Loc: Florida, USA
It was only a matter of time that a computer geek installed a computer into their vehicle. Use to only see law-enforcement and a few company vehicles with them.
The secret to the proper carputer is very easy. Everyone that has installed one was very close to a flawless system. People don't seem to grasp that you will run into problems and the one system you build isn't going to be the only one. I myself built three systems and still had some trouble. In this guide you will learn the right and wrong ways of building a carputer.
80% of carputers fail because people want massive large amounts of storage space that they will never need. You do not need more then 20GBs of space total and even that is way too much. The ideal storage is just enough for a Operating System, FrontEnd, GPS and maybe OBD-II software. 10% is from faulty wiring. People never think enough about the wiring. It can be a bad ground, wrong power type or the cable is just too long and you loose resistance. The remaining 10% is cooling. I've seen people toss their system under the seat and expect things to run smooth. Dirt can easily get in from shoes and the carpet can choke the system.
STORAGE Lets talk about Storage. As I said before you don't need a whopping huge storage device. Last thing you even need in a car is a hard drive spinning 7,200 RPMs or higher. Vibrations will kill a hard drive. Think you're safe with a laptop hard drive? Better think twice. The best solution is Solidstate or SSD. I know it sounds expensive but you can whip something up for the price of a typical hard drive. The only moving parts you want in your system is a fan or two and your optical drive.
SSD has been around for a long time but recently has made headway for chips that hold more data. To build your own SSD you have a few options. If you plan to use a UNIX based operating system such as Linux or MacOS X you can do wonders with a USB hub and a handful of USB jump drives. Linux and OSX offer a software based RAID system that works with almost any storage application. So a USB hub and four 1GB jump drives and build a simple RAID array you can have a single partition of 4GB that is plenty for a slimed down OS and a front end. If your a Windows fanboy you can use CompactFlash and a IDE or SATA adapter. Most motherboards have a built in RAID system so you can load up your controllers with 4GB compact flash cards and build a RAID array.
Now for music and videos you can use your MP3 player for that so you have them on the go or use a jumpdrive to store your music and videos. It is that simple.
Now SSD runs faster then a typical hard drive so the boot time will decrease some but if you want faster boot times check out LinuxBIOS project if you're planning to use Linux. For Windows you could go the BartsPE route or even the Windows XP Embedded system. Since the dawn of OSx86 a lot of headway has been made to slim down the OS and if used in the right hands you could have a groovy little setup in no time.
ELECTRICAL Now for the electrical portion. My hobbies are Cars and Computers. I know the ins and outs of typical automotive electrical systems and a lot about computers so read closely. When selecting your power supply for the carputer you can go with a DC-DC power supply that takes the 12volts from a car battery and converts it to 5 and 3 volts. It also lowers the amps for 12volt leads. Some power supplies come with a built in shutdown circuit that tells the carputer to shut down properly when you turn off the ignition rather then just total power shutdown. You want to use a nice gauge primary wire for wiring up your power supply, nothing too heavy duty like a car amp but 14 gauge is a nice gauge to use. The whole vehicle is grounded so you can attach the ground to a bare metal spot inside the car. As for the power you want to be close to the battery but it's not going to happen unless you put the carputer inside the dash. The remote connection is for ignition power, so when you turn the ignition to Accessory and such it closes a circuit for a 12volt lead. If you want you can use a toggle switch and use a constant 12volt lead so you don't always have to power up the carputer.
If you want to cheap out and use a desktop power supply you will want to invest into a power inverter. Power inverters come with then small gauge wires that are great for temp use but if you're going to power a computer with it everyday you want to upgrade those wires to 4 or 8 gauge. If you use the OEM 14 gauge wires that came with it too long you can kill the inverter and create a fire hazard. Also do not use extension cables at all when you use a power inverter. If your power cable doesn't reach then buy a longer power cable. Longer power cables will be thicker due to heavier gauge wire and thicker sleeving.
Another thing to think about is the video cable. You can use extensions if needed but if you go too long then you will loose resistance and end up with a blurry/fuzzy picture. USB can be picky, a lot of cheap USB hardware will use a thin gauge cable so after three foot it losses resistance. Even if the cable looks thick it can still have a very thin gauge wire and have a lot of sleeving. A few people have tried using extremely long ribbon cable for drives and face data loss. Standard computer ribbon cable has no insulation or protection from electromagnetic interference. 18inches is the maximum length. Some people have taken to time and used CAT5 cable and created their own cables. SATA cables have a maximum of one meter so keep that in mind.
ENCLOSURE & LOCATION People come up with wacky things like putting a case on the floor or live in a hot humid climate and toss it into the trunk. The floor and trunk are the worse locations for a PC. Lets use a car amp for a example on this. A car amp casing is a huge heatsink. When you open up the amp you will see all transistors and such that create heat are mounted to the casing with thermal compound. A PC is only cooling the CPU, GPU, north/south bridges and sometimes RAM. Not to mention the car amp is completely sealed but a PC has vents and intake/exhaust ports for fans. The ideal room temperature for a computer is 70*F. We all know that isn't going to happen with a PC. When you build a carputer don't use your typical indoor home preferences like making the system quiet. You want some high rated wind tunneling sound CFM fans. If you have the guts you can install the carputer inside the dash and reroute a A/C vent to the carputer. Or if you know about A/Cs you could route a A/C line to the CPU and do some vapor cooling . But really turn that glove box into a enclosure, you will be happy in the end. If you own a SUV then putting it in the back works just as well. A friend of mine had a nice setup in his Honda Passport, the system was in the car jack storage box. If you want to use the floor then build a amp mat. The pros uses this for sound competitions. It's a plate that is a inch or so bigger then the case and uses a one inch stand off. So if the case is 8x10 then use a 9x11 or 10x12 inch plate. This way the bottom of the case will stay cool. Also be sure you and your passengers wipe their feet before you ride out.
My future system Not sure on the CPU and motherboard but there will be SSD, wireless, bluetooth, touch screen and GPS. The system will run Linux, I have been tinkering with Coreboot (LinuxBIOS) and seems like a killer idea for a carputer. As for the frontend I have been playing with flash and thinking about building my own frontend from scratch. My iPhone will be used as a storage for music, video and will use it for internet access. So far the GPS software is kinda weak for Linux so I might have to use WINE to run the GPS software. I would like for the system to be small enough to fit inside the single din slot in the dash. Maybe the best route for me is to look at some embedded boards.
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