Alan B. Pearce wrote:
> 
> But hand on, why use wireless? If it is an irrigation system, then there are
> pipes wandering around the show, that he will not want to put his plough
> through, so why not have power/signal cables in the same trench? Or if the
> pipes have to come from a central point above ground to some spray unit in
> the middle of a field, why not have the cable laced to the pipe?

I think the main reason is that the pipes are already there and buried - 
digging them up again would be another ~month's work.  And then if the 
cable does get damaged somewhere, finding and fixing the problem might 
require digging it up again.  I don't know that /all/ the pipe runs are 
buried, but my recollection is that most are.  I'll confirm that, though 
- we should make sure we're not just using wireless because it's cool.  :)

I read another farmer's account of a similar project where he decided to 
use buried cables for simplicity and ended up regretting it - feeling 
that wireless would actually have been simpler in the long run.  And 
that was before these new low-power wireless protocols started coming 
out (or before I was aware of them).

One other note on the project - another benefit could be increased 
fault-tolerance.  The night before the last time I visited the farm, 
some valve had broken or come detached or something, and so they'd been 
pumping water at maximum pressure onto the ground (NOT near the crops) 
for an hour or something.  Half-drained their reservoir pond and didn't 
do the crops any good.  If there were a pressure sensor out at that 
valve, sending readings back to home base, it could have detected that 
and shut down the pump automatically.  Another feature that might be 
well worth the cost.
-- 
Timothy J. Weber                 http://www.lightlink.com/tjweber
tjweber@lightlink.com
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