POE 48vdc to 24-26 vdc

[mike sessi]

The Netgear POE switch outputs 48 at 15.4 watts
The Ubiquit Nano Beam radio needs 24 at .5A ... about 100' to 200' away using cat5 cable
How to... Dc to DC 48 to 24 ?
LM317 ?

Thanks

 

[duke37]

I do not know the resistance of your cable, you could look this up. You can then calculate voltage drop, remember that the current has to go out and back.

The LM317 will drop the voltage in a linear manner so producing heat.
If you use a buck convertor, the input current will be almost half the output current and if this is installed at the far end of the cable, then less power will be lost in the cable.

 

[BobK]

You are right on the edge of having enough power. A linear converter will not work. the 48V at 15.4W supply can only supply 320 mA and you need 500 mA.

A DC to DC converter with efficiency of 80% or more might work.

Bob

 

[Frankchie]

As others have implied the LM317 will not work because it is a linear device and cannot provide more current than available at it's input. Think of it as an automatically adjusting resistor.

This might work for you..I would put it on the far, Nano Beam end, of the wire.

http://vi.vipr.ebaydesc.com/ws/eBay...descgauge=1&cspheader=1&oneClk=1&secureDesc=0

 

[Kiwi]

Has the Cat5 already been run?

Can you run another cable as a dedicated power supply?

What is the exact cable length?
100' to 200'(30m to 60m) is a pretty wide range.

Could you use a POE injector with a higher rating?