[aprssig] NMEA output GPS or compass?

[John Gorkos]

So, does it just want GPHDT?  Putting together a microprocessor that
reads a 3DOF compass sensor and outputs the NMEA sentence once per
second is an Arduino-101 project.  Hardest part would be getting the
signal levels correct going to the back of the LD-250.  The entire thing
would fit in an altoids tin (but shouldn't... you know... the whole
magnetic field sensor doesn't like that).

de AB0OO

On 6/29/18 13:41, david vanhorn wrote:
> The GPS really would add nothing to the system.  Their map is static.
> 
> 
> On Fri, Jun 29, 2018 at 11:52 AM, John Gorkos <jgorkos at gmail.com
> <mailto:jgorkos at gmail.com>> wrote:
> 
>     I'm a little late to this, but what input is the LD-250 looking for?
>     If it's straight NMEA with GPHDT sentences, why not just build your own
>     little device to do that?  Seems to me, you could do the whole thing for
>     about $80:  a $10 Atmega µProcessor like a trinket, a $15 triple-axis
>     accelerometer board with a LSM303DLHC chip on it, and a $40 GPS board
>     with NMEA out.  Throw in a $10 level converter to get the output signals
>     up to "true" RS-232 levels, and put a little glue code in there to
>     generate the GPHDT sentence and mix it with the NMEA stream from the
>     GPS, and put it all in a nice little box with a power plug on it.
> 
>     Heck, send me $80 and give me a week, and I'll send you the box.  I've
>     got everything I need sitting here on my test bench.
> 
>     John Gorkos
>     AB0OO
> 
>     On 6/29/18 10:27, david vanhorn wrote:
>     > Thanks all. 
>     >
>     > I am going to hold off till I find a fluxgate compass.  The GPS route
>     > would "work" but this thing has enough issues already.
>     >
>     > The Boltek LD-250 is " Long Range detection Designed for mobile
>     use in a
>     > moving vehicle with a GPS or Compass connected " (From their web site)
>     > However..
>     >
>     > Their software doesn't work with any known map program.
>     > The unit sends strike information as bearing and distance relative to
>     > the front side of the sensor.
>     > If you add a compass, the strikes are rotated accordingly.
>     > The strikes are not converted to anything like an object at a
>     coordinate
>     > though, so if the vehicle is moving, they are "smeared" across the
>     map.
>     >
>     > It's only really useful while moving if the strikes are converted to
>     > absolute rather than relative coordinates, and then the image is
>     rotated
>     > and panned accordingly to the vehicle rotation and motion.
>     > I could easily live without an actual map
>     >
>     > The GPS wouldn't give me workable heading data when not moving,
>     and the
>     > LD-250 doesn't give useful data while I am moving..
>     >
>     > With a compass, at least I could park in whatever direction works, and
>     > I'd get a display rotated so that it's oriented north up.
>     >  
>     > It's a fixed location instrument in a mobile package.   The only
>     plus is
>     > that it doesn't require a full PC with PCI slot to run.
>     >
>     > Basically, in the 10 years since I last used it, the half-assed
>     > implementation of their software hasn't improved at all.   I need
>     it to
>     > be at least 3/4 assed. :)
>     >
>     > It would be really cool if some working mobile app/program whatever
>     > could be trained to hear their data and plot it on a working map.
>     >
>     >   $WIMLI,<ddd>,<uuu>,<bbb.b>*<cs><cr><lf>
>     >  
>     > <ddd> - corrected strike distance 0-300 miles
>     >   <uuu> - uncorrected strike distance 0-300 miles
>     > <bbb.b> - bearing to strike 000.0-359.9 degrees
>     >        <cs> - checksum in hex
>     >    <cr> - carriage return
>     >    <lf> - line feed
>     >
>     >
>     >
>     > http://www.boltek.com/manual-ld-250.pdf
>     <http://www.boltek.com/manual-ld-250.pdf>
>     >
>     > On Thu, Jun 28, 2018 at 7:25 AM, david vanhorn <kc6ete at gmail.com
>     <mailto:kc6ete at gmail.com>
>     > <mailto:kc6ete at gmail.com <mailto:kc6ete at gmail.com>>> wrote:
>     > 
>     > 
>     >     I'm reactivating an old project, and I would like to find an NMEA
>     >     output GPS unit like the old Garmins with their four pin connector,
>     >     or a compass with similar output.
>     > 
>     >     What I've seen in compasses are crazy expensive ($500), and GPS
>     >     units seem to all be USB output now if they have any external data
>     >     connection at all.
>     > 
>     >     What I absolutely need at a minimum is a compass or GPS with an NMEA
>     >     output. The system has NMEA+ NMEA-, +12V power to compass/GPS and
>     >     ground.  If it's a GPS unit, I would prefer some sort of simple
>     >     "puck" style unit rather than something with a display and buttons
>     >     to misconfigure.
>     > 
>     >     Any sources coming to mind?
>     > 
>     > 
>     >     -- 
>     >     K1FZY (WA4TPW) SK  9/29/37-4/13/15
>     > 
>     > 
>     > 
>     > 
>     > -- 
>     > K1FZY (WA4TPW) SK  9/29/37-4/13/15
>     > 
>     > 
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> 
> -- 
> K1FZY (WA4TPW) SK  9/29/37-4/13/15