[aprssig] BOUY 4

Dave Baxter Dave at emv.co.uk
Thu Aug 7 08:38:00 EDT 2008

Many SAR EPIRB's use a similar system.  No where near as complicated as
hall sensors etc, if they are in the holder, a magnet in the holder
pulls a read swtich, so it opens the battery connection.

Once removed from the holder, the read's NC contact makes again (no
magnet) and the things burst into life.

For your Bouy project, just a clip on, or "push-in-a-hole" (a "blind
hole" so water doesnt get into the bouy inards) small bar magnet should
do the trick.  They don't have to be too strong a field either to flip a
read switch...

Or, even try a "Clunk" switch.  Turn the whole thing upside down, and it
powers off.  Right way up, it powers On.   Simple to engineer too.   A
toggle switch near a slide, where a weight can pass by and flip it one
way or the other.   I forget where and on what, but I've seen that done
too for some marine application or other.


Dave G0WBX

> -----Original Message-----
> From: Steve Noskowicz [mailto:noskosteve at yahoo.com] 
> Sent: 06 August 2008 19:26
> To: TAPR APRS Mailing List
> Subject: Re: [aprssig] BOUY 4
> Hmmm.  The Hall sensor still needs a power supply, but I 
> don't know the draw.  I have some in my well stocked studio 
> B, but haven't played with them yet.  See my previous about 
> reed switches.  I like the idea of a magnet-in-a-tube + reed 
> switch.  You can even have something for the magnet to sort 
> of "stick to" in the ON position, so it takes inversion *and* 
> a shock to set it free down the tube and to turn it OFF..... 
> the wheels are turnin'.
> FYI: STRONG magnets   Gauss Boys  http://www.gaussboys.com/ magnet 
> --
> 73, Steve, K9DCI
> --- On Wed, 8/6/08, Ben Jackson <ben at ben.com> wrote:
> > From: Ben Jackson <ben at ben.com>
> > 
> > ...snip... daydream about from time to time I was
> > planning to use
> > a hall sensor so that a properly placed external magnet
> > would turn off
> > the buoy.  I figured a metal plate on the inside would give
> > it something
> > to stick to, and the sensor would be weak enough to require
> > some super-
> > strong magnet (like one out of an old harddrive).  Then the
> > magnet would
> > have a float that would remove it in case of accidental
> > deployment w/
> > magnet.
> > 
> > -- 
> > Ben Jackson AD7GD
> > <ben at ben.com>
> > http://www.ben.com/
> > 
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