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[on:]

I got this idea from recent news stories about messages in bottles being found on the shores of various places in the world after many years at sea.  I combine that concept with something I and a friend did as kids - we filled party balloons with homemade H2 with an attached, pre-addressed questionnaire post card in a plastic sandwich bag and a length of aluminum foil for visibility during a balloon's eventual descent - you can see one flashing in the sky for an amazing distance on a sunny day, long after the balloon would otherwise be invisible.  We received as I recall about five returned cards, all from several US states away (~300 miles) except for one which was found on a New Jersey beach about 1000 miles from its launch point.

I ask here for brainstorming about an Arduino environment developed, lowest possible cost, low-power, solar powered (with recharging battery) ATtiny system to act as an intelligent message in a bottle designator.  While floating at sea, it would not attract any attention to itself and would simply keep the long-shelf-life battery (or cell) charged whenever necessary during daylight hours.  When it senses that it has come to rest on a beach, it would wait for nightfall and set off a slow repetition rate LED strobe in the early hours of the evening, never using more battery power than could be restored in a few days by solar recharging.  A pre-addressed post card explanation and questionnaire (ex., "when and where did you find this?") would be included in the bottle.

I have no idea about the odds of something like this ever being found after sea launch, so it would need to be as inexpensive as possible to make it worthwhile.  It wouldn't be a mass effort by one individual, it would be a large number of individuals building (or buying one pre-made) and launching on their own.

[Reply #1 on:]

Good link that describes the power issues: http://tomtor.blogspot.com/2012/09/solar-powered-arduino-and-attiny.html

In sleep mode my attiny84 uses 0.004mA. When calculating it uses about 20mA, but it is sleeping most of the time. Running at 8MHz it will only execute code for about 1ms every 10 seconds, so it's average contribution to the power usage is 20/10000= 0.2mA.

As he mentions you could run an ATTiny for a year on a couple AA batteries (2200mah batteries / .2ma = 458 days) and even the smallest solar cell would power it "forever".  Not sure how you get a solar cell in a bottle though

[Reply #2 on:]

Great idea!  I've launched hundreds of large solar hot air balloons made with black trash bags.  Some had the ability to send their location using Wifi.  Others logged their path with GPS.  The last generation I could bring down using RF from miles away.  None had lights.  All of them had a laminated post card.  Most of them I got back when people found them, some hundreds of miles away.  Fun!

[Reply #3 on:]

Would be good advertising/competition for a soft drinks company (not to throw in the sea, all those bottles..)

Imagine a "limited collectors edition" bottle, that had a flashing message when it was empty.

[Reply #4 on:]

Make something a satellite can pick up at sea, then they might help as data on the trash-sargasso's.

[Reply #5 on:]

I have a satellite modem that could send the location from a bigger bottle.  Not so expensive!

[Reply #6 on:]

I'm just throwing this out there for anyone to work on if they chose to.  I'm nowhere near an ocean and have plenty of other projects to work on.

This would be a fascinating and challenging project to work on with all kinds of engineering decisions to make in order to produce something at very low cost that could remain at sea for years and still work upon landfall.  For instance, would the transparent PET plastic jar (wide mouthed for interior access and easiest type to get as it is the most common food packaging plastic) become sufficiently opaque over years of UV exposure to interfere with the solar cell output to a fatal extent?   Would algae accumulation (if any) do the same and would there be any commonly available product that could be used on the exterior of the plastic jar to prevent or reduce it?

The internal components would need to be mounted securely in a way that could withstand potentially years of high-g loads experienced within storm waves, preferably without any penetrations through the wall of the jar.  What commonly available adhesives should be used for that and for encapsulation of the ballast (ex., BBs or lead shot).  Heat due to solar insulation would be an issue to deal with (use Al foil inside jar as solar shielding above waterline except, of course, in front of solar cell).  Hail impacts on the somewhat flexible skyward wall of the jar would need to be considered to avoid damage to the solar cells(s) (ex., recess solar cell(s) from skyward wall).  And on and on.

The design should use through-hole components to allow easy kit assembly.  Off the top of my head, I don't know of any accelerometer ICs in DIP form for wave motion sensing and landfall detection.  I'd suggest using a UV LED as a UV photodiode as shown in my illustration below.  Below the waterline, UV would be low.  Once landed, the UV detected would be much higher.

UV resistant text would be used for the message and the jar would be marked in some way with something like "Message in a bottle" in several languages.  Which languages?  English, Spanish, French and Chinese?

Here's the concept:

http://www.slickpic.com/s/zjGMiyNNDOLGjj/_201210261017/photo?view=2369211#2369211

[Reply #7 on:]

I have a satellite modem that could send the location from a bigger bottle.  Not so expensive!

Wouldn't need to be as long as the led faces up and always the same color. There are satellites with spectrometers and after enough lights show up the measure would be analog.

Really it seems that a lot of trash accumulates in these places, if they knew how many bottles got tossed in then some data on roughly how many got into the mess might be useful.

[Reply #8 on:]

As he mentions you could run an ATTiny for a year on a couple AA batteries (2200mah batteries / .2ma = 458 days) and even the smallest solar cell would power it "forever".  Not sure how you get a solar cell in a bottle though

Roll it up and stick it down the neck...

[Reply #9 on:]

As he mentions you could run an ATTiny for a year on a couple AA batteries (2200mah batteries / .2ma = 458 days) and even the smallest solar cell would power it "forever".  Not sure how you get a solar cell in a bottle though

Roll it up and stick it down the neck...

Or simply use a wide mouth PET plastic jar as show in my concept jpg linked to above.  That would make the unit very easy to build as it provides easy access to the interior of the seagoing vessel.

[Reply #10 on:]

As he mentions you could run an ATTiny for a year on a couple AA batteries (2200mah batteries / .2ma = 458 days) and even the smallest solar cell would power it "forever".  Not sure how you get a solar cell in a bottle though

Roll it up and stick it down the neck...

Or simply use a wide mouth PET plastic jar as show in my concept jpg linked to above.  That would make the unit very easy to build as it provides easy access to the interior of the seagoing vessel.

Well sure if you want to do things the easy way...

[Reply #11 on:]

Discarded plastic is a real problem. Here is a project where there are so many flip-flops washing up on an Indian Ocean beach people can specialise in re-cycling them!!! Not only does that give a feel for the scale of the waste problem but the level of poverty in many areas;
http://www.swahili-imports.com/home/si3/page_5146/uniqueco__the_flip_flop_project.html

I don't know about you but every beach/coast I go to is plagued by this problem.
How does so much waste end up in the sea?

[Reply #12 on:]

Have you heard about the concentration in the Pacific Ocean?
http://en.wikipedia.org/wiki/Great_Pacific_Garbage_Patch

My friend has been studying it for years.  Want to know the truth about it?  Check out the images online.

[Reply #13 on:]

How does so much waste end up in the sea?

It is because -average- consensus awareness of trash has the garbage pail emptying into a black hole. Same way that water comes from faucets and disappears down another black hole, and electric just comes out of walls.
And whenever something is different there is upset until put back the same but don't remind people of what they don't want to know. The issue is solved for the majority through ignorance and denial, it is not enough to change an election so only gets lip service.

Hey, pollution's been an issue for me since 1969. I'm used to being in the minority.
Someone should give rich kids 'Jersey Beach Whistles' just to slap their parents heads.

[Reply #14 on:]

Well then I guess this project should probably use a relatively thick-walled glass bottle or jar, especially non-colored glass.  While there is still an issue of some creature accidentally eating it, a glass vessel if broken up would eventually be turned into small pieces of glass.  Common non-colored glass is almost three quarters silica (SiO₂), similar to a lot of the natural sands, along with some sodium oxide (Na₂O) and lime (CaO).  So even though it probably won't break chemically, if it does there's nothing involved that would be innately poisonous in small amounts.  Also unlike polymers, even small piece of glass wouldn't stay suspended in the water column indefinitely.  Instead it will act much like small rocks or sand, depending upon the size.

I'm certainly not in favor of adding to the oceanic pollution problem, but if this device is never found again it looks like a glass container would pose less long-term problems than a plastic one.  Of course that's not taking into account whatever is inside the container...