The CarPC in the Austin relies in a collection of passive sensors (Unlike the BMW install where
all the data comes from the car’s IBUS via an IBUS to serial COM port convertor).
There are two temperature sensors, one monitoring the coolant temperature and the other measuring
the external temperature. These sensors output a linear voltage that the Fusion Brain can read.
The engine revs are picked up from the 12V feed from the distributor to the ignition coil. (With a standard
4 cylinder engine the coil will spark once for every 2 RPM). This sensor has a potential divider that drops the
ignition supply voltage from 12V to 5V, then measures the frequency and outputs a linear voltage for the Fusion Brain to read.
To pick-up the fuel tank voltage and monitor if the indicators are in use, a simple potential divider
is used to drop the voltage from 12V to 5V. The Fusion Brain can monitor these directly.
The Fusion Brain is a USB interface that can monitor 13 analogue voltage inputs and can drive 12 digital outputs.
The job of this device is to measure multiple voltage levels (from the sensors) and feed the values from them into
the Road Runner PC software. This device was quite simple to set-up (from a software point of view) as all of its
functions are already incorporated into the Road Runner software.
The Mini-ITX is running Windows XP with all possible non-essential services disabled. For durability a High Speed
compact flash card can be used as a disk drive. Previously I have used an 8GB Sandisk Extreme CF card. This has reads
and writes of 60MB/s so functions well as a disk. I have now upgraded to an SSD and the whole PC can boot up from cold
in about 45 seconds.
I have used Road Runner software (more recently renamed to Ride Runner) to provide the front-end GUI. This software
is skin driven so you can easily create your own ‘look’. Road Runner is set-up to seamlessly incorporate, Winamp (or Foobar)
and many other external apps. (USB Radio tuners, Tyre pressure monitors ….the list is endless)
For more information see. http://www.mp3car.com/road-runner/
Creating the gauges took me a little more time, (I am a Hardware Engineer not a graphic designer!)
I started by putting the actual speedo from the Austin on a flatbed scanner and then scanning that in so I could
create the basic outline of my digital dash. This outline and all speed markings are a.JPG image that is a static background.
The Speed needle and all other gauges are individual Flash animations created with Swishmax 3. These Flash animations
essentially create an animation with 120 frames. E.g. Frame 1 being 0 MPH and Frame 120 being 70MPH. The roadrunner
software passed a speed value to the Flash animation and the animation decides which frame it should display.
I have an external USB GPS receiver. This not only provides location information to the Sat-nav but also provides
the speed signal for the main speedo (the only drawback is my digital speedo doesn’t work if I’m in an underground
car park, not much hardship)
A simple program called Xport can share a single GPS source with multiple programs.
Initially I used a USB touch-screen display, however I soon tired of this as it put an unwieldy amount of strain on
the USB bus (CPU, resource and physical power). Playing a DVD was impossible and it was not too bright in normal daylight.
(Also as it’s USB you don’t see any POST information from the motherboard and it only kicks into life once Windows
has loaded the drivers)
I now use a HDMI touch-screen display. This puts much less stress on the system and is much more reliable.
I used a specific 12V to 24V Car to PC power supply. This is designed to work in cars and provides many functions :-
1) Monitor the ignition voltage and turns on 5 seconds later, thus removing any voltage spikes associated with cranking the car over.
2) It can send the PC to Sleep or Shutdown when the ignition turns off.
3) This Sleep or Shutdown can be programmed to be sent 5 seconds to 4 hours after the ignition is turned off.
4) Low battery voltage shutdown. If the supply voltage drops below 11 volts (ish) it will turn the computer off to save you having a flat battery