h a l f b a k e r y"My only concern is that it wouldn't work, which I see as a problem."
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You go to a meeting room with your laptop. Three others do the same. One person jacks into the ethernet connection. Everyone else has to wait. Why?
What we need is a mini ethernet switch as per many of the palm sized 5-port ethernet switches available... but I don't really want to lug the power
sypply round as well as the hub.
How about building 5 port ethernet switch with a USB connection? The USB link can be used to provide power from one of the laptops, and ethernet connectivity to that laptop. The uplink port connects into the wall socket, leaving 4 remaining ports for other laptops.
An alternative would be a battery powered version.
A little related: "Mini Ethernet Hub"
http://www.halfbake...ni_20Ethernet_20Hub
A halfbakery idea from Sep 2000. [bristolz, Oct 04 2004]
(homebrewed) Battery-Powered Ethernet Hub
http://www.kan.org/...ing/batteryhub.html
02 Feb 03 | Someone's explanantion of how he adpated a small hub to battery power. Has photos and QTVR movies. [bristolz, Oct 04 2004]
USB Ethernet adapter
http://www.hiru.aob...a/USB/usbether.html
A year old, so many of these may no longer be made as companies focused on their core products. [st3f, Oct 04 2004]
Power over Ethernet
http://www.hyperlin...eb/what_is_poe.html
PoE is an emerging standard to use unused wires in CAT5 cable to pass DC voltage to access devices. [krelnik, Oct 04 2004]
4-Port Switch powered by PoE
http://www.netronixinc.com/pe2805.html
[krelnik, Oct 04 2004]
USB Powered Switch
http://www.w-linx.c...twork/mini-hubs.htm
Pretty close to the spec, but doesn't offer ethernet over USB, and I can't find a UK supplier [andybryant, Oct 04 2004]
Baked!
http://www.retracta....php?products_id=66
[nhackett]'s link as a link [krelnik, Oct 04 2004]
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I think this is a useful idea and have been in need of it for the reasons you describe. |
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I think that power through the ps2 port would be simpler - and possibly home-bakable. |
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On a related note, I once tried powering a switch through a mongrelised HDD power splitter and one of those detachable plugs from a DC adaptor: reverse polarities through those switches *will* blow them! |
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Anybody know the specified power requirements for an Ethernet hub? The USB 2.0 specification says a "high power" device can draw 500mA at 5V from the bus. |
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It seems like its in the right ballpark, but I'm guessing from the specs on the wall warts for two 4-port hubs I have handy: one is 1.2A at 12V, the other is 500mA at 7.5V. Would be nice to know some real numbers from the specs. |
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Perhaps one could incorporate a Network Interface Card as well, so as to only have the USB cord? |
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Instead of a central unit, the interface should take advantage of the USB 2 daisy-chain option. Power, um.... well I'm not certain what to do about that. Keep it all integrated with the laptop I guess. |
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3Com used to do a self-powered USB to Ethernet adaptor (single port so not a switch), but now... they don't... and they've taken it off their website. Never mind. Here's a table of USB to Ethernet devices. <link> Probably no switches as there may not be enough power to run one. |
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Just stumbled across something called "Power over Ethernet" (PoE) this morning (see link). The idea is to pass DC voltage over some unused wires in CAT5 cable, thereby powering remote devices like wireless access points that don't have access to AC (mains) power where they are. |
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You could get rid of the USB component of this idea if there were a laptop Ethernet adapter that supported PoE. There are already small hubs and switches that can get their power this way. |
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Perhaps I’m reading too much into this, but it seems ‘inexpensive’ is one of the objectives – otherwise there would be ample wall jacks. PoE is very expensive. |
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PoE is expensive? How the heck can it be expensive to run 12V DC down currently unused wires in a Cat5 cable? |
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It requires new PoE compatible equipment to deliver PoE service to these rooms. There’s signaling on the power lines. In this example we’re trying to get around the limitation of having only 1 jack in each room. If putting 3 additional jacks in each room is prohibitively expensive, then purchasing PoE server hubs is absolutely out of the question. Again, I’m assuming this is a cost issue. Love to hear from [andybryant]. |
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Or… [krel], were you thinking of running continuous unmanaged power to the jacks manually. No problem there, but will it work without the signaling? I’m curious… Also (your assumptions), we don’t know if this *is* Cat5, and we don’t know that there’s any more than 4 wires in the jack. We need to hear from the author. |
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I think you misunderstood me. I said put PoE into the LAPTOP ethernet adapter. Thus the laptop's battery supplies the power for the hub. Thus we don't require anything special out of the wall jack, and we don't have to fuss with both USB and Ethernet cables. |
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I have a 3Com USB-Ethernet adapter (3C460B), and it is indeed fully USB-powered. |
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I'm not sure whether USB could power a whole switch, though. |
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Said generic power packs do exist and are marketed to business travelers, Rods. Saw two ads for them in the in-flight magazine just last week. (Not solar or windable though, just a big flat battery pack). |
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Over at thinkgeek.com (I think?), they have a PCI card that is a 4 port switch. 1 outlink, and the rest just go throuh it, tiny router indeed. Same size as a Audigy card, plus with a good built in packet sniffer, you can look over the traffic going out of your comp. I plan to get about 3 of these things, to network all the computers in my room (even an old IBM dos box) networked. |
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Does it really need to be a switch? |
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Some Thinnet/10Base2 cable, tees, a couple of terminators and a handful of baluns to connect to your twisted pair patch cable...no power required. Ethernet is a logical bus topology and it can work passably in a physical bus configuration. |
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Not terribly compact due to the theoretical minimum distance requirements between nodes. If passive electronic compensation for that limition were possible, you might be able to come up with a passive, pocket sized hub. |
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That’s the ‘old fashioned’ way [half] – additional power is required to electronically simulate the cable tap distance(s) in a hub. Certainly nothing against you half, I just think the author is non-existent (see my previous anno). |
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Yep, old fashioned. That's just the kind of guy I am. Sometimes the simple way is overlooked. |
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Wasn't sure about the electronics part. I don't recall the technicalities behind the "minimum distance" thing and can't remember who borrowed my communications book that contains that sort of stuff. Just thought I'd toss it out there as a possibility. Thanks, [Shz]. I guess a big ol' wad of coax would not be terribly convenient to tote around. |
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Well, I tried to prompt a response from [andy], but he doesn’t seem to exist. </conclusion> |
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Yes - I do exist, but haven't had a chance to check back recently. To comment on a few of the comments |
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- Power/PS2 - yes, this would be fairly easy, but you couldn't run a network connection over the same port, so would need an ethernet connection as well. It is actually easy to get 5V 500mA from a USB port. Just cut an extension cord in half and connect up to the appropriate wires. The only trouble is that you would also need a seperate connection for network. The Linksys palm size hub is close, but requires 7.5V 700mA |
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- WiFi would be good, but isn't deployed at my company site due to security concerns. |
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- USB ethernet adaptor - yes... that is the functionality I need on the USB port of the switch to allow ethernet + power over the same cable. |
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- Power over ethernet... another good idea, but for this to work I need a laptop that provides a PoE port. I've not seen one of these yet, and can't think of a good business case for a laptop vendor to build one in. As one of the earlier messages suggested, it would be out of the question to rewire all existing room connections with PoE switches. |
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= Since I posted this, I came across a company that makes a USB powerable version of a 5 port switch, with a USB power cable. The only problems are that it doesn't offer ethernet over the USB, so you need an additional netork cable; and I can't find a local UK supplier.
http://www.w-linx.com.tw/products/network/mini-hubs.htm |
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//WiFi would be good, but isn't
deployed at my company site due
to security concerns.// |
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there's your problem right there.
wifi is only a security problem if
it's not set up properly. when they
say they are not deploying because
of security concerns, what they
mean is, "we're not capable of
doing this, and we don't want to
put in the time/money to learn
how." |
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sorry, but i have no patience for
someone equating "i can't do it"
with "it shouldn't be done" |
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I now have stock of the very thing in UK. See http://www.retractacable.com for details. Both a hub and switch are available. |
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At last someone did it!!!! Go to http://www.byteccusa.com and look for the 5 port USB powered mini switch. Now lan parties won't be the same..... |
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I started getting these for a few friends - have been amazed how popular they have become.
Now have both hubs and switches - with USB, PS2 and mains power options. Recently added 9 port version - as well as 5 port version.
http://www.retractacable.com/ |
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