Two DH+ networks

digitalfist · Mar 23, 2005

Ive got two seperate DH+ networks in two seperate plants. I would like to keep them seperate but be able to access the two networks from either plant. (approx. 200 feet from each other) I have a PLC5-40 with channel 1 and channel 2. Can I have the two DH+ networks tie into this processor and would i be able to access both networks thru this processor.

Thanks

Ken Roach · Mar 23, 2005

The simple answer is no. The PLC-5 controller does not bridge between DH+ networks.

You can do this very easily with ControlLogix network bridge modules. A 4-slot chassis, a power supply, one 1756-ENBT and one 1756-DHRIO will provide you an Ethernet to 2 x DH+ network bridge that can be easily navigated by RSLinx.

Unregistered · Mar 24, 2005

What do you mean by "access"? If you want to use a PC to monitor or program either channel then a dual-channel KTX card would fit the bill.

Ken Moore · Mar 24, 2005

I vote for Ken Roach's solution. Once the bridge is in place you could also send/resieve messages between processors on different networks. Plus IMHO the CLX bridge would be more robust, I wouldn't want to depend on a PC.

BUT, if you did want to hook up a PC you could do so with the ethernet connection and not have to purchase any additional hardware.

Ken

rsdoran · Mar 24, 2005

Kens approach is expensive, some of us have a hard time getting management to open the wallet.

The simple solution is to combine the 2 DH+ networks.
The next simple solution was mentioned, either a dual channel or 2 KYX card(s).

Ken Moore · Mar 24, 2005

Depending on the number of nodes on each network, you may or may not be able to combine them, at best you will have a performance loss. DH+ uses token ring protocol, so each node has to wait on the token. The more nodes on the system the longer the wait.

Ron,
I'm familiar with the tight wallets of management, a lot if times it's hard to get the funds for the best solution, instead you can get the money for a half-a$$ed one, and then management complains about the results.

What I would do is price out all the options listed, along with the pros and cons of each option, and then let someone higher up the food chain decide which way to go.

Just my $1.0298

Ken

davidg68124 · Mar 24, 2005

Both Kens are absolutely right here.

Combining both networks will almost always cause unintended consequences. Not to mention having to reconfigure duplicate nodes and panelviews, ect.

a dual channel KTX or 2 KTX cards will be expensive unless you have some lying around. Ken mentioned the other day they are around $1700 if I remember correctly.

The Rack/ENBT/DHRIO/Power Supply may be a little more than the KTX card, but it will be infinitely more usable in the long run.

I have just such an animal in a couple of plants. They work great for the application.

David

Tester · Mar 24, 2005

If you need to only monitor PLC programs, another cheap solution is to use an A/B switch box to physically switch between the 2 networks. Sounds scary but I saw it done at a plant where they had a 5-way switch box that switches between 5 different DH+ networks. It works reliably for their maintenance guys and for myself as well as far as doing online programming.
KTX is inexpensive (ebay ~$70) but you need a pc with an ISA slot. PKTX can run from $200-700 on ebay depending on whether it's new or old.
I've been in alot of plants that have tight budget and can understand finding the least costly solution JUST to get the job done.

Operaghost · Mar 24, 2005

Well, concerning the original question,

"would i be able to access both networks thru this processor"

Possibly. If your processor has channel 1A and channel 2A configured for DH+ then you can use the two round mini-din style connectors. Plug into the lower one and you can view the network connected to channel 1A. Plug into the upper one and you can view the network connected to 2A.

As mentioned, there is no bridging. You must physically plug into the proper port to see that network. You will not see the other network without first disconnecting (short of using two comm cards in your pc).

OG

digitalfist · Mar 24, 2005

Thank you for your replies;

I thought I may of been able to access the second network from a built in bridge in the processor but it seems like i need a seperate bridging card. I will need to look into all my otions.

I would like to leave my options open as far as sending data from one network to the other. The reason why there is two networks is because our plant installed our network a few years earlier than the other plant and the two plants have there own managers who do not communicate what so ever. An electrician got fired in the other plant and we didnt know about it for 6 months.

If anyone has any other idea's I would love to hear them before I take a crowbar to the company wallet.

rsdoran · Mar 24, 2005

Looks like this will bridge the 2 networks but not sure you could program across the 2 networks.
http://www.woodhead.com/data/current2164/exlink.pdf

They also have interface cards:
http://www.woodhead.com/products/automation/networkinterface/nic/datahighway/

The dual KTX cards list at the AB store for $3000 which probably can be discounted if you are a major AB user.

I know you can do pass thru from Ethernet to DH485, can it be done with DH485+ too? If so could both networks be put on ENET and bridged that way?

I doubt any of these options will be cheap though and Ken Roach probably offered the best option.

Oakley · Mar 25, 2005

If you are looking at being able to pass data between the two networks, then I'd go with the ControlLogix based gateway setup. I have used this in the past (and currently), and it works wonderfully. Put a ENBT in the chassis, and a DHRIO module (or 2 if you are running high speeds). The ENBT would allow for TCP/IP connectivity from your lan, and you could program both highways from any location (without KTX or PCMK) card in your computers. This also allows for an easier HMI management (in my humble opinion).

Two DH+ networks

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