DeviceNet on Micrologix 1500

Allan Barnes

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Join Date
May 2004
Location
Woodstock ON
Posts
122
I am looking at setting up a devicenet network using 15 or more Micrologix plc's.
The plan is to use the 1769-SDN scanners on every MicroLogix. This should give me a huge speed increase over conecting them by the Net-DNI modual(cheaper too). There will one "Master" and the rest will be slaves. I searched the AB website, and there seams to be some Knowlege base documets that support what we are trying to do.
Our sales rep was dropping a PV+400 off, so we asked him if any one else was doing this on DeviceNet. He toldus that a Dnet scanner can not scan anothet Dnet Scanner.
So what I am wondering is this: Has any one else done read and write to other PLC's connect to Devicenet via a Dnet Scanner?
 
All the A-B DeviceNet scanners support simultaneous Master and Slave modes. You can make a 1769-SDN into a Master of some I/O while also allowing it to be a Slave to another scanner (1769-SDN or other). In RSNetworx, you have to enable a Slave Mode connection in the 1769-SDN Module properties tab before you can use it in the scanlist configurator.

This would not be my first approach to the application, though. Using Net-DNI modules as a "super-DH485" network would be my recommendation. This allows 64 nodes on a peer-to-peer communication network and doesn't bog down like DH485 does.

The big advantage to the Net-DNI method is that you can randomly access MicroLogix data tables by address, instead of figuring out where the data is in the I/O table. You can even go into a 1764-LRP through a 1769-SDN across the backplane !

The Net-DNIs should be a lot cheaper; $250 USD versus around $650 for the 1769-SDN.
 
I have played with this between 1771-SDNs on PLC5s. The 1769-SDNs support Slave mode so you will have to set up one as master and the rest as slaves. Slave to Slave communication will have to be passed through the master.
 
Thanks

My only major consern with using the the Net-DNI is that I am now limiting my network to 19.2kb because of the seiral link.

I absolutly must be able to remotely go online/program over Device net, can this be done throught the Net-DNI?

I realy like the COS/Heartbeat option that can done with the scanner. Can this be done with the Net-DNI?

Also is there any way I can put a Panel Veiw Plus onto DeviceNet, or do I have to have my main HMI talk sierialy to a Micrologix?
 
Lets take a step back to the purpose of the network.

Is this a peer-to-peer network where an HMI has to get data from each controller, or is it a master/slave sort of arrangement where one controller manages or monitors the functions of all the rest ?

How much speed do you actually need ? Is it OK for data to take 250 milliseconds to get from A to B, or do you need 25 milliseconds ?

There are a lot of different functions available on the 1769-SDN and 1761-Net-DNI (Master, Slave, Slave/DF1, and PCCC Encapsulation) and I don't want to start slinging jargon (whoops, already did !) until we understand the purpose of the network.
 
Well let me try to awswer those questions Ken.

Right off the hop, 250 milliseconds is no good.

What I have is 12 or more "Slave" Procesors, With one "Master", controlling a web offset printing press.

Each "Slave" has a Local HMI(conected through RS232)and an Emerson Servo(I have not desided If it will be on Device net or use the other com port on the PLC for Modbus). Each slave controls a process unit, and recives press speed refrence, and other control requests from the master.

The "Master" Collects the Information from the "Slaves", and does the Press Wide Controls. At pressent there is a main HMI that will get all its data from the master. What I would like to do is have the HMI be able to get the data directly from the slaves.

Over all my control system is more like a DSC, just implimented with PLC's. We have gone with Micrologix 1500 for several reasons.
#1 the 1500 comes with high speed counters and High speed outputs
#2 We only need a little more I/O than what come on the Base Unit.
#3 To use a SLC, or even Compact logix for our system would cost 5x the amount(because of the High Speed I/O)
 
I understand better now.

Your application does sound like an ideal one for 1769-SDN's in Slave Mode in all the "Slave" controllers. You could send a handful of reference and command bytes with COS connections very fast from the 1769-SDN at the Master.

You could also *maybe* use this same DeviceNet network for general HMI work. I know that RSLinx 2.4 can access MicroLogix 1764-LRP (not the -LSP) controllers via the 1769-SDN. This is a unique feature among A-B DeviceNet scanners and controllers.

I don't know if PanelView Plus can use that communication path. With PV+, I always test before I recommend. I'll try to use a 1761-NET-DNI and 1769-SDN/1764-LRP with a PV+ application this afternoon.
 
I am trying to set up a device net system on a micro 1500
How do you get the information from I/O on the devicenet to the processor. I have tried to use the message function but i don't think I am doing it right. I have all the inputs and outputs from the devices mapped and the SDN is on.
please help
Paul
 

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