Need to network 40 SLC 5/03's

[gbeaker]

Hi,

I need to network 40 DH485 SLC's for a scada project. I would like to keep the costs down since I will be replacing the processors in a few years.

So far the options I've come up with are:

DH485 -> Ethernet converter for every processor
-too expensive

Serial -> Ethernet converter for every processor (generic Ebay)
-price is right
-never used one before, might be a pain in the a$$

DH485 network with a single Ethernet converter
-Lots of blue hose to run, will be redundant with switching to ethernet processors in the future

Any thoughts?

Thanks

 

[Aabeck]

...Serial -> Ethernet converter for every processor (generic Ebay)
-price is right
-never used one before, might be a pain in the a$$...

I have used Ethernet serial ports a few times & find them very reliable - I even carry one around with my laptop that doesn't have a serial port, a lot better than putting up with a USB/Serial port.

And if you ever do change to Ethernet CPU's the cables are there.

 

[geniusintraining]

I would like to keep the costs down since I will be replacing the processors in a few years.

Push for the upgrade early?

Or 1761-NET-ENI 550.00 each

I have tried the ebay ethernet and yes they are a pain but 40 of them and the cost saving it maybe worth it...

 

[Ken Roach]

Option 3 would be molasses slow and would require at least two networks because DH485 only handles 32 nodes.

Common drawbacks of no-name Ethernet/Serial devices are that they aren't optimized for short packets like are used by DF1 or Modbus, and that their mode of operation is generally to provide a virtual Serial Port.

When you have a device like the 1761-NET-ENI or Digi One IAP or the Lantronix DR2-IAP, it's aware of DF1 protocol and doesn't waste time trying to time out and forward two-byte ACK packets. And it converts EtherNet/IP to DF1 natively, which lets you set up one EtherNet/IP driver in RSLinx (or your favorite comms software) instead of 40 separate COM port drivers.

If it were my system, I'd start with Qty. 1 of whatever Ethernet/Serial device you want to use.

 

[gbeaker]

Speed isn't much of an issue right now - remote programming would be ideal but I can save that for ethernet.

I could get by with 32 nodes until upgrade time, would dh485 still be too slow? I am only collecting a few bits and integers every 5 minutes from each processor.

Or are we in agreement that ethernet to serial is the way to go?

I'd rather not run Rslinx on the server, can Kepware or similar OPC server handle the dh485 and/or serial/ethernet network?

What would you guys do?

 

[OkiePC]

Speed isn't much of an issue right now - remote programming would be ideal but I can save that for ethernet.

I could get by with 32 nodes until upgrade time, would dh485 still be too slow? I am only collecting a few bits and integers every 5 minutes from each processor.

Or are we in agreement that ethernet to serial is the way to go?

I'd rather not run Rslinx on the server, can Kepware or similar OPC server handle the dh485 and/or serial/ethernet network?

What would you guys do?

If you use the NET-ENI or Digi One IAP, (serial to ethernet) I think you will find that it will work just fine with Kepware, although I have not used that particular combination. I find the Digi to be better than the Net-Eni in performance, price, and has a smaller panel footprint. It also has two serial ports. I have not used any 3rd party drivers for DH485 ... except for those in Red Lion HMIs and they are also just fine. That is another possibility I suppose, split your network with Red Lion gear and use that as a DH485 data concentrator.

If you stick with DH485, it will be terribly slow, but if the polling is as slow as you stated, that might be acceptable in your application. The largest DH485 network I had to deal with was about 12 nodes and it was faster to carry my laptop up the ladder to the catwalk and 100 feet down to plug into the serial port directly rather than wait on the DH485 network when it came time to do any serious programming. With 7 nodes it was acceptable even for uploading and downloading. Once I was offline and the nodes were just doing infrequent messaging, it was just fine. With 32 nodes, I think you may be able to pull it off, just don't expect to use RSLogix 500 over that network for programming them.

What sort of segment lengths are you looking at between nodes?

Do you have the "plumbing" done already?

If not, it might be wise to plan the final Ethernet network and design so that you can pull cables for both types of network all at once so if you hit a bottleneck at say, 20 nodes, you can split it there, stick a protocol converter in and access the rest of it over Ethernet. When you get ready to start switching over to modern processors, the Ethernet cabling will already be there.

 

[Paullys50]

I would go with the 1761-NET-ENI, simply because the network cabling and IP addressing will all be setup and compatible for the future processor upgrades. Years ago we would use the 1761-NET-ENI on 5/04's where the DH+ network was used for PLC-PLC comms and the ENI used for the local PanelView comms. So from a reliability standpoint, you can be pretty confident that you won't have problems.

But if it's too expensive, shelve the project until the processors can be upgraded. If you are only collecting data every five minutes, it certainly doesn't seem like it will justify a high investment.

Why no love for RSLinx? It's an OPC server and RSLinx Gateway is meant to serve up data at the server level.

 

[padees]

End of life has been announced for the 1761-NET-ENI and the price of $959.40 reflects that. Ouch!!!

 

[OkiePC]

End of life has been announced for the 1761-NET-ENI and the price of $959.40 reflects that. Ouch!!!

All the more reason to use its cousin:

http://store.digi.com/index.cfm?fuseaction=product.display&Product_ID=202

http://www.digikey.com/product-detail/en/70001777/602-1498-ND/5248084?WT.z_cid=ref_neda_dkc_buynow

 

[rguimond]

If you only need a few bits and integers and you have spare slots in your racks, you could use multi-conductor cable and a "BCD" coding system by hard-wiring outputs from one PLC to inputs of another. You will have to run cable to make a DH-485 network, so running a single 16+ multi-conductor cable shouldn't be a huge problem.

There are different ways to transmit the data, but I would set up a routine on each plc to convert integers to physical outputs in a pre-determined sequence, with a particular value to indicate to the PLC receiving the data where the "start" is.

For instance, if I wanted to end the integer stored in N7:0, I would copy the contents of N7:0 to O:x.0 (x=location of output card). The 16 outputs will represent the value stored in N7:0. The outputs are directly wired to an input card in another PLC that reads the data. I wouldn't bother with handshaking, as it would be fairly safe to assume the data was "transmitted" correctly. The "start" indication could be a particular value, or a particular value latched in for a particular time. Once the cycle is complete, start over.

I think I would install a few ethernet-ready PLC, like a Micrologix 1400, to "gather" the data using multiple 16 or 32-point input cards. Just use your SCADA system to poll the ML1400's.

Another alternative would be to daisy-chain from one PLC to another, accumulating data as you progress down the chain. The last PLC would have the data from all the others. No MSG instructions required.

I bet you could accomplish this for <$12,000 USD and it would be bullet-proof. The draw-back would be that it would require some programming changes.

If you think this is feasible, PM me and I'll send a sketch

 

[Firejo]

One thing to consider when converting Ethernet to serial using a device like the NET-ENI is that these devices are typically limited in the number of Ethernet connections they will accept. If all 40 of your 5/03’s are going to be connected (at the application level) to one or two host PLC’s, HMI’s, etc… then probably not an issue but if you need multiple PLC’s talking to multiple PLC’s you might run into problems.
This device is another option. One thing nice about it is it’s a pretty simple device and if you’re not going to be doing messaging from DF1 to Ethernet then all you have to do is give it an IP address and set it up to be an EtherNet to DF1 bridge. Having said that if you do need to message from the DF1 side then all that you need to do is setup the node table (just like the NET-ENI). This device will accept 10 connections.
http://www.data-linc.com/custom.htm

 

[gbeaker]

What about a new approach? What is the cheapest ethernet PLC on the market? Maybe I can add an ethernet PLC to each cabinet and transfer my data to it using the slc 503 rs232 port or BCD using i/o. Then I network all of the cheap PLCs for my scada system.

 

[rguimond]

You can get surplus Micrologix 1100s for about $660 CAD each. Cheaper to buy a few, add digitial I/O and run multi-conductor cables, IMO.

 

[rguimond]

I'm not vouching for these, but check it out:

http://www.triplc.com/ezw1616.htm

 

[GaryS]

For a DH485 network you are fast running out of options as stated they have reached their end of life cycle. And nothing you can use will be cheep.

Note: The DH485 network does not use the Blue Hose Cable for the connections it requires a 4 conductor + shield cable. The Blue Hose is used on Data Highway, Data Highway Plus and Remote I/O.

My first choice would be to split the 40 SLC 5/03's into 2 DH485 networks 21 nodes per network
[20 SLC's plus the HMI on each network]
You will need a 1747-AIC and cable for each SLC and a 1747-KF for each network
Both are still available on Ebay and other online sources Rockwell may even still have some available.
Set up the HMI to use 2 posts each connected to one of the 1747-KE module (Separate DH485 networks)
Then configure the OPC Servers to communicate with the SLC's.

The other option would be to use a Ethernet to RS232 converter for each SLC 5/03
You could connect all the SLC's on the same network but remember each SLC will appear as a separate comport in the HMI if it will support that many com ports
Then configure the OPC Server to communicate to each port
You may be able to RSLinx Pro to communicate with everything

It would depend on the ability of the HMI to communicate to multiple comports at the same time

From a cost standpoint it's about a wash when you add up all the costs
You are still looking at about $10,000 till your done