Toggle Between Two LED Lights

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.

/* Use a button to toggle between single color LED lights */ int pressCount = 0; //Create a variable called 'pressCount' that is an integer (whole number) and starting value of 0 void setup() { pinMode(8,INPUT_PULLUP); //button pinMode(2,OUTPUT); //LED pinMode(7,OUTPUT); //LED } void loop() { if(digitalRead(8)==LOW){ //if button 8 is pressed pressCount++; //increase the value of pressCount by 1 delay(250); //delay gives you time to release the button before a press is counted twice } if(pressCount==1){ digitalWrite(2,HIGH); //turn on LED 2 digitalWrite(7,LOW); //turn off LED 7 } else{ //if pressCount is any value other than 1 digitalWrite(7,HIGH); //turn on LED 7 digitalWrite(2,LOW); //turn off LED 2 pressCount = 0; //reset the pressCount variable to 0 } } // (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!

Video Notes for Code Lab Users:

Your button is connected to port 8 instead of port 6 as the video says.
Your second LED is connected to port 7 instead of port 13 as the video says.

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 ‘if’ statement. How small can you make the delay before the button press is unreliable? Once the delay is very small, can you get LED 2 to stay on? It’s a speed challenge for your fingers!

If you have a small delay in the ‘if’ statement (smaller than 10), what happens if you hold down the button?

Change the code inside the ‘if’ and ‘else’ statements so that the button press turns on and off the LEDs together instead of switching back and forth between them.

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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