This project turns your arduino into a sos morse code sender. It sends the code using a LED connected to the digital pin 10. 

To build this project you will need:

• 1 Arduino board
• 1 LED
• 1 220ohm resistor

Build the circuit like the picture above.

Then, upload the following code:

// LED connected to digital pin 10 
int ledPin = 10;

// run once, when the sketch starts
void setup() 
{
// sets the digital pin as output
pinMode(ledPin, OUTPUT); 
}

// run over and over again 
void loop() 
{
// 3 dits
for (int x=0; x<3; x++) {
digitalWrite(ledPin, HIGH); // sets the LED on
delay(150); // waits for 150ms
digitalWrite(ledPin, LOW); // sets the LED off
delay(100); // waits for 100ms
}

// 100ms delay to cause slight gap between letters
delay(100); 
// 3 dahs
for (int x=0; x<3; x++) {
digitalWrite(ledPin, HIGH); // sets the LED on
delay(400); // waits for 400ms
digitalWrite(ledPin, LOW); // sets the LED off
delay(100); // waits for 100ms
}

// 100ms delay to cause slight gap between letters 
delay(100); 

// 3 dits again
for (int x=0; x<3; x++) {
digitalWrite(ledPin, HIGH); // sets the LED on
delay(150); // waits for 150ms
digitalWrite(ledPin, LOW); // sets the LED off
delay(100); // waits for 100ms
}

// wait 5 seconds before repeating the SOS signal 
delay(5000); 
}

When finished, the arduino will start blinking the LED with the SOS morse signal.

That's it!

References:

http://arduino.cc/en/

http://www.labdegaragem.org/loja/index.php/47-livros/arduino-basico...