mirror of
https://github.com/letscontrolit/ESPEasy.git
synced 2026-07-28 04:07:47 +00:00
36 lines
2.1 KiB
Plaintext
36 lines
2.1 KiB
Plaintext
|
|
Ethernet with PoE
|
|
-----------------
|
|
|
|
Some ethernet boards support Power over Ethernet (PoE), so only a single (ethernet) cable to the ESP is needed, and the ESP (and any sensors) will be powered via an onboard converter.
|
|
|
|
For Olimex boards in the ESP32-POE range, the supplier has documented this warning:
|
|
|
|
.. warning::
|
|
**Important notice**: Olimex ESP32-PoE has **no galvanic isolation** from Ethernet's power supply, when you program the board via the micro USB connector the Ethernet cable should be disconnected (if you have power over the Ethernet cable)!
|
|
|
|
Consider using Olimex USB-ISO to protect your computer and board from accidental short circuit. Also consider instead using Olimex ESP32-PoE-ISO board, which *is* insulated.
|
|
|
|
Most likely, this warning is applicable to other brands as well.
|
|
|
|
|
|
Ethernet Isolation
|
|
------------------
|
|
|
|
Most Ethernet RJ45 phy (the connector on the PCB) have isolation transformers in them.
|
|
This does isolate the TX/RX pins to make sure there is no direct connection between the long cables and the Ethernet controller chip.
|
|
The isolation does protect the Ethernet chip from picked up high voltage spikes and ESD surges when inserting the Ethernet cable.
|
|
However not all ESP boards with Ethernet have these installed.
|
|
|
|
Apart from the isolation of the TX/RX pins the metallic enclosure of the phy should also be isolated from the rest of the circuit of the ESP board.
|
|
Typically this is done by connecting the metal enclosure of the phy via a capacitor to GND of the rest of the circuit.
|
|
A lot of boards with Ethernet have these directly connected to GND, which may impose a problem when connecting the ESP board to your PC.
|
|
|
|
.. warning::
|
|
**Important notice**: For ESP boards with Ethernet which need debugging, never use Ethernet cables with metal shielding on the Ethernet connector.
|
|
|
|
Using shielded Ethernet cable will connect the metal shield of the RJ45 phy to the ground of the switch and this may be connected to other appliances which may be badly grounded.
|
|
This will add a significant voltage offset between the ESP board and your PC while debugging.
|
|
Such a high voltage is very likely to destroy electronics.
|
|
|