One of our units has a PLC (Simatic 7 with CPU 315) and an operating panel -OP17 DP. Recently the operating panel has started to show two fault messages; "#551 PLC address -3 not possible" and "044 transfer error NO: 8". If any one knows the solution, please inform.

As we couldn't program the new OP, we did not replace the operating panel. The new OP that we tried to program through protool software is not establishing connection with laptop. We do not know which suitable baud rate for COM1 port & OP17.DP is? Detailed OP17 programming procedure is highly appreciated.

 

Hello GAF
Generally error $551 is meaning that the remote partner (the PLC) is not answering the OP's calls.

This is achieved by:
-failure of the cable between plc and OP17 and the connectors (the
connector especially for long distances must be terminated)

-failure of one of two ports (MPI or Profibus?) of HMI or CPU

I think that OP17 isn't fault, isn't necessary to reload the program.

For testing ports is required at least one scope (10 or 20MHz bandwidth is good) and/or a way to connect you laptop to the cpu (serial adapter/usb
adapter/pcmcia adapter/ethernet adapter by siemens or other vendor).

Check the trasmission way from OP to CPU, check in the back of OP if the green led is blink (this is meaning that the HMI is requesting data), check on the connector DB9 female pin 3/8 vs pin 5 (or A1 / B1 vs cable shield on terminal block of the connector if is Siemens's one)if there's square waves (the level is 0 to 5V and isn't a problem: if there's waves them are of the correct value), check the same on the other connector on the cpu (in this case you must check on the DB9 male of the connector from OP, not on the cpu port, because the active part is the HMI not the CPU), finally you can try to connect with step7, accesible nodes, on this cpu, with the OP connector not plugged on, the faulty item will be clear.

The correct way to program an OP7 o 17 is avaiable on protool manual and/or on the OP7/17 HMI manual. Before connecting with laptop a programmed OP must be put in transfer mode, achievable by System Menu (if avaiable) or a
multiple key pression on the bootup (be sure to press the correct keys:
there's also a combination for factory reset of the OP, included user program loosing)

Regards
Gabriele Corrieri

 

Hi,

Sorry for jumping in but I need your help since it seems like you know your way around these devices. I have a Simatic OP7 controlling my temperature chamber. It has a RS232 connector but I do not how to connect it (What are the parameters?). Also, I do not have any reference to its control commands such as decreasing/increasing temp. Do you know something about that? Do you have any reference or did something like that before. My goal is to build a C program that will control the OP7 using its RS232 interface.

Thanks in advance,
Moshik

 

A Siemens OP7 is a display for a SIemens PLC. It doesn't do any actual control itself. In order to use the OP7 in a different control system you would have to emulate the PLC's communications protocol. There is more information about the OP7 including the communications ports on the Siemens web site.

As for how to use your OP7 to increase or decrease temperature, that depends upon how it was programmed. The OP7 requires a program written using special OP programming software. The person programming it for each application decides what is on each screen and what most of the various keys do.

If you are designing your own control system, you would probably be better off using some other sort of display.