POE hacks or other uses?

[trauts14]

Does anybody have any links or tutorials on how to use extra POE ports for non POE devices like powering a LED to light up my "data center" which is in a cabinet? If i have the cat5 and extra POE ports i would like to run a LED or computer fan. I this possible, if so how do I know which wires in the cat5 to use?

 

[Coffeeguy]

Using 'extra' PoE

It can be done, just with the caveats that what you do may affect other devices already connected to the switch/router as well as the switch/router itself.

PoE *usually* runs over pins 4,5,7 and 8 of an RJ-45 connector (4&5 being positive, and 7&8 being negative), and it is usually 48 VDC. You can use a patch cord with one plug removed and the wires stripped, to see what you get from your particular piece of equipment.

Some units put out 48VDC by default, and some have capability to autonegotiate with whatever's drawing from the PoE, that is, if a PoE camera or whatever only requires 5 volts, that's what the switch/router puts out over that particular port. If you find that you're getting the standard 48 volts, then you can use a linear voltage regulator to drop that down to whatever you need for your LED's, computer fan or whatever. Unless it's designed for PoE, it probably won't be 'plug and play' and you'll have to do some modding or make a very simple voltage regulator circuit. You'll have to know things such as the specs for the router/switch (maximum output for each port), and the specs for whatever you're connecting to it, but the main thing is to learn and have fun.

 

[matthelm]

You need a PoE "splitter". Like CoffeeGuy said, some just give you 48 volts, but I know at one time I saw one that had selectable output settings. (like 5V, 12V, etc.) You will be limited on the max power, but you could run anything in that power range.

You will always need a PoE "device", as PoE devices "talk" to each other, to setup the power. If you just try and get power, the switch will limit the output to a VERY low rating. I have no tech specs here, but just look up any of the chips made to do this. It isn't "hard" to do this, but you just can't hook the wires up. (I think it's just a few resistors to create a DC voltage that the PoE source reads, but it's been a while since I've researched this) I'd advise a fuse for DIY, with the cost of PoE switches!

 

[sfx2000]

Just be careful tinkering around with POE - 48VDC is enough to hurt someone if not careful. current isn't so high, but the voltage potential is enough to cause trouble...

 

[thetoad30]

Just be careful tinkering around with POE - 48VDC is enough to hurt someone if not careful. current isn't so high, but the voltage potential is enough to cause trouble...

This isn't true. Current is what kills.

Proof? Static shocks are 1000s, if not tens of 1000s of volts. Current is near zero.

You need to have a voltage high enough to push the current across the heart, and not to just "skim" over the skin layer. High current does that. I was shocked the other day by 120v at 15 amps and it went up one arm and down the other - I was lucky, yes, since it stayed on my skin and didn't go through my body. But it really does take more effort to electrocute someone than common misconception states.

I'd be more fearful of shorting out the switch and causing a fire than I would electrocuting myself with a POE port.