5.8 Turn the Knob

A potentiometer is a three-terminal device that is commonly used to adjust the resistance in a circuit. It features a knob or a sliding lever that can be used to vary the resistance value of the potentiometer. In this project, we will utilize it to control the brightness of an LED, similar to a desk lamp in our daily life. By adjusting the position of the potentiometer, we can change the resistance in the circuit, thereby regulating the current flowing through the LED and adjusting its brightness accordingly. This allows us to create a customizable and adjustable lighting experience, similar to that of a desk lamp.

Required Components

In this project, we need the following components.

It’s definitely convenient to buy a whole kit, here’s the link:

Name

ITEMS IN THIS KIT

LINK

ESP32 Starter Kit

320+

ESP32 Starter Kit

You can also buy them separately from the links below.

COMPONENT INTRODUCTION

PURCHASE LINK

ESP32 WROOM 32E

BUY

ESP32 Camera Extension

-

Breadboard

BUY

Jumper Wires

BUY

Resistor

BUY

LED

BUY

Potentiometer

BUY

Available Pins

  • Available Pins

    Here is a list of available pins on the ESP32 board for this project.

    Available Pins

    IO14, IO25, I35, I34, I39, I36

  • Strapping Pins

    The following pins are strapping pins, which affect the startup process of the ESP32 during power on or reset. However, once the ESP32 is booted up successfully, they can be used as regular pins.

    Strapping Pins

    IO0, IO12

Schematic

../../_images/circuit_5.8_potentiometer.png

When you rotate the potentiometer, the value of I35 will change. By programming, you can use the value of I35 to control the brightness of the LED. Therefore, as you rotate the potentiometer, the brightness of the LED will also change accordingly.

Wiring

../../_images/5.8_potentiometer_bb.png

Code

Note

  • Open the 5.8_turn_the_knob.py file located in the esp32-starter-kit-main\micropython\codes path, or copy and paste the code into Thonny. Then, click “Run Current Script” or press F5 to execute it.

  • Make sure to select the “MicroPython (ESP32).COMxx” interpreter in the bottom right corner.

from machine import ADC, Pin, PWM
import time

pot = ADC(Pin(35, Pin.IN)) # create an ADC object acting on a pin

# Configure the ADC attenuation to 11dB for full range
pot.atten(pot.ATTN_11DB)

# Create a PWM object
led = PWM(Pin(26), freq=1000)

while True:
    # Read a raw analog value in the range of 0-4095
    value = pot.read()

    # Scale the value to the range of 0-1023 for ESP32 PWM duty cycle
    pwm_value = int(value * 1023 / 4095)

    # Update the LED brightness based on the potentiometer value
    led.duty(pwm_value)

    # Read the voltage in microvolts and convert it to volts
    voltage = pot.read_uv() / 1000000

    # Print the raw value and the voltage
    print(f"value: {value}, Voltage: {voltage}V")

    # Wait for 0.5 seconds before taking the next reading
    time.sleep(0.5)

With this script run, the LED brightness changes as the potentiometer is rotated, while the analog value and voltage at this point are displayed in the Shell.