Exchanging the SatNav unit (Volvo) in the DB9
The SatNav unit that was built in the ca. 2006-2008 cars was the Volvo unit, which was already outdated by that time.
System and maps were stored on a DVD and the DVD player located in the trunk.
Depending on weather conditions, (humidity, temp.), there might be lots of read errors due to condensation.
What a shame if you get lost in the middle of nowhere in such a car du to a lame SatNav!
Also map updates are expensive and if they are issued, they already are outdated.
No TMC or other fancy stuff was included those days. So the decision was made ...
The unit needs to be replaced
But there are some user requirements
that need to be met:
- No standard SatNav that sticks to the windscreen (in addition to the existing one, which then won't be used any longer).
- But: use affordableoff the shelf standard SatNav like TomTom or Garmin with all the latest features (voice recognition, speed recognition, TMC, life time maps...)
- The swiveling motion of opening/closing the lid needs to remain!
Nice to have, but not mandatory:
- operated via the original SatNav knob and buttons; at least opening and closing
Decision was made for a 5 inch Garmin 2598 LMT
Since all teh infotainment stuff in the car is connected via MOST bus and just taking out one part would result in errors on the bus due to unavailability of that unit.
It was decided to take out the original display unit only
and leave the brain (inside the DVDplaver unit)
in the car in a switched off state. This means we make sure that no route is active, when we take out the unit and that the voicevolume is turned off.
The display should be replaced by a whole new SatNav system mounted in the same position as the original one.
The new unit should be powered up as soon as the
lid is lifted and should be switched off as soon as it is closed.
Swiveling the lid should be similar to the original motion. I experimented with a motor/gearbox-combination
first, but that was not satisfying. Therefore i decided for a RC servo. Dueto the weight of the lid the assembly later on becomes quite heavy.
So lots of torque from the servo is required. A low profile landing gear servo (brand: Spectrum) was chosen.
The whole motion should be controlled via a microcontroller that would allow the following:
- when switched on, the SatNav should receive power as well and the lid should be opened
- and when switched off, the lid should close and SatNavshould lose power conection
- for fine tuning the upper and lower lid position, some adjustment buttons need
to be installed and the latest positions for up and down position of the lid should be saved.
- If not required the servo should be powered off. Otherwise there might be an annoying sound resulting from the servo.
How it was accomplished
- Standard Volvo GPS in dashboard was taken out including the mechanical drive that lifts the screen up
- all the other mechanical assembly related to the opening mechanism removed
up to that it was easy, now the work begins:
- designed the new mechanism and related hardware and match it up with the Garmin that was supposed to go in there
- printed the parts on a 3D printer
that took me several iterations plus i wasn’t satisfied with the overall print quality.
I did several designed experiments to find out the optimum printing parameters and the best filament brand (Verbatim, white)
- designed soft- and hardware based on an ATMega 328 processor that controls the RC servo motor
- fiddling around with the Garmin power supply to allow traffic messaging and charging without using the original power cable and bulky connector
- designed a new cubby box that goes into the center console instead of the original empty box. It serves as inclined iPod rest,
holds the buttons for a) GPS on/off up/down b) GPS screen micro adjustment (to slightly tilt the screen to avoid reflection of sun),
Fuse 22 switch for opening up the exhaust valve :-), plus two spare places for other switches for future extension. Plus left and right of
the iPod rest some storage space for parking garage ticket etc.
- 3D printed parts were covered with black velours or grey leather matching
All the original parts are stored and can be refitted to original state if necessary.
There's room for future improvements, still:
- increase screen size from 5 to 7 inch (possibly by switching to a Garmin Dezl, which also would allow connection of a rear view /front view
- slightly tilt the screen to the driver; that would even more reduce reflections
- hack into the body CAN bus to use
the original SatNav buttons in the center console, but that will be a major workload since i don't yet have any infos on the protocol and low level
commands that AM uses here.
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