Car PC: Part 1 – The Hardware
After my exams had come to an end, I decided I needed a mini project to keep myself occupied for at least a few weeks, so I decided as any normal, sane and non-geeky person would, to put a PC in my car.
I spent countless hours researching various components and determining what the best route to go down would be. Installing a computer in a harsh environment such as a car needs a bit more thought than your average ‘buy-the-components-and-slap-them-together-bob’s-your-uncle-fanny’s-your-aunt’ kinda thought process.
– There are space considerations. The entire computer needs to fit comfortably into a small area without sacrificing functionality.
– There are operating constraints. The computer should be sufficiently cooled to prevent it melting and destroying your car and perhaps most importantly, it needs to be low power so as not to drain the battery when working or when idle.
Taking this all into account, the core specifications for the computer were as follows:
VIA EPIA M10000 ‘Nehemia’ This board is based on the mini-ITX form factor (it’s really, really tiny), has an integrated 1GHz processor, graphics, sound, USB and LAN. It is extremely low power and as such runs quite cool. The integrated graphics is more than sufficient for in car purposes as are the other onboard components. Coupled with this platform, I chose to fit 512MB of RAM (mainly because that’s what I had lying around at the time – yes, I have have RAM lying around, ok?)
I chose to use a 2.5″ laptop hard drive as they tend to be a bit more resilient towards shocks which will be ever present in an automotive environment. Alternatives include booting from a sizeable Compact Flash card and appropriate adapter but due to the limited write cycles as well as other limitations, this method, although fast, requires much more work on the software.
To provide the computer with power I used an M2-ATX automotive PSU. Why not take a 12V DC supply straight from the battery? Well, besides from the obvious hassle of having to install a manual switch to turn the computer on and off, running a line direct from an in-car 12V source leaves sensitive PC components open to large voltage fluctuations. For example, the battery voltage can vary from 11-14V depending on the operating status and during engine cranking can jump up to 10’s of Volts higher.
The M2-ATX, which is rated at 160W, protects against these surges and also allows remote turn on of the PC via a switched 12V ignition feed. That is, when the key is turned in the ignition, the computer begins to boot.
– External Devices:
Nearly all the peripherals connected to the computer are via USB. A mains powered hub was used and modified to work with the M2-ATX. Essentially, the 5V USB standby voltage was isolated within the USB terminal so that rather than drawing power from both the USB port and external power, the hub was exclusively external powered. Accessories included: USB GPS receiver, Bluetooth, FM Radio, Wi-Fi, USB touchscreen.
Stick it all in a well ventilated, home made case (containing custom hard drive mounts made from picture frame hooks!) and you have 1x Car PC.
Part 2 coming soon. That goes into details regarding the software used both behind the scenes and as a front end.