Host Engineering Forum
General Category => ECOMs and ECOM100s => Topic started by: keith on November 11, 2014, 04:36:41 PM
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I have used ECOMS on numerous jobs for network communications, and I really like the product. However, we are now using multiple C-More panels communicating with the PLC through the ECOM link, and they really get slow after using about 4 of them.
I realize that the C-More panel is not your product; however, I am using it with your product.
My understanding is that the ECOM can only do 1 transfer per PLC scan, which can be a large block or a single word.
I think the problem is that the panel reads every controls tag without any kind of optimization.
All of the data I need to communicate between the two devices is in nice small blocks. It would be nice if the C-More had a way to read a small block of words, then slice them into smaller internal tags to use with the controls (even a single word, then slice it into bits would be ok). Too bad there is not some kind of generic driver which could read a tag (like a word from the EOM) and break it into smaller internal tags.
I know I can play with the timeout and poll time, but I haven't found a combination which works great. Too bad the C-More is so wasteful when it comes to bandwidth.
Does anyone have any suggestions ?
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I know that some people use multiple ECOMs due to a combination of the heavy traffic and needing fast update times. FYI, depending upon the CPU and frequency and amount of data, an ECOM can get 1 to 4 communication requests per PLC scan.
If you have any extra ECOMs, I would definitely try it before buying just to make sure it works as good as you need.
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For some reason I thought that I remembered that the C-More did in fact optimize. Maybe I'm thinking of another HMI. You might also try using a different driver such as Modbus that's supported on both ends of the wire. One driver might be optimized where the other is not. Also, I believe it's pretty common in multi-HMI scenarios, to have one HMI be the master and handle all PLC comms, and then serve information to the others, which aren't connected to the PLC. I know both Idec and Kep (the flowmeter company that makes HMI's, I believe unaffiliated with Kepware) offer this as an option.
If none of that works, I'd suggest looking for an HMI that does optimize it's list. When I'm writing a driver, I'll even block across small gaps in the list. Plus the Idec TFT's are IMO far superior to the C-More's. C-More's have got a lot brighter over the years, but the resolution and color saturation lag far behind the ones used by Idec, and Idec's software is no worse that anyone else's.
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C-more does in fact optimize communications as best it can given the limitations of whatever driver you happen to be using. ADC has written a white paper on getting the best speed out of your C-more. You can find it here (http://support.automationdirect.com/docs/an-ea-010.pdf).
Yes I realize that the document says "Screen Update Performance", but screen updates have a direct bearing on how fast communications happens in C-more.
BTW, 4 screens can be pushing the limit on ECOM performance depending on how much data you are trying to shove through the pipe. The backplane on a DL205 can only handle about 250 bytes per scan per module.