Building an In Car PC

Monday, December 01, 2008

Bulding a Car PC

By Chris Bibby

After getting into the whole moving map GPS Navigation thing with a Pocket PC, I found the size of the screen on the Pocket PC to be a bit limiting, so I started to look into building an in Car PC. Apart from the advantages of being able to Navigate using a larger screen, I also wanted to be able to dump photos from the digital camera to the hard drive, store and play music and video, and also connect to the internet if need be.

Version 1 consisted of a non touch screen and a pretty crude rig up built out of old PC bits I had lying around. I built my own mounting board and powered it using an inverter and used a Touch Pad mouse for screen control.

It worked, sort of, well for a little while at least, the inverter and power supply combination chewed a huge amount of power, and in the end the modified sine wave inverter fried the power supply and in turn the motherboard. I also wasn’t happy with the touch pad to control the mouse, so I scrapped that project and started working on Version 2.

From the lessons learned in version 1 it seemed imperitive to get the whole power supply bit right and use a low power small form factor board. After researching on the MP3Car Forums (www.mp3car.com) I came up with the following solution.

Power Supply

The power supply I chose was a M1-ATX Smart Car PC Power supply, this power supply can work within a wide range of voltages from 6 - 24 volts and is specifically designed to work with the varying voltage output from the cars alternator. It also senses battery deep discharge and will shutdown if battery voltage drop below 11V. The M1-ATX also has a remote power on/off switch that can be linked to the vehicles ignition or a seperate switch on the dash for booting up or sending a soft shutdown to the PC upon shutting down.

m1-atx power supply

Motherboard

For a motherboard, I used the VIA MII-1000 LVDS Mini ITX. This board is a low voltage low noise small form factor bord (17cm x 17cm) with an embedded 1ghz CPU. It also has onboard VGA, USB and sound as well as built in Compact Flash and PCMCIA ports. The Compact Flash card is ideal for transferring pictures from the digital camera and the PCMCIA port allows me to add a wireless network card for transferring files from my home network to the Car PC whilst the car is in the driveway. The board also has a composite video out for connecting an additional screen, perfect if you wanted to add a screen to the back of the vehicle for the kids to watch.

The MII-1000 also works well with the MI-ATX power supply.

To the board I added 512 MB of PC2700 DDR 333 RAM (Memory).

motherboard

Case, Hard Drive and DVD Drive

The next thing to get sorted was the case, Hard Drive and a DVD Drive. For a case I went with a generic Black Mini Itx case with front and rear USB and firewire and room for a slimline DVD/CD.

For a hard drive I used a 20gig 3.5in Maxtor drive that I had lying around and for a DVD I purchased a panasonic DVD/CD-R Slimline drive.

Installing all the bits into the case is a bit of a task as there is not alot of room in there! You also need to install the M1-ATX power supply into the case and run 4mm wiring though the back of the case. I removed the standard power supply connector and drilled out the hole to take the 3 4mm wires through the back of the case.

mini itx case

Touch Screen

This is one of the most important parts of the Car PC system, I believe. As mentioned earlier, I had tried using a standard 8" VGA screen with a seperate touch pad, but the touchpad and its cable was just way too cumbersome, offroading the thing would go flying and end up tangled around the handbrake, and was pretty impractical to use whilst on the move. A touch screen is much easier to work with.

There's quite a few different screens on the market at the moment, and there are a heap of cheap decent quality ones coming out of Hong Kong that you can purchase through Ebay. Regardless of what screen you go for, it has to be a proper VGA monitor for use with a PC, not just a screen that connects via a composite video connection. If you don't get a proper VGA screen you wont be able to see much on the screen at all.

The size of the screen is the next thing you need to choose, the most common for Car PC use is either 7" or 8". The 7" screens are usually in widescreen format and I have found they lose a bit of valuable screen real estate. I went for the 8" 800x600.

The way the screen mounts is the next thing to decide upon, you can get screens that sit inside a single DIN slot in your dash and fold out at the push of the button, you can also get screens that mount in an overhead console and then there's the standard screen which is up to you to mount

In Dash Touch Screens

Having already used up both DIN slots in my dash and the fact that most of fold out screens are 7", I went for the standard variety. Mounting the screen has been a bit of an issue, especially off road where vibrations and shock run riot. Initially I made up an aluminium bracket which connected to the screens existing mounting point, which worked fine on the bitumen, but didn't work too well on the corrugations offroad. The result was the failure of the screens existing mounting point, it pretty much just disintegrated.

Original Screen Baket

Back to the drawing board, my mate Hayden came up with the perfect solution. As you can't drill through the back of the screen case because of the circuitry attached to the back case, he made up an aluminum bracket with drilled holes for ventilation and glued this to the screen. From that aluminium bracket he then connected a standard speaker bracket from Bunnings (used to mount home theatre speakers) to the screen and the dash. The result is a sturdy movable mounting point, which has so far proved to be indestructible.

Screen Mounted Successfully

Installation/Mounting the Case

This is another area where a bit of trial and error came into play. Originally I mounted the case under the front passenger seat using velcro to hold the case in place to restrict the movement. Again this worked great on road, but off road it caused problems. The constant shock and vibration would cause the memory unit to come loose from the motherboard, causing the system to crash and become unstable.

The fix was to use some special foam that is used to line camera equipment cases underneath the Car-PC case. This is quite a firm density foam that whilst absorbing shock isn't too soft to cause the whole case to bounce around. The foam is available from Clark Rubber and is about $15 for a 50x50cm piece. The foam was fitted securely ender the seat and velcro is used to mount the Case to the Foam. This solution has worked very well so far and after doing over 600k's of driving on corrugated roads over the Easter period, including a couple of very large bumps the system hasn't faultered.

Camera Case Foam

Wiring

Wiring it all up is relatively straight forward just a little fiddly. I got an Auto Electrician to do the main wiring from the auxilliary battery through to a point behind the seat. From there I ran another wire from the switch of the PC's power supply through to a switch on the dash. The switch on the power supply is usually connected to the Accessory switch on the vehicles ignition so the PC boots up when you turn the car on and turns off when you turn the ignition off. However I didn't want to have to have the car on to use the PC and also didn't want the PC on every time the car was started.

The next step was hiding all the wires, I took the dash apart and ran the screen power, USB and VGA cables through the dash then under the centre console and then under the passenger seat into the PC. The end result was quite neat. The only thing I needed to get was a VGA extension lead and a USB extension lead.

All Wired Up

GPS

Another area where there are heaps of options, I've chosen to use a simple USB mouse type GPS, mainly because it was cheap and I didn't need the full functionality of a hand held GPS as the software on the PC provides all of that.

You can, however hook up your handheld GPS with a data cable directly to the PC. (if your GPS has that facility)

Tunes

I've used a small FM Radio transmitter that connects into the line out of the PC and broadcasts on an FM station. Similar to how the iPods connect.

The reason I went down this path is because my stereo does not have a line in. I'd definately recommend connecting the pc via a line in on your stereo as the FM transmitter seems to pick up a bit of interference with the Car Fridge.

Software

There's a lot of options here, but I've found the best way is to keep it all relatively simple. For an operating system I have used Windows XP. I have tweaked XP to automatically log on so you don't have to enter a password each time and automatically hide the taskbar to maximise the sreen real estate available.

For offroad navigation I use Oziexplorer and for onroad vector guidance software I use Map Monkey, which is basically a PC port of the Pocket PC application Destinator.

I also wrote a small touchscreen friendly (read big buttons!) "front end" application to launch the various navigation applications and also to control Windows Media Player.

There are literally hundreds of different applications available and if you want to get right into it I'd recommend checking out the www.mp3car.com forums.

Lessons Learned

Don't bother using an inverter they use too much power. A modified sine wave inverter can damage the power supply and other PC components.
Use a proper automotive power supply and low voltage board. My setup draws less than 1 amp.
Get a touchscreen, they are only $50 or so dearer.
Pay particular attention to the vibration issues if using your car pc offroad.
Interestingly the hard disk drive handles vibrations better than one would expect. In my case the main issue caused by vibration was the memory coming loose from the motherboard.

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