> I didn't think 422/485 would handle the long runs. That sure would
> make life easy if it could work with it.

You can use repeaters to increase the length and number of nodes handled.

> The actual data I'm dealing with is very limited. For the most part it consists
> of exchanging a few bytes of data every few minutes. My concern was that
> the overhead from using ethernet would choke the pic.

This sounds like rs-485 to me.

> Part of the reason for considering tcp-ip/ethernet was the number of required
> sensors  On this demo sized field I'd guess I need to talk to around 250 nodes.
> On a large field they would deploy anywhere from 3,000 to over 10,000 nodes.

You can do this with rs-485. You just need to use a protocol that has that
much address space.

And an rs-485 node can be much less expensive than an ethernet node, which
might matter if you have 3k to 10k nodes.  :)

> I had considered RF but they do not want any emissions on any frequency. The
> demo is planned to be setup near a radio telescope so I guess they want to
> be good neighbors.

This sounds interesting. I would definately use good shielded cable.

Please let us know how it comes out.

> Actually the more I look into this I think a nice paper route is the way to
> go....be my own
> boss, flexible hours...;-]

I had the paper-route. I had to get up to early and was too disorganized.
That's why I've worked at the university level for the last 25 years or
so.  :)

> Now I'm sitting around here trying to think what kind of sensor you use for
> dinosaurs or bigfoot...

Well, they sound like they have heavy footsteps. How about some sound or
accelerometers mounted underground? Even seismic sensors might do it.  :)

Of course, since nobody can seem to actually find these things on demand,
maybe they've gotten stealth over the years. You may need a ninja detector.
--
D. Jay Newman           !
jay@sprucegrove.com     ! Xander: Giles, don't make cave-slayer unhappy.
http://enerd.ws/robots/ !

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