Raspberry Pi 4 Project 01

LED Bar Graph Pulsating Project

This project involves creating a 10-LED bar graph that pulsates light using a Raspberry Pi 4 and Python code. The LED bar graph will have 10 bars, each controlled by a GPIO pin on the Raspberry Pi.

Required Materials

To complete this project, you will need the following materials:

• Raspberry Pi 4
• Breadboard
• 10 Segment LED Bar Graph | Part COM-09937 (or 10 LEDs in a pinch)
• 10 220-ohm resistors
• Jumper wires

Each LED is connected to a GPIO pin on the Raspberry Pi through a 220-ohm resistor. The GPIO pins used for each LED are as follows:

• LED 1: GPIO 21
• LED 2: GPIO 20
• LED 3: GPIO 16
• LED 4: GPIO 12
• LED 5: GPIO 7
• LED 6: GPIO 8
• LED 7: GPIO 25
• LED 8: GPIO 24
• LED 9: GPIO 23
• LED 10: GPIO 18

Python Code

The Python code for this project is shown below:

import RPi.GPIO as GPIO
import time

# Set the GPIO pins for the LED bar graph
led_pins = [21, 20, 16, 12, 7, 8, 25, 24, 23, 18]

# Set the GPIO mode to BCM
GPIO.setmode(GPIO.BCM)

# Set the LED pins as output
for pin in led_pins:
    GPIO.setup(pin, GPIO.OUT)

# Set the initial duty cycle for the LEDs
dc = 0

# Loop forever
while True:
    # Increase the duty cycle from 0 to 100 in steps of 5
    for dc in range(0, 101, 5):
        # Set the duty cycle for each LED
        for i in range(len(led_pins)):
            GPIO.output(led_pins[i], dc > (i*10))
            # ^^^ If the duty cycle is greater than the threshold for this LED, turn it on.

        # Wait a short amount of time
        time.sleep(0.05)

    # Decrease the duty cycle from 100 to 0 in steps of 5
    for dc in range(100, -5, -5):
        # Set the duty cycle for each LED
        for i in range(len(led_pins)):
            GPIO.output(led_pins[i], dc > (i*10))
            # ^^^ If the duty cycle is greater than the threshold for this LED, turn it on.

        # Wait a short amount of time
        time.sleep(0.05)

# Cleanup when the program is stopped
GPIO.cleanup()