Fade an LED Up and Down

Code

The code in the editor below is ready to run! Plug your Code Lab in to your computer's USB port with the cable and hit 'Upload Your Code!' to see what it does. Change something in the code, like a delay or pin number. Try to add something new to the program - it's yours to tinker with! You can always press the 'Restore' button to return the code to the working example.

/* Fade up an LED light from 0-255 brightness and then back down to 0 brightness*/ void setup(){ pinMode(3,OUTPUT); //LED on an analogWrite port. LEDs 3,5,and 6 can use analogWrite } void loop(){ /*create a 'counter' variable with a starting value of 0 and, as long as the variable is less than 256, run the code between the curly braces, then increase the value of the 'i' variable by 1 */ for(int i = 0; i < 256; i++){ analogWrite(3,i); //use the value of 'i' to set the brightness of LED 3 delay(25); //wait 25 milliseconds (0.025 seconds) before running the 'for' loop again } /*create a 'counter' variable with a starting value of 255 and, as long as the variable is greater than 0, run the code between the curly braces, then decrease the 'i' variable value by 1*/ for(int i = 255; i > 0; i--){ analogWrite(3,i); //use the value of 'i' to set the brightness of LED 3 delay(25); //wait 25 milliseconds (0.025 seconds) before running the 'for' loop again } //Once the 'for' loops have ended, the void loop will start over, running the 'for' loops again } // (c) 2021 Let's Start Coding. License: www.letsstartcoding.com/bsdlicense

Walkthrough Video

Watch the video for a line-by-line explanation of how the example program works. Then you'll be ready to make some changes of your own!

Challenges

Can you complete the challenges? Change the code in your code editor above. Upload your code to see the effect when you're finished. Complete a challenge? Check it off the list!

Change the delay in the first ‘for’ loop. Predict how this will change the fade before you upload your new code.

Now change the delays in both of the ‘for’ loops. How does that change the program?

Change the variable in the second ‘for’ loop from i to j (another common ‘counter’ variable name). Notice that the ‘i’ variable used in the first ‘for’ loop is totally different from the ‘i’ variable in the second ‘for’ loop.

Concepts

These are the new code concepts covered in this example program. To become a great coder, read through these concepts to learn new vocabulary.

Quiz

If you're having trouble, try to run an experimental program or look at the example code to help you find the answer.

1. Which syntax ends the entire 'void loop' function?

semicolon ;
parentheses )
closing curly brace }

2. Which syntax ends a single code command?

semicolon ;
closing curly brace }
period .

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