On 29/07/2018 16:36, Richard Ashbery wrote:
> I would be a little concerned about loading my ethernet cable with say a
> Raspberry Pi but I guess some of you are finding it works OK.

People load the lines with all sorts of stuff. But anyway "do the math"
as our US friends say.

48V in to 5V out. So the voltage in:out ratio is 48/5 is 9.6. It will
provide 2.5A at 5V so will need 2.5/9.6 approx 260mA at 48V. Those are
perfect figures. In reality the PoE adapter will be be 80-95% efficient,
so the current will be higher.

But as long as you can pull 300mA say over your long length of CAT5/6
cable you'll be laughing. CAT5 is 24AWG ISTR wire and that has 5Ohms
resistance over 60m length. You have 2 lengths in use so 10Ohms. Ohm
says V=IR so 10 x .3 = 3V.

So 48V in should give 45V at the far end. Plus or minus. Looks like it
may work as that unit is stated as 44-57V input.  Probably we should
make the limit 50m to give a bit more margin.

I may have dropped a googly in all those calculations, but I'm not proud
so feel free to correct any mistakes!

--- SoupGate-Win32 v1.05