Running ~175ft of cat5 solid cable with 12v/5v at the end

[StealthRT]

Hey all i am just wondering what type of DC voltage i would need to start out with in order to get 12v at the end of a 175ft run over cat5 solid cable? This is to be hooked up using the standard power over ethernet (PoE). I'm just not sure what i need to start out with in order to have a constant 12v with 500mA or 1A at the end or 5v as some only need 5v to power them up.

Thanks for your time!

 

[audioguru]

Look up the wire guage used in cat5 cable (24 guage) then look up its resistance for 175 feet long (about 5 ohms for each wire so a total of 10 ohms for the two power wires). Then use Ohm's Law with the current you need to calculate the voltage lost.

I made a quick calculation: 22V input and 12V at 1A output.
If the current varies then the voltage at the far end will also vary.

 

[ChrisP58]

Hey all i am just wondering what type of DC voltage i would need to start out with in order to get 12v at the end of a 175ft run over cat5 solid cable? This is to be hooked up using the standard power over ethernet (PoE). I'm just not sure what i need to start out with in order to have a constant 12v with 500mA or 1A at the end or 5v as some only need 5v to power them up.

Thanks for your time!

Standard POE uses a nominal 48 Volts (often 56 volts) at the source, and then a DC to DC converter at the load end to make the regulated 5 and 12 volts.

 

[KeepItSimpleStupid]

You need to watch the POE stuff closely. The cheapskates just pump power over the wires and are not complaint. I think the standard is 802.11af (13 W). POE is also wierd because of POE+ 802.11at (25 W) vs POE. See: http://www.akrossilicon.com/poeplus I do believe that there are ways to get it even higher.

51 W seems to be achieveable. http://en.wikipedia.org/wiki/Power_over_Ethernet Remember that the power is input power, not power available at the device.

Here is a 30W midspan injector. http://www.digikey.sg/product-detail/en/POE31U-1AT/993-1142-ND/2773969

Now all you need is the receiver which can do the power negotiating.