Hello and welcome to post #12 of my blog on building an in-car computer entertainment and navigation system. In this post I'll cover the reasons why, and how, I integrated a USB3 hub into my vehicle. I also replaced the signal cable that runs from the computer to the amplifiers. This post will be slightly more brief than the others as I don't consider it a vital part of the build, and I have some catching up to do on other progress that has since been made on the system.
 |
| Finished product |
The hub I installed is a four port high speed USB3 hub which supports an external power supply as well as power from the host computer. It has four switches to individually power up the USB ports.
Parts List (From eBay):
(From local electronics store):
- 2X Round SPST switches (though one of any switch will do)
- Wiring and crimps
- 4X 10mm M2 stainless screws, nuts and vibration-proof locking washers
- Electrical Tape
Tools needed:
- Solder, soldering iron, ect.
- Dremel or die grinder
- Drill
- Marking pens, scribe, rule
- Screw drivers
- Bench grinder
- Pliers, side cutters, ect.
Reasons for fitting the hub:
- Increased potential for charging phones and devices. USB3 supports a maximum current of 900ma though with the use of an external power supply this can be greatly increased
- Ease of access for plugging peripherals into the computer - Plugging in USB mice, keyboards and other interface and/or storage devices is somewhat difficult due to the concealed nature of the computer overhead in the roof console
- Increased transfer speeds for storage operations such as copying movies or TV shows to/from the computer onto storage devices
- Aesthetic appeal
The hub is located on the back of the centre console (the armrest/storage container located between the front seats) and will replace an existing system that I fitted a couple of years ago. The old system had four USB2 ports for charging devices, a cigarette lighter port for light duty power applications and a light for ease of use in dark conditions. In the coming photos the holes for the old components are obvious. The new hub covers these up nicely.
The first step was to isolate the power source to the back of the console then disassemble the back of the console. On my vehicle (GU Nissan Patrol) there are four screws holding the back of the centre console on and a couple more that hold the hinged lid on. All of these were removed to expose the back of the console, then I removed the console back plate from the vehicle and took it to the workshop.
 |
| Inside of the console with the old wiring present |
I removed all of the old wiring bar the positive and negative connections coming into the system from the battery, then removed the old USB2 ports and cigarette lighter socket.
 |
| Back view of the inside of the console. The holes for the old USB2 ports and cigarette lighter are clearly visible. Also note this is a rear view of the finished product, the usb and power input cables are visible at the bottom of the photo. |
The next step was to mock up the position and fit of the USB3 hub and design a way to mount it securely to the console. The hub easily disassembled via internal plastic tabs into three main components; the case, the backplate and the circuit board. I started by placing the backplate flush with the console then placing the case on top. It became clear that due to the shape of the centre console and the angled sides of the flat plate some material would need to be removed to ensure a snug fit and to allow the two cables to pass through the left side of the console and into the hub.
 |
| Note the angled sides of the plate where the hub has been fitted. Material was removed on the left side to hide the plugs. |
I progressively drilled out then sanded away the plastic of the console with a drill and die grinder, regularly checking the fit until I was satisfied that the hub would fit nicely. Once that was complete, the next step was to make sure that the power input and USB3-B type plugs would fit without intersecting the back of the console. USB3-B is the current plug standard for high end smartphones and it incorporates the old USB2-Micro B type plug with a USB-3 micro plug. It became clear that the plug end of the supplied USB3-B cable was too thick to fit properly and was putting stress on the solder joints of the socket on the PCB. To resolve this problem I carefully sanded off the plastic outer casing of the plug end with a bench grinder until the wires and solder joints were exposed. I wrapped the lot in electrical tape to insulate it. I also used the grinder to create a flat face on the power plug as well.
 |
| PCB with the modified USB3-B plug inserted. |
Once I was satisfied that the plugs would fit properly I carefully inspected the back of the PCB and backplate to find places to drill holes for the mounting screws in places that would not hit the underside of the PCB and cause short circuits. This was slightly tricky as in addition to this the holes must avoid the empty space underneath where the old components were installed in the console. Once I was satisfied I could securely mount the backplate to the console I drilled the holes in both the backplate and console and fastened the M2 screws.
 |
| Back view with the backplate mounted and the screws fastened |
Moving to the front side the console I applied tape over the screw heads to prevent shorting on the PCB.
 |
| Backplate with tape over the screw heads. Note that the two screw holes at the bottom (the console is upside down in this photo) need to be accessed later to fit the console back to the car. Luckily the chamfered edge of the hub made this possible without removing the hub. |
I then assembled the power plug by soldering two wires onto it and plugged it into the PCB along with the USB3-B plug, then fitted the PCB to the backplate and case onto the backplate. I trimmed the sides of the two switches on the bench grinder to ensure a snug fit.
The next step was to test the hub for correct function. To do this I used a car battery and an adjustable step-down converter, set to 5V (The standard voltage for all USB interfaces).
 |
| Testing the hub |
After I was satisfied the hub was working properly It was time to wire the assembly into the car. The old system I used to power the USB2 hubs used two of the adjustable voltage regulators pictured above stacked on top of each other and wired in parallel, but testing revealed that the current output was insufficient and there was an issue with the two regulators "Fighting" each other for current suply. This was caused by minute voltage output differences between the two regulators which resulted in a high pitched whining sound coming form both regulators; an interesting phenomenon.
 |
| Old power supply system |
To rectify this I fitted a sealed high output step down converter that I had as a spare.
On my vehicle there is a convenient plastic rail inside the console which made mounting this very straightforward.
 |
| DC-Dc step down converter mounted on plastic rail |
Once the converter was mounted I carefully wired the its +12V input wire to the top switch, ensuring the 5V output leads were correctly connected to the hub via the plug I assembled earlier (12V supplied to the hub would probably cause it to explode!). Since there was a second switch left over from the old system I added a LED bar light as an afterthought just so it would do something.
 |
| LED bar light mounted on console |
The next step was to do some cable management and run the USB3 extension up one of the pillars and through the roof to the computer.
 |
| System powered up with the bar light shining brightly. Note an ashtray goes in the centre of the console but due to my USB3 extension being delayed in the mail I left the USB3 cable hanging out of it until I could fit it. |
The final step was to fit the console back onto where it belongs and do a final current output test if the system using my in-line USB current/voltage monitoring device and a large load. The system performed flawlessly.
 |
| Final current output test. Note the system is probably capable of more current output but due to the limitations of the load I was using this was the maximum I could get out of it. |
--------------------------------------------------------------------------------------------------------------------------
The next tweak to the computer system was to improve the reliability of the audio cable which supplies an audio signal from the computer to the amplifiers. I originally used a 5M long 3.5mm to RCA jack, but I inadvertently ordered a poor quality cable with even poorer quality plugs fitted to it. Consequently both plug ends of the cable were extremely temperamental and would regularly cause feedback from the computer to play through the speakers or simply not work at all. This problem gradually became worse over time.
To fix this I bought 6M of high quality signal cable from my local electronics store along with two sets of male RCA plugs. I then soldered one pair or RCA plugs to the computer end of the cable (I changed the interface from 3.5mm a stereo plug to RCA plugs as the computer's case has RCA outputs connected to the front panel output header on the motherboard). After that the old cable was removed and the new one ran in its place. It was then cut to length and RCA plugs attached to the other end before plugging them into the amplifier.
That's it for this post. Stay tuned for future updates and thanks for reading.
I would like to thank my friend for helping me with the audio cable rework and removing and refitting the console for the 3rd time - you know who you are :).
No comments:
Post a Comment