AB device net

[micah_garrett]

I have 68 micrologix 1000's that I need to network to a slc=503.
If I use DH485 and net-aic's for this I only have 32 nodes available.
If I use D-net I have 64 (I think). I was wondering if you guys have any good ideas. I thought about using a ethernet EIN at each drop but they cost $572.00 each, (or $38,896.00)!. The 1761-net-din is $219.00 each ($14,892.00) and should provide several words of data into and out of the micros, however I still need 68 (or more) nodes. I was wondering if you could set up 2 device net networks on the same SLC-503, then this would free up my DH485 for an office computer on this network. The next stage will be to add an office computer to monitor and adjust these micros, most likely RSVIEWS. Any ideas? Maybe another company makes something compatible to an AB EIN module?
Maybe you guys have something much better in mind. Thanks..

 

[Alan Case]

Hi, Very strange setup. 61 is a more practical limit for DNet nodes as you need 1 node for a method to program the network and node 63 is usually left free (reason being that most out of the box items come configured as node 63 and this allows them to be added to the system and then configured. Also if you use automatic device replacement then node 63 is reserved for that function) The limit on DNet will be the number of words available in the scanner. From memory the SLC scanner only has 32 words of input and 32 words of output per scanner.
You can use multiple scanners but it gets expensive.
Again I am only going from memory here but I think a Micrologix 1500 DNet scanner can read 256 words in and out. (If I am wrong someone will correct me) You could MSG over DH485 to an ML1500 and let it take care of the network. I assume speed of response is not an issue here.
Ethernet I am not to sure of but I think you would need an SLC505 in the system. I think a net-eni is only good for 5 connections so I think this method will cause you a problem.
Are the Micrologix PLCs in place.
Another way maybe is to make 3 DH485 networks with each network coming back to a comms card in the SLC backplane. Cant remember the model number but they are available.
Hopefully Ken will shed some light on this and we will all learn something
Regards Alan Case

 

[corkers]

Hi,

Another approach maybe to use a Control Logix Gateway setup with an ethernet card and 2 devicenet scanner cards in the control Logix chassis and an ethernet interface to the SLC. You don't need to have a processor in the Control Logix Chassis just the three interface cards. From what I understand you set up a routing table on the CTLX to route messages from Ethernet to Devicenet. BTW this also works to DH+ and ControlNet.

Andrew

 

[Ken Roach]

Part One

Okay, sixty-eight MicroLogix 1000 controllers that need to be communicated with by a single SLC-5/03 controller and/or a supervisory office PC application.

DH-485 networking is out of the question. After about 12 to 15 nodes, DH-485 starts to earn it's nickname "Data Sidewalk", and it only addresses 31 nodes anyway.

Ethernet networking is unlikely. If the central application is a SLC-5/03 with Net-ENI, we run out of connections once the SLC-5/03 sends out it's first four TCP connections. If the central application is an SLC-5/05 controller, we run out of connections after (I think) 24 connections.

If the central application isn't a SLC at all, if it's RSLinx, then we can use Net-ENI's to network all of the MicroLogix 1000 to Windows, which can (typically) support 256 TCP connections.

Net-ENI are fairly expensive, but I do have customers who use hundreds of them and think the price is worth the ease of use and ease of integration into their factory TCP/IP network.

So, let's ask the questions about the purpose and scope of this connection.

Is it meant to transfer small amounts of data relatively fast ?

Or is it meant to transfer undetermined amounts of data relatively fast ?

Or may it transfer undetermined amounts of data relatively slowly, with attention to cost ?

 

[lesmcw]

Hi: Just curious...What are you doing with 68 ML1000's

 

[Ken Roach]

Part Two

Okay, what I'm getting at (It's 2 AM, what do you want ?!) is this:

------------------------
Small Data volume, fast: 2x 1747-SDN and two networks of 34 (or some other division between the two) 1761-NET-DNI's. The 1747-SDN handles 180 I/O words between the discrete and M-file data areas.

360 data words / 68 controllers = 5 words I/O each (one word reserved for heartbeat). This could run as fast as about 50 milliseconds for a total update.

------------------------
Undetermined amounts of data, medium low speed. You can connect 1761-NET-DNI to a DeviceNet network with no scheduled traffic and use it to route DF1 Full Duplex packets from DNI to DNI. You could put up to 62 MicroLogix connected to one PC serial port running RSLinx DF1 Full Duplex driver, so you'd need two serial ports and two DeviceNets.

DH-485 bogs down after about 12-15 nodes, with performance decreasing rapidly up to 31 nodes. "DeviceNet Peer DF1" network performance levels out around 15 nodes and stays constant out to 64 nodes.


-------------------------
Undetermined amounts of data, very low speed. You could use 68 1761-Net-AIC modules in DF1 Half Duplex mode at 19200 baud, because DF1 Half Duplex addresses up to 255 slave nodes. The SLC-5/03 or a computer would be the DF1 Half-Duplex master and the all the MicroLogix (as long as they're fairly new and support DF1 HD Slave) can be DF1 half-duplex slaves on a RS-485 network. Several RS-485 networks are necessary because RS-485 can only support 31 physical nodes. These can be connected back-to-back with Net-AIC's via their Port 0 RS-232 connections, but I would have to check to see if you can connect more than two RS-485 segments back-to-back that way.


So.... what's the application ?

 

[PhilipW]

Heroic Ken...just heroic. ;-)

 

[Alan Case]

I am impressed. (I forgot the MFiles in an SLC for the extra data words) I submit to the guru. Alan

 

[mike1234]

can't get back on

Kem, I'm having a lot of trouble getting back into this format, I've been here before, but it don't like my user name or password. Anyway, it's me Micah Garrett.
I think the way for me to go will be the dh485 cards plugged into the slc-500 backplane. I'm not to familiar with "M" files, I ran across this a few years ago. If I understand you correctly, I can plug in 2, 3, or 4 of the dh485 cards into the backplane and address the micros thru "M" files. I don't need speed, I need cost. How much can I do with "M" files over the dh485's, I need to transfer 6 or 8 words into and out of the micros to allow setpoint changes and a few bits of a word for operational info. Tell me more..
For the one who asked, the micros were programmed and installed by me (not my choice) and they operate rubber curing presses for simi-pnumatic rubber tires (like push mowers ect.)
Thanks for all the help..
mg

 

[mike1234]

9 pin plug

Ken,I think I misread. You are talking about the 9 pin plug on the net-aic, connecting them to each other? to tie 2 dh485 networks together?
mg

 

[akreel]

Re: Part Two

Undetermined amounts of data, very low speed. You could use 68 1761-Net-AIC modules in DF1 Half Duplex mode at 19200 baud, because DF1 Half Duplex addresses up to 255 slave nodes. The SLC-5/03 or a computer would be the DF1 Half-Duplex master and the all the MicroLogix (as long as they're fairly new and support DF1 HD Slave) can be DF1 half-duplex slaves on a RS-485 network. Several RS-485 networks are necessary because RS-485 can only support 31 physical nodes. These can be connected back-to-back with Net-AIC's via their Port 0 RS-232 connections, but I would have to check to see if you can connect more than two RS-485 segments back-to-back that way.

You can extend RS485 beyond 31 nodes by using 485/485 isolators. This can also be used to correct any problems with the physical locations of the nodes that might affect the (preferred) daisy-chain topology.

So, theoretically, the limit on the number of nodes is in how many addresses you have available. You'll also need to consider the rate at which you want the master to complete a poll of the entire network.

I'm currently working on a system which should have up to 60 nodes on modbus RS485. By just using isolators I expect the poll time to be a few seconds. I want to use PLCs as concentrators to speed that up a bit.

AK

 

[bwheat]

This is kind of along the lines of this thread. I am looking at installing about 20 AB MicroLogix 1200 units to monitor a few parameters on injection molding machines. I'm considering the MLX 1200's because of cost and maybe scantime vs network update time. Am I opening up myself for years worth of headaches by using the MLX 1200's and Ethernet AIC's going back to a PC runnig RSView32 or is this not such a bad idea? The cost of any AB processor with an "E" in the part number is expensive. I dont need the data from each machine but once every cycle ~ 60 sec.

 

[micah1234]

I wonder if RS485 isolators will work on DH-485. The best I can tell, they are the same except for Allen Bradleys language. Maybe I could use these isolators every 31 nodes (or less) and go with half duplex communication (which I don't understand) and put all 70 or so nodes on one network? So far AB's been no help. What would be perfect would to find some AB SLC 500 cards with extra DH-485 networks on them, plug them into the SLC rack and divide up the nodes among them. I've been staring a this stuff for 3 days now, with no good way to do it yet.. I posed the idea of having several DH-485 networks and switching from one to the next to extract data on each network individually, but so far I've gotten a lot of hits and no response on this idea, must be pretty dumb, anyway, HELP!.. Thanks.. mg

 

[akreel]

The best I can tell, they are the same except for Allen Bradleys language.

They'd BETTER be! A 485/485 isolator should be transparent to the devices on either end. Only the lag time (minimal) of going through an extra device should affect your communication.

But, on the other hand, I'm assuming that the AB DH-485 protocol is REALLY RS485. RS485 is an electrical standard, nothing else. So if you want to put Modbus, DF1, ASCII, or any other serial data protocol on it you will be able to.

Don't fall into the trap of thinking you need AB hardware (except if you expect to get technical support). Blue hose is just a BELDEN cable, the SLC programming cable is just a Female-Female null modem cable (you can build one from Radio Shack parts), and the panelview programming cable is a straight-through Female-Female cable. Likewise, if you want to network processors you SHOULDN'T need an AIC module.

The AIC is an RS232-RS485 converter with some added features: like the extra port (I think there may be a brain for flow control). I'd be surprised if there is any protocol conversion going on inside the unit, but I've never had anyone from AB confirm my theory. It doesn't really matter, anyway, because the DF1 protocol should support addressing.

AK

 

[Mickey]

Akreel,

Have you tried using a thrid party RS232/RS485 converter with AB
PLC's. I'am going to install two Micrologix 1500's and have been
wondering if I had to buy the AIC's or just the above converters.
(Telebyte,Blackbox or whatever). I want my SCADA PC to communicate
with them out it's serial port.

Mickey