HSC Calculations & RIO Traffic

Question
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What is your method for determining the need of high speed inputs and counters? How do you go about determining the PLC needed? I only have RSLogix 500 so would need to get approved to buy 5000 if I needed a compactlogix. There is a limit to how many HSC modules you can add so how do you go about drawing a line. I would think someone has a spread sheet made up they might be willing to let me peak at.

Also, my reject point, rehanging point, and inspection point, are all separated from each other by a long distance. How would you run that remote IO? Would you place ML1100's and run the counts over ethernet, or would devicenet be fast enough?? I just imagine a lot of network traffic.

Also how do you determine if your sensors are going to be fast enough?

This is something that HAS TO WORK. I will have redundant sensors to insure that, but this will further congest network traffic.

I would just like to know how to go about determining these things so I would know for the next time.

Details
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I've been asked to look into another project at my food plant for a bad product reject system. I have product hung from 'shackles' mounted to the overhead line. Product travels on one overhead line then a part of it is separated and hung two parallel lines.

I'm looking at 840IPM line speed, on the first line, and half that on the two lines after. Everything is set at a 6" pitch. This gives me 70ms to detect a 1 inch target and 30ms to detect a 3/8" target. These things are already part of the line. I then have to have some other sensors to track the product as its rehung.

If inspection, located on the slower parallel lines, rejects product the product remaining on the first line has to be rejected as well. I am basically trying to index the shackles and make a decision to reject based on the indexed line counters.

The current system works on timers and wastes a lot of product. I have to track the 'shackles'.

Anyone have any suggestions? Or a tech note on calculating scan times or RIO traffic over ethernet?

http://www.beiied.com/PDFs2/H20_Incremental_Encoder.pdf
ML1100's and run the counts over ethernet

Thanks bce. I that's a good looking encoder. I was thinking about running 3 prox switches off the drive sprocket teeth, but I could just place two of those on the drive and be redundant! Much easier.

Do you have a way you like to mount those from a mechanical sense? I would run directly off the drive motor which is connected via cog belt to a 90 degree worm over planetary drive.

Also I would basically be building an association table with multiple integer files, one for each stage of the 'rehanging' process, and using indexed addressing with at least one helper file. Would you try to send a explicit message every scan or try to build an association for say 100 'shackles' then send one to keep the network from bogging? Or on the other hand do you think its a good idea to only use the 1100 for remote I/O and message all its inputs?

I was thinking of using a RL G3 and data blocks to control the comms since I need a HMI anyway.

Sorry for the so many questions everyone. This will be my first project with RIO and HSC. So I'm just trying to get clear on this part.

alot of variables? total scan time of the 1100 how many plcs just 2 or 3 try and use the local plc for local i/o and just send updates between the 2 or three should be simple w/the msg over enet.encoder mounting depends on shaft use flex coulping and you should be allright. just be sure and use the ip66 rated if its in a wash down area. I have not used the g3 so no help there but there lots of folks here that have.