ESP32 - Potentiometer fade LED

This tutorial instructs you how to use ESP32 with the potentiometer to change the brightness of LED.

If you want to trigger LED when the voltage of potentiometer reaches a threshold, see ESP32 - potentiometer triggers LED tutorial

Hardware Used In This Tutorial

1	×	ESP-WROOM-32 Dev Module
1	×	USB Cable Type-C
1	×	Potentiometer
1	×	(Alternative) Potentiometer Kit
1	×	(Alternative) Potentiometer Module with Knob
1	×	LED
1	×	220 ohm resistor
1	×	Breadboard
1	×	Jumper Wires
1	×	(Optional) DC Power Jack
1	×	(Recommended) Screw Terminal Expansion Board for ESP32
1	×	(Recommended) Power Splitter For ESP32

Or you can buy the following sensor kits:

1	×	DIYables Sensor Kit (30 sensors/displays)
1	×	DIYables Sensor Kit (18 sensors/displays)

Disclosure: Some of the links in this section are Amazon affiliate links, meaning we may earn a commission at no additional cost to you if you make a purchase through them. Additionally, some links direct you to products from our own brand, DIYables.

Introduction to LED and Potentiometer

We have specific tutorials about LED and potentiometer. Each tutorial contains detailed information and step-by-step instructions about hardware pinout, working principle, wiring connection to ESP32, ESP32 code... Learn more about them at the following links:

Wiring Diagram

This image is created using Fritzing. Click to enlarge image

If you're unfamiliar with how to supply power to the ESP32 and other components, you can find guidance in the following tutorial: How to Power ESP32.

How To Program

Reads the input on analog pin (value between 0 and 4095)

int analogValue = analogRead(36); // GPIO36 (ADC0)

Scales it to brightness (value between 0 and 255)

int brightness = map(analogValue, 0, 4095, 0, 255);

Sets the brightness LED

analogWrite(LED_PIN, brightness);

ESP32 Code

/* * This ESP32 code is created by esp32io.com * * This ESP32 code is released in the public domain * * For more detail (instruction and wiring diagram), visit https://esp32io.com/tutorials/esp32-potentiometer-fade-led */ #define POTENTIOMETER_PIN 36 // ESP32 pin GPIO36 (ADC0) connected to Potentiometer pin #define LED_PIN 21 // ESP32 pin GPIO21 connected to LED's pin // the setup routine runs once when you press reset: void setup() { // initialize serial communication at 9600 bits per second: Serial.begin(9600); // set the ADC attenuation to 11 dB (up to ~3.3V input) analogSetAttenuation(ADC_11db); // declare LED pin to be an output: pinMode(LED_PIN, OUTPUT); } // the loop routine runs over and over again forever: void loop() { // reads the input on analog pin A0 (value between 0 and 4095) int analogValue = analogRead(POTENTIOMETER_PIN); // scales it to brightness (value between 0 and 255) int brightness = map(analogValue, 0, 4095, 0, 255); // sets the brightness LED that connects to pin 3 analogWrite(LED_PIN, brightness); // print out the value Serial.print("Analog value = "); Serial.print(analogValue); Serial.print(" => brightness = "); Serial.println(brightness); delay(100); }

Quick Instructions

If this is the first time you use ESP32, see how to setup environment for ESP32 on Arduino IDE.
Copy the above code and paste it to Arduino IDE.
Compile and upload code to ESP32 board by clicking Upload button on Arduino IDE
Open Serial Monitor on Arduino IDE

How to open serial monitor on Arduino IDE

Rotate the potentiometer
See the LED fading
See the result on Serial Monitor. It looks like the below:

COM6

Send

Analog value = 6 => brightness = 1 Analog value = 34 => brightness = 8 Analog value = 89 => brightness = 22 Analog value = 149 => brightness = 37 Analog value = 214 => brightness = 53 Analog value = 297 => brightness = 74 Analog value = 365 => brightness = 90 Analog value = 431 => brightness = 107 Analog value = 510 => brightness = 127 Analog value = 589 => brightness = 146 Analog value = 695 => brightness = 173 Analog value = 790 => brightness = 196 Analog value = 970 => brightness = 241 Analog value = 996 => brightness = 248 Analog value = 1018 => brightness = 253 Analog value = 4095 => brightness = 255

Autoscroll Show timestamp

Clear output

9600 baud

Newline

※ NOTE THAT:

This tutorial uses the analogRead() function to read values from an ADC (Analog-to-Digital Converter) connected to a potentiometer. The ESP32 ADC is good for projects that do NOT need high accuracy. However, for projects that need precise measurements, please note:

The ESP32 ADC is not perfectly accurate and might need calibration for correct results. Each ESP32 board can be a bit different, so you need to calibrate the ADC for each individual board.
Calibration can be difficult, especially for beginners, and might not always give the exact results you want.

For projects that need high precision, consider using an external ADC (e.g ADS1115) with the ESP32 or using an Arduino, which has a more reliable ADC. If you still want to calibrate the ESP32 ADC, refer to ESP32 ADC Calibration Driver

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