Which protocol to implement on a home brewed diving computer ?

[Anton Lundin]

On 17 March, 2015 - Thomas Schrein (mailinglists) wrote:

> Robert,
> 
> Am 16.03.2015 um 17:35 schrieb Robert Helling:
> >Thomas,
> >
> >>On 16.03.2015, at 14:29, Thomas Schrein (mailinglists)
> >><tsx508 at schrein.de <mailto:tsx508 at schrein.de>> wrote:
> >>
> >>The housing of oDiCo is made from plexiglas version 0.1 and filled with
> >>silicon oel. The next housing 0.2 will be milled from POM and the
> >>electronic will be an industry factored PCB. Awating to have it in the
> >>lake in June ...
> >
> >once you are in the habit of making housings, you might be interested in a
> >project idea that came up here a while ago: We all love to have cylinder
> >pressure graphs in our logs. But for the dive computer to records those
> >you either need a hose that tends to be in your way or a radio
> >transmission which is hard to make reliable. The idea was, during the dive
> >to stick with an analogue gauge (as the history is mainly important in the
> >log only) but attach a little data recorder with pressure sensor directly
> >to the first stage to be read out later together with the dive computer.
> >
> >I did not really pursue this idea much further since all the pressure
> >sensors I could find that fit the specs (up to 400bar with at most a few
> >bar resolution an simple readout) almost costed as much as the pressure
> >radio transmitters (120-150 Euro/pcs) and, more importantly, my total lack
> >of experience in building watertight housings.
> >
> >You might be at least the solution to part two of the problem. What do you
> >think?
> 
> Nice idea, never thought about such a logger.
> 
> Let me first give you an overview about our approach:
> We have an 400bar industry sensor in test. We will connect it to our
> hardware version 0.1 in the next weeks and go diving.
> We made an adapter to connect it to the high pressure hole on the regulator
> and connect it with an M12-Sensor wire to the existing odico housing.
> http://www.skin-diver.org/skd/export/sites/default/sdiv/bastelecke/odico/odico-entwicklung-2014/IMG_2159.JPG_1997443631.jpg
> It works on the land, but we are not sure if its really watertight, that we
> will see in the dive.
> http://www.skin-diver.org/skd/export/sites/default/sdiv/bastelecke/odico/odico-entwicklung-2014/IMG_2179.JPG_1997443631.jpg
> 
> One option (may be you better say vision ;-) in our project is to use the
> odico electronics to control a rebreather using CANBUS (the controller has
> it build in already) and therefore the high pressure sensor would act as an
> CANBUS node with its own buildin controller, in particular a STMF1x, less
> then 5€ each.  The electronics could be sealed with casting resin.
> For our rebreather approach we accept the existence of wires, so we don't
> need to care about energy and communication. The pressure sensors cost about
> 80€, plus the adapter for the high pressure, plus the wiring, but that costs
> are not a big deal to run a rebreather.
> My fellow, Marco, also doesn't care to much building even an self made
> pressure sensor with build in electronics . He has a degree as mechanical
> engineer and he's really gifted for job!
> So we don't care too much to get it water tight.
> 
> From my point of view a logger could be designed like this:
> - located at the high pressure hole of the first stage
> - length about 5 - 10 cm, cylindrical
> - collecting data for pressure + time
> - as an option: collection depth+temp
> - energy by an AAA or 1/2 AA lithium 3v cell than could be replaced once a
> year
> - communication via radio (bluetooth, ...)
> - shop price < 200 €
> 
> Again, I never thought that would be worth to think about it. I will discuss
> with Marco!
> If you like we can discuss more.
> 

I would be interested in such a device, even if they would be built as
one off jobs.


Only thing i would argue is really important is to make sure they fail
in a sane manner, and doesn't leak or dump my gas.



Now this one is seriously OT but a idea i hand a couple of mates had as
a idea, a depth/time logger with a accelerometer/gyro and try to use that
as a mapping device to try to figure out how your movements under water
actually where.

I talked with another mate who's in the defense industry and they have
such devices on there (semi)autonomous rovs, but they combine the
accelerometer/gyro with sonar and doppler radar against its surroundings
for more input to their odometry models.


That would be really cool =)


//Anton


-- 
Anton Lundin	+46702-161604