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Portable Hubs?
Nahdude asks: "A friend of mine and I tend to have frequent mini-LAN parties in odd places like diners or parks with our laptops. We've been using a crossover cable with no problems, but recently we've attracted some attention from friends, and even some strangers, who want in on the action. So I've looked (without success) for a portable networking solution. Has anyone found and had luck with a battery powered network hub? Keeping in mind that wireless, although neat, will probably be a bit difficult because the expense of mobile wireless cards could be out of range of a lot of the people interested (we had 15 people last week in a bar, woot, but only 2 player games with crossovers because they wouldn't let us plug in a hub)." I haven't seen many of these now, but maybe if someone plants the idea in people's heads we'll see these several years from now...
http://www.w-linx.com.tw/products/network/mini-hub s.htm
Nothing personal Cliff, but shouldn't their be a "Google Filter" for postings to Ask /.?
/. is probably the most interesting part of the site (apart from trolltalk of course) but you also get some of the lamest submissions!
For example, this is the device you're looking for.
How did I find it? Like this. Note the search words; battery powered ethernet hub. Ok, so its a hub, not a switch, but still!
Ask
None are more hopelessly enslaved than those who falsely believe they are free. Johann Wolfgang von Goethe.
Try this hub. It is powered from a standard keyboard socket and they can be cascaded together.
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Political Correctness is doubleplusungood.
You can pick up a basic 802.11b card for $30, so price is a flimsy excuse. If they can't afford $30, maybe your friends should play battleships on paper instead? Or maybe they can't afford that fancy paper either?
When I was in college, we used to do the same basic thing but none of us had a hub. The solution we found was to get combo ethernet cards that had rj-45 connectors as well as coax connectors (I think that's what they're called). But a few lengths of coax along with t-connectors and terminators and there's no need for a hub. Works great and is (relatively) portable, just throw all the cables and connectors in a bag.
--trb
For one:
:) Getting back the 9V vs. AA, a 9v 150 mAh battery is approxibately equivalent to a 4.5v 300 mAh battery. 4 AAs gives you 4.2v at 1200-1500 mAh or more, which is 4x or more the capacity at the same price.
Price is a useless excuse for not going wireless. If you search, you can get WLAN cards for $30 on sale these days. And as many pointed out, if you plunked down $1000-2000 for a laptop, you can afford a WLAN card even if it's $100.
That said, for another year or two, strangers are less likely to have WLAN cards. (But this is changing VERY quickly... It's getting to the point that having a laptop without getting a WLAN card is just plain silly.)
So your two solutions are:
PS/2-powered hub. Good if you have a decent mobo, but some laptops don't quite meet the PS/2 power supply spec... And there's no way to tell w/o risking damage to the mobo. Also, it'll drain your battery.
Homebrew battery-powered hub. IMO this is the way to go. There were a few links to a 9V powered one. Note that trying to find the smallest hub might not give you the one with the lowest power consumption. Also, 9V batteries have VERY low capacity compared to AA/AAA batteries. 4 AA rechargeables will cost you about as much (or less than) a 9V rechargeable and last much longer. I think most 9V rechargeables are 15 mAh rated, "cheap" Walmart AAs will be 1200-1300 mAh. Sears has the best deal on NiMhs I've seen - 1500 mAh units, $10 for 4. I have tons of DieHards now.
4.2V will be a bit iffy with a 5V hub, but it'll be easier to charge than having more than 4 batteries. Plus the more rechargeables you have in series, the more likely you are to have problems with cell imbalances. With a step-up regulator (not expensive if you're comfortable with homebrewing some elctronics - Maxim sells some great switching regulator ICs at http://www.maxim-ic.com/), you can power 9V hubs from 4 AAs.
Don't discharge the battery pack below an average of 1 volt/cell (4.0 volts total) - Any lower and you risk a cell reversal, which will kill the cell for sure and possibly damage other cells in the pack. (Not as much of an issue if each battery is individually removable - it matters more for packs of cells.)
retrorocket.o not found, launch anyway?
Nearly any cheap hub you can find today will be running on 5VDC internally.
Even expensive hubs, like the (older) 10/100 Kingston rackmount that I have here runs at 5VDC internally, despite its direct connection to 120VAC. Even the fan is 5VDC. (and, yes, that did take some time to find a replacement for, but the bearings in the new Sunon are doing justfine, thanks.)
The wall-wart they come with will deliver a stiff 5 volts, or 7.5 volts, or 12 volts, or whatever. First thing that happens inside of the hub is that it goes through a regulator to bring things down to 5VDC, and this regulator cares not about what the voltage is (within reasonable limits), as long as it is >=5VDC.
[note: some hubs may have low-voltage AC power supplies. avoid these unless you feel like modding them to bypass the internal AC -> DC conversion.]
So. What you need is a way to get 5 volts in a portable fashion. Something like this keyboard power tap would make a smooth way to do it.
All you'd need, given the above, is a durable-looking portable hub and a length of wire with appropriate connectors. You've already got the former, and RadioShack will provide the latter. Or, just cut and splice your existing wire into the adapter. There's a thousand ways to go about it, and they're all sensical and easy.
If you suspect that your laptop won't supply sufficient power from its keyboard port to power a hub, as some posters have suggested might be a problem, look to Ebay for an all-in-one kit labeled as a "USB Cell Phone Charger."
USB supplies - you guessed it - 5VDC. Current is spec'd to be something like 500 milliamps, or 2.5 Watts, so you might get pinched if your hub is inefficient about its power draw. (If in doubt, have one of your technologically-inclined LAN-buddy friends measure it.)
If you feel like it, grab one of those USB cables you've got in a drawer, and hack it into a power supply for a hub.
I've got a tiny 4-port 10baseT Netgear hub here with what I'd like to say is the same connector as my Nokia cell phone, FWIW. They've probably also got 6- or 8-port versions that are the same. (it's also small, lightweight, and made of steel - great for throwing into a backpack.)
Else, run it from its own battery supply. Feed it with 6 D cells in series, and it'll outlive any laptop which happens to be connected.
Other people have suggested sources for seriously low-power ethernet hubs, so I'll skip that research.
Just don't make the project any harder than it needs to be. You've probably, between you and a few friends, already got everything you need to make it work.
Kid-proof tablet..