Change the Blink Speed

Part of the First Circuits section of Coddy's Arduino journey. Lesson 3 of 22.

delay() counts in milliseconds (ms), thousandths of a second. delay(1000) is one second, delay(250) a quarter of a second.

One blink is the time the LED is on plus the time it is off. With two waits of 1000 ms, a blink takes 2000 ms. Smaller numbers make shorter waits, so the LED blinks faster:

digitalWrite(13, HIGH);
delay(100);   // on for a tenth of a second
digitalWrite(13, LOW);
delay(100);   // off for a tenth of a second

delay() only takes whole milliseconds. delay(0.2) is not a fifth of a second: the board drops the fraction and waits 0 ms. For a fifth of a second, write delay(200).

Both waits matter. Without the second one, the LED turns off and is switched straight back on, so it looks like it never goes off.

Challenge

Easy

The starter blinks slowly. Make it fast:

on for 200 ms
then off for 200 ms

Press Run to watch it, then Check.

Try it yourself

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

void loop() {
  digitalWrite(13, HIGH);
  delay(1000);  // make this wait shorter
  digitalWrite(13, LOW);
  delay(1000);  // and this one
}

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 LoopChange the Blink SpeedAn 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 float A Blink That Speeds Up

Practice on your own: Arduino playground