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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. "
But isn't it time for power over wi-fi?
I guess it won't be compatible with gigabit over cat5e, since that uses all eight wires.
Power over Ethernet?
Internet over Powerlines?
What crazy things will they think of next? Power over powerlines and internet over ethernet?!?
I for one would like to have my ethernet hubs use the standard wiring for power rather than a brick and AC adapter that I have to find an outlet for. Since telephones already do this it's just the next step in the direction of USB everything. Which seems to be a good thing (tm). Now I know how to set up a LAN in an unwired munitions bunker...
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?
Try not. Do or do not, there is no try.
-- Dr. Spock, stardate 2822-3.
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.
Click here or here.
Why does every DC-using device come with its own adapter, and uses its own voltage? Why could not we standardize that?
Maybe, this "power over Ethernet" initiatives (together with the "power over USB") will spell the end of power-strips with curiously shaped "bricks" constantly falling out of them...
In Soviet Washington the swamp drains you.
So for new construction, it's probably not a big deal. But for adding new devices to an existing facility, it could be a lot easier/cheaper.
I may twist orthodoxy to partly justify a tyrant. But I can easily make up a German philosophy to justify him entirely.
There goes the only type of devices I don't repeatedly electrocute myself on. =(
Damn you! Damn you to heck!
All rites reversed 2010
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..."
MORTAR COMBAT!
I've seen this implemented in a local school (in the UK) that issues all staff with laptops. The laptops then have a student register application running on them, and the staff can wander across the building using it. They've put up lots of D-Link access points scattered all over their buildings, just mounted to the wall on wooden boards - an ethernet cable appears out of the wall, or from a socket, into a little box (size of PCMCIA card, but thicker) which then has two cables (power + ethernet) going into the access point.
Appears to work very well for them.
Don't send it in the form of electricty..send it in the form of radiation energy just like how the Sun provides us energy wirelessly. Even NASA tested a Laser-Powered Aircraft last year.
...is the world coming to?
Power over ethernet! Internet over power lines! Human sacrifice! Dogs and cats, living together! Mass Hysteria, people!
+1 Insightful, -1 Troll. What can I say, I'm an Insightful Troll.
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?"
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.
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.
See what I've been reading.
The usb spec already provides a certain amount of power to drive things like small gameboy lights or memory stick readers, but these don't always work. For instance, you sometimes have to get a Powered USB Hub just to drive devices such as card scanners. And then you have to plug that in.
Six score characters.
Brevity being wit's soul
I have enough space.
Right now it triples the price of a switch. (Compare the 2626 and 2626-PWR, for example.)
So no.
Finally convincing the fucking cat to not chew on the cables?
-Peter
Interesting all the comments here about PoE. I wonder how many posters have acutally used it in anyway?? I personally am using it in my small business. About a year ago, we upgraded our phone system to a Mitel 3300 based IP system. Problem is these phones require power. They all have a power jack on them - and optional wall transformers. Problem was, these are "smart phones" and take like 90 seconds to boot. Also, I didn't want to have a simple power bump cause dropped calls. But running power and having UPSes out in remote warehouse locations was not an option. The vendor was already quoting a HP-2626 Procurve switch because of it's VLAN management. When I asked about using PoE to power the phones all from the network room, they suggested a seperate PoE power injector. But when I saw the price, I found that the HP 2626 -PWR version was the same amount more money as the power injector. So I purchased one of those and now have one piece of equipment doing both. It's much cleaner - and all phones are powered by the big rack UPS in the network room.
I've done some "playing" with that switch and I see it somehow detects that the ethernet device is able to handle PoE and then turns that on. You plug in normal ethernet devices it does not supply power to them. I'm sure this is specified in the 802.3af specification - something I've not had time to read! But I somehow doubt that this switch would cause any problems with old ethernet devices. Even if you are worried, you can log into the switch and turn the power on/off on a per-port basis. We even tried inseting a single port power injector down stream from this switch - and it then would not supply power to that port - and the injector was. So it all "just works" or at least from what I've found so far!
So if your box get 0wned the lights go dim?
Engineering is the art of compromise.
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.
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 am very easy to get along with, but I don't have time to waste being nice to people who are being stupid. -Theo
Just to fuel your imagination, I've put in some nice uses:
- Networked camera's (more zooming, tilting and maybe even lighting with 39 W)
- Networked printers
- Home server appliances (my VIA EPIA runs great with DVD player and 3.5" HDD on 53W, it would run just great on 39W without the DVD player)
- Media players (MPEG4 & MPEG 2 layer 3)
- Downlink switches
And I do not have a clue why they never use this for PDA's. Use a common network plug to synchronize your PDA, and give the customer a nice powered switch or network adapter instead of those stupid cradles.
Currently the standard is mostly found in Remote Access Points. I would have put my access point (which is at the best place for RF, but not for cables) on power over ethernet, but these components are hard to find. Just putting 5 V and splitting it at the end does not seem to work, probably because of the distance.
... 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.
/and/ a wall-wart.
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, 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?)
First picture of compatible cable :)
But what I want to know is can I run ethernet over power on top of power over ethernet?