XBoard V2 Power Over Ethernet?
dpancoe 2015-06-04 08:45:19 2245 Views2 Replies I see in the XBoard V2 schematic that pins 4 and 5 of the RJ45 jack, which are normally the ones used for Power over Etherent (PoE) connections, are tied through an inductor to the 3.3 V supply, with a filter cap to ground. I wondered what was the intended use of these connections? Was it to provide power to other devices or to power the XBoard through the Ethernet cable?
If the intent was to power the XBoard over the Ethernet cable, it might have been better to tie RJ45 pins 4 & 5 to the Vin of U3 so that you could put up to 12 V on the Ethernet cable to allow for resistive losses over the length of the cable. Commercial PoE systems use 48 V for this reason. As it is now, you would have to estimate the voltage loss over the length of the cable and boost the supply by exactly that much to get an accurate 3.3 V at the XBoard.
If the intent was to power the XBoard over the Ethernet cable, it might have been better to tie RJ45 pins 4 & 5 to the Vin of U3 so that you could put up to 12 V on the Ethernet cable to allow for resistive losses over the length of the cable. Commercial PoE systems use 48 V for this reason. As it is now, you would have to estimate the voltage loss over the length of the cable and boost the supply by exactly that much to get an accurate 3.3 V at the XBoard.
2015-06-08 18:30:49 Hi,
XBoard V2 doesn't support PoE power supply now. But there is a new board, in which you will be interested. You could check this link:
https://www.dfrobot.com/wiki/index.php? ... U:_DFR0342
W5500 PoE mainboard. You could power it over Ethernet cable. Grey.CC
XBoard V2 doesn't support PoE power supply now. But there is a new board, in which you will be interested. You could check this link:
https://www.dfrobot.com/wiki/index.php? ... U:_DFR0342
W5500 PoE mainboard. You could power it over Ethernet cable.
Grey.CC 2015-06-05 09:29:37 I found this data sheet that explains the situation. Ethernet uses Manchester code that has voltages both above and below zero, so the 3.3 V is applied to center-taps of two transformers to shift the whole signal above zero volts.
Pins 4 and 5 on the output side are not even connected to pins 4 and 5 of the RJ45 itself, which are instead tied to ground. So there is no chance of using PoE with the XBoard without using a breakout cable such as this one from Adafruit. dpancoe
Pins 4 and 5 on the output side are not even connected to pins 4 and 5 of the RJ45 itself, which are instead tied to ground. So there is no chance of using PoE with the XBoard without using a breakout cable such as this one from Adafruit.
dpancoe 