problem for ControlNEt

[angi]

Hi guys

I got a problem when I try to update a COntrolNet system, they use a 1756 CN2/B in the local chassis, I am going to add another 2 1756CN2/ in 2 different remote chassises, I update the Logix5000 code first, add the bridge 1 into program, then open RSNetWorx for ControlNet, select the edit mode, I could see the chassis I just added in, everything looks ok after I save it. the problem came out when I try to do the same thing for second bridge, when I try to save it alway show me "exceeded the 100% bandwidth", how to fix the problem?

Thanks

 

[daba]

When you hit save in RSNetworx, do you get the option to "Optimise and rewrite the schedule", that is what I think you need to do.

Care !! re-scheduling needs to put the Controller(s) into Program Mode. Make sure that is OK to do before proceeding !!

 

[Ken Roach]

"Exceeded 100% Bandwidth" is a configuration problem: you have more data scheduled on the ControlNet than the ControlNet has time to transmit that data.

The most common culprits for this issue are large connections that are scheduled with small RPI values. I know you're using remote 1756-DNB modules, so those are the most likely cause.

You should determine the actual size of the Input and Output data tables for the 1756-DNB and make the Connection in RSLogix 5000 that size. You should also make the RPI no faster than 1/2 the DeviceNet scan rate, though many networks are composed of devices like motor starters or drives running process control) that do not require high speed updates.

 

[angi]

Thanks for you guys replay.
Ken, how to determine the actual size of the Input and Output data tables for the 1756-DNB? in RSNetWorx?and how to make the Connection in RSLogix 5000 that size?

 

[Ken Roach]

Look at the Input and Output data maps for the 1756-DNB that you created in RSNetworx for DeviceNet software.

There are 124 DWORDS of data available, but you probably didn't use it all.

I recommend making the I/O connection size just a little bigger than what you used, to allow for a little expansion later.

In RSLogix 5000, you defined how many DWORDS you wanted in the Input and Output connections when you created the 1756-DNB in the I/O tree. Go back and change (you'll click the "Change" button next to the I/O definition) that to match the actual DWORD sizes you are using.

 

[angi]

Hi Ken

I tried to reduce the size of the input/output data and increase the RPI time, but the average sceduled band before I add another remote ControlNet bridge still keep as 88%, and when I add a new bridge it will be more than 100%, any idea?

Thanks

 

[kamenges]

You may want to increase your Network Update Time to the next available step up. This will allow more time between network updates to get data packets through.
Also, keep in mind that regardless of your RPI setting data can only be transmitted in increments of your NUT. So if your NUT is 10msec, an RPI of 11msec-19msec may not result in the data rate you expect.
Ken can answer this better but I'm not sure how careful RSNetworx is about scheduling data in terms of using all available bandwidth. For example, if you had four stations configured with an RPI of 20msec and the ControlNet NUT is 5msec, I would think that Networx would schedule one station every network update. However, if it schedules all the statiions to transfer in the same network update then changing the RPI will have little effect.

Keith

 

[Ken Roach]

If you can post the RSLogix 5000 project and *.XC file (or send me a PM with your e-mail address if you do not wish to post it publicly) I can take a look and advise you on how to optimize this system.

I don't think that it will be effective or efficient to do general tutorials on ControlNet principles and procedures here on the PLCTalk forum.

 

[angi]

Thanks guys

how to change the current NUT? because it always been grayed out.

 

[Ken Roach]

The network NUT is in the "Network Properties" dialog. You can only change it in offline mode, prior to a complete network download.

 

[angi]

Hi Ken

in offline mode, the current NUT is gray off, only thing I could do is to update the pending NUT, but I need to change the current one, right?

 

[kamenges]

Pending is the one you want to change. Current is what is active as of the last configuration download. It can only be changed as a result of the next configuration download.

Keith