Best way to fix possible Xbee Pro Line of Issues

bsnut

I'm in the planning stages in setting up Xbee Pro's to be setup in "Line Passing" mode to control and monitor our signal system at the Baltimore Streetcar Museum (Trolley Car museum).

The problem is that the Xbee Pro's that was thinking of using will not be in a direct line of sight of the other Xbee Pro that will be 1/2 mile away from the other Xbee Pro due to a slight curve in our trolley line and also our shop building that is at the beginning of this curve will make the two Xbee's not being in direct line of sight of other.

One of the ways I was thinking of fixing this issue, was using 1 or 2 Xbee Pro's to be used as repeaters setup on the roof of the shop building to help with the line of sight issue and I wanted to know is this the best way to fix this issue.

Duane Degn

I'm pretty sure the ZB version of XBee has this sort of router capability. I don't think I've ever used it myself. I'm not positive is the other version (formerly Version 1) can hop messages without the aid of a microcontroller.

Either way, I'm sure it's possible (you might need a microcontroller to configure the middle XBee).

What version of XBees do you have? What are you using to communicate with the XBees.

Another option would be the 900MHz long range version of the XBee. It still requires line of sight though and the signal may still be blocked my the buildings.

Franklin

You could also consider high gain directional antennas for a stronger (more focused) signal.

bsnut

What version of XBees do you have? What are you using to communicate with the XBees.

I currently have the XBee Wireless Kit from Parallax that was sold at Radio Shack on clearance and was going to order the XBee Pro (Parallax #32407) to handle the work, since the ones from the Wireless Kit can handle only 400ft outside and the signal is around 500ft away (up the line) from the shop building.

I'm pretty sure the ZB version of XBee has this sort of router capability.

That is what I'm hoping for. That would mean I need 3 XBee Pro with good antennas on them. But, I don't know if router part will work in "Line Passing" mode.

To help you all understand location of the museum trolley line here's a link to Google maps<iframe width="425" height="350" frameborder="0" scrolling="no" marginheight="0" marginwidth="0" src="https://maps.google.com/maps?f=q&source=s_q&hl=en&geocode=&q=Baltimore+Streetcar+Museum+Streetcar+Rides,+Maryland+25,+Baltimore,+MD&aq=1&oq=baltimore+streetc&sll=38.728376,-77.34375&sspn=4.644844,7.064209&t=h&ie=UTF8&hq=&hnear=Baltimore+Streetcar+Museum+Streetcar+Rides,+Maryland+25,+Baltimore,+Maryland+21211&ll=39.31232,-76.620712&spn=0.023243,0.036478&z=14&iwloc=A&output=embed"></iframe><br /><small><a href="https://maps.google.com/maps?f=q&source=embed&hl=en&geocode=&q=Baltimore+Streetcar+Museum+Streetcar+Rides,+Maryland+25,+Baltimore,+MD&aq=1&oq=baltimore+streetc&sll=38.728376,-77.34375&sspn=4.644844,7.064209&t=h&ie=UTF8&hq=&hnear=Baltimore+Streetcar+Museum+Streetcar+Rides,+Maryland+25,+Baltimore,+Maryland+21211&ll=39.31232,-76.620712&spn=0.023243,0.036478&z=14&iwloc=A" style="color:#0000FF;text-align:left">View Larger Map</a></small>
The visitor center would be one XBee location (microcontroller location), shop building midway up the line for a router XBee and the signal location about 5 poles up the line from the shop near the switch before going to single track.

Tracy Allen

Yes, the first thing to try is the XBee Pro, XBP24, see how it works out. The XBee with the SMA connector is most versatile and the rubber duckie antenna is a bit more effective than the little whip antenna. A high gain directional antenna could help a lot. One approach to that would be to pick one from the list of antennas you can find in an appendix to the XBee manual. The DIY option (cheap) is to find one of the many references on how to extend the range of your wifi, same 2.4GHz frequency as the XBP24. There are pringles cans, beer cans, and DIY parabolic reflectors. Example, follow links here. The important thing is signal-to-noise ratio, so find a quiet channel among all the 2.4GHz traffic.

The only Digi modules that have "line passing" per se are the XB24 and XBP24 802.15.4 series 1. Line passing allows two XBees to work together without any other microcontroller, so that digital inputs on one come out as digital outputs on a remote, and analog inputs on one come out as PWM on a remote. Strict limits on what it can do. Series 1 modules do not have much repeater capability, however, you can achieve one hop by enabling one device in the middle as a coordinator. It is a bit harder than peer-to-peer to set up.

Other Digi modules do not have "line passing" but they do have "line monitoring" or "line sampling". A remote XBee can acquire and transmit digital and analog data periodically or on change of state, without needing a micro attached, but the receiver on the other end does need a micro to read the data. No automatic binding of pins. That applies to the XBP09 (900MHz) modules, and to the series 2 XBee ZB (Zigbee) modules, and to the Digimesh modules.

bsnut

Thanks for the info Tracy, that's what I was looking for.

Other Digi modules do not have "line passing" but they do have "line monitoring" or "line sampling". A remote XBee can acquire and transmit digital and analog data periodically or on change of state, without needing a micro attached, but the receiver on the other end does need a micro to read the data. No automatic binding of pins. That applies to the XBP09 (900MHz) modules, and to the series 2 XBee ZB (Zigbee) modules, and to the Digimesh modules.

I was planning on using the Propeller to be attached at one end anyway for controlling the signal states.

A high gain directional antenna could help a lot. One approach to that would be to pick one from the list of antennas you can find in an appendix to the XBee manual. The DIY option (cheap) is to find one of the many references on how to extend the range of your wifi, same 2.4GHz frequency as the XBP24. There are pringles cans, beer cans, and DIY parabolic reflectors. Example, follow links here. The important thing is signal-to-noise ratio, so find a quiet channel among all the 2.4GHz traffic.

One of the big problem for the "line of sight" issue is not much the curve in our line its the hill that forms the curve that the line follows. Will directional antennas do any good or is it better "hop" to the other building instead?

Tracy Allen

The hill is definitely a factor. I've heard of people putting a passive reflector at the top of a hill so that they could connect to the free wifi at a cafe on the other side. I don't know how that really worked out.

I think you'll just have to try to see how far it will go once you have the radios. Use the XCTU or some other range test program that monitors the error rate as you walk it away. 900MHz would probably fare better than 2.4GHz. Radio propagation can be funny. Even if you get it working one day, success may also depend on weather and how many others around are using the channels, etc. Indeed, the most reliable would probably be more hops to bring it around the hill.

bsnut

I am going consider this thread solved, since I will be going to (more in likely) use the 900MHz Xbee module due to the fact of the being able to extend the antenna and locate the Xbee module near my micro.

Tracy Allen

Please let us know how that works out. Note that Digi is in transition with the 900MHz modules. The XB09 series is being discontinued and they are coming up with the XB9P series, ostensibly better performance, but the two series are not compatible.