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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...
How difficult would it be to coble together some form of power delivery device that one could carry in a backpack. Total wait of the entire contraption (hub + power device/battery) should not exceed 30lbs (I'm being generous).
Bonus points will be given for: integrated solutions, solutions under 15 pounds, solutions under 5 pounds, solutions with integrated firewall and/or 802.11b support and grand mal bonus points for something that's recharge-able.
First person to market wins my undying loyalty, gratitude and all the beer, soda and junk food I can provide on my meager salary.
http://www.w-linx.com.tw/products/network/mini-hub s.htm
Or, more simply, I just checked out my Netgear MR314 (wireless router, but has 4 wired ethernet ports). It has a DC 12 volt power supply on it (rated at 1.2 amps), so in principle you can run it off a (car?) battery directly. Car batteries come in different sizes, are rated at ~60-200 ampere hours, so you can size your battery on portability basis and on how long you want it to last.
If you do use a car battery, check the voltage before you connect it, 12.5 volts or so should be OK, but car batteries are only around 12 volts, I've seen them go as high as 13.5 volts (particularly while charging), that could fry your router. So you could connect it up to your car, but it might not be a good idea to leave the engine running in that case.
-WolfWithoutAClause
"Gravity is only a theory, not a fact!"The wall wart of my 5 ports Linksys 10/100 switch gives 7.5VDC at a maximum of 700mA, which is about 5W of power. I'd have to check with a multimeter or use one of the DC power supplies at school, but under normal usage I'm sure it's way lower than that maximum. Even with a 12Ah 12V battery, plus a voltage regulator, you'd still have enough juice to outrun the laptops.
That's something just thought about: your laptops will drain faster than the hub. So even a smaller battery than the 12Ah I mentionned would do the trick. Pick a rechargeable battery if you don't wan't to throw away too much metal in the trash.
The only thing you'll need to do is a small package to transform the 12V to 7.5 (7808 or even a small transformer), and wire it to the right DC plug for the hub, and there you go!
So these people dropped $1000 or more on a laptop but can't afford a $50 WiFi card?
Is this a joke?
Sorry, I don't have a link.
I saw it in a shop (in Rome, Italy) last year: a small 5-port (with 6th connector also, which is 5th port but crossed over) which would run off a 5v DC power supply or a little pass-thru PS/2 adaptor which would suck the power off the port.
I know PS/2 only gives very little power, but evidently it was enough.
I don't know by how much it would shorten a laptop's battery life, but heck, that was a nice, and Tiny! thing to carry along.
Vacuum cleaners suck. Kings rule.
Did you read the question at all? He likes to start impromptu lan parties at bars and parks and stuff, outside. This pretty much means laptop. And that the places he goes there are frequently other people with laptops that want to join in, so he needs something more than a crossover cable!
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?
One of the problems with using a UPS (notwithstanding the "heavy" issue) in this setup (in my experience with APC anyways) is that they will not power on without being plugged in first.
I have seen some that work otherwise, but my suggestion would be to get something a little "easier" on the weight requirement. I believe Radio Shack has "D" size Nickel-Metal Hydride (sp?) batteries that are 4-6 AH. Select the right amount of batteries, grab a battery holder while you're at it (as well as a plug if you don't want to castrate the original power supply), hook it all together, and you've got a cheap, rechargeable portable solution.
Oh -- you will have one more cost -- you'll need a charger for the batteries as well. Maybe it's not the cheapest solution, but it will definitely be lighter than a UPS.
Karnal
Don't know too much about it, but, check out Power Over Ethernet (POE). Runs things like hubs by delivering electricity over cat5.
You need a special "injector", to get power into the cable, though.. might be able to find a battery operated injector.
Worth a check, at least.
S
Not possible to network over USB - the bus is host-based, all transfers are scheduled and controlled by the host.
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
Maybe the bar across the street would.
I never ask if im plugging in somenting small and non dangerous, like my cellphone charger or laptop, and noone has ever had a problem with it. It also helps that i generally go to places im at regulary, and i always tip well. Wen i usually drop 30 buks an evening, and a pretty good tip on top of that, i dont think thryre going to worry about the 25 cents of electricty im getting.
All Troll + "offtopic" mods are meta moderated as "Unfair", because you abused the system.
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?
...and then buy a sealed lead-acid 12 volt battery and charger, and pick up the proper plug at Rat Shack.
There are places that'll sell you this whole thing for cheap. I power my Tascam portable DAT deck with something similar; the battery set with charger cost me about $200, but you can make one yourself (as long as you have the charger) for probably $50.
- A.P.
"Remember when the U.S. had a drug problem, and then we declared a War On Drugs, and now you can't buy drugs anymore?"
The only thing you'll need to do is a small package to transform the 12V to 7.5 (7808 or even a small transformer), and wire it to the right DC plug for the hub, and there you go!
See, this is one of my pet peeves: people talking authoritatively about stuff they have no concept of.
Well, I'll give you a half point, you did say 7808 which is an 8-volt regulator. But...a small transformer? That's right off the scale. Transformers don't work on DC.
The regulator is definitely the best way to go, and you'll need a battery voltage that's decently higher than required supply. The reason is that your battery voltage will drop as the hub runs, and I'm not sure how low it will go before the hub quits working. So, don't pick up five 1.5V nickel-metal-hydride AA's to get 7.5 volts.
A small 12V gel cell battery would be ideal. Put everything into a project box and add a charger, and you've got a solution.
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That's right off the scale. Transformers don't work on DC.
My knowledge about transformers is, I confess, rather limited. That's why I put the 7808 before in my list of possible solutions.
Of course, thinking more about it, since it's DC there's not change in the voltage in the input coil, so no current is inducted in the core of the transformer. No core current, no voltage at the output coil. So yes, the transformer was a very bad idea, unless you want to drain the battery rather quickly :)
Thank you for pointing out the obvious.
Another point against 5 1.5V AA batteries is that the energy they have is somewhat limited. So not only their output voltage will drop, but even if they keep their output voltage somehow they won't be able to power the hub (or anything else) for as long as your gel cell battery.
Bonus question: why do they need 7.5V? I've handled a couple hubs/switches (5 to 8 ports, 10 or 10/100Mbps), and they all need 7.5V. Normal chips need 5V or lower. Is it to drive the Ethernet signals?
Yea, but doens't the thing usually beep to tell you it's no longer getting power? I don't think what ever place he is in would be that happy if they were all sitting there playing and had some box making some high pitched beeping noise constantly :)
(Score:0, Interesting)
Looking at the cheapy $40 hub (they go for much less these days) I see that it has a wall wart attached to it. DC, 7.5v.
So, what you do is you get yourself a hub with a wall wart. Ditch the wart. Wire up a bunch of batteries (five in series, then more in parallel if you need more run time) and plug it into the hub.
If you are truly '733+, then get a plastic box from someone, and hack things together so that the batteries and hub fit in one box.
Jesus was all right but his disciples were thick and ordinary. -John Lennon
It's harder to find theses days, but you could also make one if you wanted.
A Passive hub, which uses no power, as opposed to an Active hub, which you asked about.
You aren't reaching your 150meter limit on 10bT cables, so there should be no problem.
~DW
~Donald / Just RTFM
Most transciever circuits do operate from 5 VDC. I'd bet the wall wart is a very inexpensive unregulated one, and the real regulator is inside the hub. So, technically, you could look inside and find the 7805 on the hub, and maybe just bypass it with your own regulated battery source. That would be more efficent than 12V > regulator > 8V > regulator > 5V.
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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
You guy obviously don't drink enough. A group of 15 regulars who are going to show up en mass and stay for hours, and on a weekday. Heck I'd figure they'd let you plug in your own rack of routers.
use a crossover-y cable and route
-I like my women like I like my tea: green-
Better still, if it's already got a regulator, why bother with another one outside? Or... Why not just get 6 D-size nicads, for a nominal voltage of 7.2v, or 7, for a nominal voltage of 8.4v, and run them off that?
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..
Bluetooth is another choice: tiny USB dongles and standardized. Up to 1Mbps. The software isn't quite as mature yet, but it's getting there.
I've done what you've said with a variety of hardware - notebooks, all sorts of test equipment, etc. You -must- use a in-line fuse if you are powering something off a battery source that isn't going to have one internally. If there is a short, the battery can easily source enough current to cause a fire hazard. An in-line fuse will run you a few bucks.
.5A or 1A fuse.
I definately think the way to go is just get the smallest hub you can find (d-link has a great one) and then put batteries on it. Just don't forget that fuse. One thing companies do to protect their equipment is use a reverse-connected diode on the power supply pins. If for some reason you ever hooked something up backwards, for example, that diode can draw enough current to vaporize of a battery. With a in-line fuse, you'd just blow that. Most electronics are fine with a
The optimal solution is to go wireless, but this requires a little more long term planning on the part of all your friends.
..don't panic
When I last priced NiMHs, Wal-Mart had 1200s or 1300s for $11-12 per 4-pack whereas Sears had 1500s for $10.
:)
Maybe Wal-Mart has improved prices then.
retrorocket.o not found, launch anyway?