Remotely Control a Relay with Arduino UNO 

This section presents a simple example that shows how to remotely control through Internet a Relay connected to an Arduino Uno board with µPanel.

This example uses the same panel presented in the Basic Examples, which consists in a Switch and a LED indicator. Arduino will be waiting for the user to change the switch state and will update the Relay and the LED status accordingly. 


Please note that for programming Arduino Uno, the RxD line (blue wire) has to be disconnected from the WiFi Module

µPanel definition 

The panel definition includes a text for the panel title, a standard green LED and an On/Off default switch.

D!282;T*15:Arduino Relay;=*20/L1G:0:Relay;/*10W1:0;

Arduino Code

void setup() {

  // Initialize Serial Port
  // Let uPanel start 

  // Discharge old partial messages
  // Send The Panel (A LED and a Switch)
  Serial.println("$P:D!282;T*15:Arduino Relay;=*20/L1G:0:Relay;/+*10W1:0;");
  // Initialize digital output pin
  digitalWrite(8, 1);

String Msg;

void loop() {
  int c;
  while ((c = > '\n') Msg += (char) c;  // Read incoming chars, if any, until new line
  if (c == '\n')                                       // is the message complete?
    if (Msg.equals("#W10")) {digitalWrite(8,1); Serial.println("#L10");}    // Turn OFF LED 1 and Relay if switch is OFF
    if (Msg.equals("#W11")) {digitalWrite(8,0); Serial.println("#L11");}    // Turn ON LED 1 and Relay if switch is ON
    Msg = "";


Control Two Relays 

We can easily modify the previous example in order to control two relays. To do that, we have just to connect another Arduino's digital output to a second Relay and change a few lines of code:

  • we change the panel definition in order to add the second control channel and to make the panel nicer:

    D!g11;/5T*25fb:Arduino Relay;=*16/30{mL1G:0;|*12W1:0;|T:Relay 1;}/{mL2G:0;|*12W2:0;|T:Relay 2;}/30*20T#FF0ht3,000:&#956Panel;

      Serial.println("$P:Dg11;/5T*25fb:Arduino Relay;=*16/30{mL1G:0;|*12W1:0;|T:Relay 1;}/{mL2G:0;|*12W2:0;|T:Relay 2;}/30*20T#FF0ht3,000:&#956Panel;");

  • we add four lines of code in order to manage the second switch:

      digitalWrite(9, 1);
      if (Msg.equals("#W20")) {digitalWrite(9,1); Serial.println("#L20");}    // Turn OFF LED 2 and Relay if switch is OFF
      if (Msg.equals("#W21")) {digitalWrite(9,0); Serial.println("#L21");}    // Turn ON LED 2 and Relay if switch is ON

Watch the video of this example: