DH+ speed

arekk

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Aug 2007
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Hi,

I have question about DH+ speed. Now I have 19 SLC500, 7 PanelViews and one PLC 5 connected on DH+ (2 cards 4 channels)to contrologix ethernet gateway. Now the speed of DH+ is 57,6kb/s, what I would have to do to increase the speed. I mean what are the limitations of the DH+ when we have maximum speed. I would like to increase the speed because I prepare the MES system, where there will be one or more Data Servers and I dont know if current speed of DH+ is enough. I wonder if you had cases like that before
 
arekk said:
Hi,

I have question about DH+ speed. Now I have 19 SLC500, 7 PanelViews and one PLC 5 connected on DH+ (2 cards 4 channels)to contrologix ethernet gateway. Now the speed of DH+ is 57,6kb/s, what I would have to do to increase the speed. I mean what are the limitations of the DH+ when we have maximum speed. I would like to increase the speed because I prepare the MES system, where there will be one or more Data Servers and I dont know if current speed of DH+ is enough. I wonder if you had cases like that before
Click to expand...

If you have the 1756-DHRIO card, be aware you can only have 1 channel per card in use if the speed is 230K, this would be channel A. Channel B can be used if speed is 115K
 
There is a 150KB/s setting, which I don't recall ever seeing in use, and the 230K.

Depends on hardware, of course, you will have to check that.

Also, AB has a technote, that I recall from several years ago, about maximizing throughput by ensuring that your transfer data fits within 40 word blocks.
 
SNK said:
Some of the newer AB DH+ stuff is capable of 230kb. Do a check on all of your equipment before you change the baud rate....
Click to expand...

Ditto the above.
The weakest link in the chain makes the decision.
 
RoTaTech said:
Also, AB has a technote, that I recall from several years ago, about maximizing throughput by ensuring that your transfer data fits within 40 word blocks.
Click to expand...

Thx I didnt know that.
Now I want to make it other way, To my gateway add controllogix processor to make it data server from DH+. All signals taht I need from DH+ will be gathered by this CLX and then to the MES data server. It is the simpliest and the cheapiest way to get what I need - information from DH+ without changing topology or changing PLC's I think, but maybe you got other ideas ???
 
See www.ab.com Knowledgebase, ID 36830, Best Practices for Data Collection systems on Data Highway networks.
trnsp.gif
 
An alternative could be to install PKTX cards in the MES system. You could then use OPC if the MES system supports it (maybe it already uses OPC with the current ethernet/DH+ setup).
Not sure if a direct DH+ connection will be better or worse than Ethernet/DH+ at the same DH+ speed.
So you would need 4 PKTX cards to replace the 2 dual channel DHRIO modules. But then you could run all cards at 230k.

By the way, I think an SLC5/04 only supports 57,6k and 230k, not 115k.
 
JesperMP said:
An alternative could be to install PKTX cards in the MES system.
By the way, I think an SLC5/04 only supports 57,6k and 230k, not 115k.
Click to expand...

I didn't think about putting PCI card directly to the computer, I would have to consider that option.
I thought about full logix platform and put in the gateway CLX processor and map all the registers needed from DH+ in the CLX.
 
So you havent actually purchased anything yet ?
Anyway, as far as I understand, the CLX dont need a CPU in the rack to pass data between the various networks. So you should not have to set up any "mapping" in the CLX or even use a CPU.
I havent actually tried this myself.
 
JesperMP said:
Anyway, as far as I understand, the CLX dont need a CPU in the rack to pass data between the various networks. So you should not have to set up any "mapping" in the CLX or even use a CPU.
I havent actually tried this myself.
Click to expand...

In the gateway there is a communication processor which manage of all communication between SLC, I think that better way to communicate to SLC is not ask them directly to not generate large traffic but to ask CLX which will be a data server to a DH+.
Maybe I'm wrong, maybe someone have similiar experience.
 
How do you then exchange all the tags ?
By passing all data cyclically ? That will ensure maximum traffic on both networks !
I dont know what your MES system is doing exactly, but most HMI and SCADA's handle the data exchange intelligently by only requesting data when it is needed. One example is when a recipe is transferred. Another is the tags on a HMI page, these tags are then only requested when that page is opened by the user.
 
JesperMP said:
How do you then exchange all the tags ?
By passing all data cyclically ?
most HMI and SCADA's handle the data exchange intelligently by only requesting data when it is needed. One example is when a recipe is transferred. Another is the tags on a HMI page, these tags are then only requested when that page is opened by the user.
Click to expand...

That's good question. That's why I wanted to maximize the speed of the DH+ to 230 kb/s, then I think the traffic in the DH+ even with MES would be acceptable. In MES data don't have to be collected so often, Then cyclically yes but not to often. Time between the cycles depends on the needs of the users, which haven't been defined yet. What do you think about that?
Knowing that exchange of the SLC to Contrologix or Compactlogix in few cases is too expensive.
 
I can imagine that the data traffic for a system that has to exchange all data cyclically will be 5-10 times heavier than when you only exchange data on demand.

I believe that a CLX gateway (without having to pass over a CPU !) automatically directs the data all the way to/from the MES system to the SLC's.
 

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