communication between different PLCs 1

[automation99]

I have one AB compactLogix PLC and one GE 90-30 PLC (client prefered), if I choose DH+ to communicate between these two, do I need to have any converter for the GE PLC or just plug these two and they can talk to each other? I am new in this field, please help. Or should I insist to have AB series PLC instead of GE (have to have long long talk to client for this).

Thanks,

 

[chakorules]

DH+ is ONLY an Allen Bradley communication protocol. GE doesn't support DH+. It depends on how much data you are wanting to share but a common OPC server might be one way or choose a device network like DeviceNet or Profibus that can be used in each PLC to talk to each other.

Chris Elston
Automation & Controls Engineer

http://www.mrplc.com

Download Sample PLC Ladder Logic Code
at MrPLC.com

 

[automation99]

Thansk, Chris. If I use common OPC server, do I get real time response from one to another? Is there time delay? There are about 20 discrete signals and 5 analogs. Does AB and GE both support Modbus?

 

[chakorules]

OPC server will share some lag time. Looking at you data, it doesn't seem that it would be that much.

One thing I forgot...SST makes a card that drops into a GE 90-70 rack. You didn't say which GE model you have.

If you have a GE 90-70, then SST has what you need.

http://www.mysst.com/cards/ab/sdvme.asp

http://www.mysst.com/bcm/content.asp

Chris Elston
Automation & Controls Engineer

http://www.mrplc.com

Download Sample PLC Ladder Logic Code
at MrPLC.com

 

[JesperMP]

20 discrete signals and 5 analogs ...

Hmmm, I know that it is yesterdays technique, but pulling a number of discrete + analog signals between the two can be the easiest and cheapest way to do it.
Off course, its not so flexible, but if you arrange for a number of spare signals then it cant go completely wrong.

Dont use OPC for realtime data transfer. There will be significant timedelays (0.5 secs cycle time is not unheard of).

AB supports Modbus out of its serial port. Dont know about GE.

Probably DeviceNet is the most native to the CompactLogix, but I am not sure if it is as easy as one thinks to make the connection between an AB and a GE.
It is certainly possible, I just thought that I ought to mention the arcaic way of doing it.

 

[automation99]

Thanks, JesperMP. I do need real time and precise control between these two PLCs, the AB compactlogix is BMS which contains important information. Isn't DeviceNet AB's proprietary network? Can GE support it? I believe GE support Modbus, but that will be even more complicated to involve third parts network.

 

[lrob]

I had a project were I put a devicenet module (Horner APG) into a 90-30 rack and passed information between a 90-30 and a SLC500. Thus worked very well. There is some memory mapping and I had more problems from the A-B than setting up the Horner module.

 

[Wfacac]

Both processors support ethernet, why can't you just connect them and read registers?

 

[OldPfart]

Device Net is not an AB proprietary network but is open. Go to

http://www.odva.org

for a staggering list of manufacturers.

GE does support Modbus. You can roll your own in a processor card or buy the Horner one which has the code already in it. Much easier.

Be prepared to write a lot of ladder to get the communications going. I found some samples on the GE-Fanuc website.

 

[lrob]

With the Devicenet module from Horner is installed in the GE rack. I had only about 3-4 rungs of logic in the AB. They were mostly for communication housekeeping. From the GE side I do not remember that I had any logic to support the horner module. With the Compactlogix do you have to buy a Devicenet scanner or do you already have Devicenet on that system? You may need Devicenet modules for both PLC's.

Don't SHOOT, however I have to asked. Since your client is GE is the AB system small enough to convert it to GE. At first thought it may sound bad, however there may be merit to do this. I did 2 GE Devicenet systems then my client had me convert the GE to AB. In retrospect I wished I would have converted the first two. Just food for thought.

 

[automation99]

Thanks, Irob.If I am not mistaken, using DeviceNet means treat the AB compactLogix as remote I/O, all logic will be done in GE PLC. That is not what I want, AB compactLogix is come with its logic and programm from vendor. GE will be the upper level supervision and only shutdown function from it to AB. I can use hardwire link for that. But the data from AB has to be real time for other control function in GE PLC. Convert AB to GE is not an option for me.

 

[lrob]

automation99,

With the Devicenet module both PLCs can run their own logic. You can map I/O tables and registers directly to each other. Example a word of Q outputs would be mapped to the Input image table in the AB.The same would be true for data registers. The delay would be Scan time plus Devicenet Communication time.

 

[germantrade]

Where is possible to get the basic theory about PLC ?
I need What steps I could take in account ? for to fix or trobleshooting in field.
thanks

 

[MrJP]

'germantrade' -

http://www.plcs.net

may be the best place to start.

'automation99' - It's not going to be cheap any way you do it. DeviceNet or Modbus will work, but it is going to require more hardware for at least one or both to achieve it.
DeviceNet = Scanner module for Controllogix + Horner's DeviceNet slave for GE. (don't forget the expensive cable, resistors, power supply for the network and $2000+ for RSNetworx)
Modbus = Prosoft Modbus Master for Controllogix (I believe the 90-30 should support ModbusRTU, depending on the CPU you have). You will have to read-up on Modbus if you are not familiar w/ the protocol. It's going to take more than 30 minutes to do this either way you look at it.

'Wfacac' - MAN ... I wish it was that easy! So far in the industrial world of PLCs everyone's Ethernet protocols are proprietary just like the old serial protocols. (Just because your telephone will plug into the PLC doesn't mean you can call it. ;-)). There are some expensive protocol converters available, but I can not speak from experience on how any of them actually perform.