Jee Labs Talk

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1. ericvrp
   

   Hi,

   I am a freediver (as long/far/deep as possible on a single breath of air) that trains a lot in pools and also in lakes/seas (up to 60+ meters deep). I'm working on an Arduino/Jeenode based pool training tool. Instead of buttons I will use an accelerometer that detects taps on the various axis. I was thinking about buying a simple transparent waterproof box (like the Otterbox 1000) so I will be able to read the lcd. But does anyone perhaps know of a way to make an Arduino waterproof to a depth of over 100 meter?

   cheers Eric van Riet Paap, Utrecht, Netherlands.

   Posted 22/02/2011 11:54:56

2. lurks
   

   I'm a 'tech' scuba diver and I've done this. Not with an arduino exactly but it still applies. 100m is extremely difficult, 11 atmospheres. I used a machined block of a type of plastic, the same technique used to make low production run dive computers and so on.

   It works okay but we're talking about a fair bit of work to get it in and out of the box and any sensor/connections to outside the box are extremely problematic. I had holes drilled and ran solid metal through which I used as electrodes to detect hitting the water, and running signals to a pressure sensor.

   There are probably less elaborate ways of solving this, particularly if you really don't need 100 meters. Since the free diving record is something like 80 meters, you can probably scale it back a bit. :) Machined out acrylic would be fine well past 50m. I'd say drilling fine holes through and running wires through the holes filled with epoxy resin would work pretty well.

   The wires need to be held though, otherwise they'll be pushed into the case, epoxy or not. Then again I guess you're only dipping down and back right?

   Posted 22/02/2011 13:01:59

3. ericvrp
   

   Freediving world records are far deeper than 80 meters. 124 with a monovin right now and in the no-limits discipline the record is over 200 meters deep. The dutch no-limits record is 80 meters indeed. And thats because the interest in that discipline among dutch freedivers has just started growing. WR: http://en.wikipedia.org/wiki/Freediving#AIDArecognizedworldrecords NR: http://www.dfa.nu/?pageid=47

   Anyway... I agree that deep diving with an Arduino has no purpose apart from an experimental point of view. But I am hoping for a solution where I can take it with me without being worried it will not survive.

   During these deep dives it is indeed dive down and up again at an average speed of 1m/s so dives take anywhere between 2 and 4 minutes.

   Posted 22/02/2011 17:56:10

4. jeroen
   

   Pffff freediving on a single breath of air, 60 - 80 meters? And you are worried that the hardware will not survive ? For me the hardware part is the least I would worry about. But what do you think of molding everything in epoxy.

   Posted 22/02/2011 18:12:59

5. ericvrp
   

   Would that actually work? I think a battery would produce gasses. And would epoxy be (and stay) translucent enough to be able to read a display?

   Posted 22/02/2011 18:39:16

6. templar
   

   Perhaps fill the enclosure with oil? It doesn't short the circuit and counteracts the outside waterpressure. I 'm not sure about pressurizing DIP packages, is it liquid proof?

   Posted 22/02/2011 21:29:31

7. markt
   

   DIP packages are solid, not going to be a problem I think but the crystal or resonator can could be crushed. Potting the whole circuit is probably the most reliable method - and starting with a small version like the Mini or Mini Pro would make things easier (and a bit cheaper in case of failure).

   At high pressure a battery isn't going to make gasses, they stay dissolved. The problem is liquids forcing their way into the battery via the pressure-relief vent?

   Posted 23/02/2011 00:03:31

8. ericvrp
   

   an update...

   I've put one Jeenode with graphics lcd, piezo speaker, stripped Nunchuck and an AA power board in a transparent Otterbox 1000. Another Jeenode with a 16x2 lcd and lcd plug I put in a bigger Otterbox 2000. These boxes are affordable yet waterproof till 100 feet (thirty something meters) and are good enough for my current experiments leaving even deeper experiments as a future exercise.

   Last week I took the small box to the bottom of the pool (3.5m) to see how well a big clock on the graphics lcd would look. It was visible up to about 5 meter. Today I let the two boxes send each other wireless messages to see how that would work under water. I expected 10cm at most but was surpriced that 1 meter from either side of the bath to the other worked fine. Tomorrow I'll do a more extensive test in the pool. I'm currently using the default speed at 868 Mhz.

   I intend to recheck with a lower speed on wednesday and perhaps on another frequency if someone thinks that would be better.

   Than on friday I will take the two Jeenodes to the bottom of a 20 meter deep pool.

   - Eric

   Posted 14/03/2011 23:09:15

9. johno
   

   Very interesting - good luck on Friday.

   Posted 15/03/2011 07:01:02

10. tankslappa
    

    Sounds fascinating. From my rather more boring air based test, the range does increase quite significantly by dropping the baud rate.

    Don't forget to try to keep the antennas aligned. If one is horizontal and the other vertical you could seriously impact the range just with the mixed polarisation.

    And don't forget some pictures http://www.flickr.com/groups/jeelabs/ ;-)

    Posted 15/03/2011 08:02:13

11. ericvrp
    

    Ok, an 'entertaining' video on http://www.youtube.com/watch?v=tUleZbPKjgs and a picture in http://www.flickr.com/groups/jeelabs/

    The small Otterbox with the bigger Graphics lcd is setting a pixel every time a wireless packet is send and acknowledged. The other box is displaying the number of received packets. Every 100 packets it briefly turns of the lcd backlight, which is visible on the video.

    Posted 15/03/2011 08:19:03

12. tankslappa
    

    Excellent! Looks like you need to reduce the buoyancy a little... More batteries?

    When I see them glowing in the sink I can't help but wish for a remote control and direction thrusters :-)

    Eric's bathtime fun!

    Posted 15/03/2011 08:31:28

13. ericvrp
    

    I like the fact that it's floating up. Not much fun to sprint after sinking equipment. The big box is perhaps to buoyant but that is just the backup device anyway.

    I'd love to build a programmable underwater vehicle/thingy actually but such a project would be to big for me on my own at this stage in my makers career. Perhaps some people in the Netherlands have experience with building something like that? ;-)

    Posted 15/03/2011 08:47:42

14. tankslappa
    

    I didn't mean a full size diver propelling device, or wreck exploring mini-sub! Just something you could drive round the bath tub for ummm absolutely no reason!

    I'm not sure if those in the flat country like playing with water, they seem to spend most of their time sticking fingers into walls to keep it out! :o)

    Posted 15/03/2011 09:54:29

15. ericvrp
    

    In the pool it only received packages up to about 30cm or double that if I keep the devices against a wall/floor. Will try slower transmission and different frequencies next time.

    Posted 16/03/2011 09:36:36

16. jcw
    

    I suspect that 433 MHz will work better, but with a 868 MHz unit you're not going to get good 433 MHz results as the on-board circuitry is really tuned to 868. I don't have 433 MHz units, unfortunately.

    Your next best bet is to lower the transmit rate and reduce the bandwidth. There have been posts about this on the forum, by Jeroen IIRC.

    Posted 16/03/2011 12:59:13