Hello Blinking LED

Apparently the post title here is the universal Hello World for physical computing. I am a newbie and had no prior knowledge in electronics. I will try to write a few posts which will serve as a work log for me so that I can revert to these when needed/forgotten due to focusing on other priorities of life over time.

Wiring up an Arduino

I’m using a Seeeduino ADK (a Arduino Mega 2560 variant) for this post. I have simply plugged it to the computer via Micro-USB cable. I have also used a breadboard and connected a LED and a 220 ohm resistor between ground and pin 15. The register here prevents the LED from taking a damage due to 5V on which Arduino runs on.



You will notice that without doing anything the LED blinks randomly along with another LED which is in-built.

Blinking from a Program

How about we write a program that can systematically after each second blinks the LED? Download and install the Arduino software from here which comes with a minimal yet effective IDE. I’ve written the following code which is quite self-explanatory:


I’ve pressed Control + U, then it took a few seconds to upload to the processor, and voila! The program that I have written is now successfully making the LED blink every accurate second.

Blinking Two LEDs in a Particular Order

Now I would like to exercise more power of code and blink 2 LEDs, red twice each 2 seconds and green just once when red is done. I have organized the circuit in a slightly different way now:

DoubleLEDblink_bb-cropped I have used pin 13 and pin 12 now in order to blink green and red in turn, and written the following code:

int green = 13;
int red = 12;

void setup() {                
  pinMode(green, OUTPUT);     
  pinMode(red, OUTPUT);     

void loop() {
  digitalWrite(red, HIGH);
  digitalWrite(red, LOW);

  digitalWrite(red, HIGH);
  digitalWrite(red, LOW);

  digitalWrite(green, HIGH);
  digitalWrite(green, LOW);

Here’s the final outcome:


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