Cheap PoE with Uno & Ethernet Shield

Hello everyone

many of you certainly know PoE, i.e. Power over Ethernet (802.3). PoE is a surprisingly complex subject with a lot to consider. PoE is becoming increasingly popular and has been used more frequently recently. Professional solutions currently work with 48V, but the standard is constantly being expanded. Rebuilding a professional PoE solution is not easy, as many parameters need to be included. For example, the thickness of the wires in the line is decisive and only a small voltage drop is permitted (return and return). There are now devices on the market that can pull up to 100W. 100W with 48V in the same cable as the data lines generates massive faults, which also convinced hobbyists fail. Active PoE injectors and splitters with appropriate filters are essential and relatively expensive in this performance range. The Arduino Foundation produced for a time PoE Shields for the Uno, which are now hardly available. 

That's why today we are testing cheap, passive PoE adapters

In my opinion, the product description of the article should be enjoyed with caution.

Connecting IP cams to these adapters has been common practice for years, but when used with a PoE switch, high power required or longer cables (from 15m) this can cause problems. For a UN, however, that is enough.

For our experiment, we use a Uno with Ethernet ShieldA 10m Cat. 6 Cables Depending on the power supply, you may need to DC-DC Module. As an example sensor, we use our Soil moisture sensor 1.2

We use a 12V power supply because the UN can tolerate a voltage of 12V via the current socket, via the DC-DC module this can be reduced if necessary. A 9V power supply should be best suited.

Our test setup:

We slightly modified the sample code from the Arduino Ethernet Libary:


 Web Server

 A simple web server that shows the value of the analog input pins.
 using an Arduino Wiznet Ethernet shield.

 Ethernet shield attached to pins 10, 11, 12, 13
 Analog inputs attached to pins A0 through A5 (optional)

 created 18 Dec 2009
 by David A. Mellis
 modified 9 Apr 2012
 by Tom Igoe
 modified 02 Sept 2015
 by Arturo Guadalupi


#include <Spi.H>
#include <Ethernet.H>

Byte Mac[] = {   0xDE, 0xAD, 0xBE, 0xEF, 0xFE, 0xED

Ipaddress Ip(192, 168, 1, 177);
EthernetServer Server(80);

Void Setup() {   Serial.Begin(9600);   Ethernet.Begin(Mac, Ip);   Server.Begin();   Serial.Print("Server IP: ");   Serial.println(Ethernet.localIP());

Void Loop() {   EthernetClient Client = Server.available();   If (Client) {     Serial.println("New Client");     Boolean currentLineIsBlank = True;     while (Client.Connected()) {       If (Client.available()) {         Char C = Client.Read();         Serial.Write(C);         If (C == 'n' && currentLineIsBlank) {           Client.println("HTTP/1.1 200 OK");           Client.println("Content-Type: text/html");           Client.println("Connection: close");           Client.println("Refresh: 2");           Client.println();           Client.println("<! DOCTYPE HTML>");           Client.println("<html>");           Client.Print("Analogpin 0: <b>");           Client.Print(analogRead(A0));           Client.println("</b><br />");           Client.println("</html>");           Break;         }         If (C == 'n') {           currentLineIsBlank = True;         }         else If (C != 'A'r') {           currentLineIsBlank = False;         }       }     }     Delay(1);     Client.Stop();     Serial.println("Connection closed");     Serial.println("");   }


The sensor will be read out as expected:


Until the next post :)


YourS Moritz Spranger

Team AZ-Delivery

For arduinoProduktvorstellungen

1 comment



Guten Tag,
wenn ich auf den Link “Ethernet Shield” gehe komme ich auf die Seite von Amazon. Bei “UNO” kommt eine Fehlermeldung. Beim Bodenfeuchtesensor komme ich auf eure Seite. Warum, das entzieht sich meiner Kenntnis.

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