A-D networking choices

tommy23t · Aug 3, 2004

Hi all:

I have a project looming where I have to network 8 DL06 plcs with eztouch 6" screens and 10 DL06 with no screens attached. We would be using this for data collection, not real time processing so speed is not an issue. In looking at the DA-NET manual, I think I could do a multi-drop with RS485.
We will be using a pc to track this, and although I have DSDATA on
another application there, I would like to move to Dataworx, as it seems to do what I need so far as the actual data collection.

What is the best way to approach this?

A multidrop for all with the master using a H0 ECOM, a dedicated master, or a touch screen central to the system with an ethernet card to the pc and RS485 to the plcs? I thought about using the H0 ECOM modules in each, but I think the cost would be prohibitive.

Thanks for any opinions.
tommy23t

Peter Nachtwey · Aug 3, 2004

tommy23t said:
I thought about using the H0 ECOM modules in each,

Excellent.

tommy23t said:
but I think the cost would be prohibitive.

The cost isn't that much compared to the benefits. Just think, you will be able to program all the plcs from one place. The PLC programming will go faster due to faster response and downloads.
Once you get used to programming via Ethernet you will be spoiled.

elevmike · Aug 3, 2004

I tend to agree with Peter. Ethernet will cost more up front, and will require a slot in each PLC but there are long term paybacks that may outweigh the initial costs.

ArikBY · Aug 3, 2004

I will join to Peter and Mike and recomend the E-Com.
The speed is big benefite and compensate for the missing of on line edits.

Tom Jenkins · Aug 4, 2004

I'm not saying ethernet isn't good, but I've had success on similar networks using RS-485 serial communications. It is generally more noise immune than ehternet, and if you use Modbus communications, which AutomationDirect.com supports, you have an unlimited variety of devices that can hook into the network. Ethernet, on the other hand, is not usually transportable across a lot of different manufacturers.

Peter Nachtwey · Aug 4, 2004

yeah, but

Tom Jenkins said:
I'm not saying ethernet isn't good, but I've had success on similar networks using RS-485 serial communications. It is generally more noise immune than ehternet,

Perhaps if the RS-485 is using shielded twisted pairs it may be more noise immune. The question I have is that AD doesn't really advertise RS-485. They speficify RS-422. At least they do on my DL250. Our customers use Ethernet as the main method of communicating between PLC and motion controllers. I have heard of no cases where Etherent noise is a problem and there have been thousands installed. Our customers that use AD use Ethernet over Modbus almost all of the time. There may have been a system or two that used Modbus.

Tom Jenkins said:
and if you use Modbus communications, which AutomationDirect.com supports, you have an unlimited variety of devices that can hook into the network. Ethernet, on the other hand, is not usually transportable across a lot of different manufacturers. [/B]

Nothing prevents one from using the RS-232/422 port on the PLC for field devices. That big serial connector is now free for field devices. As Ken said in another thread, there is a practical limit to how many devices one can put on RS-485. I believe Rs-422 is limited to 10.

icky812 · Aug 4, 2004

Not to be a wet blanket, but RS-485 will not work except with MODBUS RTU protocol out of port 2 on the DL06. Somehow, this important fact was missed in the manual. The next revision of the manual will contain it.

I tend to agree that if speed isn't the issue, that the H0-ECOM might be the best way. However, ethernet can bottleneck with large quantities of data.

If you are dead set on serial, please spend the extra few cents a foot and go with RS-422. You will be much happier with the way it performs.

Just like everything else there is a theoretical limit and a practical limit to everything. RS-422 can handle up to about 28 devices before you need to install a signal booster. For more information see B & B Electronics they are specialists in RS-422 and RS-485 devices.

elevmike · Aug 4, 2004

Dash is using AD DL-06 which has an RS-485 configuration for the 2nd port. In such a large project (18 PLCs) I would be very tempted to go E-net, and leave the second port available for HMI, future expansion etc..

Just my two cents...again.

icky812 · Aug 4, 2004

Uhm, I am sure that RS-485 will not work on port 2 of a DL06 unless he uses MODBUS protocol. I would know if something was changed with that regard...

I don't know of anyone getting it to work with any other protocol and I did a fair amount of research to verifiy that it wouldn't.

Tom Jenkins · Aug 4, 2004

icky - there is a posting on the AutomationDirect.com forum site confimring what you are saying. However, if you use the RS232 and 232/485 converter I think you are OK. Check their site.

A lot of the old ADC documentation used RS-422 and RS-485 interchangeably or incorrectly. The port really is RS-485.

bernie_carlton · Aug 4, 2004

Tom - are you saying that port 2 on the DL06 is incapable of operating as RS422 even though the transmit pair pins are seperate from the receive pair pins? It seems like, wired in the RS422 manner - 2 wires for transmit - 2 wires for receive - that DirectNet could operate. Just as a note - I've done RS422 DirectNet with the 405 but not the 06.

icky812 · Aug 4, 2004

A new avatar perhaps will clear things up...

Yes, using it with a FA-ISOCON or FA-ISONET will work with RS-485. The port by itself will not work with RS-485 unless using MODBUS protocol.

And again you are correct that in the past ADC used RS-422/485 interchangeably. They are striving to distinguish between the two now. There are differences. RS-422 is considerably more noise resistant than RS-485, at least with ADC equipment.

Bernie, RS-422 works fine with all ADC PLCs that support it with any protocol. RS-485 on the DL-06 and the DL-260 processor is only for MODBUS RTU.

elevmike · Aug 4, 2004

So icky, I'm assuming that your a member of the AD support staff??? If so, what's you thoughts on the Origional question? E-com or serial?

Nevermind I see that you already answered that.....

icky812 · Aug 4, 2004

I am pretty sure that I have talked to you on the phone elevmike. I know that I have talked to Bernie Carlton and Tom Jenkins many times.

For those in the Denver area that will be attending the Profibus Trade Organization seminar next week (8/11/04), stop by and say hi.

tommy23t · Aug 4, 2004

Thanks for everyone's input. Since I am NOT a communications guru and don't need any more grey hairs, I will recommend the ethernet. I'll let you know how I make out.

-Tom beerchug

A-D networking choices

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