Lesson 1 Dual-Color LED

Introduction

A dual-color light emitting diode (LED) is capable of emitting two different colors of light, typically red and green, rather than only one color. It is housed in a 3mm or 5mm epoxy package. It has 3 leads; common cathode or common anode is available. A dual-color LED features two LED terminals, or pins, arranged in the circuit in anti-parallel and connected by a cathode/anode. Positive voltage can be directed towards one of the LED terminals, causing that terminal to emit light of the corresponding color; when the direction of the voltage is reversed, the light of the other color is emitted. In a dual-color LED, only one of the pins can receive voltage at a time. As a result, this type of LED frequently functions as indicator lights for a variety of devices, including televisions, digital cameras, and remote controls.

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Required Components

  • 1 * Raspberry Pi

  • 1 * Breadboard

  • Several Jumper wires

  • 1 * Dual-color LED module

  • 1 * 3-Pin anti-reverse cable

Experimental Principle

Connect pin R and G to GPIOs of Raspberry Pi, program the Raspberry Pi to change the color of the LED from red to green, and then use PWM to mix into other colors.

The schematic diagram of the module is as shown below:

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Experimental Procedures

Step 1: Build the circuit.

Raspberry Pi

GPIO Extension Board

Dual-Color LED Module

GPIO0

GPIO17

R

GND

GND

GND

GPIO1

GPIO18

G
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For C Users:

Step 2: Change directory.

cd /home/pi/SunFounder_SensorKit_for_RPi2/C/01_dule_color_led/

Step 3: Compile.

gcc dule_color_led.c -lwiringPi -lpthread

Note

If it does not work after running, or there is an error prompt wiringPi.h: No such file or directory, please refer to WiringPi to install it.

Step 4: Run.

sudo ./a.out

Code

#include <wiringPi.h>
#include <softPwm.h>
#include <stdio.h>

#define uchar unsigned char

#define LedPinRed    0
#define LedPinGreen  1

void ledInit(void)
{
    softPwmCreate(LedPinRed,  0, 100);
    softPwmCreate(LedPinGreen,0, 100);
}

void ledColorSet(uchar r_val, uchar g_val)
{
    softPwmWrite(LedPinRed,   r_val);
    softPwmWrite(LedPinGreen, g_val);
}

int main(void)
{
    int i;

    if(wiringPiSetup() == -1){ //when initialize wiring failed,print messageto screen
        printf("setup wiringPi failed !");
        return 1;
    }
    //printf("linker LedPin : GPIO %d(wiringPi pin)\n",LedPin); //when initialize wiring successfully,print message to screen

    ledInit();

    while(1){
        ledColorSet(0xff,0x00);   //red
        delay(500);
        ledColorSet(0x00,0xff);   //green
        delay(500);
        ledColorSet(0xff,0x45);
        delay(500);
        ledColorSet(0xff,0xff);
        delay(500);
        ledColorSet(0x7c,0xfc);
        delay(500);
    }

    return 0;
}

For Python Users:

Step 2: Change directory.

cd /home/pi/SunFounder_SensorKit_for_RPi2/Python/

Step 3: Run.

sudo python3 01_dule_color_led.py

Code

#!/usr/bin/env python3
import RPi.GPIO as GPIO
import time

colors = [0xFF00, 0x00FF, 0x0FF0, 0xF00F]
pins = (11, 12)  # pins is a dict

GPIO.setmode(GPIO.BOARD)       # Numbers GPIOs by physical location
GPIO.setup(pins, GPIO.OUT)   # Set pins' mode is output
GPIO.output(pins, GPIO.LOW)  # Set pins to LOW(0V) to off led

p_R = GPIO.PWM(pins[0], 2000)  # set Frequece to 2KHz
p_G = GPIO.PWM(pins[1], 2000)

p_R.start(0)      # Initial duty Cycle = 0(leds off)
p_G.start(0)

def map(x, in_min, in_max, out_min, out_max):
    return (x - in_min) * (out_max - out_min) / (in_max - in_min) + out_min

def setColor(col):   # For example : col = 0x1122
    R_val = col  >> 8
    G_val = col & 0x00FF

    R_val = map(R_val, 0, 255, 0, 100)
    G_val = map(G_val, 0, 255, 0, 100)

    p_R.ChangeDutyCycle(R_val)     # Change duty cycle
    p_G.ChangeDutyCycle(G_val)

def loop():
    while True:
        for col in colors:
            setColor(col)
            time.sleep(0.5)

def destroy():
    p_R.stop()
    p_G.stop()
    GPIO.output(pins, GPIO.LOW)    # Turn off all leds
    GPIO.cleanup()

if __name__ == "__main__":
    try:
        loop()
    except KeyboardInterrupt:
        destroy()

You can see the dual-color LED render green, red, and mixed colors.

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