Digitrak only needs basic positional information from the GPS on a regular
basis.
It will use this information to fly the track that has been set on the Digitrak.
If a route is programmed in to the GPS, it will fly that too (with different
commands
being set at the Digitrak control head to enable this), so long as the
GPS is also putting out the crosstrack error signal; not all of them do.
Duncan McF.
> On 10 November 2022 at 10:31 Dpc <dpc@knightonweb.com> wrote:
>
>
>
> Thanks, Duncan.
>
> Interesting observations re magnetometer-driven track following and also the
effects of damp/winter!
>
> Im being rather slow here but Im still not clear: If we want the Trutrak to
> control
by GPS input rather than by its own magnetometer input (which seems to
be wobbly), do we need to have a desired ROUTE programmed into the GPS, or can
the Trutrak just use the actual GPS track flown as its input (or maybe the GPS
cant provide actual track info without a desired one first being programmed
in?)
>
> The mysteries of GPS NMEA output data are eluding me!
>
> David
>
> > On 10 Nov 2022, at 09:44, D McFadyean <ami-mcfadyean@talktalk.net> wrote:
> >
> >
> > Digitrak will show a different display if it has defaulted to magnetometer
input.
> > Personally, I've found the magnetometer function to be pretty useless,
> > irrespective
of calibration; maybe too much interference.
> >
> > As an aside, I'd be interested to hear whether others experience
> > misfunctioning
during winter dampness; mine wouldn't work in winter until about 1/2 hour
in to a flight when things had warmed up. Last year the circuit boards were
dusted
and sprayed with silicone and the problem seems to be cured (for now at
least).
> > Also often experienced is an offset of 3 or 4 degrees between displayed
> > track
and actual track (both referenced to GPS).
> >
> > Duncan McF.
> >> On 09 November 2022 at 16:10 Alan Burrill <alanb@dpy01.co.uk> wrote:
> >>
> >>
> >>
> >> According to the manual after calibration - I have just recalibrated mine-
it will then continue to use the internal magnetometer when the GPS is
disconnected/failed.
> >>
> >> I need to test that concept when the Wx and the state of the strip lets me
fly again.
> >>
> >> Alan
> >>
> >> Sent from my iPhone
> >>
> >>>> On 9 Nov 2022, at 15:53, Dpc <dpc@knightonweb.com> wrote:
> >>>
> >>>
> >>> Alan
> >>>
> >>> Just so I am clear, does the Trutrak need the GPS track data that it uses
to set up the compass cardinals every time it is switched on or is this just
a one-off requirementduring initial commissioning?
> >>>
> >>> If the latter then that would mean I wouldnt have to have the GPS
> >>> permanently
installed?
> >>>
> >>> Maybe thats too much to hope for!
> >>>
> >>> David
> >>>
> >>>> On 7 Nov 2022, at 19:18, Alan Burrill <alanb@dpy01.co.uk> wrote:
> >>>>
> >>>>
> >>>> Not familiar with the Skymap but worth checking if it has a srail port
> >>>> and
the ability to send the NEMA message set then worth investigating.
> >>>>
> >>>> If that doesnt work then borrow a Garmin 196 or 295 with a data cable and
that will certainly get you the data you need to set up the AP so it can then
default to the internal magnetometer.
> >>>>
> >>>> The internal magnometer needs the initial GPS output, with the track
> >>>> data,
to allow it to set up the compass cardinals after which it will then allow
AP to follow input track on front panel without the need for the GPS data If
you follow the setting up in the manual you dont need a route in the GPS.
> >>>>
> >>>> One of the many reasons I dont use a tablet GPS inflight is that I have
the ability to display traffic, Drive the AP and also input frequencies direct
into the Com without fiddling though the 8.33 knob twiddling.
> >>>>
> >>>> You could just buy a second hand GPS to replace the skymap which would at
least let you use the AP how you want. Plenty old Garmin stuff around at not
much money.
> >>>>
> >>>> When you have it fitted let me know and I could fly over and assist, I
> >>>> have
an old 196 which would get you sorted if you cannot find one. I fly out of
Brimpton.
> >>>>
> >>>> Alan
> >>>>
> >>>> Sent from my iPhone
> >>>>
> >>>>>> On 7 Nov 2022, at 18:48, Dpc <dpc@knightonweb.com> wrote:
> >>>>>
> >>>>>
> >>>>> Alan.
> >>>>>
> >>>>> Thank you very much for the detailed reply. You clearly know a lot about
this!
> >>>>>
> >>>>> I was not planning to link the AP to follow a flight track which I had
pre-programmed into a GPS as I only use SkyDemon on an iPad for GPS navigation,
and that has no output capability (as far as I know). However I was planning
to use the APs controller display to manually input the GPS track I wanted and
for the AP to get its reference about whether to turn or not, from a dedicated
GPS feed, which is where the idea of the puck came in (since the pucks looked
small and neat). I hadnt planned to get it to follow a magnetic heading using
the APs own magnetometer (unless Im missing something here - why would it then
need a GPS if its just controlling to a magnetic heading that it senses itself
?)
> >>>>>
> >>>>> However, it seems that the pucks wont (easily) give me what the AP needs
to steer a manually inputted GPS track.
> >>>>>
> >>>>> Do you think my not-currently-used-and-rather-clunky Skymap IIIC might
give the GPS output required for the AP to follow a manually inputted desired
track?
> >>>>>
> >>>>> Many thanks for all your advice.
> >>>>>
> >>>>> David
> >>>>>
> >>>>>>> On 7 Nov 2022, at 17:29, Alan Burrill <alanb@dpy01.co.uk> wrote:
> >>>>>>
> >>>>>>
> >>>>>> I think its more fundamental than that.
> >>>>>>
> >>>>>> I have a DigiTrack TruTrack fitted to mine and connected to a Garmin
> >>>>>> 796,
previously a AVMAP EKP V, and it needed the RMB and RMC data from these to
work. Id have to check but I dont think the GPS Pucks give out those messages.
> >>>>>>
> >>>>>> If you have the manual then the 4800 baud is recommended so as not to
overrun the input processing of messages and giving false steering.
> >>>>>>
> >>>>>> The Pucks can be programmed as you say but you need to make sure that
the new settings are retained, usually with an internal battery which if not
retaining
its change will lose the almanac and any changes over time as the battery
deteriorates.
> >>>>>>
> >>>>>> The TrueTrack needs RS232 at +/- 12v most pucks are 5v logic levels and
wont drive it.
> >>>>>>
> >>>>>> f you are only using a puck I guess you are not using the track
> >>>>>> following
---From a GPS mode but wish to use the internal Magnetometer to steer a magnetic
track and you will need the RMB and RMS messages from the GPS to set it up
to start with after that it should just work from the internal magnetometer.
> >>>>>>
> >>>>>> Alan
> >>>>>>
> >>>>>>
> >>>>>>
> >>>>>>>> On 7 Nov 2022, at 17:06, Davidcripps <dpc@knightonweb.com> wrote:
> >>>>>>>
> >>>>>>>
> >>>>>>> I have a pre-used Digitrak Trutrak AP that I plan to fit to our
> >>>>>>> Europa.
Are there any experts out there that can tell me whether the Garmin GPS 18x
5Hz puck that I have been offered, will work as a feed to it? As far as I can
understand from the various manuals, the Trutrak can only be set up to 9600
baud,
whereas the default baud in the 18x 5Hz is 19200. It seems possible to reprogram
the 18x 5Hz to 9600 baud but the process looks very complicated for those
of us not used to Garmin code (and who also don't have a PC with serial port!)!
Alternatively, are there any simpler 'plug and play' GPS 'pucks' that have
been found to work well with the Trutrak? Thanks!
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>> Read this topic online here:
> >>>>>>>
> >>>>>>> http://forums.matronics.com/viewtopic.php?p=508531#508531
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>
> >>>>>>
> >>>>>>
> >>>>>>
> >>>>>>
> >>>>>
> >>>>>
> >>>>>
> >>>>>
> >>>>>
> >>>>
> >>>>
> >>>>
> >>>>
> >>>>
> >>>
> >>>
> >>>
> >>>
> >>>
> >>
> >>
> >>
> >>
> >>
> >
> >
> >
> >
>
>
>
>
>
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