Idea for Openmoko application: Tide updates

Al Johnson openmoko at
Fri Sep 19 12:46:58 CEST 2008

On Friday 19 September 2008, Michael Shiloh wrote:
> Denis Galvão wrote:
> > On 18/09/2008, at 01:56, Adam Bogacki wrote:
> >> I like the concept and would like to volunteer to test a prototype in
> >> New Zealand conditions.
> >
> > For sure Adam.
> >
> > Like Michael said, we should start something in the wiki.
> >
> > I was looking for something similar and found this:
> >
> >
> > This is what Im looking for, at least as a water proof case.
> >
> > Is this possible to use the actual GTA_02 hardware version to do:
> > - Compass ?
> > - Altimeter ?
> >
> > How should be the best way to have this information on the phone?
> > Using an external hardware module?
> I'm thinking we need to make a generic expandable water proof (or at
> least harsh conditions proof) case for the FR.

Have a look at - their 1900 and 3600 cases may be what you're 
looking for. I'm going to ask them about custom cases for the openmoko, 
either as something to clamp around as they do with their other 
phone-specific cases, or as a total case replacement.

> For rapid prototyping, the very best interface would be USB. Future
> applications might tie in at a more intimate level. At least for the
> sensors mentioned so far the data rate is slow enough that our USB could
> easily handle it.
> I'm envisioning something that looks like a Pelican case, one of the
> smaller ones, with the guts of a FreeRunner and room for additional
> hardware, perhaps an Arduino board, extra sensors, and an extra battery,
> but still handheld.
> Some Pelican cases have a clear cover.
> I've wondered if there exist waterproof button activators that transmit
> force via a magnet, like magnetic stirrers or pumps, so that there is no
> hole in the case, no gaskets, and no place to leak (assuming the
> original case is waterproof in the first place). Anyone know of such a
> thing?

I have seen such things but they were large and expensive. They'll also play 
havoc with your magnetometer ;-) They should be fairly easy to DIY though - 
hall effect sensor or reed switch on board inside the case, magnet outside. 
You may be able to reuse the membrane from a keyboard to hold the magnets in 
place. Hall effect sensors probably give more scope for setting the trigger 
level if you're doing this. Inductive or optical sensors might be worth a try 

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