Allen Bradley PLC-5 -> Siemens S7-200

[Guest Data]

Hi, I'm a uni student currently on an industrial placement as part of my degree course. The first project I have been assigned to do is to completely replace a machine running with an Allen Bradley PLC-5 system with a Siemens S7-200. I'm currently working out what hardware changes will be needed, but I'll also need to consider software changes. Does anybody know of a program that could possibly convert the Allen Bradley programming files into Step7-micro/WIN files? Or is there any other way of converting them? I really do not fancy re-writing all that myself! Thankyou for your time.

[Crossbow 296]

There is no direct way to convert one vendor's code to another. Especially not with older products like the PLC5. You're going to have to rewrite it from scratch. Be careful about the way you rewrite your program. When changing vendors, items like timers and counters sometimes act a different way. Siemens S7-200 uses either the Siemens Simatic instructions or new IEC61131 compliant programming. The PLC5 was all proprietary AB language, as was the SLC500. I have limited experience programming AB, but have done many projects with the S7-200 if you need help.

[Data 0]

Thanks, although that really wasnt the answer I was wanting to hear, it was the one I expected. I'm currently reading the pdf mentioned on this forum - its actually the most informative read I've found so far. Has cleared up some confusion I had. One other thing - the PLC-5 has something like 340 inputs and 190 outputs on it. I dont know whether or not there is more than just the PLC (I think one can have up to 1K inputs?) as I haven't actually had a chance to see the thing yet. Atm, all I have seen is the program listing, which at almost 1000 pages is rather large. What I'm wondering is the fact that the S7-226 can have 128/120/248 - inputs/outputs/max channels over 7 expansion cards. Does this mean the total inputs can only be 128, with 120 outputs, or can you have a total of 248 inputs and 0 outputs? Either way I believe I will need to network 2 or more S7's together. I have read up on the hardware aspect of this, but I can't seem to find any information on the programming side. Does having the S7's networked mean changing the program in any specific way? ie. how do you go about accessing an input on a different PLC? Fair amount of questions there! I cant seem to find the answers on the net or the books I have here so hopefully some of you will be able to help!

[mjrx 1]

With that number of I/O and an apparently large program size, it seems odd to be downgrading to an S7-200. In reality, I don't think many would go this route. I think program size is going to be an issue, and trying to distribute the control to networked PLC's is going to be messy. This should be an interesting project, good luck.

[Data 0]

Well, I think I've finally worked out what I'll need for this - 3 networked S7-226s with appropriate expansion cards. However I'm not entirely sure how to network them - should I use an Ethernet connection, or use the MPI/PPI connection? Would I be right in assuming that I would have one Master and 2 slaves - the master would use NETR to get the status of the inputs from the slaves and save this to memory on the master itself. Also a similar process for the outputs I would assume. I can foresee a potential problem with this - the program already uses a fair amount of flags, so I don't know whether or not I would actually manage to store all this data on the one PLC. Also, the Allen Bradley uses some make of viewing terminal (HMI), will i need to get a new siemens version of this to make it work with the new program and PLC? I cant actually atm remember what make it is. I'm just really needing to know whether or not I am on the right sort of track, though any help you can give me will be greatly appreciated!

[Ken Moore 23]

I would consider using One large PLC for this versus three networked smaller ones. I thing in the long run you will regret the small networked decision. Just my $1.298