A Blink That Speeds Up

Part of the First Circuits section of Coddy's Arduino journey. Lesson 17 of 22.

delay(waitTime) waits for whatever waitTime holds at that moment. Change the variable while the sketch runs, and the blink changes with it.

waitTime = waitTime - 100;   // the next blink is 100 ms shorter

Put that at the end of loop() and every blink is shorter than the one before.

Watch what happens when it runs for a while. The wait shrinks to 0, and then below 0. delay() cannot wait a negative time: it reads -200 as an enormous number, about 49 days, so the LED looks frozen. A sketch has to decide for itself when to stop shrinking, and that is what the next lesson is about.

Challenge

Easy

Make the LED on pin 13 blink faster and faster:

at the top, make int waitTime = 1000;
in loop(), blink with delay(waitTime) for both waits
at the end of loop(), make waitTime 200 smaller

Press Run and watch until it freezes, then Check.

Try it yourself

// make waitTime here

void setup() {
  pinMode(13, OUTPUT);
}

void loop() {
  digitalWrite(13, HIGH);
  delay(1000);
  digitalWrite(13, LOW);
  delay(1000);
  // make waitTime smaller
}

Test yourself

This lesson includes a short quiz. Start the lesson to answer it and track your progress.

All lessons in First Circuits

1Hello, Board

Blink an LED Setup and Loop Change the Blink Speed An LED of Your Own Two LEDs Taking Turns Comments in Your Sketch

4Decisions

Decisions with if Choosing with if and else Comparing Values Combining Conditions Read a Button

2Talking to Your Computer

Hello, Serial Monitor Print Versus Println Printing Numbers Your First Variable Counting Up When an Int Runs Out

3Math on the Board

Named Constants Arithmetic Operators Integer Division Decimals with floatA Blink That Speeds Up

Practice on your own: Arduino playground