Headlight Switch with Code Car

Using a variable, set the 'mode' of the headlight to on or off with the press of a button, so you don't have to hold a button to keep your headlights on all the time!

Code

The code below already works and is ready to upload! Upload the code to Code Car and see what happens. Then, you'll 'take apart' the code to learn what each piece of the program does.

/* * Press a button that 'locks' the headlight on until you press it again */ int pressCount = 0; //create an 'integer' variable called 'pressCount' void setup() { pinMode(4,OUTPUT); // headlight pinMode(8,INPUT_PULLUP); //button to control headlight } void loop() { if(digitalRead(8)==LOW){ //if the button is pressed pressCount = pressCount + 1; //increase pressCount by 1 delay(250); //wait 250 milliseconds before increasing pressCount again } if(pressCount == 1){ //if pressCount is equal to 1 digitalWrite(4,HIGH); //the headlight is on } else{ //otherwise, turn the headlight off and set pressCount to 0 digitalWrite(4,LOW); pressCount = 0; } } //This brace closes the void loop // (c) 2017 Let's Start Coding. License: www.letsstartcoding.com/bsdlicense

Walkthrough Videos

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

Challenges

How many can you complete? Change the code according to the challenges below. Upload your code to see the effect when you're finished. Complete a challenge? Check it off the list!

Update the code so that the button turns on and holds the brake light on instead of the headlight.

Restore the code to the example. Now try to add code so that the headlight and tail light turn on together so that with one button press, you're ready for night driving!

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.

New Concept: Variables to Set "Modes"

If you spell out the logic of this program, the press of your button sets the value of the variable pressCount, then the value of pressCount determines whether or not the LED is lit. Because the program can 'remember' the value of the variable, when you use the button to change the variable, you're changing the 'mode' of that LED. You have probably flipped on a light switch today or maybe turned a key in a lock. Those are physical representations of 'on/off' or 'locked/unlocked' like what you're recreating in code. Unlike the key or the lock, though, your code variables can have any number of 'modes' or values, so that pressCount = 1 does something different than pressCount = 2, 3, 4, or so on.

Quiz

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

Why is it important to set pressCount=0 in the 'else' statement?

Without that, it will keep a value of 1 forever.
Without that, pressCount will increase by 1 each time the button is pressed, going up to 3,4,5, and so on.
Without that, pressCount automatically increases by one every time the loop runs.

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