Arduino Tutorial #4 – Digital Pin PWM Output | Arduino LED Fading

Hello friends! Welcome back to ElectroDuino. This is the Arduino Tutorial #4Digital Pin PWM Output | Arduino LED Fading. After understanding Arduino Programing Language | How To Program Arduino in the Arduino Tutorial #3. In this blog, we going to describe what is PWM (Pulse Width Modulation ), Arduino digital pin as PWM output,  and Arduino LED Fading using analogWrite() function.

What is PWM (Pulse Width Modulation) Output

Pulse Width Modulation, or PWM, is a technique that is used to get analog results with digital means. This technique is used to create a square wave, a signal switched between on and off. This on-off pattern can simulate voltages in between 5 Volts (ON) and 0 Volts (OFF) by changing the portion of the time the signal spends on versus the time that the signal spends off.

This duration or period is the converse of the Pulse Width Modulation (PWM) frequency. The Arduino’s PWM frequency is about 500Hz, each green line would measure 2 milliseconds. In the Arduino program, we call a function analogWrite(), which is on a scale of 0 – 255. For example, When the analogWrite() value is 255 it means a request for a 100% duty cycle (always ON), and the analogWrite() value is 127 it means a request for a 50% duty cycle (on half the time).

What is PWM (Pulse Width Modulation)
What is PWM (Pulse Width Modulation)
  • analogWrite(0) for 0% Duty Cycle
  • analogWrite(64) for 25% Duty Cycle
  • analogWrite(127) for 50% Duty Cycle
  • analogWrite(191) for 75% Duty Cycle
  • analogWrite(255) for 100% Duty Cycle


analogWrite(pin, value)

Where, the pin is a PWM pin of Arduino and the value is the duty cycle between 0% – 100%.

Use Digital Pin as PWM Output 

We can get analog output from some digital pins of the Arduino board. These digital pins are known as PWM pin. Arduino UNO has 6 PWM pins these are  D3, D5, D6, D9, D10, and D11 pin.  Also, we need to use the analogWrite() function in Arduino programming to get analog output from these pins. The analog output in the range of 0 to 255. The output switching it off and on very fast and with different ratio between on and off time.

Arduino LED Fading using PWM Output

LED Fade is an interesting lighting project, where the LED intensity or brightness increases from the low to high, and again the intensity or brightness decreases from high to low, it is run gradually. Here we will learn how to make Arduino LED fade using PWM output.

Components Required

Components Name Quantity
Arduino Uno Board1
USB cable for Arduino Uno1
220Ω Resistor1
Connecting wireAs required in the circuit diagram

Arduino LED Fading circuit diagram

LED Fading using Arduino circuit diagram
LED Fading using Arduino circuit diagram

Circuit Wiring

LED PinArduino pin
LED positive (+) terminal connected to Arduino D6 pin through a 220-ohm resistor
LED negative (-) terminalconnected to Arduino GND pin

Arduino LED Fading Program/sketch

Code Description

Code LineDescription
int led = 6;It is declared your LED pin connected to Arduino pin 6 and named as led.
int brightness = 0;Take a variable brightness. it is used to set the PWM value. At the starting of the code, we set the value at 0.
int fadeAmount = 5;This is another variable. it used to increase or decrease the brightness value, Each time through the loop. The increase or decrease of value is 5.
pinMode(led, OUTPUT);Declare the pin 6 as an output.
analogWrite(led, brightness);The analogWrite() function that you will be using in the main loop of your code requires two arguments: One, telling the function which pin to write to and the other indicating what PWM value to write.
brightness = brightness + fadeAmount;This line of code is used to Change the brightness for next time through the loop

if (brightness <= 0 || brightness >= 255)


   fadeAmount = -fadeAmount;

If the LED brightness value is Low (0/off) or High (255/on), then fadeAmount is changed to its negative(-). It means if fadeAmount is 5, then it is set to -5, or If it is -5, then it is set to 5. As a result, brightness is change continuously.
delay(30);It means that wait for 30 milliseconds to see the dimming effect of the LED.


As a result, you can see the LED brightness increases from low to high, and again, the brightness decrease from high to low, it is run gradually.


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