[TowerTalk] Motorized tower auto-lower

[Dave]

At 01:47 PM 08/06/2000 -0700, WK6I wrote:
>
>
>hi Dave - nice writeup! I do see that your needs are different, and of course 
>that's cool.
>
>And for the record, poorly protected swimming pools and auto-lowering towers do
>concern me equally - good analogy, actually. Both cause many tragedies
around here, 
>I'm sorry to say...

We had a small tornado through a few months ago. A lady was standing outside
when a sign struck and killed her. The family is suing the sign company and
the hotel she was staying at. I am sure the insurance company will settle
out of court as this seems to be the way things work these days. When you
think about it, can anyone build a sign that will stay up in 100 - 300 mph
winds? Maybe the families of people killed by nondeterminate flying debris
during a tornado can just sue all the surrounding neighbors. Maybe the
governement can start requiring molecular serialization of all materials in
order to trace the origins. This would greatly facilitate lawsuit
preparation... Don't get me wrong, I am sorry the lady died, but considering
how many other signs were blown away during the storm, I can't see this as
some manufacturing defect. Maybe it is just the cost of being in the sign
business. Likewise, there is an inherent liability in having a tower,
driving a car, walking, etc....

>Regarding debounce: I was presuming the wind speed was indicated with a series
>of pulses from the measuring device. Even if the measuring device
pre-conditions
>the pulses to be clean, noise can still be a factor (is it single-ended or
>differential signaling?). Just taking a generic example, a pulse train with a
>bad leading edge can make a 30mph indication look like 60mph wind, just from
>double clocking. If you don't mind that then no big deal, but it sounded like
>you care about maximizing up time, so accuracy is important. These simple
counter
>devices can be very sensitive to edges, so conditioning inputs is important,
>as I expect you know.
>
>The cool thing about a PIC (or something like it) is that you can make a lot
>of changes and adjustments without making hardware changes. A PIC could be your
>counter, timer, and receiver/conditioner - and could also be part of the
process
>to raise the tower later. Maybe this project would be a good vehicle for
learning
>about this stuff...?

I have thought about using the PIC on a number of occasions, but I usually
end up using a Motorola micro for the job. For most of the stuff I do, the
PIC is usually not quite large enough in regards to I/O.

>good luck on the project - hope this helps!-) - js
>
>ps: please educate me, because I am mercifully clueless about tornados, but it
>would seem that if a tornado hits your tower, it is toast cranked up OR
down...?

True to a point. We have a lot of 70+ feet trees around here. They make a
substantial wind break for lower objects. We have been through 6 tornadoes
in our current house and only lost most of the shingles on our roof a couple
of times, but we had a lot of tree damage. The interesting thing is that
damaged trees that aren't out right toppled over, tend to be broken 15 - 25
feet up. The same effect is often witnessed by pilots close to landing. Even
a 100 feet above the runaway you can experience winds that would preclude a
safe landing, only to find them less powerful (and within managable
tolerences) 3 feet off the deck.  
One particurally interesting storm left a path of trees with the tops
twisted off 20 or so feet of the ground. The length of the path was about
half a mile. That was truly an odd sight :-)
Being in the direct path of a tornado in the F3 or better size leaves little
room for much of anything to survive. Fortunately, the bigger ones are rare,
although we did witness an F6 a few years ago. Obviously, we were not in a
direct path. I think HBO has a program they put together on that one.

73,
David W4DLB

>-- 
>jeff stai
>WK6I DM13
>NAR #21059 TRA #3356 L2
>jstai@home.com / wk6i@arrl.net
>ROC web page: http://www.rocstock.org/


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