> For the complete documentation index, see [llms.txt](https://robotlabs.gitbook.io/docs/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://robotlabs.gitbook.io/docs/esp32/platformio/3.1-pwm-led-fade.md).

# 3.1 PWM - LED Fade

We have used LED to make a running light before. In this example, we will learn how to make a fading light with PWM. The brightness of the LED light will change as the PWM duty cycle. 

{% embed url="<https://youtu.be/VBuEXz_m4G4>" %}

## Introduction

PWM stands for Pulse-Width Modulation, a technique that uses a varying duty cycle to represent a signal as a rectangular wave. It's used to control the average amplitude or power of an electrical signal.

The two primary components of a Pulse Width Modulation (PWM) signal are frequency and duty cycle:&#x20;

* **Frequency**The rate at which a PWM signal switches between high and low voltages, measured in Hertz (Hz).
* **Duty cycle**The percentage of time a PWM signal is at a high voltage, expressed as a ratio or percentage.

<figure><img src="/files/3SKnXiaBybqWbPT9uUVA" alt="" width="563"><figcaption></figcaption></figure>

PWM can be used to control the brightness of an LED by adjusting the duty cycle. If We generate a PWM signal to the anode(+) pin, the LED's brightness is in proportion to PWM duty cycle. PWM duty cycle varies from 0 to 255. The bigger the PWM duty cycle is, the brighter the LED is.

<figure><img src="/files/qqjx9cjl2GOAa0Ctl5t6" alt="" width="375"><figcaption></figcaption></figure>

## Hardware Circuit

### 1. Parts Required

Here’s a list of the parts to you need to build the circuit:

* ESP32-S3-N16R8
* LED
* 330 - 1k Ohm resistor
* Breadboard
* Jumper wires

### 2. Wiring

Before proceeding, you need to wire a circuit with an LED. The positive pole of the LED is connected to the pin 14 of the development board, and a resistor is connected in series. The negative pole is connected to GND, as shown below:

<figure><img src="/files/dbE6KnGqYMbd4hjiGSde" alt="" width="361"><figcaption></figcaption></figure>

{% hint style="info" %}
Usually, it requires a resistor to protect LED from burning. The resistance's value depends on the LED's specification.
{% endhint %}

## Coding and Testing

### 1. Arduino functions for PWM

The `analogWrite()` function writes an analog value (PWM wave) to a pin. Can be used to light a LED at varying brightnesses or drive a motor at various speeds. After a call to analogWrite(), the pin will generate a steady rectangular wave of the specified duty cycle until the next call on the same pin.&#x20;

```arduino
analogWrite(pin, value)
```

* pin: the Arduino pin to write to. Allowed data types: int
* value: the duty cycle between 0 (off) and 255 (on). Allowed data types: int

Copy the following code to your IDE.

```cpp
#include <Arduino.h>
// define GPIO pin number
#define LED_PIN   12

void setup() {
  // set GPIO pin
  pinMode(LED_PIN, OUTPUT);

}

void loop() {
  // Brighter control
  for(int i=0;i<256;i++) {
    // Set brightness
    analogWrite(LED_PIN, i);
    // Delay 10ms
    delay(10);
    }
  // Fading control
  for(int i=255;i>=0;i--) {
    // Set brightness as the analog value
    analogWrite(LED_PIN, i);
    // Delay 10ms
    delay(10);
    }
}

```

### 2. Uploading the Code

Refer the previous tutorial: [2.1 GPIO - LED Blink](/docs/esp32/platformio/2.1-gpio-led-blink.md)

## Summary

In this section, we use analogWrite() function writes an analog value (PWM wave) to a pin to change the LED brightness.

Finally, if you want to learn more about other controllers, take a look at our Youtube channel:

{% embed url="<https://www.youtube.com/@RobotLabs>" %}