Potentiometer, NeoPixel RGB

Video Tutorial

you can watch this video tutorial

Hardware Required

About this project

Introduction to LED Strip

please review our tutorial about LED Strip

Introduction to Potentiometer

The potentiometer (also known as rotary angle sensor) is used to change the settings (e.g. the speaker's volume, room's temperature, lamp's brightness...)

potentiometer Pinout

A potentiometer usually has 3 pins:

• VCC pin: connect this pin to VCC (5V or 3.3v)
• GND pin: connect this pin to GND (0V)
• Output pin: outputs the voltage to ESP32's input pin.

How Potentiometer Works

The potentiometer's shaft can be rotated from 0° (closest to GND pin) to an angle (closest to VCC pin), called ANGLE_MAX.

The voltage in the output pin is in direct proportion to the angle position of the shaft, varing from 0 to VCC. The below table shows the relation between the angle and the voltage on the output pin:

ESP32 - Rotary Potentiometer

The ESP32's analog input pin converts the voltage (between 0v and 3.3V) into integer values (between 0 and 4095), called ADC value or analog value.

We can connect the potentiometer's output pin to an ESP32's analog input pin, and then read the analog value from the pin.

The analog value from input pin can be rescaled into another value. Let's see the use cases:

• Rescale the analog value to the potentiometer's angle.
• Rescale the analog value to the potentiometer's voltage.
• Rescale the analog value to the the setting value (e.g. the speaker's volume, room's temperature, lamp's brightness...)

Rescale Range

Wiring Diagram

Breadboard Connections with LED Strip

Image is developed using Fritzing. Click to enlarge image

Breadboard Connections with potentiometer

Image is developed using Fritzing. Click to enlarge image

click to see ESP32 pin out

ESP32 Code

#include <Adafruit_NeoPixel.h>

#define potPIN           4

#define NeopixelPIN      15
#define N_LEDS 60

float potValue;
int ledCount;

Adafruit_NeoPixel strip = Adafruit_NeoPixel(N_LEDS, NeopixelPIN, NEO_GRB + NEO_KHZ800);

void setup() {
  strip.begin();
  pinMode(potPIN,INPUT);
  Serial.begin(9600);
}

void loop() {
  potValue = analogRead(potPIN);
  ledCount = floatMap(potValue, 0, 4095, 1, 60);
  uint32_t c = strip.Color(255, 0, 0);

  for(uint16_t i=0; i<ledCount; i++) {
      strip.setPixelColor(i  , c); // Draw new pixel
      strip.show();
      //delay(25);
  }
  for(uint16_t i=0; i<60-ledCount; i++) {
      strip.setPixelColor(60-i, 0); // Erase pixel a few steps back
      strip.show();
      //delay(25);
  }
}


float floatMap(float x, float in_min, float in_max, float out_min, float out_max) {
  return (x - in_min) * (out_max - out_min) / (in_max - in_min) + out_min;
}           

Book Tutorial

We are considering to make the book tutorials. If you think the book tutorials are essential, you can download it. download book

See Also

• ESP32 - Button - Debounce
• ESP32 - Button - Long Press Short Press
• ESP32 - Button Toggle LED

References

• Arduino IDE
• ESP32