(From personal perspective)
So, you have been shopping for a “Car Computer” system and, probably, as
confused now as I was when I started my project. Carputer is not your regular
pc, it is a computer designed to be used in car environment. That presents many
challenges to the design of the system, such as being easy to use and be able to
work from car’s internal power.
Car’s power is very different from AC outlets and batteries. It varies depending
on the conditions. When the car is off, the power is supplied by the battery,
which is around 12.3 Volts fully charged. When the car is on, the voltage goes
up to 14.1-14.5 Volts and is supplied by the alternator. The voltage increase is
needed for the alternator to take over and to charge the battery. One of the
biggest issues, however, is cranking. During cranking, a very high power load is
applied to the battery, which it is designed to handle, but during that time the
car voltage drops significantly.
A computer must have power supplied to it at all times when it is ON. The
software is loaded into the memory (RAM) and if the power drop occurs, it is
immediately erased. Hard drive, writing information to a track when power is
lost, will not be able to write it all the way, possibly making a section of the
hard drive corrupted. The hard drive will not be “killed”, it just means that
“scandisk” program needs to be run to find any possible errors and
inconsistencies in the information flow and fix it.
You’re, probably, now wondering how to handle the power problem. The first thing
to ask about a system is what voltage does it take? Most will claim 12Volts, but
the real question is if it is 12Volt Regulated or 12 Volt unregulated. If it is
“regulated”, then it means it cannot be used directly with the car’s power. A
special DC-DC converter is needed to convert car’s power into a regulated 12
Volt output. If it is unregulated, then how far down and how far up can it go?
It should be below 10 Volts and above 15 Volts in order to work properly in a
car. Now, to the most important question: “DOES IT SURVIVE THE CRANK?” Be sure
to ask this question. There are a very limited number of power supplies that do
this right out of the box. If that is not the case, it means a “Tank Circuit”
needs to be built in order for the system to be on during cranking. A Tank
Circuit consists of an extra battery and a relay or high power diodes, which
power up and isolates the system from car’s power during cranking.
The next thing is how the system power-up and shut-down is done. Power-up is the
easy one, once the system has power, turn it on. Many motherboards support this
option if it is enabled in the BIOS. The shut-down is the difficult part. I
simply cannot see myself pushing the shut-down button every time I park my car.
So, the next question is if there is a hardware controller supplied/built-in
with the system, or should one be bought separately to make it work. I find it
extremely convenient just to turn off the ignition and get out of my car knowing
that my system will shut down automatically.
One more thing needs to be mentioned about power. What would happen if it did
not shut-down? Are the jumper cables a necessity if you have a PC in your car?
The high-end power supplies will shut down the system if the battery voltage
drops below normal operating range. I leave my system powered up when I am home
so that I can upload music into it wirelessly, so the extra peace of mind that
my battery will not die is truly worth it.
With the power issues behind us, let’s take a look at the system design. I see
so many small units with DVD drives built into them. Unfortunately, none of
these units can be fit inside of my relatively small car so that the drive would
be accessible. That means going with an external drive and mounting the system
in a remote location, such as trunk. That presents the next issue of how to
power an external DVD drive. My external drive requires regulated 12V DC power
supplied to it. The good news is that the system already has regulated 12 V DC
power output, unfortunately, not all systems provide an outlet for it, so the
case needs to be opened and one of the power connectors spliced-in. The next
step is extending the power wire for the DVD, which requires soldering to be
properly done, and connecting it to the power outlet from the system. I don’t
mind soldering, but not many people are proficient in this field, so if a DVD
drive comes already with a power harness and the system provides a regulated DC
output, its installation becomes a snap.
Now, let’s take a look at the system’s performance. Most of the Mini-ITX units
are running a little above 1GHz in speed. Even “economy” desktops have that
beat. That speed may be enough for basic applications, but it just doesn’t cut
it for me. My favorite Winamp plug-in visualizer refuses to work smoothly under
this speed. Some may claim increasing memory size will help, but that is
partially true. Increasing memory is effective only up to a certain point – the
amount of memory used by the system. I have found that I rarely go above 256MB
in memory usage. Increasing memory speed would be more helpful. Memory, just
like CPU, has speed. It is also measured in MHz. There are 2 major types of
memory in today’s market, DDR and SDRAM. DDR is the newer type and stands for
“Double Data Rate”, which is twice as fast as the same speed (MHz) SDRAM. So, my
preference would fall on the faster DDR memory system, instead of the same old
SDRAM, as it can feed data to the CPU at a much quicker rate. The new technology
called “Dual Channel Memory” is even more appealing to me, as the memory data
transfer rate once again is increased dramatically. Next, let’s take a look at
the FSB (Front Side Bus) speed. Since the motherboard physically cannot handle
the speed throughput of the CPU, it is divided in chunks. Those “chunks” are
called “FSB”. The less “chunks” there are, the faster the system will be, so the
higher the “FSB” number, the quicker the system is. A new technology from
Intel called "Hyperthreading"
makes a very noticeable jump in processor's performance. If you think of
information flow through a processor as a pipeline, this new technology splits
the pipeline in two, making it easier for the data streaming to run.
Without it, if an application is using the pipeline to its full capability, even
for a fraction of a second, the rest of the flow is slowed down. With "hyperthreading"
second pipeline takes care of processing when first one is loaded, making
overall flow very efficient. Even MS Windows Operating System sees one processor
as two.
The next part of the system
that the speed is dependant on is the hard drive. I’ve seen the small factor 2
½” laptop hard drives in action and they are not your quickest runner. They are
designed to be small, consume less power at a price of the performance. Due to
my demand for speed, they were out of the question for my system. I have found 3
½” factor 7200 RPM drives to be an excellent choice for being quick, generate
little heat, be relatively quite and be more cost-effective. I’m sure you will
appreciate the large capacity offered, if you have a huge MP3 library, as well
as some movies in digital format.
Does size really matter? Those Mini-ITX cases are so appealing because of a very
small footprint. However, due to the small size, the speed and system
capabilities are limited. Therefore, Micro-ATX seems to be the obvious solution,
as it is not large, yet some of the quickest systems are built on it. I spent
long hours looking for a nice Micro-ATX desktop case, thinking I could use that.
On the pictures, it looked so small, I even ordered one. It is still laying
around somewhere because it was huge compared to the space I have in my trunk. A
case specifically designed to hold a Micro-ATX board, yet be small and be
intended to be mounted in a car is certainly a requirement. What is it with
those systems that are sold as “car computers”, yet have no direct mounting
options anyway? With the current technologies and no call for an internal DVD
drive, there is no need to waste the extra case space on expansion cards and 5
¼“ drive-space. The next issue that I think is important is the temperature
control. So many cases I see just don’t allow the air to flow easily or to add
extra fans for extreme temperature areas. Since we are on the topic of
temperature, I see no reason for the cooling fans to be on all the time. A
system must be smart to decide if the fans should be turned on and at what
speed. Having software monitoring of the fan speeds, as well as 3-point system
temperature and system voltage, is not a lot to ask for either. Another issue
that was brought to my attention is the hard drive mounting. Even though today’s
hard drives are able to withstand extreme conditions, I don’t feel confident
enough in a case that has no dampening device to reduce shock and vibrations
associated with driving. If it is a true “car computer”, it must have that for
me. Looks are also important. Pure aluminum look is the latest fashion. Even my
cellular phone is partially aluminum. Bottom line, an enclosure for a Car
Computer has to be specifically designed for it, be relatively small, be able to
withstand extreme conditions and look good while at it.
Input devices, those things are so important in a mobile environment. The
introduction of the touchscreen technologies took the graphic interface to the
next level. However, while it is nice to be used while parked, I urge not to use
it while driving because looking at the screen takes away attention from the
road. The solution is simple, to find a nice small IR remote that can control
most accessed functions of the system. The next problem you can run into is that
the remote needs a nice slim IR receiver with software. If you are going to add
something visible to your car’s interior, it should be small, slim and out of
the way. I found just that, in a USB format for easier installation and cabling,
and you cannot even notice it under my Double-DIN dash. Navigation through MP3s
has never been easier. I can be driving, shifting and holding the remote in my
hand at the same time. I don’t need to look at it either, as I can feel the
right button with my thumb. I’ve seen some using touchscreen with a small
keyboard application to type things in. I am sorry, but I find it to be very
inefficient. Therefore, a nice and small wireless keyboard that could fit into
your glove compartment is a requirement. The best thing about it, it come
bundled with an in-air mouse, which uses latest “gyro” technology to determine
where the mouse moves while in the air. I use it as an alternative to
touchscreen, as it can be more precise. In-air is only a half of its abilities.
Set it on a flat surface and it becomes a regular optical mouse. Now, my armrest
just became a mouse pad.
Now, let’s talk about sound. Nice sound system was the main reason I started my
project, and I’m sure it is important for you also. There are different ways to
deliver sound. A Car Computer only provides output enough to power headphones,
the rest must be taken care of by the vehicle’s sound system. An easy way to get
the sound to the speakers is to utilize the factory or aftermarket stereo
already installed in the vehicle. There are 3 ways to do this. First, is to use
a tape adapter, if the stereo has a tape player, and plug it into the Car
Computer’s sound output. An extension cable is available for it. Another way to
do this is by the means of a FM modulator. Such devices are sold in most
electronics stores. It plugs in between car’s antenna and the head unit and
broadcasts sound on a certain frequency. You simply need to tune the radio to
the right frequency. The third way is to use AUX input of the head unit to feed
the sound in. Limited number of head units have them, mostly aftermarket, and
not all have them enabled (secret key sequence may unlock it). If such is
supported, a cable, preferably of a good quality, such as Monster Cable, is all
that is needed. I used to have FM modulator installed, but the sound quality was
not great. Therefore, I decided to get rid of the factory stereo, install an
aftermarket amplifier and use my PC as a head unit. I was successful. The only
downside is that at the time, I was using on-board sound. Due to the way factory
drivers are configured, rear speakers only worked as an addition to a surround
effect. There were 2 options to go around it, parallel the front and the rear
channels using a Y-splitter, or download a plug-in to make the sound being
output constant to all 4 channels. I decided on neither of the two and added an
external USB 2.0 sound adapter Sound Blaster Audigy 2 NX by Creative Labs. Once
again, it needed regulated 5 Volt power, which worked the same way as the 12
Volt DVD described above. The extra money spent was truly worth it. With
Creative’s CMMS (Creative Multimedia Surround System) technology, all 4 channels
are on all the time. After configuring the digital signal processor, the sound
delivery is just amazing. Best of all, I can even listen to DVD audio disks,
where there are over 6 channels already encoded.
A small VGA LCD Monitor is what’s going to make your project much easier. It has
not been long since they were introduced on the market. More and more options
become available. Touchscreen is now almost a standard feature. There are two
major brands out there, Lilliput and Xenarc. Xenarc is significantly more
expensive, but I find it to be of a better quality. Their service and warranty
are excellent. I selected Xenarc for my system just for those reasons. I was
able to retro-fit it into a Double-DIN opening, replacing my factory head unit,
which took quite a bit of work. Many people have done the same thing, so there
is much information to be found on how to get it done. There are even
non-motorized enclosures available to fit a VGA monitor directly into a
Single-DIN slot. Even more options will be available in the close future.
Choosing a right operating system is also important. Many people used Linux;
however, due to a limited drivers support, Microsoft Windows XP is a better
choice for compatibility reasons. There are no driver issues with the current
hardware and the network, wireless that is, is easy to configure with the
existing setup I have. If you are not computer proficient, be sure to have one
installed for you. All of the installation CDs, as well as Certificate of
Authenticity must be provided, if an operating system is to be installed.
In the end, I would like to mention system expandability. Most of the computer
hardware can be purchased now in a USB version. Introduction of USB 2.0
interface, which is 40x faster than the previous 1.1 version, enabled the use of
high speed data transfer devices, such as DVD/CD-RW drives, external TV tuners /
capture adapters and high speed wireless network adapters. So far, the USB
devices I have are: DVD/CD-RW drive, Touchscreen, Mini IR Receiver, GPS, RF
Keyboard / Mouse receiver, Sound Blaster Audigy 2 NX audio, D-Link Wi-Fi
adapter, which totals 7 devices. Has it not been for a system supporting 8 USB
devices to begin with, I would've needed to install a USB 2.0 hub, which is
recommended to be powered to support multiple devices. Once again, the powering
of a USB hub goes back to a regulated power outlet or splicing of the connector
wires inside of the system, then soldering an extension cable and so on. Of
course, there are pre-made USB 2.0 hubs available. Being able to avoid the need
for it to begin with may save some headaches down the road.
I hope you find useful information in this article.
Feel free to drop me a line if you do:
editor@carcpu.com
Not responsible for any typographical or specifications errors.
Information presented in this article is the views and opinions of its writer
only. Copyright © 2004 CarCPU, INC. No distribution or copying is
allowed without direct consent of CarCPU, INC.
