How to fade LED in a time period?

How to fade-in and fade-out LED in a time period without using delay() function?

Answer

To fade LED smoothly without blocking other code, we can use millis() instead of delay(). Let;s see example code for:

Wiring Diagram

Arduino LED Wiring Diagram

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How to fade-in LED in a period without using delay()

/* * Created by ArduinoGetStarted.com * * This example code is in the public domain * * Tutorial page: https://arduinogetstarted.com/faq/how-to-fade-led-in-a-time-period */ const int LED_PIN = 9; // the PWM pin the LED is attached to unsigned long FADE_PEDIOD = 3000; // fade time is 3 seconds unsigned long fadeStartTime; // the setup routine runs once when you press reset void setup() { pinMode(LED_PIN, OUTPUT); // declare pin 9 to be an output fadeStartTime = millis(); } // fade-in in loop, and restart after finishing void loop() { unsigned long progress = millis() - fadeStartTime; if (progress <= FADE_PEDIOD) { long brightness = map(progress, 0, FADE_PEDIOD, 0, 255); analogWrite(LED_PIN, brightness); } else { fadeStartTime = millis(); // restart fade again } }

How to fade-out LED in a period without using delay()

/* * Created by ArduinoGetStarted.com * * This example code is in the public domain * * Tutorial page: https://arduinogetstarted.com/faq/how-to-fade-led-in-a-time-period */ const int LED_PIN = 9; // the PWM pin the LED is attached to unsigned long FADE_PEDIOD = 3000; // fade time is 3 seconds unsigned long fadeStartTime; // the setup routine runs once when you press reset void setup() { pinMode(LED_PIN, OUTPUT); // declare pin 9 to be an output fadeStartTime = millis(); } // fade-out in loop, and restart after finishing void loop() { unsigned long progress = millis() - fadeStartTime; if (progress <= FADE_PEDIOD) { long brightness = 255 - map(progress, 0, FADE_PEDIOD, 0, 255); analogWrite(LED_PIN, brightness); } else { fadeStartTime = millis(); // restart fade again } }

Function References

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