Introduction & Design

Hello world :) This is my first blog so here goes.

To start off with let me introduce myself. I'm a young engineer who lives and works in Australia. my biggest passions are driving through challenging off-road areas and camping. Another passion of mine is technology, I like building computers and fiddling around with electronics. So, I thought I'd combine both an extensive  and ambitious project.

I created this blog to document my progress on how I'm designing and building an in-car computer system for my car. This post will be a big one, because I'm well into the build, but I'll try to write shorter ones as I make progress.

Why put a computer in a car you ask? Well to answer that question I'll tell you a bit about myself and my situation.

As it it stands, my vehicle of choice is a 2003 Nissan Patrol. For those of you who don't know this is a Japanese-made large SUV that has an excellent reputation for being both reliable and tough. It is unique from many other off-road capable SUV's in that it is built like a truck underneath, with a chassis and front and rear live axles. I've allready made many modifications to it to vastly improve its off-road capabilities, including a suspension lift, engine performance improvements, differential lockers, large mud tires, ect.

My Rig

So to make the car even better, I wanted to build a system into the car that is capable of doing the following things:

• Monitoring engine parameters (oil pressure, boost pressure, coolant temp, ect) in real time
• Navigating on and off the road
• Hosting a full entertainment suite (music, movies, internet hotspot,ect)
• Monitoring and controlling equipment
• Monitoring parameters of the electrical system

In addition to these the following design requirements must be met:

• Systems critical to the function of the vehicle (eg the engine's electrical system) must not be adversely affected by a failure of any part of the computer system.
• PC must turn on automatically when the key is set to the accessory position
• PC must shut down automatically when the key is removed and have a safety feature to automatically power off after being left idle to prevent draining the auxiliary battery

So to make a system that does all this, I needed to come up with a solution that is versatile, modular and upgradable. After thinking about this, I decided to build a pc that is both compact and powerful enough to run all of the functions listed above concurrently, but is also durable enough to withstand the harsh conditions of the Australian environment. This is no easy feat, but I have a plan to make it work.

My plan for the basic layout of the system will be to have the computer mounted in the highest point in the car, away from the water, dust and sand. To control it I'll be running a touch screen mounted in the dash, in place of the factory double sized radio. 

Now to build the computer - I chose components system with power efficiency given slightly higher priority than performance. The biggest concern for me was power consumption, as in later stages I plan to leave the computer running from a separate battery when the car's engine is off, but in order to get good life from the battery it can't draw too much current. I found a local supplier here that sells computer cases and power supplies that adapt the 12V DC from the car's battery to the necessary voltages and currents that the computer needs. 

I chose the following power supply & case combo as they are designed for vehicle use and have some handy features that will make integration into the car's electrical system easier later on.

PSU

Case

The PSU is capable of 140W max sustained output, which for a computer is not much at all (to give a comparison the one in my home computer is rated at 750W)

The case takes a Micro ATX form factor motherboard, which is basically a mini version of the boards found in most desktop PC's. The advantage of this is you can have a motherboard with all the onboard features of a regular desktop PC in a super compact package.

To save space and installing extra components, I wanted a motherboard that has onboard WiFi and Bluetooth. I settled on the ASUS Z97I-PLUS because its a solid motherboard that meets these requirements and has heaps of handy features for power saving, as well as a complementary software suite for monitoring and control. 

For the CPU I chose an Intel i3-4360. It has a low TDP (54 watts) but still packs a punch with a 3.7ghz clock speed. 

I chose 8gb of relatively cheap Kingston KVR16N11S8K2/8 memory, it's not the fastest or best quality but crucially it is very low profile which was nessicary to fit it inside the slim computer case.

I chose Window 8.1 as the OS (this was current at the time but has since been updated to 10), as obviously it has a huge range of applications made for it and it has the advantage of already being optimized for touchscreen use. 

For fast boot times and extra shock-proofing I chose a 250GB samsung evo 840 series SSD 

I  also bought a Samsung USB powered DVD-RW drive for watching DVD's but I didn't end up using it. Now, to start the build:

As with any PC build, one of the first steps is to prepare the case for mounting the motherboard. The power supply is designed for the case, so it was a simple matter of screwing it onto the stand-offs on the motherboard tray. 

Then I mounted the motherboard and installed the CPU:

Note the black 8 pin connector on the motherboard in the upper left corner next to the heat sink, and the 24 pin connector in the upper right corner

Next was to install all the wiring to hook it up:

The wiring is partially complete in this photo

This is where I ran into the first major challenge of the build. The power supply has the standard 20 pin ATX connector that supplies power to the motherboard, and a 4 pin connector for CPU power. This is an outdated design, as modern motherboards use a 24 pin connector for the motherboard power and an 8 pin connector for the CPU power (my motherboard has these in the photos above). 

I connected the power supply to a car battery to power on the computer for testing, and lo and behold, it didn't boot. In fact, it didn't even pass POST. This had me scratching my head for a while, and I eventually worked out that the computer wasn't getting enough power to the motherboard and CPU, and this was preventing booting. 

I needed to create a solution. I used a schematic from the internet to figure out which pins do what, and what voltages of the 4 extra motherboard pins require, then I spliced into the wires from the PSU connector and wired them into a spare 4 pin plug to make up the extra 4 pins.

For the CPU power, the wiring is quite simple, half of the wires are +12V and the other half are for earth. I simply cut the wires going from the 4 pin CPU plug on the power supply and bifurcated them, running one wire to each 4 pin plug so that the 4 pin connector on the power supply end became two 4 pin connectors on the motherboard end.

I didn't have the 4 pin connectors I needed, so I had to make a trip to a couple of local computer stores and asked them if they had any spare 4 pin and 8 pin cables, which one of the salespeople kindly gave me for free as they were leftovers from previous builds.  Alternatively, you could probably scavenge them from old power supplies. 

With that problem solved, I moved the computer to my computer room, and borrowed my home PC to power the motherboard and other components while I installed windows onto it. 

The car computer (sitting on the table to the right) next to my main PC. The main PC isn't actually running, its power supply is powering the car PC. The lights are on because some of the main pc is still connected to its power supply.

The last step was to so some cable management and fit the computer into its case. I should note that it was a very tight squeeze as there was no clearance between the plastic fan bracket on the CPU cooler and the top of the case. Choosing a more powerful CPU wouldn't have been possible as the coolers on them are taller and would not fit in the case.

You can see how little room there is between the CPU fan bracket and the case

This is the final assembled PC:

Perspective View: The VoomPC logo lights up blue when the computer is running

Back view: The white connector on the far right is for the power supply connections for easy removal.

Top view

Side view with the case upside down. You can see that the motherboard tray slides into the black case from one end. Its held in by screws that screw into the back of the computer. The SSD tray uses a similar system and is on a separate rail that slides in behind the front of the case.

The next step was to design a way to mount the computer in the car. Keep reading for the next step.