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 | × | Potentiometer | |
| 1 | × | ADS1115 ADC Module | |
| 1 | × | LED | |
| 1 | × | 220 ohm resistor | |
| 1 | × | Breadboard | |
| 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
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.