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'[PIC]: mini 16F876 datatogger'
2002\03\08@124913 by Drew Vassallo

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>That sounds like a very tough problem.  Unless these loggers are almost
>exactly the same density as the water, they will get caught somewhere in 8
>miles.  Probably even then.

My thoughts exactly.  Not so much the density problem (which will, of
course, vary with changes in temperature, requiring the ball's material to
also change in the exact rate as the water, which is for all practical
purposes, impossible), but in 8 miles of cavernous obstacles, passages,
submerged rocks, etc., what makes you think that a ball of size "X"
(presumably it will be several inches in diameter) will make it through
EVERY possible obstacle in 8 miles?  Perhaps the water filters through rock
and silt layers before it gets to the spring, in which case the datalogger
balls will simply pile up at the first aquaclude.  I would think that you
would want to send some "blanks" through first, say of the same diameter but
no internal components, just to make sure an object of that size can pass
through.

My recommendation for the problem of sinkage or floatation of the ball is to
make it such that it floats, but only barely.  Say, with a specific gravity
of 0.90 to 0.95 or so.  This will prevent it from getting hung up on
obstacles above the water (the ball will simply get knocked downwards into
the water for a short time), while keeping it off of any submerged
obstacles.

--Andrew

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2002\03\08@131155 by Eoin Ross

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But then there is the question of what happens in a large pool where the exit is under the surface - the balls would end up being stuck there floating.

The variation in displacement may be necessary ... but could be a little tough on the battery.

I'm picturing a tube flush to the exterior of the ball (and running inside the ball) with a piston driven by a solenoid. The ball should have a specific gravity of one (at the temperatures one is expecting) with the piston 1/2 way along it's travel.

I agree with the doing a trial of dummy balls - evidently the dye gets through which may suggest there is not TOO much filtering,
but a 2"/50cm ball is another story.
(but if one uses SMT and a higly integrated PIC the size could be squeezed further)
I believe Joe Colquett has a temp curve for one on the timers/oscilators on a PIC?

>>> spam_OUTsnurpleTakeThisOuTspamHOTMAIL.COM 03/08/02 12:49PM >>>
>That sounds like a very tough problem.  Unless these loggers are almost
>exactly the same density as the water, they will get caught somewhere in 8
>miles.  Probably even then.

My thoughts exactly.  Not so much the density problem (which will, of
course, vary with changes in temperature, requiring the ball's material to
also change in the exact rate as the water, which is for all practical
purposes, impossible), but in 8 miles of cavernous obstacles, passages,
submerged rocks, etc., what makes you think that a ball of size "X"
(presumably it will be several inches in diameter) will make it through
EVERY possible obstacle in 8 miles?  Perhaps the water filters through rock
and silt layers before it gets to the spring, in which case the datalogger
balls will simply pile up at the first aquaclude.  I would think that you
would want to send some "blanks" through first, say of the same diameter but
no internal components, just to make sure an object of that size can pass
through.

My recommendation for the problem of sinkage or floatation of the ball is to
make it such that it floats, but only barely.  Say, with a specific gravity
of 0.90 to 0.95 or so.  This will prevent it from getting hung up on
obstacles above the water (the ball will simply get knocked downwards into
the water for a short time), while keeping it off of any submerged
obstacles.

--Andrew

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2002\03\08@135711 by M. Adam Davis

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Better yet, put a 3 axis accelerometer and gyroscope in there, as well
as a very very slow radio link (10 bps or slower).  Then you can have an
outside transciever recieving the info, and you can tack its path.  If
it seems to be stuck you can manipulate the piston yourself.

Maybe too ambitious, but fun to think about.

-Adam

Eoin Ross wrote:

{Quote hidden}

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2002\03\08@141812 by Eoin Ross

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Thought about that - a map of the caves would be a good bonus, guessing that cave divers aren't able to go through the cave concerned -  the original poster is in Italy it seems

THe radio link would have to be slow due to the frequency you'd be forced to use, UHF,VHF,SW,MW,LW would all be too high in frequency to penetrate the rock/water.

You'd be forced into used the similar frequencies used for communication with Subs :) They use 40-80 Hz electomagnetic waves (yes you read correctly - no multplier)

Found an interesting link the other month while looking for something completely different.

http://www.fas.org/man/dod-101/navy/docs/scmp/part07.htm http://enterprise.spawar.navy.mil/spawarpublicsite/docs/fs_clam_lake_elf.pdf

>>> adampicspamKILLspamUBASICS.COM 03/08/02 01:54PM >>>
Better yet, put a 3 axis accelerometer and gyroscope in there, as well
as a very very slow radio link (10 bps or slower).  Then you can have an
outside transciever recieving the info, and you can tack its path.  If
it seems to be stuck you can manipulate the piston yourself.

Maybe too ambitious, but fun to think about.

-Adam

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2002\03\08@142028 by kent

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How about making the ball soft, pressurize it and put some muscle
wires into it. Let it squeeze itself every 2 hours or so to avoid
obstacles up top.

Or - get a small lump of a solid freon with a sublimation point of 20
degrees C. Heat slightly to inflate the ball and thus get it off
obstacles down low.

Kent

{Quote hidden}

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2002\03\08@154112 by Olin Lathrop

face picon face
> My recommendation for the problem of sinkage or floatation of the ball is
to
> make it such that it floats, but only barely.  Say, with a specific
gravity
> of 0.90 to 0.95 or so.  This will prevent it from getting hung up on
> obstacles above the water (the ball will simply get knocked downwards into
> the water for a short time), while keeping it off of any submerged
> obstacles.

This will get caught in the first pool that has an outlet under the water
surface.  Such things are common in caves.


********************************************************************
Olin Lathrop, embedded systems consultant in Littleton Massachusetts
(978) 742-9014, EraseMEolinspam_OUTspamTakeThisOuTembedinc.com, http://www.embedinc.com

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2002\03\08@154117 by Olin Lathrop

face picon face
> Better yet, put a 3 axis accelerometer and gyroscope in there, as well
> as a very very slow radio link (10 bps or slower).  Then you can have an
> outside transciever recieving the info, and you can tack its path.  If
> it seems to be stuck you can manipulate the piston yourself.

You're not going to get radio waves from a 2 inch ball to go thru any
significant amount of water and rock.


********************************************************************
Olin Lathrop, embedded systems consultant in Littleton Massachusetts
(978) 742-9014, olinspamspam_OUTembedinc.com, http://www.embedinc.com

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2002\03\08@154123 by Olin Lathrop

face picon face
> You'd be forced into used the similar frequencies used for
> communication with Subs :) They use 40-80 Hz electomagnetic waves
> (yes you read correctly - no multplier)

Yeah, and with a miles long antenna in northern Michigan.  Think about what
fraction of a wavelength the 2 inch ball is.


********************************************************************
Olin Lathrop, embedded systems consultant in Littleton Massachusetts
(978) 742-9014, @spam@olinKILLspamspamembedinc.com, http://www.embedinc.com

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2002\03\08@162757 by Drew Vassallo

picon face
> > My recommendation for the problem of sinkage or floatation of the ball
>is
>to
> > make it such that it floats, but only barely.  Say, with a specific
>gravity
> > of 0.90 to 0.95 or so.  This will prevent it from getting hung up on
> > obstacles above the water (the ball will simply get knocked downwards
>into
> > the water for a short time), while keeping it off of any submerged
> > obstacles.
>
>This will get caught in the first pool that has an outlet under the water
>surface.  Such things are common in caves.

This is correct, of course.  Someone else mentioned this.  I didn't consider
hidden pools.

But I also don't consider any of the mechanical squeezers viable options,
either.  Provided that this is battery powered, constantly changing the
pressure with a servo/piston would consume much power, particularly since
the 8-mile journey will likely take several weeks to occur, if at all.  And
if you put a 2-hour time frame on pressure changes, it may take days or even
weeks just to get past a 100-yard section filled with obstacles.

Remember, earlier in this thread people were suggesting using low power PICs
and shutting everything off between samples just to conserve a few
microamps.  Now you're talking several hundred milliamps to operate your
pressure system every 2 hours over what's likely a several-week period of
time.

I don't know what the size of this underground spring is, but I don't think
we're talking "Old Faithful" here.  Generally, they're more like a slight
trickle through a series of small cracks in the soil.  I could be wrong,
though.  Even artesian wells only fill very slowly.  I don't think there are
any 2" diameter channels through the earth for the water to travel.

--Andrew

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2002\03\08@171339 by michael brown

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>You'd be forced into used the similar frequencies used for communication
with Subs :) >They use 40-80 Hz electomagnetic waves (yes you read
correctly - no multplier)

If you can figure out a way to actually radiate anything measurable at that
frequency from inside of a ball (less than 500' in diameter), you will be
the King of antenna theory.

<GRIN>

michael

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2002\03\08@193840 by M. Adam Davis

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You'd have to have a /really/ /really/ sensitive receiver, that was
essentially measuring changes in the magnetic field.  The transmitter
would have to use some spread spectrum signalling.  Using a pretty
powerful computer with a sensitive receiver on the top should do ok.

The transmitter would essentially be a small electromagnet putting out a
pitifully small magnetic field.

Getting the ball to receive something from the top would be tricky, but
since we have lots of space and power on the top, it really shouldn't be
overly hard.

Also given that you know the location and orientation of the ball you
can use some array of receivers and advanced filtering algorithms to
detect the signal better.  This would be complicated by the changing
composition of the materials in between, but that could simply be
another thing to learn about...

But then, anything is possibly with enough time, money, and research.
This is not practical, especially for the project at hand.  But I bet
the poster could get a grant for it, if they wanted to invest time in a
system to map underground caves... ;-)

-Adam

Olin Lathrop wrote:

{Quote hidden}

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2002\03\08@194047 by M. Adam Davis

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A small electromagnet in the ball, and some /very/ sensitive hall effect
sensors on the surface in a large array.  Couple that with a
supercomputer and you should be able to extract the signal...

-Adam

michael brown wrote:

{Quote hidden}

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2002\03\08@201426 by Dave Dilatush

picon face
M. Adam Davis wrote...

>But then, anything is possibly with enough time, money, and research.
> This is not practical, especially for the project at hand.  But I bet
>the poster could get a grant for it, if they wanted to invest time in a
>system to map underground caves... ;-)

I found this page, at some point in my Web meanderings:

http://radiolocation.tripod.com/

A whole web site on through-the-earth radiolocation; check out the photo
gallery to get an idea of the hardware required.  Doesn't look like the
sort of thing that'll fit in a 50mm ball.

Dave

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