Networking Solution

[manav 0]

I have a pre sales enqiuiry from a client requiring networking on existing PLCs: 1. PLC-2/17 - 1No. - DH+ port 2. PLC-5/30 - 1No. - DH+ port / RS232 port 3. SLC-5/03 - 1No. - DH485 port / RS232 port I usually work with Micrologix or CLX series. Done one odd project ages ago on SLC/PLC5. The client wishes to give information from these 3 controllers to a yokogawa DCS on modbus serial. My understanding of configuration regarding communication details is given above. What optimal solution can I offer the client?

[rpraveenkum 5]

Replace SLC 5/03 with 5/04 network all in DH+ Or use any of these converters from DF1 to DH+ http://www.abgateways.com/product_dl3500_dhplus_df1.html or DH485 to DH+ http://www.abgateways.com/product_dl3500_dh-485_df1.html Network in DH+ network

[manav 0]

Thanks. What about getting the data from DH+ to modbus serial? I can goto modbus serial thru Flex or Microlgx. I have to offer a Modbus RTU Slave to the DCS. Any converter / messaging solution to get data on Flex or uLgx from DH+. Any other direct slave converter from DH+ to modbus??

[BobLfoot 301]

Not possibly the cost optimal solution, but for longevity I like what I am about to propose. Add a 1756-A7 chassis with 1756-PA72 power supply. Use a 1756-DHRIO to reach the PLC2/17 and PLC 5/30 for now. Use a 1756-ENBT or 1756-EN2T to reach the 1756-LXX Cpu for programming. Add a 1761-Net-ENI to the SLC5/03 to put it on Ethernet. Use the built in serial port of the Processor to reach the Yoko DCS with modbus serial. Later on you could come back and repalce the PLC2/17 with a 1771-ACN15 and the PLC 5/30 with a 1771-ACN15 and add a1756-CNBto your CLGX rack and port all code from PLC2/5 to controllogix. They'd have the faster procesor and no change in I/O Hardware. Kind of depends on how forward looking this client is.

[manav 0]

Yep sounds good. A cleaner solution I am looking at right now is to replace 5/03 with 5/04 and take all 3 devices on DH+ into CLX and use its serial port or prosoft module to act as RTU slave on modbus. I am sceptical of 1771-ACN15 as I have used them and the data gathering has limitations and reliability is not good. Being a burner management process being involved which is extremely safety critical, I would not put the PLC I/O on a network. Any cheaper solution than this though? Remember, even if the modbus link fails, no problem as only data gathering will be affected, so a cost optimal solution can be looked at. Application is only safety critical at the I/O level. Edited 12 Dec 2006 by manav

[rpraveenkum 5]

no need for clx network the PLC2 & PLC5 in DH+ place MCM prosoft in PLC5 rack & SLC take Data to dCS Note:- Collect PLC2 data in PLC5

[BobLfoot 301]

Yep sounds good. A cleaner solution I am looking at right now is to replace 5/03 with 5/04 and take all 3 devices on DH+ into CLX and use its serial port or prosoft module to act as RTU slave on modbus. I am sceptical of 1771-ACN15 as I have used them and the data gathering has limitations and reliability is not good. Being a burner management process being involved which is extremely safety critical, I would not put the PLC I/O on a network. Any cheaper solution than this though? Remember, even if the modbus link fails, no problem as only data gathering will be affected, so a cost optimal solution can be looked at. Application is only safety critical at the I/O level. You miss my point. The proposal was a two stage implementaton. Stage 1 - Use the DH+ and NET-ENI for data gathering. Stage 2 - Replace the PLC2 and PLC 5 with ControlNet. If your burner app is implemented like we do here in the US then each burner has a stand alone controller which takes all the safety function and the PLC is only to coordinate multiple burners. IF you are concerned you could use the 1771-ACNR15 and the 1756-CNBR which is dual coax and automatic swap from primary to secondary comm path in event of ailure. As far as cheaper do you have the memory space in the PLC5/30 to pass data from the PLC2/17. IF you do the use a layered approach. PLC 2 and PLC5 connect by DH+, PLC5 and SLC connect by DH-485 from their serial ports. Use a Micrologix with two serial ports. On to reach the SLC and PLC5 and th other to do the modbus rtu.

[rpraveenkum 5]

I hope customer won't like to replace existing setup you can use above option for your network it will be cost effective

[paulengr 44]

Option #1: There's some Modbus code floating around to talk Modbus through the serial port on a SLC. It was written by AB engineers. It's not pretty but it works. It is easily modified to work on a PLC-5. Option #2: Buy Digi One IAP cards. At $650 each, this is very inexpensive. These are protocol converters. They can do Modbus RTU, ASCII, or TCP, and DF-1 as a minimum. I'm not sure if they support DH-485 or not. You get 2 serial ports per card. In addition, it has an Ethernet port and it is easy to set up the PLC's to talk Ethernet even if they are originally RS-232 only. Option #3: Don't bother with the Contrologix CPU (no need). You can already talk across the backplane of the Contrologix system (it appears as a gateway on DH-485 & DH+ networks). That is a possible future upgrade option. Option #4: Buy a KF-2 box. This can bridge DH+ and DH-485 networks. It is about half the price of the Contrologix solution (but still outrageously expensive). Poll the other two PLC's from the SLC and then use the RS-232 port on it to link up to the DCS. Frankly, I like Option #2. It is relatively inexpensive and the most flexible. If you bring in a CLX backplane, somebody still has to set it up. I looked at virtually the same problem before in my plant and the CLX option is a money pit until you get a chance to upgrade processors. Replacing it all with Contrologix is a $20K solution ($10K just for the hardware, and another $10K for the software). Is their budget going to support something like that? By the way, AB has moved the price points on virtually all their SLC and PLC-5 processors up into the $5K-$10K range. They are "obsoleting" them the same way they did with the PLC-2 and PLC-3....make it so cost prohibitive that nobody will buy another one unless they are desparate.

[manav 0]

Thanks mates. There seem to be a lot of scenarios to find a solution in. Lots of options to explore and discuss with client. Just one concern, since I have mostly worked on CLX / uLgx and Enet,Cnet,Dnet, I am not confident about messaging between SLC / PLC and that too over DH485/DH+. What is the learning curve for this and how good is the support / reliability from RA for this? How complicated is the messaging process itself? I still prefer the DH+ gateway in CLX chassis as that would be easy to implement and I have coordinated a project using the gateway in the past. The 1771-ACNR15 I used to read the PLC5 I/Os had limitations in reading analog modules. In some cases only half the rack could be read. I was already using CNBR and ACNR for media redundancy. Since that client soon after upgraded the complete PLC5 system to CLX including I/Os the issue did not become critical for us. But at an implementation level I am still skeptical of 1771 I/Os read by CLX on CNet. Can I go thru a gateway on the CLX chassis (without CLX processor) directly from MicroLgx 1100 on ENet? I can then use the Serial port on the 1100 to act as modbus RTU slave. But will this be possible? I have heard a few horror stories in the forum regarding 1100 ENet messaging. Edited 12 Dec 2006 by manav

[rpraveenkum 5]

Don't go another messaging(Enet) Use MVI(prosoft) In clx chassis it has extended feature then mL1100 DHRIO not realy strong on messaging over DH+ , with PLC5 concern bit strong on messaging over DH+

[manav 0]

But for MVI module can I get data from the gateway into MVI module directly or do I have to use a CLX processor to for a link between the 2?

[rpraveenkum 5]

see this reply No need for CLX, network the PLC2 & PLC5 in DH+ place MCM or MVI prosoft in PLC5 rack & SLC take Data to dCS gate way directly Note:- Collect PLC2 data in PLC5

[manav 0]

Can I put a prosoft module in the PLC2 rack? Or do I have to message between PLC & PLC5 on DH+? I dont have the rack details with me so the existing racks might not have spare slot for the prosoft module.

[rpraveenkum 5]

you have to message between Plc 2 & plc 5 you can place the prosoft module in remote chassis also No prosoft module avaliable for PLC2

[manav 0]

Thanks mate. Good to go ahead now with various options.

[BobLfoot 301]

I've done several PLC 2 and PLC 5 conversions to ControlNet and ControlLogix. When the IO is strictly digital it works great and has proven quite reliable. When the application involves analog we've switched from ControlNet to DHRIO {remote IO at 230K} for that rack and run dual network topology. Have two of these sytems going as well with none of the CNET 1771 Analog issues AB reported. Just for the record.

[rpraveenkum 5]

Note this points when go Clx configuration on Cnet RSLogix 5000 version 2.51 also adds support for 1771-series discrete I/O using the 1771-ACN®15 series B, revision G. There is no support for 1771-series analog/block transfer modules RSLogix 5000 version 10.0 added support for ControlNet-based "block transfers" using the MSG instruction's Block Transfer Read and Block Transfer Write Message Types. RSLogix 5000 does not support SLC-500 family I/O on ControlNet using the 1747-ACNR15 adapter, nor does it support 1769-series I/O on ControlNet since there is no 1769-series ControlNet adapter. http://rockwellautomation.custhelp.com/cgi...amp;p_topview=1

[JesperMP 2]

Does this Yokogawa DCS only support Modbus ? Maybe it supports OPC. If this is the case, it will be trivial to hook everything op via DH+. This will be the simplest and thus also the most reliable and costeffective solution.

[rpraveenkum 5]

Here mostly Yokogawa DCS will be connected to AB PLC through Modbus only