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Homemade lunchbox: is it feasible?

Last response: in Systems
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July 14, 2010 11:20:59 PM

Hi. I am planning to build a portable computer (in the original sense). I don't mind lugging around around 10 kg, but weight should be kept down if possible. Overall I would also want a high-performance system good enough for current games, some audio editing and the like.

I don't want a laptop since they are difficult to upgrade, impossible to self-service, and suffer from vendor lock-in. Lunchbox chassis vendors build more-or-less what I want, but they charge a mint for ruggedness I don't need, and the vendor lock-in problem remains since many of them seem to use proprietary parts here and there. So please read the rest of this post knowing that even if I propose silly methods to do things, I am set on building it some way or other.


(1) "Portable" ideally includes batteries for an hour or two of active usage. I plan to go with a large 12V lithium battery pack. As I am getting desktop parts the capacity has to be even higher than that in notebooks, but this site suggests that isn't a problem. In that case using a DC-DC PSU (eg. Mini-Box) seems inevitable. Mini-Box only makes PSUs up to 250W, which doesn't sound enough. Another vendor offers larger PSUs at much, much higher price. I won't try building one myself -- no electronics tools at hand so the voltages will be off.

Laptop LCD screens use LVDS and no desktop cards output that, but a desktop screen connects to wall AC. Should I look for a desktop screen with external AC-DC adapter, or try something else?

(2) How should I build the case? I think finding a corrugated box (light) and reinforcing the edges with aluminium brackets (strong) should be sufficient. Then I can somehow attach the mainboard to the brackets. I suppose it's then simplest to attach the screen to the outside of the box and make a separate lid for it. If I then attach a mouse and keyboard to the lid, it will look uncannily retro. Advice appreciated from any case-builder or modder.

Dimensions: My tentative plan is to use a 19" widescreen, which is around 41x26 cm, so the case would be slightly bigger than that. However, 19" desktop screens with WUXGA or 1080p seem non-existent, so if I want that I have to go all-out for 22" or heavier. The depth depends on PCI card selection, but I can't see any compelling reason to use an old half-height card just to reduce the depth. So it can be assumed as 15-20 cm.

Since cardboard is not metal, the electronics might have problems with grounding and cooling. I'll also have to waterproof it. Are there other potential problems in this approach?

(3) Cooling might be another issue. The chips I'd like to use are i5 750 and HD 4850/GTX260 or better. Cutting a big hole in the case for a fan might work, or might not. For those of you with air-cooled LAN party rigs, do you ever worry about them getting left in a spot with no ventilation?

(4) Preparing to void some warranties:
* Stripping down an LCD monitor, to get a flat profile.
* Possibly stripping down a keyboard, for the same reason.
If you can think of any other components I'll have to break, do tell.


Other notes:
* Budget is quite generous, at least US$2000. This is partly offset by the fact that I live in a strange country and may have to mail-order some parts. (Customized a M17x with similar specs and got quoted for $2600. Go figure.)

* Cost estimates for parts: mainboard $200, CPU $200, 4 GB RAM $150, screen $150 to $250, graphics card $250, hard disk $100, battery pack $250, power supply $100, mouse and keyboard $100. If you need more precise numbers, I'll visit the local shops. Correct me if I'm way off, but that leaves about $400 for other parts.
* Optional parts: liquid cooling (if fan isn't enough), optical drive (already have external one), speakers.

* Wild weight estimates: mainboard and everything on it 3-4 kg, screen 2 kg, power supply 2-3 kg, case 1 kg, peripherals 1-2 kg. If only stores listed product weights...


That's roughly it for now. Thanks for reading and feedback.
July 16, 2010 1:05:17 AM

1 big problem. Desktop parts use a ton of power. There's a reason why laptops don't use desktop chips.

You would literally need a car battery to power a gaming rig at load for 5 minutes.
Throwing in a desktop monitor doesn't help. This is assuming it even provides sufficient Amperage (which I doubt).

Cooling would also be a nightmare. If you look at the system builders marathon 3 or 6 months ago, when the did mini atx builds, you can see some of the issue they encountered. Cramming things into a lunchbox...well I've go no idea how to solve that one.

As for liquid cooling...um there's a very good reason no one makes portable liquid cooling rigs ^^

You're supposed to drain and dry out any liquid cooling system before transport.
!