Possible uses for Power over Ethernet

jsailor writes "Power over Ethernet allows devices to draw power from the Ethernet cable they use for networking. Power is provided by the LAN switch (end-span) or an intermediary device (mid-span). The current spec. is 802.3af and was covered on slashdot before. It provides approximately 13W at the end of a 100 m cable and is commonly used for IP phones, wireless access points, and increasingly security cameras. The technology saves costs associated with running power to the odd locations access points find themselves in and allows IP phones to be moved around with out carrying a power brick. The industry is considering a new standard that would provide up to 39W to a network device. Bizarre uses include electric razors. "

Comments

Easy enough,

[00null00]

But isn't it time for power over wi-fi?

Re:Easy enough,

[xpyr]

Obligatory bash quote, see bash

harm_: today this one lady got pissed off cause we dont carry i quote wireless power supplies
ogregasm: a what
harm_: thats what i said
harm_: maybe you want an adaptor for a wireless router o rsomething??
harm_: shes goes no no i read online about this i wannit i wannit :harm_: then she got pissed when i told her that kind of technology doesnt exist
ogregasm: heh :harm_: i tried to be nice but it got to the point where i was like"get back to us in 30 years"
harm_: "once we attain the secret of positron deflector shields, wireless power supplies shall become a reality"
ogregasm: why bother being that much of an ass to the poor woman
harm_: well shes the one who got all up in my face asking for the store manager
harm_: i told her he had just teleported to a corporate meeting in tokyo

Ah gotta love bash :)

Re:Easy enough,

[timster]

As I recall the whole "power lines cause cancer" thing was an example of irrelevant correlation. Turns out that statistically it tends to be poor people living next to high-voltage power lines and poor people have higher cancer rates for all sorts of other reasons.

Re:Easy enough,

[the pickle]

You do realise that RF is nonionising radiation, right? And that *ionising* radiation is required to cause the mutations in DNA that lead to cancer, right?

Just checking.

p

Stop the craziness!

[__aaitqo8496]

Power over Ethernet?
Internet over Powerlines?

What crazy things will they think of next? Power over powerlines and internet over ethernet?!?

13W could be dangerous...

[Sheetrock]

Depending on the voltage and amount of power involved.

There are a couple of drawbacks to this plan: first, the increased caution that will be necessary in working with network cable (everybody's used to them being safe as phone lines) and second the possibility of burning out devices that weren't built with this standard in mind. Who's to say that a cheapie network extender installed in a rat's nest of cabling five years ago wouldn't start a fire when you hook something like this up?

Re:13W could be dangerous...

[dourk]

You may assume telephones are safe, but the have a ring votage over 40v. Wiring up a the last jack in my house, stripped one of the wires with my teeth just as my buddy called.

It fucking hurt.

Re:13W could be dangerous...

[shoppa]

Dude, that's almost as funny as the guy who built a glass case around a 10K ohm resistor with a sign that reads "DANGER! 10000 ohms!"

Re:13W could be dangerous...

[ScrewMaster]

60 Hz. was selected as a national standard because Tesla worked out the numbers and George Westinghouse went along with him, and the rest of the country ended up going along with Westinghouse. Westinghouse was concerned about power transmission and 60 Hz. was selected for efficiency with the generator and transformer technology of the day. Remember Tesla's proficiency with those.

Your professor is a bit confused about the electric chair business: it was Thomas Edison who claimed publicly that Westinghouse's 60 Hz. system was much more dangerous than Edison's own direct current power system. This was strictly a marketing ploy: he and Westinghouse were going head-to-head in an all out corporate war and Edison wanted to win, badly. He had no scientific basis for his claims. In other words, he lied, publicly and repeatedly. He even went so far as to have a major correctional institution that was building a new electric chair facility install Westinghouse generators in order to "prove" how dangerous alternating current could be. The reality is that Edison was way off base: direct current is substantially more risky than alternating: for example, if you grip a pipe charged with 120 VAC, you will get a nice shock but will be able to release your hold. The jolt might cause your heart to fibrillate but most likely you'll survive. Grab that same pipe with 120 VDC and your muscles will lock and you won't be able to let go ... your heart will also stop dead if the current happens to pass through it. A lot of lives were spared over the years because we didn't go with Edison on that one. The other reason to rejoice is that a DC power distribution system would have required power plants plastered all over the place since transformer operation (and hence high-voltage landline transmission) would have been impossible. Today we could probably do it with high-powered DC-AC inverters, but that technology was way beyond Westinghouse and Edison.

The only thing that saves us from instant death the first time we walk across a carpeted room in dry weather is our epidermis. That layer of dead tissue makes an excellent electrical insulator. Otherwise, the first static spark you drew touching a doorknob would stop your heart. Remember, the insides of your body are an ionized, highly-conductive mess: a hundred-odd pounds of adulterated salt water. If you stuck a couple of pins in each index finger, and put those pins across a flashlight battery, you would probably die. Your bloodstream would conduct that tiny current flow directly through your heart. But touch those same terminals with the outer layers of your skin intact: no problem.

And I'm not making this up: if you've ever been in a hospital burn unit, you would see that everything in those rooms is heavily grounded, and extreme precautions are taken against static discharge or any other electrical artifact reaching the patient. It's amazing. I worked in a lab at a major teaching hospital / university for a while, and I noticed that there were these odd metal plates with heavy-duty green leads hanging out of them, sticking out of the walls and floors. I asked, and was told that the lab space was a converted burn unit. People that have had significant areas of their skin burned off are fatally susceptible to even minor electrical discharges.

Short circuit

[totallygeek]

I went to a company that cabled about 100 drops. When certain network items did not work properly, they tried everything to figure out what the problem was. Finally, one device was plugged in and did not work at all. It turns out that the cabling was wired with "just the same colors on one end as the other". The installers actually created an elaborate mapping on paper saying, wire 1: red, red/white, blue, blue/white, brown, brown/white, green/white, green. They would look up each cable on this run sheet before punching down the other end. The device that did not work evidently was not "looked up" correctly, and so there were no valid pairings. If this had been POE, something would have been fried.

Another company I worked with found out that their cable guys simply wired everything with 2 pairs only. They would punch down 1,2,3,6 and then cut the remaining wires completely. POE wouldn't work there either.

It is amazing how some companies attempt to save money by getting monkeys to install cables.

amperage and death

[MORTAR_COMBAT!]

well this random post seems to claim that 1 mA can kill a sick person, and 100 mA can kill a healthy person... so my "an amp can kill a person" should actually say "an amp could kill 1000 sick people... or 10 healthy people... or some combination thereof..."

Re:Gigabit ethernet?

[enigmals1]

Yes you can. The power is running on the same wires as the data. This is roughly the same technology as Broadband Over Power. The power is 60Hz but the data is MHz...or in your case, GHz. Little to no crosstalk.

Ethernet Enabled Electric Razors?

[Tezkah]

I'd really like to see an electric razor that had a version of Windows on it. You'd be shaving your face, and then a holographic Clippy would pop up: "It looks like you're shaving your face, would you like tips on shaving your junk?"

I'm pretty sure that should be the prompt he'd give you no matter what you're shaving. "It looks like you're shaving your head, would you like tips on shaving your junk?"

Lower cost per AP

[ccbutler]

earlier this year I converted our warehouse of 250,000 square feet to 802.11b WiFi using Cisco 1200 series AP's. Our cost per AP was 1900.00 (CDN) using power over ethernet. This cost includes contractors, electricians, cat5e, fiber, and even antennas. Im not here to toot any horns for 802.11b or Cisco or anything... but our cost per AP would have been WAY higher if it weren't for power-over-ethernet technology.

Electric razors?

[RealAlaskan]

Bizarre uses include electric razors.

I'm trying to think of places where I have seen an ethernet jack but no wall power. Hmmm .... zero. Never seen such a place.

Now I'm trying to think how many times I've wanted to shave in a room which contained an ethernet jack. Hmmmm .... zero.

So, come on, somebody, tell me why you would buy a power-over-ethernet razor. I'm stumped.

Re:Electric razors?

[Drishmung]

On the other hand, if you've every travelled outside North America, you've probably seen a wall socket into which your razor would not plug (without an adaptor). http://users.pandora.be/worldstandards/electricity .htm, http://www.powercords.co.uk/standard.htm

Now, imagine a universal, world-wide standard for low power devices. Would that be useful?

Possible Uses?

[pete-classic]

Possible uses for Power over Ethernet

Finally convincing the fucking cat to not chew on the cables?

-Peter

Re:Seems Kinda Weird / Wired

[rcw-work]

In other words, no transformer brick needed for the device.

Transformers are not used to convert AC to DC. Transformers only convert AC to a different voltage AC. The rectifier portion of the average brick (the part that does convert to DC) is very tiny. Often it's only four diodes and a capacitor.

So basically, if you needed a transformer to power a device from AC, you're just completely screwed if you try to power it from DC, unless it was regulated at the right voltage beforehand. Since we're discussing PoE, that would be a giant no.

Switch-mode power supplies are just as efficient with DC as with AC. They are very small and lightweight, and that's what you'll find in most 802.3af-powered devices. However, if you want to keep discussing alternative forms of local power distribution, those transformers also become very small and lightweight if you change the operating frequency from 50/60Hz to, say, 100kHz.

already works for cable chewing cats

[puzzled]

I lived with this chick that had a cable chewing cat some years ago. One day one of my college roomies stopped by and as we were talking kitty walks out and starts in on the phone line in the living room.

Mike looked at me, got the *biggest* grin you've ever seen, then whipped out his cell phone and pressed redial ...

Kitty rang, backed up, hissed, then bit the cable again just in time for the third ring. Now I liked that cat and I have a long hair tortoise shell of my own, but I sure was glad that Mike cured that cat of ripping up cables.

I don't know about you, but..

[Myself]

... lots of smaller devices (PDAs, older laptops) draw under 20 watts. The wall-wart for the Vadem Clio (sitting right here) only puts out 11 watts, and that's enough to apply a mild charge to the batteries while running the device.

Around the time HPNA powerline ethernet came out, I waited eagerly for a laptop maker to announce an AC adapter which would also bridge the machine to the network. No such device ever emerged. I'd love to be able to curl up on the couch with a network-connected device and not worry about the battery. I'd be happy to drop an RJ45 outlet in the corner. Will someone make a device that'll use both signals from the same cable?

Being low-voltage, you don't need to call an electrician to move network cable around. Thank goodness. There are murmurs within the electrical industry of trying to legislate a change to this, be watchful and let your representatives know that low-voltage wiring is not hazardous and should remain unregulated.

One problem with PoE is deciding which device gives and which receives. Right now, the cable modem, the router/firewall, and the 8-port switch all have wall warts. With PoE this could be reduced to one, but which one? For a simple star layout, it's simple. I fear the mess of adapters isn't going to get much cleaner, however.

Cameras and APs are the obvious early beneficiaries of this. Another poster mentioned doorstrikes and cardreaders. How about motion detectors, thermostats, and other environmental sensors?

If the HVAC system is plugged into the ethernet anyway (Or just running back to the same wiring closet, even if it's on separate hardware) then let's toss the duct dampers and other controls onto the same system. Wire the whole building with one type of wire, run it all back to one place, and have flexibility later.

And since we're replacing all the building's auxilliary systems with PoE connections, how about overhead music / paging systems? Individually addressible bidirectional speakers would enable all sorts of talk-and-listen applications, as well as point control of which programs go where.

13 watts is also enough for things like cash register scales, receipt printers, barcode scanners, and the like. A lot of that stuff runs on USB now, which is great. I can see applications where remote scales might take advantage of ethernet's distance capability. Also consider that powering down the USB host takes all the devices with it, but with ethernet-attached devices, the network can still "see" the RFID scanner if the register takes a crap for some reason.

Things like JetDirect print servers would also benefit from wallwartlessness. Yes, decent printers have a slot they sit in and receive power from, but there seems to be no shortage of standalone ethernet print servers.

How about postage scales that print "electronic postage" from a company's central account? They're great, they never need recharging, but they still need a network connection /and/ a wall-wart.

And, dare I say it, credit card terminals? We'll just make the manufacturers promise not to transmit the card stripe data in cleartext. (ATMs use some serious encryption, why can't Lowe's?)