2005 Scion xB with Centrafuse plus AMD X2 64 5600+ and 17" touchscreen
This project is a culmination of bad ideas into a fun solution... and it has been a great time!!
I think in the same way most databases start life as excel spreadsheets, I think most car PC's start by running a laptop on the passenger seat.
My job requires that I have access to a fully functional PC almost all of the time. If you want the long story for why I have built such an overkill system, read the background at the bottom.
My project requirements:
1. Powerful PC with full size screen
2. Always on Internet
3. Navigational system
4. MP3 player
then I got started on the wish list...
file synchronization with home server
text to speech email
hand-free operation for phone
remote control of PC
separate battery system
I currently have the following completed or purchased on the project:
15" ELO touchscreen installed
AMD 4200+ dual core, 2GB, 80GB, DVDRW
Sierra 595 Air card with Linksys WRT54G3G-ST
350watt delco DC-AC inverter
BU-353 Weather-proof GPS Receiver
OPUS 320W Intelligent DC-DC PSU-- not installed
home-made battery isolator
IBM Keyboard with built-in trackball
Microsoft lifecam 3000
2nd battery charging system: I researched several battery isolator systems and the cost of them-- I just could not seem to justify 60-$120 for an isolator that I did not need. So.... I designed a simple cheap charging/islation system.
It consists of 2 relays and some wire. The CB1F-12V 40AMP relays cost $4.22 each from mouser electronics. My system works like this: When the car is running(charging) it connects the 2nd battery to the charging system and allows it to charge. When the car is off, it opens the circuit and leaves the 2nd battery to fend for itself while protecting the primary battery from being drained. On these relays the posts work like this:85 & 86 are the control circuit, so if you put 12V power to these to poles it triggers the relay. The other 3 poles are 87, 30, 878. 30 is the input, 87 is the Normally open ouput, 878 it the normally closed output.
If you wanted to get creative with these relays, you could reverse the input/output roles and have 87 Be the input for Battery A, 878 be the input for battery B... with 30 being the output. Then you could select either source by the control circuit.
It is quite simple to setup: 2 relays, 4 or 5 post are fine. The relay connections are like this, 2 seperate circuits. The switched circuit and the controlling circuit. The switched circuit is the circuit that gets opened and closed based upon the controlling circuit. So, in my example- relay one has the charging system positive as the switched circuit. relay two has charging system negative as switched circuit.
The control circuit has positive and negative leads. I supply constant negative and only suppy positive when the ignition is turned on. I also installed a 30amp inline fuse at both batteries-- this is just in case i have a line short in the middle of the connection-- it wil pop the fuse at either or both ends. I will upload a diagram of this system later-- but it is very versatile. By simply adding a 3 position On-Off-On switch you can have complete control over your charging system. Like this-- On-1(controlled by car running/orr) off(no charging) on-2(batteries connected) This on-2 position seemed like a not required solution... unless you run the main battery dead by leaving the headlights on and want to charge it from the 2nd battery. Simply flip the switch and wait 3-5 minutes for the 2nd battery to chage the 1st battery... My car doesn't take much too start... so I can flip the switch and start without popping my 30amp fuse... but your situation may vary.
Background for this project: I am a field engineer and also do most of the technical sales support for our sales staff. Which means they call me frequently and expect me to have detailed technical specifications for thousands of parts in my head-- reality says that I have them in a collection of 50+ PDF documents and neatly tucked away within google. While traveling I would have my laptop running on the passenger seat waiting for a phone call. I would then pull over and lookup the information they need-- One tragic day, in the lovely Atlanta traffic, everyone stopped short. Since I already had my coffee in my right hand, it was not able to save my laptop from the high speed trip to the floor. The result was one broken power-port on the motherboard. That's when I started dreaming of a "real" computer in my car...
I started shopping for the right screen size-- and nothing was usable with windows. Sure, the 10" screens work-- but I felt myself settling for less than I wanted and since I was going to build this, I was going to build it for my needs. I found a 15" ELO touch screen on ebay-- NEW IN BOX and sniped it for $200.
I practiced fitting the screenin the car using velcro straps and connecting it to the laptop-- this screen was truly to big for a stealth install... but it functioned perfectly, very bright, well built... so it became the center piece of my project.