Look at any expensive car and you’ll see an LCD for displaying navigation, TV
and sometimes DVDs and a reversing camera. Get to drive that car and you’ll find
yourself using all of those facilities – and enjoying them a helluva lot... So how
can you get those features in your own machine? Sure, the stuff is available
commercially but it doesn’t take long to find that car navigation systems cost
heaps, DVD (with decent screens and audio) is a lot of money, and an in-car TV
with good reception is hardly cheap.
But there is a way of achieving all of these features – and a lot more as
well - at a vastly lower cost. In short, what you do is run a full PC in your
car. Nope, not a lap-top, but a full PC. The benefits are huge – and most can be
summarised in one word: cost. Because of the popularity of PCs, they’re
ridiculously cheap, easy to upgrade and are available with lots of functions.
Sounds obvious? – and it kinda is... but usually not in relation to cars.
Once you have a PC and good in-car screen running, rather than spend
thousands on a car DVD, instead shell out less than a hundred dollars. With that
in-car PC up and running, voice-directed navigation costs around a quarter a
normal car system. MP3 player with a huge storage capacity? – already there.
Want to play games?... easy! Like to constantly run the software for a
programmable engine management system? No problem. Want to have a virtual
instrument display courtesy of standard engine data being read from the OBD
port? Can do.
And because you’re running a full PC, the in-car system won’t get outdated
any more quickly than a home or office PC. IOTW, you can do normal upgrades just
like you already do – that’s a b-i-g
difference from dedicated car systems that can be kept current only by selling
them and starting again...
So what’s involved in putting a PC in your car... especially if you’re not a
full-on computer geek but instead are more interested in what it can do for your
in-car entertainment and convenience?
Well, we’re going to do it in two different forms – the first using an old PC
(got for nothing!) running Windows 98 and a Pentium 2 processor. If you like,
this is the entry point – cheap, effective and capable of MP3 and (with a decent
screen) able to also run a reversing camera.... as well as word processing and
digital camera storage, of course! Then later we intend upgrading to a DVD,
navigation and multi-screen capable system. It’ll cost more, but the saving over
doing it with conventional car components will be nothing short of massive.
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It’s important to note two things. The first is that we actually did what we
will cover in these articles, including finding – and overcoming – lots of
problems along the way. And secondly (as mentioned in the main text but worth
stressing), this series is not designed for computer nuts but instead for those primarily interested in
cars...
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The System
An in-car PC is made up of these components:
- The
PC
- A
power supply
- A
screen (or how to see things)
- Audio
output (or how to hear things)
- A
mouse or other pointing device
Not included in that list but worth thinking about the car implications are a
keyboard, card reader and DVD/CD player.
Let’s skip the PC for a moment and move onto #2 – the power supply.
Conventional PCs run a power supply that provides the required internal
voltages needed by the PC. These can comprise 12V, 5V and 3.3V. In other words,
the mains power coming into the PC is not just dropped down to one voltage and
changed from AC to DC, but altered to a number of DC voltages. The total power
required (found by multiplying each voltage by the current that can be drawn and
then adding them up) can be summarised as, for example, 200 or 400 watts.
Mains power supplies for PCs are extraordinarily cheap. In fact as we covered
in DIY Budget 12-volt Bench Supply,
PC power supplies are so low in cost they make a good bench power supply. The
reason that they’re cheap is something that we’ll come back to time and time
again in this series – they’re made in huge quantities.
Power supplies for PCs that work off 12V (ie car battery voltages) are also
available. But they’re not cheap –
try something like ten times the price of a normal mains power supply!
So while it sounds a bit like working backwards, the cheapest way of getting
an in-car PC power supply is to use an inverter to boost the car battery voltage
up to mains voltage before connecting it to the PC power supply – which then
drops it back down to the right DC voltages. Suitable inverters are available
from about AUD$150.
We’ve covered in-car inverters in a specific detailed article (Mains Power for Your Car!) and that
article gives you all the information you need to purchase an inverter and then
install it in your car.
Do it Yourself Power Supply?
During the development of these projects we had a chat to the guys at the
electronics magazine, Silicon Chip.
Couldn’t they come up with a cheap do-it-yourself car power supply for a PC, we
wondered? The answer was ‘no’ – with the amount of current and the variety of
voltages required, it would be far cheaper to simply use an inverter...
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The easiest way of maintaining full compatibility with a PC is to select a
dedicated in-car LCD that takes a direct VGA input. That means that a cable can
be used to connect directly between the video card of the PC and your car
screen, without the need for adaptors or special cards. The screen is the single
most expensive part of a low-cost in-car PC system, especially if you budget for
a screen that will suit any likely short-term PC upgrades (so has a decent size,
quality, etc).
We bought a Lilliput XVGA-compatible 7-inch TFT LCD screen from
Hong Kong for about AUD$400, including freight.
A basic PC sound card has a line-level stereo output – more sophisticated
ones have more channels, including a dedicated subwoofer output. However,
whatever the number of channels, you’ll need to find a way of feeding them to
the car speakers.
A couple of approaches can be adopted. One is to use a dedicated amplifier
feeding dedicated speakers, but this will cost a lot and is poorly integrated
with the existing car sound system. Another approach – which does integrate well
– is to feed into an existing auxiliary input, such as a ‘CD’ jack on the face
panel. However, lots of systems don’t have such a jack. So what about feeding
into existing CD-changer inputs, with just a changeover switch to let you play
PC or CD? This sounds neat but the trouble is some head units look for certain
‘CD playing’ signals from the changer before opening the inputs. Hmmm.
In short, we decided the easiest way of integrating the PC audio output with
a typical car stereo system is to use a high quality FM modulator that connects
in-line with the aerial. That way, by selecting a dedicated FM channel, can you
can hear the PC audio loud, clear, and with surprisingly good quality – all
through your normal car sound system.
Given that having a keyboard in a car is unwieldy, how are you going to
communicate with your in-car PC? One approach is to use a compact programmable
numeral-only keypad, where pressing one button executes a number of commands
(like, open the MP3 player and play folder #4). However, these keypads are expensive and
require lots of user memory – hmm, did Number 1 key do this or that?
We think that a mouse is a crazy option so that leaves three other
alternatives: use a touchscreen LCD (best), use a track-ball (good), or use a
joystick running mouse-conversion software (potentially good but we haven’t
tried it).
For our initial installation we used a small trackball (shown here) and found
it not dissimilar to the control system in the current Audi A8 – the trackball
cost AUD$30.
We’ve left this one to last because in a basic system, it’s literally of
least importance. Any PC capable of driving a screen and – for example – playing
MP3 tracks is potentially useful in a car. It also helps if it uses an ATX power
supply – ie one that has just a low voltage switch to turn it on and off. (This
makes remote control of the PC easier – for example, it can be modified to turn
on when power is applied.)
The Budget, so far
Keep in mind that if you’re only going to play MP3s, this system is expensive
for what you get. However, if you’re going to explore some of the options that
having a full in-car PC opens up, the system is cheap, cheap, cheap.
| Inverter – 400 watt, modified square wave |
AUD$150 |
| LCD Screen – 7 inch touchscreen | AUD$400 |
| FM Modulator – direct aerial connection |
AUD$90 |
| Trackball mouse |
AUD$30 |
As we said at the beginning, we got the basic older PC for nothing as a
discard, so we’re up for AUD$670 so far. Hmm, isn’t that a lot? Nahhhh, not when
you start realising what you can do!
But don’t start
getting too excited. Next week we’ll cover getting sound from your PC into your
car’s system – and there are a helluva lot of traps to look out for. We know; we
fell into each one....
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