Raspberry Pi - Potentiometer fade LED

In a previous tutorial, we discovered how a potentiometer can be used to trigger a LED. This tutorial instructs you how to use Raspberry Pi to adjust the brightness of the LED based on the output value of the potentiometer.

Hardware Preparation

1×Raspberry Pi 4 Model B
1×ADS1115 ADC Module
1×220 ohm resistor
1×Jumper Wires
1×(Optional) Screw Terminal Adapter for Raspberry Pi

Or you can buy the following sensor kits:

1×DIYables Sensor Kit (30 sensors/displays)
1×DIYables Sensor Kit (18 sensors/displays)
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Overview of LED and Potentiometer

If you are unfamiliar with LED and potentiometer (including pinout, functionality, programming, etc.), the following tutorials can help:

Wiring Diagram

The wiring diagram between Raspberry Pi and Rotary Potentiometer LED

This image is created using Fritzing. Click to enlarge image

Raspberry Pi Code

Detailed Instructions

  • Make sure you have Raspbian or any other Raspberry Pi compatible operating system installed on your Pi.
  • Make sure your Raspberry Pi is connected to the same local network as your PC.
  • Make sure your Raspberry Pi is connected to the internet if you need to install some libraries.
  • If this is the first time you use Raspberry Pi, See how to set up the Raspberry Pi
  • Connect your PC to the Raspberry Pi via SSH using the built-in SSH client on Linux and macOS or PuTTY on Windows. See to how connect your PC to Raspberry Pi via SSH.
  • Make sure you have the RPi.GPIO library installed. If not, install it using the following command:
sudo apt-get update sudo apt-get install python3-rpi.gpio
  • Install the Adafruit_ADS1x15 library by running the following commands on your Raspberry Pi terminal:
sudo pip install Adafruit-ADS1x15
  • Create a Python script file potentiometer_fade_led.py and add the following code:
# This Raspberry Pi code was developed by newbiely.com # This Raspberry Pi code is made available for public use without any restriction # For comprehensive instructions and wiring diagrams, please visit: # https://newbiely.com/tutorials/raspberry-pi/raspberry-pi-potentiometer-fade-led import time import Adafruit_ADS1x15 import RPi.GPIO as GPIO # Create an ADS1115 ADC object adc = Adafruit_ADS1x15.ADS1115() # Set the gain to ±4.096V (adjust if needed) GAIN = 1 # Define the GPIO pin for the LED LED_PIN = 16 # Change this to the appropriate GPIO pin # Set up GPIO for the LED GPIO.setmode(GPIO.BCM) GPIO.setup(LED_PIN, GPIO.OUT) # Define the PWM parameters PWM_FREQUENCY = 1000 # PWM frequency in Hz PWM_DUTY_CYCLE = 0 # Initial duty cycle (0 to 100) # Create a PWM object pwm_led = GPIO.PWM(LED_PIN, PWM_FREQUENCY) # Start PWM with the initial duty cycle pwm_led.start(PWM_DUTY_CYCLE) # Main loop to read the analog value and control LED brightness try: while True: # Read the raw analog value from channel A3 raw_value = adc.read_adc(3, gain=GAIN) # Convert the raw value to voltage voltage = raw_value / 32767.0 * 4.096 # Assumes 4.096 V range for GAIN=1 # Print the results print("Raw Value: {} \t Voltage: {:.2f} V".format(raw_value, voltage)) # Map the analog value to a duty cycle percentage (0 to 100) duty_cycle = int((raw_value / 32767.0) * 100) # Update the LED brightness with PWM pwm_led.ChangeDutyCycle(duty_cycle) # Add a delay between readings (adjust as needed) time.sleep(0.1) except KeyboardInterrupt: print("\nExiting the program.") # Stop PWM and clean up GPIO on exit pwm_led.stop() GPIO.cleanup()
  • Save the file and run the Python script by executing the following command in the terminal:
python3 potentiometer_fade_led.py
  • Turn the potentiometer.
  • Check out the LED's brightness.
  • Check out the output on the Terminal.
PuTTY - Raspberry Pi
Raw Value: 19736 Voltage: 2.39 V Raw Value: 19075 Voltage: 2.31 V Raw Value: 18409 Voltage: 2.23 V Raw Value: 17747 Voltage: 2.15 V Raw Value: 17086 Voltage: 2.07 V

The script runs in an infinite loop continuously until you press Ctrl + C in the terminal.

Video Tutorial


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