Xbee

XBee & XBee Gateway XBee - 802.15.4
1

Am using xbee digi’s product, my question is up to how many Xbee devices i can connect so that i can establish a network. i got to know from my experiment one xbee can coomunicate with the other in the range of 50 meters. If i have 10 xbee modules with me then the maximum range will be??
and how many xbees i can conncet to maximum??

2

In a true case, with 802.15.4 protocol you can communicate with 64k devices in a network

3

Yes - in theory.
But I think many of us are interested in the practical limitation.
I, quite frankly, am seeing some connection and communication issues when I start putting 30 devices.

Maybe the throughput is an issue.
9600 BAUD communication.

I suppose metering and spreading out the communication so that I don’t slam 100 units of communication all at once and then get 100 units trying to reply at once is an issue.

Thus, I’ve seen some comm calcs in the Zigbee information document, but there really isn’t much in explaining how having many units online at once can mash your connections.

Also - radio interference by having dozens of XBee modules in close proximity seems to be a point of discussion well worth communicating.

Any chance anyone has had the same question answered?

Thanks everyone!

GG

4

I’d agree with Gary, plus how close the nodes are together impacts things greatly. 20 nodes spread so that each only sees a few peers is a very different design from 20 nodes close togather so each sees all traffic & broadcasts.

In general broadcasts break any design, so unicast needs to be used. Also, I would avoid any system which assumes more than 10 messages a second move anywhere, with mesh hops cutting this (so 10 nodes sending 1 hop, 5 nodes sending 2 hops, 3 nodes sending 3 hops, etc). Yes, the Xbee/mesh moves more than this, but one needs to plan for a common steady-state design.

My gut feelings after years of this stuff:

  • 2 to 20 Xbee is pretty easy (as long as the application is a good match to Xbee/mesh)

  • 20 to 50 Xbee is harder and you’ll start to need to tightly control WHO talks WHEN.

  • for more than 50, you’ll need a RF/radio sniffer and need to plan the WHO/WHEN with perfection. Literally, you need to engineer/hand-craft a solution which works by design.

I have seen systems with up to 1000 nodes (imagine light fixtures in a commercial building), but it takes several engineers a LOT of time to tune the application to work! So they spent 10% of their time on the actual control devcie and host app, 90% getting the protocol under control message-wise!