slow refresh time

I am having trouble seeing what is going on in the feild. Stuff is happening faster than I can see it on my CRT. I have spoke to Allen Bradley and tried all their tricks to no avail. Maybe I'm expecting to much.

I have a brand new top of the line Dell PC.
A/B 5/40 processor
1784 PKTX DH+
>40ms scan time
Would going to an ethernet connection help?
Any disadvantages with going to ethernet?
It looks like I am going to be forced by managment to go ethernet.
They want to send some of my data to the bean counters on the mill network. I have tried in the past to stay away from the mill network
because of reliability problems in the past. Can you guys think of any other good reasons to stay off the mill network? Thanks, Mike.

I personally have no problems using e-net. To your question of refresh times maybe you can set logic up to capture the event you want to see. We've had to set latch bits to see a speedy short-duration situation before. If the bit latches you know the event occurred (you can also trigger a counter or a self-holding timer circuit). What exactly are you trying to "catch".

Just general troubleshooting. I.E why didn't this rung go true? I see
4 or 5 bits that might be holding it out but realy only one is the problem. I'll get the information in the data table 3 to 4 sec after the fact. I have been told by the process guru that enet will solve all my problems with refresh times. I think he is full of it. Mike.

I use ethernet about 99% of the time for programming and troubleshooting, and wouldn't have it any other way. I get much, much faster update times, plus I can go online with multiple PLCs at the same time. I have no experience with AB, but I imagine that the advantages would be similar. I think you should give it a shot.

What speed are you running your DH+ network at?

Ethernet is certainly faster, but the DH+ ought to be fast enough (even at 57.6) to display anything that stays on (or off) for more than a few scans. If you are trying to get something faster than that to update on your PC (like a one-shot), I think you are out of luck - you'll have to do something like Rube suggests and use latch bits.

While Ethernet is a good thing for lots of reasons, I wouldn't connect my "control network" to the "company network" unless I really had a good reason to. You may have a good reason if people want their data realtime (and can actually use it!). Make sure you weigh all the positives and negatives though (like what happens to your processes when the network goes down? who restores the network? who restores the processes?) Also, if you use AB PLC's make sure you understand about "Ethernet Storms".

Marc

You don't mention how many nodes are on your DH+ or what they are. The token has to be passed around each node in turn and each node then gets a chance to talk. Programming terminals and HMI's create a lot of traffic, which slows down the token passing process.

You should expect significant improvement by going to ethernet - just ensure that you use switches and not hubs. And, particulary for programming or trouble-shooting, get wireless. It is tremendously useful to be able to move around a large machine or plant with your programming terminal completely untethered.

I love ethernet for PLC work. If your company is willing to spend the money for an ethernet comms card, or 5/40E, GO FOR IT!. And, for the record, you do not have to connect it to any network if you choose not to. I usually keep all of my PLC's and HMI's on a completely different network from the corporate one. If you absolutely need to bridge them, drop in a router.

That being said, if you are just trying to do some troubleshooting, you can always add some simple logic to latch internal status bits to see what is going on; No matter what communications method you use, you will miss scan or sub-scan level transitions.

I would use a histogram to catch what you are looking for in this case. The PLC5's buffer the histogram data internally and send it out as a block. This is unlike the SLC where the histogram is handled completely by the PC and you can miss stuff.
3-4 second updates do seem kind of slow. Like Gerry said, DH+ communication speeds are node dependent so if you have alot of stations on the network it can slow down performance. RSLinx can also be a bottleneck if you have multiple drivers active and browsing.

Keith

No need to invest in Ethernet !

Like the others say, if there are a lot of other nodes on the same DH+ network the refresh rates will degrade significantly.

Also, open as few windows as possible in RSLogix. Do not open ladder or datafiles unless they are really needed. close all other ladder windows (in the bottom of the screen is a tab list of all the opened ladder files, only open one at a time).

Your PLC5/40 has 4 DH+/RIO ports. Try to see if you can connect to an unused port. If you can, crank it up to 230K.

Normally DH+ is fast enough for 'most' troubleshooting purposes. 3-4 sec refresh time indicates that something is seriously wrong. There is a moving graphic in RSLogix (rotating ladders) that must move without glitches if all is OK.

Well you can see several different flavors of e-net support, can't you. Ethernet will do certain things faster, but if you are just trying to see whether something went true or false, the refresh from the PLC to the screen may not be fast enough. This is why we used bits. I've not used the Histograms in PLC5s and don't have any in my plant now, but Keith may have a good point--to set up the Histogram. At least one of the methods will help you out.
Ethernet points made by the other members all have validity; you want to set your network up as a stand alone net if you can, speeds are higher but is DH+ fast enough without buying the e-net stuff, etc.