SQD to PLC5

[lui 0]

I Need to convert some ladder logic from a Square D Symax to a AB PLC5. Could any body please tell me what are the difference from SQ D to PLC5? e.i Inputs, Outputs, Timers and Internal bits e.. (B3:0).Thanks

[paulengr 44]

In a word: a lot. I can't really give you exact descriptions since it's been 5 years since I worked in a 100% Symax plant. However, here are the differences as I remember them: 1. SQ D is very picky in the number of conditions and complexity that you can have on a single rung. If you can "read between the lines", it appears that SQ D processors have fixed length ladder rungs in terms of memory usage. There are definite limits in PLC 5 ladders that appear to be there mostly to limit stack lengths but I've never actually hit the limit. 2. The serial protocols (DF-1 and the Symax version) are obviously very proprietary and very different. 3. Synet and AB Ethernet are also very different. HOWEVER, Synet is carried as Ethernet traffic but it is NOT marked as an IP packet. This makes for a very problematic situation when it comes to interfacing. The only way these days to detect and receive the packets is by setting your Ethernet card in "promiscuous" mode...receive all packets and pick off the Synet ones. For that reason, lots of companies have installed various "translators". In contrast, AB PLC-5 Ethernet is much easier. It uses a slight variation on their serial protocol and transports data in regular TCP/IP packets. 4. Synet and AB Ethernet cabling used to use coaxial "thin" Ethernet. It is virtually impossible to find Ethernet cards supporting it these days. Fortunately for AB, they used an "AEUI" which is a standard interface where you can plug in adapters for "thin" or twisted pair CAT-5 RJ-45 connectors. The newer AB PLC 5 processors come with only an RJ-45 for CAT-5 connections (and support 100 Mbps fast Ethernet). 5. The I/O hardware on both sides is to put it politely, highly proprietary. You can get various adapters to go to other standards such as the ubiquitous Modbus. You may find yourself in a situation where you are still trying to support the old processor for a period of time as an I/O adapter until you can phase out all the old stuff.

[Crossbow 297]

The same topic was posted on the Other PLCs section, and I replied quickly over there. Posting the same message in a bunch of places is not likely to get you any more answers.