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.
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.
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.
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.
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.