Need helo communicating to compactlogix by ethernet

[teal854t 0]

Hi, I tried connecting to compactlogix by ethernet (Rj45 cable) and could not get it online. I could go online by using serial cable. Need instruction on how to go online with ethernet cable. How can I find out IP address and so on. I also have 1747 UIC and couldn't go on line with it either. Instruction said to change DF1 to DH485. How can I do that? Thanks Edited 21 Mar 2009 by teal854t

[BobLfoot 301]

If you go online with the serial cable logix should show you the PLC IP address if it set. Do you understand ethernet well enough to know when to use a straight cable and when to use a cross over? Also are familiar enough with your PC OS to manipulate your PC IP Address? When you respond to the above we can go further.

[teal854t 0]

I went on line with serial cable and looked at IP address for PLC and showed 4 sets of numbers. I then went to my PC to set IP address to same IP address as PLC or change the last nember? I'm not sure about cross over cable. Can I buy cross over adapter at Radio Shack or make it myself?

[BobLfoot 301]

OK - I am going to draft my responses assuming you know little to nothing about ethernet, apologies for any unintentional insults to your intellegence. I'll probably throw in more definition than you need, but later it may be helpful. 1. The IP address you pulled from the PLC was most likely in an IPV4 format. In other words there were 4 sets of numbers referred to as A.B.C.D. Valid values for A-D are 0 thru 255 with 0.0.0.0 and 255.255.255.255 being reserved special addresses. There are several other special addresses, for example anything ending with 255 for example A.B.C.255. We won't dwell on these. 2. Once you know your PLC IP you need to make sure that your PC IP is in the same grouping or subnet. The Subnet Mask looks something like one of the three following usually {255.255.255.0 ; 255.255.0.0 ; 255.0.0.0}. The subnet defines the address class. Class A uses 255.0.0.0 while Class B uses 255.255.0.0 while class C uses 255.255.255.0. 3. Subnet Masks are actually used as follows we'll take the example of the addresses 1.1.1.1, 1.1.1.2 and 1.1.2.1 with subnet Mask 255.255.255.0. We line them up in binary representation as follows: 1st address 00000001 . 00000001 . 00000001 . 00000001 2nd address 00000001 . 00000001 . 00000001 . 00000010 subnet mask 11111111 . 11111111 . 11111111 . 00000000 the first address and second address must be identical for each 1 in the subnet mask, thus 1.1.1.1 and 1.1.1.2 can communicate freely. Now lets look at 1.1.1.1 and 1.1.2.1 in the same manner: 1st address 00000001 . 00000001 . 00000001 . 00000001 3rd address 00000001 . 00000001 . 00000010 . 00000001 subnet mask 11111111 . 11111111 . 11111111 . 00000000 The first and third cannot communicate directly because the C section of the address has a 1 in the subnet where the first address is 0 and the 3rd address is 1. 4. So set your PC to any address in the same subnet as the PLC. for example if the PLC is 192.168.2.100 then your PC could be 192.168.2.101 and work. 5. Now as to cabling. The ethernet cable consists of 4 pairs of wires and they are colored coded. They come in two forms straight-thru and cross-over. If you are using a hub, switch or router between your PC and PLC then you need a straight-thru. If you plug the cable direct between the PLC and PC then you use a cross-over. The easiest way to tell one cable from the other is to lay the ends side by side. If looking left to right the wire colors pair up in perfect order it is a straight thru cable. If the colors flip-flop then it is a cross-over. The average cable sold at wally world or rip off shack is a straight-thru unless it was labelled cross-over. I recommend any automation tech worth his salt own 1 of each. Hope this starts to help. B.T.W. - Was the PLC set for static or dynamic IP. I recommend static therefore it will not change without you chaning it in the PLC with Logix. Hope this helps some more. P.S. - If you are using a switch on a corporate lan make sure you check with your IT people and get given the addresses to use. Changing your IP on your PC or test PLC can stop something else from working if you don't know what you are doing.

[paulengr 44]

In addition, it becomes much easier to simply buy a switch. Do NOT buy hubs. Even a cheap <$50 switch from Walmart will work just fine. If it supports Auto MDI/MDX (the switch will say this in the technical details), then it doesn't matter if you have a normal or crossover cable because the switch will automatically handle this for you. If you want a brand name, Linksys is owned by Cisco. Their stuff is not what I'd consider "industrial grade" but it is ideal as test equipment for your desk/bench until you understand networking well enough to buy a managed switch. If you are using a switch the easiest way to gaurantee that you will not cause problems with the LAN is to NOT connect it to the plant LAN. Leave your PLC and PC isolated. If you do want to connect them, then talk to IT about what the settings for the equipment should be. Note that the PLC MUST be configured with a static address. The general rule with PLC's is to always use static IP addresses at least for the PLC's themselves.

[MikeC44 0]

I need to build a small control using a DoMore BRX computer that can send and receive messages to a AB Compactlogix plc.  Im not sure what protocol the AB uses, the DoMore uses Modbuss.tcp.

[NevergoldMel 38]

THe Micrologix 1400 (latest models only) are the only AB PLC's to support MudbusTCP. The Compactlogix uses CIP protocol over ethernet. 
I expect you will not be able to do this without using a device in between, like a Red Lion DSP or the aforementioned Micrologix 1400 [which could do the whole lob itself].