Afters years of thought, I finally achieved my carPC v1.0.
Quick highlights :
- SPDIF connection to the head unit, hacking the CD changer connection
- Completely removable solution. Not a single modification to the car.
- Tank battery circuit to allow for clean shutdown.
I'll probably set-up a website to give more details, but you'll find a few pictures attached. The PC was build in a metal U shape that can be unfolded for easier maintenance. It is tailor-made to get in the center console of the Renault Scenic, under the armrests.
When I discovered that the integrated headunit had no AUX input and that the CD changer had no analog connection to it, I was seriously disappointed. I tried an FM modulator but the quality was really poor... I then found that this CD changer actually sends an SPDIF signal to the headunit, and checked with my home PC that standard PC levels were correctly recognized. I thus placed a little relay to switch the headunit SPDIF input from the CD changer to the Epia SPDIF output when the PC is on. The control wires are always connected to the CD changer, so the head unit is fooled into thinking the SPDIF comes from the CDs. Who said sound quality of EPIA motherboards is not perfect ??? :-)
One specific requirement was that I was allowed no modification to the car as it belongs to my company. No screws, no holes, no glue, nothing. The console place seemed to be the best bet as it already contains a cigare-lighter socket. I had to run 2 wires from there to the headunit (one for SPDIF, one for activating the relay) and temporarily replace the cigar-lighter socket with a more reliable one. Not easy but well, I succeeded thanks to the help of a few guys at
http://forum.planeterenault.com . One advantage is that the installation is completely hidden as the console still can be fully closed once the screen is disconnected.
Finally, as the cigar lighter socket is only powered when the accessory line is on, I had to find a solution to power the PC during its shut down (or hibernation) and settled on a 10 Farad capacitor...
Just kidding. I'm using an SLA tank battery of course :-)
The circuit - attached - uses 2 diodes (MBR3045 is a dual diode) and a current-limiting resistor, and was designed following the advices and opinions posted
here,
there and finally
there :-). The 3.4 Ah SLA is probably overkill, but if the shutdown takes longer for a reason or another... better safe than sorry.
Thanks to all mp3car forum users that helped me in one way or another :-).
Note : The screen is currently not fixed and sits in the glove box.