Industrial Networks - Explanation needed

[jb35sport 0]

Okay, I've been trying to brush up on my PLC programming skills and trying to familiarize myself with each of the AB PLC lines and the various processors (communication options). I've googled the subject, yet I'm still left with some confusion..... It seems there is 4 primary means of communication to a)program a PLC via RSLogix500 and/or b) connect the PLC to a network. ~ RS232 ~ DH485 ~ DH+ ~ Ethernet If that's true, I have some confusion and I apologize in advance for the ignorant questions. The Ethernet protocol is pretty straight forward, but if somebody could enlighten me about the other 3, I'd appreciate it. What I've learned is, RS232 is full duplex, peer to peer, used over shorter distances, more prone to interference. DH485 can have 32 nodes of equipment on the network, less prone to noise, can travel longer distances. DH+ is half duplex, 64 nodes of equipment??, even longer distance than DH485. My understanding is DH485 and DH+ are both AB protocols. My REAL SOURCE of confusion is the physical CONNECTORS used for each protocol...... It seems the RS232 and DH485 all utilize the 9 pin (DB9) connectors? So if using an older laptop w a serial port, the interface cable plugs right in. The round barrel connector on the Micrologix is considered a RS232, correct? Are all DH+ networks supported with the 'blue hose', twisted pair connections? I apologize for the sloppy post and array of questions, but without getting too technical, I just want an easy means to identify a network of RS232, DH485, and/or DH+ simply by recognizing the CONNECTORS being used...... Thanks to all that read the post.

[Guest]

this isn't meant to discourage you – but your quest is an impossible one ... consider these examples: the 9-pin connector on the front of an AB PLC-5/15 or a PLC-5/25 processor certainly LOOKS like an RS232 connection – but the only thing that you can run through that port is DH+ (Data Highway Plus) ... specifically, it will NOT handle RS232 ... the PLC-5/20 (even with a lower model number) is "newer" than the PLC-5/25 – and the PLC-5/20 has a 25-pin port which CAN be used for RS232 ... the PLC-5/20E ("E" for Ethernet) has a 15-pin port for an Ethernet connection – but you have to use something like a "transceiver" to convert the connection to an RJ-45 connector ... -------------------------------------------------------------------------- the SLC-5/05 has an RJ-45 type connector for Ethernet connections ... but ... the older SLC-5/03, SLC-5/02, SLC-5/01, and the much older SLC-500 "brick" all have the same physical RJ-45 type connector – but those ports can only be used for DH-485 ... specifically, you can NOT connect Ethernet to the ports on the front of those processors ... damage to your computer's Ethernet port will usually result ... -------------------------------------------------------------------------- suggestion: here's what I would do if I were you ... start a scrapbook ... print out a page for each of the different pieces of equipment that you run into – and make written notes on the pages of how the ports are set up ... use a separate page for each type of equipment (paper is cheap compared to time) ... you'll soon find that SOME of those ports are RECONFIGURABLE (with DIP switches and/or software settings) and "extra" pages might be required ... here are a few example pages to get you started ... ------------------------------------------------------------ see pages 1-3 thru 1-8 in this manual for PLC-5 enhanced models: http://literature.rockwellautomation.com/idc/groups/literature/documents/um/1785-um012_-en-p.pdf ------------------------------------------------------------ see page 5-2 in this manual for PLC-5 classic models: http://literature.rockwellautomation.com/idc/groups/literature/documents/um/1785-um001_-en-p.pdf ------------------------------------------------------------ see pages 81 thru 93 in this manual for SLC systems: http://literature.rockwellautomation.com/idc/groups/literature/documents/um/1747-um011_-en-p.pdf ------------------------------------------------------------ good luck with your project ... and always remember: if this were an "easy" job then ANYONE could do it ... Edited 3 Oct 2013 by Ron Beaufort

[jb35sport 0]

Thanks so much Ron. I guess the reason I was still confused is simply because there isn't a clear cut answer it appears. I like the idea of starting a scrapbook to provide notes for communications, protocols, processor types. Thanks again for the response!

[rswolff 9]

my recommendation would be to do a little research first in the difference between a hardware specification (rs232) and a software protocol (TCP/IP)......once you understand the difference then do some research on what hardware specifications are used for what.....and what protocols are used for what.....then you'll be able to determine what where and why a differential RS485 serial connection can be pushed further than an RS232 connection......even if they are transporting information using identical s/w protocols......then you can ask some questions pertaining to something more specific....... bob