Monday, August 31, 2009
The power supply for a car pc is a little bit different than a standard ATX AC/DC power supply in a home computer. Since your car's electrical system is 12V DC, there is no need to convert from AC obviously. So the M2-ATX is a DC power supply that takes the 12V from your car and feeds it to your computer. All of this is straight forward. The "unknown" part to me was the additional shutdown logic in the M2-ATX.
One of the obsticles in running a pc in your car is that there is some amount of time needed for a proper windows shutdown. In your home, when you turn off your computer, typically you don't just pull the plug. Usually you either shutdown through Windows, or your power button on your computer is configured to send the proper shutdown signal to your computer so that Windows can shutdown elegently.
This is no different in a car pc. When you turn off your ignition, the M2-ATX has some logic that allows for your computer to shut down cleanly. This logic is configurable via some jumper settings on the power supply. Basically you can set your power supply to send the shutdown signal, then wait for a configurable amount of time before cutting the power to your computer, so as not to drain your car battery.
Now, when I first connected the M2-ATX to my motherboard, I connected the J8 on the power supply to the power switch pin header on my motherboard. This allows the M2-ATX to power the computer on and off. Then I connected my case switch to J9 on the M2-ATX. This is to allow me to turn the computer on and off with the case power switch as an option instead of the cars ignition.
In the manual for the M2-ATX it states that you should not jumper any of the J10 pins if you want to use the psu in standard mode. So I hooked it up this way since I wasn't planning on using the pc in the car just yet. What I found was that the power supply would not turn on. There are three posts on the power supply for prividing a power input. POS, IGN, and NEG. Where IGN is for switched power (ignition). I had initially misunderstood the manual for the M2-ATX. In order to use the M2-atx in standard psu mode, you should only connect the POS and NEG terminals, since you won't be using the timing logic. Alternativly, you could jumper J10a which is the recommended mode and connected POS,IGN and NEG. By doing this, your case power switch emulates your cars ignition. Once Chris over at www.mo-co-so.com straightened me out on this, everything powered on and came to life!
One thing to note about the J8 and J9 pins on the M2-ATX. Some question was raised about polarity. It seems the consensus is that there is no polarity on these jumpers. Here is a photo of how my J8&J9 are connected and it is working fine. J8 is on the left, J9 on the right.
Here are a few more pictures of my setup so far. I'm hoping the hi-res photos will be helpful for others at this stage.
Saturday, August 29, 2009
Good shot of the overall computer
Here you can see the hard drive mounted under the power supply
Here is one of the I/O for the motherboard
Finally here is one of the I/O backplate on the case
I've started collecting the various parts needed for this project. Here is what I have and where I got it.
Motherboard/CPU: Zotac Ion from Mobile Computing Solutions
Power Supply: M2-ATX from Mobile Computing Solutions
Power Supply Adaptor: M1/M2/M3 Adaptor from Mobile Computing Solutions
AC/DC Switching Power Adaptor: AC/DC Switching Power Adaptor from Mobile Computing Solutions
Power wiring harness: 6 Pin Wiring Harness from Mobile Computing Solutions
Case: 4th Gen case from Mobile Computing Solutions
HD: 400Gig WD 2.5" Scorpio Blue from Tigerdirect
Sirius: SCC1 + MJS usb adaptor from a guy on mp3car forum
Ram: OCZ Platinum 2gig kit from rbc computing
Tuesday, July 7, 2009
I think this is the area where I have the most options. I haven't set a budget on my project (bad idea) but for the most part the cost variation is minimal except for screens and amplifiers. The screen in a car PC is basically fundamental. It acts not only as the display to your computer, but also as the interface. Here are my requirements for a screen.
- Can be fitted in my double din dash opening
- 1024x768 resolution
- usable in sunlight
Given these requirements, the options may not be so many. Here are some popular choices I've come across.
Both screens have a double DIN housing, and LED backlight for greater range of brightness. Both support resolution up to 1024x768. The 629 seems to be a little bit brighter.
Saturday, July 4, 2009
Powering a computer that is intended to run off your 12V battery in your car requires a different type of power supply than the one you would use in your home computer. Computers use DC power and home computers use an AC-DC power supply to convert from your AC home outlets. Since your car uses DC power already, no need to convert. So for a car PC you need a DC-DC power supply. Since this is a very specialized computer that doesn't have the same power requirements as your home pc, you don't need as much power to run it.
Wednesday, June 24, 2009
- Fits a mini-itx motherboard
- Compatible with your power supply
- Fairly durable
Probably most any mini-itx case would work fine as long as it has a spot to mount the power supply, but I narrowed my search to cases designed specificaly for car PC's.
The case that stands out to me to be the best choice is from a company called Mo-Co-So. The 4th gen Mini ITX case is compatible with popular DC-DC power supplies (specifically the M2-ATX) and has built in RCA audio output jacks located away from the power supply to help reduce electricaly interference. It can take 1 slimDVD drive and 1 2.5" HD. I had considered also the VoomPC-2 case, however, I've read that the RCA output jacks are too close to the power supply and cause too much electrical interference. And that's actually in the product description!
Tuesday, June 23, 2009
In my search for a low power consuming hardware, I came across a new platform developed by Nvidia called ION. It's a mini-itx form factor motherboard with GF9400M video on board and takes either a single or dual core Intel Atom CPU. The first company to sell just the motherboard is Zotac. There are a few different packages to chose from, but this one looks like the best choice for a car PC.
Onboard Video GeForce 9400M
Onboard Audio 5.1
CPU Socket 441-ball
FSB 533 MHz
Dimensions 6.7" x 6.7"
Memory Type DDR2 667/800
Package Contents 3 SATA cable 1 SATA power cable 1 WiFi antenna 1 WiFi bracket
Memory Slots 2×240pin
SATA 3 + 1 eSATA
PCI Express x1 1 (mini)
Form Factor Mini ITX
Video Ports D-Sub + DVI + HDMI
USB 10 (6 on back panel, 4 via pin header)
Power Connector 24 Pin
Looks like this board can be had for about $220 here. Considering the CPU and GPU and Wifi are included and the size and effeciency, it seems pretty reasonable.
Nvidia is claiming to do full 1080p video decoding with this board and I believe it. I have a home media center that I built using a GF9400 and I can do full 1080p with as little as 10% CPU overhead. That is using an AMD 5050e CPU which is faster than the dual core Atom, but not by so much that I would expect the CPU usage in an Atom based system to be that much higher. I'm hoping the CPU usage will still be under 30% when decoding 1080p.
As for mp3's, the dual core Atom is fine. My only concern is how some of the bigger GPS software packages will run on a dual core Atom. I suspect this too will be fine given that most portable GPS units are running on 400mhz ARM CPU's.
You can also get a version of this motherboard with a built in 90W power supply and AC-DC power brick. This would be great for building a tiny media center PC for the home, but for a car, I'm looking more at the DC power supplies with ignition control to manage the system startup/shutdown a little more elegently than just cutting power when you turn off the car.
UPDATE: PCCyber has this board in my area now for less than anywhere else in Canada that I could find!