Volume Knob Fitting & RCA Rework

Hello and welcome to post #15 of my blog on building an in-car computer system.

This post will cover how I mounted & permanently installed the volume control knob system from the previous post, and briefly some further improvements and functionality upgrades.

It should be noted that the black machined knob pictured below was not sold with the kit and was purchased separately from Amazon - you can find it in the "people who bought this item also bought..." section.

As discussed in the previous post the volume control knob is fully functional with the computer; the drivers set up and the led's configured to how i want them. To mount it onto the vehicle, I made a trip to my local electronics store and bought some stainless 25mm M3 screws, anti-vibration washers, M3 nuts and some threaded nylon spacers.

Nylon spacers, though they were not used for this project

The first step of installation was to find a suitable place for installation. Keeping with a more traditional layout I chose to mount the knob on the bezel that surrounds where the head unit was located. There is plenty of clearance behind the panel and running the USB cable was easy.

Unfortunately, M3 was the smallest size screws/washers the store sold, so I was forced to drill out the holes in the PCB to suit the screws.

Back of the PCB before drilling

PCB after drilling

Fortunately, due to the excessive thickness of the PCB doing this did not damage the board or  any circuitry. The next step was to mark and drill the centre hole to mount the shaft of the rotary encoder, checking for clearance around and behind the bezel.

Then the PCB was test fitted to the panel, and the positions marked and drilled for the four centre screws

Centre hole and four holes for the corner holes. Note the distortion in the hole spacing is a result of the curved shape of the bezel; the board was test fitted so that the encoder was parallel with the computer screen and not the bezel

The volume control knob was then fitted to the panel, adjusting for fit to make sure the knob aligned parallel wit the screen.

Rear view of the PCB with USB cable attached

Top view

View before fitting the bezel

It should be noted that there were some slight clearance issues with getting the mute function to work properly with the knob (the knob must be pushed in for it to work). There was too much clearance between the end of the rotary encoder and the inside of the knob, resulting in the bottom of the knob touching the screws and bezel before it could push the button built into the encoder. The solution to this was extremely simple: I inserted a conveniently sized screw inside the knob which acts as a spacer.

Screw inserted into the knob to fix the mute function

Overall, I am very pleased with the functionality of the system. It works as intended and is very responsive. However the glow of the LED knob is somewhat covered. this is not a big issue as light shines from behind the knob in the dark, making it bright enough to find at night but not too bright so as to cause a distraction when driving. 

System with the knob removed to reveal the glowing rotary encoder

In addition to installing the volume knob, I also ran the 4 meter USB 2.0 extension cable from the computer down the passenger side A-pillar, as well as a 5 meter USB3 extension cable along the same route. This USB3 cable runs inside the centre console to the USB3 hub (see post #12) installed on the back of the console. The hub is now fully functional and makes plugging devices such as mice, keyboards and storage much much easier than reaching inside the roof console to connect them. 

Back of centre console with USB3 cable connected

The last main point of work for this post was the reworking of the RCA connectors on the cable which carries the audio signal from the computer to the main and subwoofer amplifiers. I was not satisfied with the quality of the connectors, and they were causing an intermittent signal fault with the audio. New gold plated connectors were installed with the aid of a soldering iron and parts holding tool. 

Exploded view (left) of the new gold plated connectors with an assembled one on the right.

New RCA connectors installed on the car computer

Finished product with volume knob and screen installed. A very clean and almost OEM looking installation.

All in all I am very satisfied with this latest update on the project. Fortunately I did not have to remove the computer for the car to do any of the work above, which was a huge relief. Next on the agenda:

• Software UI improvements
• Fit Auxiliary audio in/USB extension cable
• Set up automatic music playlist synchronization between computer and home library
• Get turn-by-turn offroad navigation software working

Keep reading for addition updates, and as always thanks for reading :)