On Tue, 27 Sep 2005, Jim Cheetham wrote:
John Carter wrote:
So start thinking, what could we do as part of CLUG that compares?
You mean in the "just hacking" vein?
Build a cluster of "spare" machines, and compute PI to a few significant
figures ... very cerebral.
Grab some control stuff (X10 or whatever) and hook up a IR webcam for
motion detection ... powering a water pistol to shoot cats entering the
garden late at night ... :-)
Speaking of control, buy a pulsejet off Bruce US$1500, wire a GPS +
embedded linux control + wings on it. Get the Green Glowing Potting
Shed Guy to donate a payload...
Nah.
Still what the X prize guys are doing is just so marvelous.
I have one idea on the back burner.
Imagine every tramper, every backpacker, every jogger, every frail old
lady staying on her own has a very cheap, very light little device on a
wire loop necklace....
Each little device would have a unique ID.
Imagine this little device was barely enough of a GPS to wake up every
two hours, find the exact time from the GPS, and it's position to
within about 100m and then go to sleep. It doesn't have to be fast, or
smart or accurate.
At a time, once every 2 hours, predetermined by it's ID, it would wake up and
screamed a radio frequency shout that contained it NZ grid coordinate, a 4
bit status value and a CRC check. That's all. Very very short.
The status value will be one of...
* I'm OK.
* I'm OK, but delayed.
* I need medical assistance.
* I need police assistance.
* ...
The time can be very precise, GPS satellites are basically just very very
accurate clocks.
The time of the shout === the ID.
The base station listening to the shout knows when exactly when to listen.
The shout will be very very short and very very loud 2 hours apart. Maybe
a 100th of a second. So you don't need a big power source, you don't need
big heat sinks. A fat capacitor, an AA battery or a calculator solar cell
will do.
Because the shout is so very short, and the exact waveform can be computed
way ahead of time, I can think of a bunch of tweaks to the standard
modem algorithms that will allow it to be even shorter...
Scattered around the country, on high hills would be a couple of base
stations with big antennae that on hearing one of these RF squeaks
would relay the info to...
* A web site.
* Emergency services.
John Carter Phone : (64)(3) 358 6639
Tait Electronics Fax : (64)(3) 359 4632
PO Box 1645 Christchurch Email : [EMAIL PROTECTED]
New Zealand
Carter's Clarification of Murphy's Law.
"Things only ever go right so that they may go more spectacularly wrong later."
From this principle, all of life and physics may be deduced.
