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7.3. RGB LED Controller

Under construction
Short example demonstration video

Project which uses Red, Green and Blue LED that light up depending on the resistance measured by photoresistor.

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At the end of this example you will learn:

  • How to read analog value from photoresistor
  • How to control the LEDs displaying various colours
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Parts required:

  • Soldered NULA Mini Board
  • Breadboard
  • 1 x Red, Green, Blue LED
  • 3 x 330Ω resistors
  • 1 x 10kΩ resistor
  • 1 x Photoresistor
  • Some jumper wires
Under construction
Required components

Putting the components together​

  • Place the buzzer on the breadboard, connect the positive pin on GPIO 19, and other pin to GND.
  • For each pushbutton, place it on the breadboard, connect one terminal of the button to the pin declared in code, and the other terminal to GND using jumper wires.
  • Connect the LCD using Qwiic cable
Under construction
Components connected together

Code Example​

Import necessary modules.

from machine import Pin, ADC, PWM
import time

Define pins for LEDs and photoresistor

LDR_PIN = 5       # Analog input pin for photoresistor
RED_PIN = 2       # PWM pin for red LED channel
GREEN_PIN = 3     # PWM pin for green LED channel
BLUE_PIN = 4      # PWM pin for blue LED channel

Declare ADC object for photoresistor and PWM objects for LEDs.

adc = ADC(Pin(LDR_PIN))

pwm_r = PWM(Pin(RED_PIN), freq=PWM_FREQ)
pwm_g = PWM(Pin(GREEN_PIN), freq=PWM_FREQ)
pwm_b = PWM(Pin(BLUE_PIN), freq=PWM_FREQ)
PWM_FREQ = 1000   # PWM frequency in Hz

Function to map value from one range to another.

def map_range(x, in_min, in_max, out_min, out_max):
    if in_max == in_min:
        return out_min
    val = (x - in_min) * (out_max - out_min) // (in_max - in_min) + out_min
    return max(min(val, max(out_min, out_max)), min(out_min, out_max))

Main loop that reads LDR value and lights up LEDs based on that value.

# Main loop
while True:
    # Read LDR value
    ldr_value = adc.read() 
    print("LDR value:", ldr_value)

    # Map LDR value to RGB colors
    if ldr_value <= 1365:
        # Dark -> Red to Green
        r = map_range(ldr_value, 0, 1365, 255, 0)
        g = map_range(ldr_value, 0, 1365, 0, 255)
        b = 0
    elif ldr_value <= 2730:
        # Medium light -> Green to Blue
        r = 0
        g = map_range(ldr_value, 1366, 2730, 255, 0)
        b = map_range(ldr_value, 1366, 2730, 0, 255)
    else:
        # Bright -> Blue to White
        r = map_range(ldr_value, 2731, 4095, 0, 255)
        g = map_range(ldr_value, 2731, 4095, 0, 255)
        b = 255

    # Write PWM values to RGB pins
    pwm_r.duty(int(r * 1023 / 255))
    pwm_g.duty(int(g * 1023 / 255))
    pwm_b.duty(int(b * 1023 / 255))

    # Print RGB values
    print("RGB:", r, g, b)

    # Small delay
    time.sleep_ms(100)