Searching \ for '[EE:] Mounting a compass sensor in a car' in subject line. ()
Make payments with PayPal - it's fast, free and secure! Help us get a faster server
FAQ page: www.piclist.com/techref/io/sensors.htm?key=sensor
Search entire site for: 'Mounting a compass sensor in a car'.

Exact match. Not showing close matches.
PICList Thread
'[EE:] Mounting a compass sensor in a car'
2004\04\19@203906 by PicDude

flavicon
face
Howdy all,

Not surprisingly, when running a compass sensor in my car, I'm running into interference (incorrect sensor outputs) from all the other electronics and metal in the car.

Anyone know where these sensors are typically mounted in a vehicle?

Cheers,
-Neil.

--
http://www.piclist.com#nomail Going offline? Don't AutoReply us!
email spam_OUTlistservTakeThisOuTspammitvma.mit.edu with SET PICList DIGEST in the body

2004\04\19@212305 by John Tserkezis

flavicon
face
PicDude wrote:

> Not surprisingly, when running a compass sensor in my car, I'm running into
> interference (incorrect sensor outputs) from all the other electronics and
> metal in the car.

> Anyone know where these sensors are typically mounted in a vehicle?

 Short answer:  Use GPS, you need to be moving, but it's a small price to pay.

 Longer answer:
 Basically, it should be mounted anywhere where it will work within the
calibration limits of the compass.  If it doesn't have calibration adjustments
(mechanical or electronic) don't even try using it.

 My magnetic compass came with instructions to point the vehicle to north
(using other known methods) some distance from any surrounding metal, overhead
wires etc, then go though the calibration adjustment (point NSE & W) till it
reads correctly.

 I had it down to within a few degrees.

 In use, it was a different story.  Every time you remove or install a piece
of equipment in your vehicle, you have to check it doesn't interfere with the
compass, and re-calibrate if it does.

 While sitting at traffic lights, the adjacent lane (if moving) would cause
the compass to swing back and forth each time a car passed me.

 While driving in a steady straight line on the freeway (no other surrounding
cars) the compass would sometimes swing back and forth due to surrounding steel
barriers and such.


 In the end, I found it so useless (because I couldn't guarantee the "purity"
of my environment where I needed it) that I relied on GPS only.  The compass
was for backup just in case GPS went down.

 Now, if I need backup, I carry two GPS recievers.
--
      -o)
      /\\    Message void if penguin violated
     _\_V    Don't mess with the penguin

Linux Registered User # 302622                         <http://counter.li.org>
Fido: 3:712/610  BBS/FAX: +61-2-9716-8310  Internet: .....jtKILLspamspam@spam@techniciansyndrome.org

--
http://www.piclist.com#nomail Going offline? Don't AutoReply us!
email listservspamKILLspammitvma.mit.edu with SET PICList DIGEST in the body

2004\04\20@005201 by PicDude

flavicon
face
On Monday 19 April 2004 08:21 pm, John Tserkezis scribbled:
>   Short answer:  Use GPS, you need to be moving, but it's a small price to
> pay.

Way beyond what I wanted/needed, at far higher cost.


>   Longer answer:
>   Basically, it should be mounted anywhere where it will work within the
> calibration limits of the compass.  If it doesn't have calibration
> adjustments (mechanical or electronic) don't even try using it.

Well, I made the compass with a PIC, some LEDs and a sensor.  The sensor has 4 digital outputs, which with overlap, can indicate 8 different locations.  Best I can hope for in terms of calibration is to rotate the sensor.  But with a resolution of only 8 points, precision is not a problem (or even a requirement :-)


{Quote hidden}

Sort like like how aircraft compasses get re-calibrated every time any equipment is changed.  They just add a little card with correction factors (degrees) for major points.


>   While sitting at traffic lights, the adjacent lane (if moving) would
> cause the compass to swing back and forth each time a car passed me.

Ugh!


>   While driving in a steady straight line on the freeway (no other
> surrounding cars) the compass would sometimes swing back and forth due to
> surrounding steel barriers and such.
>
>   In the end, I found it so useless (because I couldn't guarantee the
> "purity" of my environment where I needed it) that I relied on GPS only.
> The compass was for backup just in case GPS went down.
>
>   Now, if I need backup, I carry two GPS recievers.

So I wonder what sensor the compass in newer American vehicles use?  I've driven quite a number of these and played with (evaluated?) the compasses quite a bit.  Seemed to work quite decently.


Cheers,
-Neil.

--
http://www.piclist.com hint: To leave the PICList
.....piclist-unsubscribe-requestKILLspamspam.....mitvma.mit.edu

2004\04\20@020823 by John Tserkezis

flavicon
face
PicDude wrote:

>>Short answer:  Use GPS, you need to be moving, but it's a small price to
>>pay.

> Way beyond what I wanted/needed, at far higher cost.

 Not really, cost of a bottom end GPS unit would be on par with a
quality compass.

> Well, I made the compass with a PIC, some LEDs and a sensor.  The sensor has 4
> digital outputs, which with overlap, can indicate 8 different locations.
> Best I can hope for in terms of calibration is to rotate the sensor.  But
> with a resolution of only 8 points, precision is not a problem (or even a
> requirement :-)

 The only built-in compass I've seen in cars is similar to what you've
outlined, with out eight direction combinations.
 What type of sensor are you using?  Only type I've seen offer some
calibration adjustments.  Yours sounds like a sealed unit with only
power input, and position output.

>>  While sitting at traffic lights, the adjacent lane (if moving) would
>>cause the compass to swing back and forth each time a car passed me.

> Ugh!

 Yes, I was impressed...  Not.

>>  Now, if I need backup, I carry two GPS recievers.

> So I wonder what sensor the compass in newer American vehicles use?

 Pretty much similar to what you're doing now.

>  I've
> driven quite a number of these and played with (evaluated?) the compasses
> quite a bit.  Seemed to work quite decently.

 They too don't have very high directional accuracy, and since they're
working with known vehicles, it's easy to implement.  They know exactly
where they stand, the calibration offsets are fixed, there's virtually
no guesswork on the production line.

 As an after-market thing, it's a different story.

 I've never bothered with it, because accuracy and more specifically,
resolution was next to useless for my purposes.

--
http://www.piclist.com hint: To leave the PICList
EraseMEpiclist-unsubscribe-requestspam_OUTspamTakeThisOuTmitvma.mit.edu

2004\04\20@031158 by Ake Hedman

flavicon
face
How do you get the compass info form the GPS?

/Ake

-----Ursprungligt meddelande-----
Fran: pic microcontroller discussion list
[PICLISTspamspam_OUTMITVMA.MIT.EDU]For John Tserkezis
Skickat: den 20 april 2004 03:22
Till: @spam@PICLISTKILLspamspamMITVMA.MIT.EDU
Amne: Re: [EE:] Mounting a compass sensor in a car


PicDude wrote:

> Not surprisingly, when running a compass sensor in my car, I'm running
into
> interference (incorrect sensor outputs) from all the other electronics
and
> metal in the car.

> Anyone know where these sensors are typically mounted in a vehicle?

 Short answer:  Use GPS, you need to be moving, but it's a small price
to pay.

 Longer answer:
 Basically, it should be mounted anywhere where it will work within the
calibration limits of the compass.  If it doesn't have calibration
adjustments
(mechanical or electronic) don't even try using it.

 My magnetic compass came with instructions to point the vehicle to
north
(using other known methods) some distance from any surrounding metal,
overhead
wires etc, then go though the calibration adjustment (point NSE & W)
till it
reads correctly.

 I had it down to within a few degrees.

 In use, it was a different story.  Every time you remove or install a
piece
of equipment in your vehicle, you have to check it doesn't interfere
with the
compass, and re-calibrate if it does.

 While sitting at traffic lights, the adjacent lane (if moving) would
cause
the compass to swing back and forth each time a car passed me.

 While driving in a steady straight line on the freeway (no other
surrounding
cars) the compass would sometimes swing back and forth due to
surrounding steel
barriers and such.


 In the end, I found it so useless (because I couldn't guarantee the
"purity"
of my environment where I needed it) that I relied on GPS only.  The
compass
was for backup just in case GPS went down.

 Now, if I need backup, I carry two GPS recievers.
--
      -o)
      /\\    Message void if penguin violated
     _\_V    Don't mess with the penguin

Linux Registered User # 302622
<http://counter.li.org>
Fido: 3:712/610  BBS/FAX: +61-2-9716-8310  Internet:
KILLspamjtKILLspamspamtechniciansyndrome.org

--
http://www.piclist.com#nomail Going offline? Don't AutoReply us!
email RemoveMElistservTakeThisOuTspammitvma.mit.edu with SET PICList DIGEST in the body

--
http://www.piclist.com hint: To leave the PICList
spamBeGonepiclist-unsubscribe-requestspamBeGonespammitvma.mit.edu

2004\04\20@031819 by Eric Christensen

picon face
Heading in degrees is included in the standard NMEA output strings.  It can
also be calculated from two GPS coordinates (current position and previous
position).  This is why one of the previous posters mentioned that you must be
moving for GPS to work.

Eric


On Tue, 20 Apr 2004 09:11:06 +0200
Ake Hedman <TakeThisOuTakheEraseMEspamspam_OUTEUROSOURCE.SE> wrote:

{Quote hidden}

--
http://www.piclist.com hint: To leave the PICList
RemoveMEpiclist-unsubscribe-requestTakeThisOuTspamspammitvma.mit.edu

2004\04\20@033312 by Ake Hedman

flavicon
face
Is there any way at all to get compass information using a GPS when you
do not move? You say two coordinates. Well, thats easy even if you stand
still.

/Ake

-----Ursprungligt meddelande-----
Fran: pic microcontroller discussion list
[EraseMEPICLISTspamspamspamBeGoneMITVMA.MIT.EDU]For Eric Christensen
Skickat: den 20 april 2004 09:03
Till: RemoveMEPICLISTKILLspamspamMITVMA.MIT.EDU
Amne: Re: SV: [EE:] Mounting a compass sensor in a car


Heading in degrees is included in the standard NMEA output strings.  It
can
also be calculated from two GPS coordinates (current position and
previous
position).  This is why one of the previous posters mentioned that you
must be
moving for GPS to work.

Eric


On Tue, 20 Apr 2004 09:11:06 +0200
Ake Hedman <akheSTOPspamspamspam_OUTEUROSOURCE.SE> wrote:

{Quote hidden}

running
> into
> > interference (incorrect sensor outputs) from all the other
electronics
> and
> > metal in the car.
>
> > Anyone know where these sensors are typically mounted in a vehicle?
>
>   Short answer:  Use GPS, you need to be moving, but it's a small
price
> to pay.
>
>   Longer answer:
>   Basically, it should be mounted anywhere where it will work within
the
{Quote hidden}

--
http://www.piclist.com hint: To leave the PICList
.....piclist-unsubscribe-requestspam_OUTspammitvma.mit.edu

--
http://www.piclist.com hint: To leave the PICList
TakeThisOuTpiclist-unsubscribe-request.....spamTakeThisOuTmitvma.mit.edu

2004\04\20@040251 by Jake Anderson

flavicon
face
its maths
a compass heading is a bearing
you need a number plane (lat/long)
and 2 points to form a line so you can determine what angle that line is
relitive to your number plane (or sphere as the case may be)


{Original Message removed}

2004\04\20@080719 by Mike Harrison

flavicon
face
On Tue, 20 Apr 2004 09:11:06 +0200, you wrote:

>How do you get the compass info form the GPS?
Direction of movement (heading)

--
http://www.piclist.com hint: To leave the PICList
TakeThisOuTpiclist-unsubscribe-requestKILLspamspamspammitvma.mit.edu

2004\04\20@082208 by John Tserkezis

flavicon
face
Ake Hedman wrote:

> Is there any way at all to get compass information using a GPS when you
> do not move? You say two coordinates. Well, thats easy even if you stand
> still.

 Not possible if you're standing still.  The heading data is based on the new,
compared with the last fix, but if you're standing still, errors will make you
wander over several metres, so the direction would be all over the place.

 That's why some GPS recievers contain a magnetic compass as well.  It covers
you for when you're moving really slowly, or standing still.

--
       -o)
       /\\    Message void if penguin violated
      _\_V    Don't mess with the penguin

Linux Registered User # 302622                        <http://counter.li.org>
Fido: 3:712/610  BBS/FAX: +61-2-9716-8310 Internet: .....jtspamRemoveMEtechniciansyndrome.org

--
http://www.piclist.com hint: To leave the PICList
RemoveMEpiclist-unsubscribe-requestspamspamBeGonemitvma.mit.edu

2004\04\20@084939 by Art

flavicon
face
Aren't there electronic units that compensate for static conditions?? Not
sure if they make them now, but remember reading about flux gate compass'
in Nuts and Volts.


At 09:21 PM 4/19/04, you wrote:
{Quote hidden}

--
http://www.piclist.com hint: To leave the PICList
piclist-unsubscribe-requestEraseMEspammitvma.mit.edu

2004\04\20@100635 by Herbert Graf

flavicon
face
> How do you get the compass info form the GPS?

       The $GPRMC sentence in NMEA output capable GPSs (which is almost every GPS
out there) contains heading information in the form of a number of degrees:
90 degrees = east, 180 degrees = south, etc. TTYL

----------------------------------
Herbert's PIC Stuff:
http://repatch.dyndns.org:8383/pic_stuff/

--
http://www.piclist.com hint: To leave the PICList
RemoveMEpiclist-unsubscribe-requestEraseMEspamspam_OUTmitvma.mit.edu

2004\04\20@100844 by Herbert Graf

flavicon
face
> Is there any way at all to get compass information using a GPS when you
> do not move? You say two coordinates. Well, thats easy even if you stand
> still.

       GPS is not a perfect technology (what is?). When standing still the output
of the GPS actually drifts a little. Most GPS units erroneously show
changing headings due to this (how can they know you're not moving?). Some
GPSs will simply hold the last valid heading realizing that you are probably
stopped. Some will just show "invalid heading". In any case, if you're not
moving there are no "two points" to get a heading, therefore anything the
GPS outputs is suspect. TTYL

----------------------------------
Herbert's PIC Stuff:
http://repatch.dyndns.org:8383/pic_stuff/

--
http://www.piclist.com hint: To leave the PICList
@spam@piclist-unsubscribe-requestRemoveMEspamEraseMEmitvma.mit.edu


'[EE:] Mounting a compass sensor in a car'
2004\06\10@171058 by Howard Winter
face
flavicon
picon face
On Mon, 19 Apr 2004 23:58:03 -0500, PicDude wrote:

> >   In use, it was a different story.  Every time you remove or install a
> > piece of equipment in your vehicle, you have to check it doesn't interfere
> > with the compass, and re-calibrate if it does.
>
> Sort like like how aircraft compasses get re-calibrated every time any
> equipment is changed.  They just add a little card with correction factors
> (degrees) for major points.

Actually, "doing a compass swing" is quite an involved process - I've helped do one.  Some airfields have a
"compass base" - a concrete circle that's well clear of any interfering metal on which you place the aircraft,
and you have to manually rotate the aircraft (I'm talking light aircraft! :-)  and repeatedly re-adjust the
compass compensators to minimise the errors overall.  This is with the electrics and the engine all running.
When you have it minimised, you then read the error at the 8 main compass points, and write it on the
correction card.  What always amazes me is that when you're flying you can't read the darned thing more
accurately than about 5 degrees, but the correction card is filled-in down to single degrees!  :-)

Cheers,

Howard Winter
St.Albans, England.

--
http://www.piclist.com hint: PICList Posts must start with ONE topic:
[PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads

2004\06\10@174831 by John Ferrell

face picon face
You would be surprised how well you can read a compass in a light single
engine airplane on an overwater flight out of radio range. I suppose GPS
changes that now days, but not enough to rid the cockpit of the compass!

BTW, unless things have changed, in the US every aircraft needs to have a
compass correction card but there is no rule that requires that it be filled
out! In all fairness, compass navigation to any real accuracy requires you
to know a lot more about the wind than you usually do.

John Ferrell
http://DixieNC.US

{Original Message removed}

2004\06\11@145127 by M. Adam Davis

flavicon
face
It would be interesting to take an optical mouse assembly and focus it
at infinity at the ground in an airplane.  They don't account for
rotation, but it would give you a fairly accurate idea of how fast you
were moving both forward and sideways.  Banking would show as a sideways
movement with a corresponding return.  Requires daylight flight, during
which you probably don't need it, but still...

I've heard people have hacked these into car speedometers.

-Adam

John Ferrell wrote:

{Quote hidden}

>{Original Message removed}

2004\06\12@050553 by Peter L. Peres

picon face
> optical mouse
> I've heard people have hacked these into car speedometers.

This seems a little far-fetched. At a car's speed any two successive
samples would have no points in common. And if you know what you are doing
then all you need is a camera and a computer to determine what you want.
There will be drift (probably much more than with a compass over any
kind of practical distance).

Peter

--
http://www.piclist.com hint: The PICList is archived three different
ways.  See http://www.piclist.com/#archives for details.

More... (looser matching)
- Last day of these posts
- In 2004 , 2005 only
- Today
- New search...