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Power-over-Ethernet: IEEE 802.3af Draft
SkewlD00d writes "Want power (~10W) and your fat 10/100Mbps pipe (1Gbps maybe) on the SAME jack. Surf the web and recharge your handheld w/o finding its clunky base/transformer, home automation, and control systems are just some of the possibilities. Using suitable hubs/switches or dongle, power can be provided over unused pairs, or possibly raise the signal offset above DC, X10-style (no link, u know why). See IEEE 802.3af DTE Power via MDI Task Force. Maxim (not that one :o) already has some goodies. They have schematics for 8.25W/12.5W single-output and 14.2W triple-output 802.3af PSU. Try FindChips if you're looking for them; they're in production and are NOT vapor-ware!"
The latest firewire standard can do 800Mb and provide up to 45W of power
I use this extensively with my Lucent/Orinoco wireless APs. Been doing it for about 2 years now. It's also part of 3Com's Ethernet switch/jack technology, and has been implemented for VoIP.
I've found it to be a godsend for my wireless APs, as I can mount my APs near the ceiling (away from students), and not have to worry about finding an outlet, or having them unplugged by the cleaning crew!
- why no links on X10 ?
Because they are misinformed. They are thinking of X10-the-company, which is notorious for pop-under ads. But what they really mean is X10-the-protocol [scroll down a bit for a good introduction], which is used by many companies.
- which maxim is obvious ?
Maxim is a "gentleman's magazine" that has been pushing the limits of how much semi-porn you can include without getting banned from shelves. Recently this and competing magazines went too far for Walmart.
bp
Quote from your link:
"Powerline communications (PLC) technology uses the existing local electric wires to provide digital communication services such as high-speed Internet access, voice over IP (VoIP), video, and in-home networking."
We're talking about power-over-ethernet here, not ethernet-over-powerline.
If you want wireless power, just hook up a good ol' tesla coil.
That's the other way round from the article! It isn't Ethernet over power, it's data over powerlines; this article is about sending electrical power over Ethernet wiring. Both are interesting, but have very different applications; power over Ethernet is already being used to power low-power devices, such as VoIP telephones and wireless access points.
Power over Ethernet is limited to a matter of watts - much less power than a normal light bulb needs - but can deliver full speed Ethernet data (100 Mbps or better). Data over powerlines isn't limited by power - you can run the house off such a powerline - but has limits on the data speed (a couple of Mbps, depending on distance and wiring condition).
here is a link to TI's PDF datasheet only $1.25 in qtys of 1000 for the device side, much cheaper than a wall wart
Free cell phone tracking
It can be annoying because if you want to run several phones on one drop, they need power supplies if you don't want to use an expensive inline power capable switch.
Have you looked at these?
They're basically four-port switches that you mount in place of your normal wall jack. They cost about a hundred bucks, support power over ethernet, and there's even a managed version.
What part of "shall not be infringed" is so hard to understand?
The Linear typical app seems to be much smaller, with fewer external components because it's actually optimized for the application.
The Maxim chips appear to be generic hot-swap IC's not optimized for power-over-ethernet. Using slashdot is an interesting way to publish an app-note and get some publicity.
Ethernet only cares about the voltage difference on a pair. This was done for noise immunity.
;-)
This means that if:
Striped, pair 1: +12 VDC
Solid, pair 1: Ground
Striped, pair 2: +38 VDC
Solid, pair 2: +50 VDC
Occurred, the ethernet card is supposed to register it as +12 and -12 VDC on each pair. A device hooked up only to the solid wires of each pair, though, would see +50 VDC of usable power.
Although, perhaps having this differential there might be dangerous to crappy ethernet cards, I'm not sure. A balun would probably take care of that, though.
But I'm not an EE, so why not find out for yourself?
Have you tried plugging an RJ45 in backwards (or sideways, or shifted one row to the left, or...)?
It is essentially impossible, approaching non-issue status. And nevermind that ethernet is specified to withstand multi-kilovolt fuckups between random pins, unlike massively-parallel/easy-to-crossconnect SCSI - ethernet devices don't mind seeing voltage potential where it doesn't belong.
Here's a larger problem that standardized POE solves:
User has two cables running to desktop IP phone. User unplugs cables to re-arrange desk, and upon plugging things back in, their IP phone smells funny and their external modem won't work.
Upon investigation, it turns out that the 12VAC power supply for their Sportster is not interchangable with the 13.6VDC PSU for their IP-600 phone.
Therein lies the problem with multiple incompatible, anonymous-looking power supplies at the desktop.
(In other news: Licking light sockets can be hazardous to your health. Also, this just in: Consuming too much water may cause accidental drowning.)
Kid-proof tablet..
There are two reasons for not going for lower voltage, number one is loss, over 100m of cabling you get a lot of power loss at lower voltages. The second is that +44 is a common telco rack voltage so a lot of telecom equipment is already setup to use it.
There are 4 boxes to use in the defense of liberty: soap, ballot, jury, ammo. Use in that order. Starting now.
...mention of the BOFH!!!
Another relevant fave found here.
The whole shebang.
I'm done with sigs. Sigs are lame.