand...
Yes, but only to Allen Bradley Panelview Standard graphic terminals. I have used the DH485 protocol on Channel 0 (RS232) a few times too, but I have not used a 3rd party HMI connected directly to a SLC DH485 port.

If your unit supports the protocol, and you have the cable figured out, then the only reason it may nor work would be due to timing problems caused by the signal converter. It is my understanding that the DH485 protocol is very finicky about signal timing.

Also, be very careful about that pin out, since 24vdc is available on at least one of those pins and may pose a risk to the connected device.

If you hit a brick wall with DH485, you may have better luck with DF1 on channel 0. I have used the DF1 protocol to send messages to compressor controllers going through a RS232 to RS422 converter and it worked fine.

Mickey posted a nice link with info about A/B DH485 pin outs just within the last day:
http://www.plctalk.net/qanda/showpost.php?p=477586&postcount=2
 
Last edited:
OkiePC said:
Yes, but only to Allen Bradley Panelview Standard graphic terminals.
Click to expand...

That's great. That's what I wanted to know, exactly. Thanks OkiePC :)

Did you have to code anything special in the PLC, for channel 1 to connect? Or just configuring it with proper baud rate and other serial frame settings was enough?


If your unit supports the protocol, and you have the cable figured out, then the only reason it may nor work would be due to timing problems caused by the signal converter. It is my understanding that the DH485 protocol is very finicky about signal timing.

Also, be very careful about that pin out, since 24vdc is available on at least one of those pins and may pose a risk to the connected device.
Click to expand...
Thanks for the info.

If you hit a brick wall with DH485, you may have better luck with DF1 on channel 0. I have used the DF1 protocol to send messages to compressor controllers going through a RS232 to RS422 converter and it worked fine.
Click to expand...
I'm dreading that option. I know that Siemens converter 6AV6671-8XE00-0AX0 can be used right away with channel 1 and my HMI serial port. But that converter is a slow item, none stocks it here, and will take weeks to arrive.

Mickey posted a nice link with info about A/B DH485 pin outs just within the last day:
http://www.plctalk.net/qanda/showpost.php?p=477586&postcount=2
Click to expand...
Great! It matches with my pinout.
 
geniusintraining said:
Are you sure... DH485 is not the same as RS485 alll of them have RS485
Click to expand...

Dear Genius, RS485 is an electrical standard that specifies voltage level and other electrical signal characteristics. DH485 and Profibus are two software protocols for interchanging information between industrial control systems. Both use RS485 at their signal levels.

Each Siemens HMI has a Profibus port, that can be configured as either MPI/PPI/Profibus or as raw RS485/RS422. If the software running in the HMI can talk in DH485 protocol, then it is "theoretically" possible to connect that HMI to an Allen Bradley CPU.
 
HMI TP177B de SIEMENS & SLC 5/03 CPU (1747-L531)

Para la conexión con los equipos existentes se debe tener en cuenta lo siguiente:

PLC: SLC 5/03 CPU (1747-L531)
HMI: TP177B de SIEMENS

Acceso a programa en PLC SLC:
Canal 0 - Puerto RS232: DH485, DF1 o ASCII
Canal 1 - Puerto RJ45: DH485
Cable CH0: Conversor USB-RS232 + Cable NULL (para DF1)
Cable CH0: 1747-UIC (para DH485 en puerto DB9)
Cable CH1: 1747-UIC (para DH485 en puerto RJ-45).

Para detalles de conexión con el HMI, ver ambas imágenes resumen.

DF1.jpg DH-485.jpg
 

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