Profibus-DP practical maximum nodes


Thread Starter

Fred Zhang

In theory, the Profibus-DP can support 126 nodes in one segment with repeaters. Since the Profibus-DP just draw a little current from the Bus, not like DeviceNet, I wonder in real application if we can have over 100 nodes in one segment, also considering the communication rate is 1.5M bps.

James Ingraham

"in real application can we have over 100 nodes in one segment?"

I've never tried it. I'm not 100% sure I see the point. It's fairly easy to add Profibus masters, and limit each one to 31 nodes. This may be slightly more expensive than repeaters, but it allows you to tackle the network in smaller chunks, which always makes setup and troubleshooting easier.

Still, I have certainly read about such installations. The 1.5Mbps is a "it works or it doesn't" variable. Unlike other networks, nothing on Profibus has a priority over anything else. That means you're going to have some fixed cycle time to update all nodes, with very small jitter. Once you get it all plugged in and working you'll see how fast you can update the network. I can't say for sure where your scan rate will fall, but I'd guess between 10 and 100 milliseconds.

James Ingraham
Sage Automation, Inc.