The Arduino Academy - Lesson 2 - Basic Outputs


Introduction: The Arduino Academy - Lesson 2 - Basic Outputs

About: Hi, my name is Mike and I am from London, England. I really like to make things and in particular like to do creative things with Arduinos and electronics. Other hobbies include astrophotography and sailing....

Lesson 2 of the Arduino Academy in which we will learn all about Basic Outputs on the Arduino.

If you have any questions then leave them in the comments and I will get back to you asap.

Don't forget to subscribe. You can follow me on Twitter @TheArduinoGuy and my blog is at

The Arduino Academy facebook group can be found at

Keep an eye out for Lesson 3 when we will learn about Basic Inputs on the Arduino.

Mike McRoberts



    • Oil Contest

      Oil Contest
    • Make it Move Contest

      Make it Move Contest
    • Clocks Contest

      Clocks Contest

    We have a be nice policy.
    Please be positive and constructive.




    Suppose I wanted these leds to cycle only three times. I created a for loop that embedded the previous for loop within it, but it never stops. My code looks like this:

    void loop() {
    for (int reps = 1; reps < 4; reps = reps +1) {
    for (int led = 8; led < 11; led = led + 1) {

    // put your main code here, to run repeatedly:
    digitalWrite(led, HIGH);
    digitalWrite(led, LOW);

    Do I need to have an if loop that says if reps =4 'just stop repeating'. I see why it doesn't stop: it starts the outside loop, then the inside loop; outside loop is advanced until it gets to 4. But then the damn things does it again and again. I'd like a way to stop it.

    3 replies

    You have a loop that repeats 3 times inside a loop that repeats 3 times so the whole thing will run 9 times.

    Apart from that I see nothing wrong with the code. it shoudl stop after 3 cycles.

    I had a single for loop embedded in another and you said it should stop after 3 cycles but it didn't. So I tried just one for loop (5 iterations) and it didn't stop after 5. I don't get it.

    Sorry, massive bugbear of mine is when people paste code into comments. Please use the correct formatting or use Pastebin for code.

    HI. I have a bunch of LEDs but no data sheet to determine voltage drop (I assume what whatever you said is basically what I have. However, how could I determine the voltage drop without the data sheet? And how do you know tht the current is .03a (without some data sheet)?

    1 reply

    The easiest way is to sacrifice an LED or two and connect them up to a variable power supply and increase the voltage till it pops. At the same time, measure the current draw across the LED.

    I asked the question below because I am planning to use a vibratory motor for a project and I have no spec sheet on that either but I don't want it to burn out.

    By the way I really liked the way you presented this lesson.