Car PC “Completion” and Installation notes

In atypical fashion, I have completed a project to a certain extent! I have my CarPC installed in my VW TDi MK4 Golf, and these are notes about the assembly, trouble shooting, bench testing, etc portion of the project. This may be my last post on the project, unless I feel that enough work goes into perfecting the usability of the system to warrant an update…

I’ll just let the pictures do the talking:

In the middle of my project, I saw this on my way in to work. Whilst my VW was gettin’ pimped, these two unfortunate brothers of mein (see what I did there?) were getting wrecked. As you can tell from the salt on the ground, the floor was slick. My suspicion is car three (which is not pictured here) turned into the spot going way too fast, and drifted into the jetta. How careless. I took a moment of silence, don’t worry.

The hardware on the bench. I used quick crimp connectors as they seem to be preferred in car installations, for whatever reason. Probably because a soldering iron isn’t easy to power from a cabin.

Internals of the Carnetix P1900. I ended up desoldering the input for the power supply, as the space got really tight. I think If I did this again, I’d desolder both sides so the install is as low profile as is possible.

I tweeted or instagrammed this picture because I thought it was funny. Apple products are said to be magical, but I’m pretty sure this takes the cake.

4″ exactly. Impressive hardware and technology density in the Intel NUC (I’m biased).

 

The HDMI cable provided with my monitor was about 5.5 feet too long (it’s a ~6foot cable). Since the HDMI cable also had a breakout for USB over HDMI (for the touch screen interface), I had to end up hacking together one of my own. This wasn’t a breeze, but I’m pretty handy with a soldering iron. Above is the desoldering of the existing solution. Looks to be a plastic, or injected glue strain relief.

Comparison of what I have to solder with what I have to solder to.

Testing the “final” product. I added hot glue for strain relief, but will probably use a product like “Sugru” next time, which is moldable rubbery clay-ish material. It’s commonly used to repair electronics. I would also like to try a right angle connector, but the base material is already pretty high profile, so I didn’t bother. I could get away with something as short as 3-5″ for this custom cable, but didn’t want to do it twice.

For anyone curious, the USB connection is as follows:

USB side [1,2,3,4] = [VCC,D-,D+,GND]

D- –> HDMI PIN17 (DDC/CEC GND)D+ –> HDMI PIN8 (TDMS SHIELD D0)

When I assembled my cable, the twisted pairs seemed to be mismatched with what I “ohmed out” with my multimeter, just a heads up to check your connections when you’re done. You can find pictoral pinouts on pinouts.ru or a google search…

Testing touch screen functionality.

Test benching the hardware. I connected to a power supply and “pulse started” by touching the Carnetix Pulse start (blue wire) momentarily with a +5V supply. In car I use the “IGNITION” line attached to my ignition switch key sense (key in, power supply on). In the MK4 2003 golf, this line is only accessible via the ignition switch bundle. You can see this on the LEFT side of the steering wheel (right above). There’s a bundle of cabling on the top of the steering wheel opposite of the ignition/keyhole. The wire is BROWN with a red stripe (NOT THE OTHER WAY AROUND). Some guides I found online said that the IGN signal was routed to the stereo wiring harness, but I found this to not be the case, and I suspect this is only true with the earliest 99.5 MK4s (the ones without the double DIN monsoon).

Side by side shot of the PSU and NUC. I used screwed together stand-offs as a stopgap solution for spacers and prototyping.

Took a flash shot to show how much “additional” room can be had by cutting out the back side of the radio cage. I have a spare cage for test fitting indoors, but I didn’t end up needing the extra space. Attached is a METRA wiring harness adapter, so I don’t have to cut/splice into the original harness. I ended up removing all non-audio cables from this harness and wiring up RCA cables to the harness. Right Front/Rear are hooked up and tied together, same with the left. This implies there’s no fader control. I’m willing to sacrifice it at the moment so I don’t have to purchase a separate amp.

GPS USB module out of case. Honestly, I don’t know why I removed this from the case… I think I just have an unexplainable fascination with voiding warranties… IIRC this is a SiRFIII chipset. If the reception sucks (behind the fuse panel), I’ll probably just end up using a bluetooth module.

ABS case taking shape. I chose ABS because it’s easy to machine/drill, and it melts together with MEK “glue.” This is extremely friendly for apartment prototyping. The down side is that I have ABS flakes all over my carpet… not sure how easy that’s going to be to get out…

Size comparison to the enclosure I’m building in. Even with a reference picture, it’s hard to tell how small my project enclosure actually is. I had a LOT of time sunk into fitting…

I ran out of ABS, as I purchased a 12″x12″x12″ piece of ABS from Amazon (raw plastic sheets are hard to find, and they aren’t cheap. If anyone knows where to source some, just let me know). Since I was working on my project mostly during nights, I didn’t have an opportunity to go out and buy material. I found a really old graphics card in my spare parts bin, and used hot air to remove all the parts I wasn’t interested in. After sawing it down, and drilling some holes, I had a spare “PCB separating” shelf.

Finished shelf.

Shelf in between the NUC and PSU. This is required because the mounting holes overlap a little bit.

Burned myself with my soldering iron while working. Still trying to figure out how the hell I did this… my track record is very good…

After test fitting, I quickly found out that using regular cables was going to be impossible due to the bulk. As I didn’t want to lose any precious real estate, I made my own right angle connector (good ones are surprisingly hard to find).

Burned myself AGAIN. This time with Hot Glue. I never imagined that hot glue guns got hot enough to instantaneously burn you, but there’s a first for everything, I guess.

Checking my screen again after everything was crammed together and test fitted.

Another shot before removing the PSU input. You can see the PCB is tilted significantly. I can’t fit the PSU cable next to the 60mm fan I shoehorned in. You’ll also notice the heat sinks on the PSU changed. I removed the outer case due to space limitations and added on my own heatsinks. Since I’m drawing (hopefully) ~<1/3 of the maximum current rating, I don’t expect anything to get too hot. I removed the Ground Loop Isolator that is required when coupling sound to the Monsoon amp. My Sound card is wedged under the PSU.

Another twitter joke: I never regret paying good money for a really excellent pair of strippers. The stripmaster is truly a godsend for anyone who works a lot with electronics. I almost impulse bought a 22-30g stripmaster to complement this one, as I generally work with much thinner gauge wires than I do in this project, but I’ll just wait.

Test fitting into the car. Cables in the back were a pain in the ass.

Shot #2, it boots!

This is just a shot to give an idea of how close quarters everything is. The 60mm fan was used because there’s a USB cable directly under it, and there is just barely enough space for the 60mm fan thickness. If I had opted for an 80mm fan, I would have lost (an extremely valuable) USB port, and I would ahve had to move everything away from the wall of the case, and that would have encroached upon the other side.

You can see where I removed the input cabling. This allowed me to avoid the PCB bending of the previous solutionThis shot shows the cabling nightmare. There’s a ton squished down into the case that you can’t really see, either. I spent many hours just starting at everything, trying to picture how it would all fit in.

Assembled shot, ready to drop into the car.

Cabling mess.

I bought a hole saw, but forgot the mandrel, so I ended up just drilling a circle outline with my hand drill. After punching it out, I was OK with the results.

Same thing happened here, except it was much sloppier.

RCA out to go to the stereo adapter wiring harness. All the cable ran to the back is not even needed at this moment in time.

Free space shot.

Another top down shot.

 

Hope you enjoyed the picture dumb, I’m propbably going to sell off a lot of junk, simplify my life, and then move on to microcontroller projects!

 

Cheers,
JD

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