POE Switch & passive poe splitter issue

[r3ddyfire]

ok so i was planning on creating a network setup with a cisco srw2008p (8 port switch with poe) and 5 random routers. i wanted to power these routers via poe. i went online and bought a set of passive poe splitters. i figured the switch would figure out the routers need power and it will kick out 12v, but that wasnt the case. am i obviously doing something like this for the first time and i appreciate any suggestion you guys have. (i have a dlink dir 655, two cisco valet m10's, cisco wrt54g2 and netgear mr814, not that it makes a difference since neither power on...)

here is the idea i had in mind in picture form:

 

[john-b691]

Sounds like you got lucky it didn't work and get fried equipment.

PoE runs at 48 volts not 12. The reason it did not work is PoE is not a passive feature it runs 802.af which actually sends messages to the switch requesting the power.
There are systems to do what you want but they are not what is commonly referred to as PoE even though the selling vendors will say that.

 

[r3ddyfire]

it was my understanding that the switch requires 48v but can provide up to 15v through the cat5/6 cabling. what kind ap's would i need to buy to make my original idea work ? the goal was to reduce on the number of outlets being used and to simply draw power through the switch, this in turn would also reduce the cabling required.

 

[john-b691]

Most device that are designed from the start to be a AP are powered by PoE. Part of the reason they tend to be more expensive than a router that can be converted into a AP.
Be very careful to not confuse watts and volts. 802.af can deliver just over 15 watts of power. Most routers are not designed for PoE so they could very well take over 15watts, which means they cannot be powered over ethernet. Now 802.at is a newer PoE standard that can provide either 25 or 50 watts but your switch is not that type. A real PoE AP will draw less than 15 watts since it is designed to stay within the restrictions. You are lucky that you have a better switch than most people that try this. All 8 of your ports can provide 15 watts of power. Many of the cheap ones can only run 4 ports and they must share only 50 watts of power..means only 3 can run at maximum.

There are small devices that will run 802.af to the switch and then convert the power to 12 volts. This is one model but I have not tried this so do your own research.
http://www.tp-link.com/en/products/details/?model=TL-POE10R#spec

The key to see if you can even do this is to carefully read the specifications for the router and see how much power it draws. Sometimes it is stated in AMPS. The conversion is volt*amp=watt. So at 12 volts it would need to draw less than 1.25 amps to stay under 15 watts. I would not even get close the box that convert it from 48 to 12 volts will take some power also and very technically the 802.af specification only guarantees just over 12watts makes it to the far end of the cable when cable loss is included.