Chapter 5 RGB LED
In this chapter, we will learn how to control a RGB LED. It can emit different colors of light. Next, we will use RGB LED to make a multicolored light.
Project 5.1 Random Color Light
In this project, we will make a multicolored LED. And we can control RGB LED to switch different colors automatically.
Component List
ESP32-WROVER x1
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GPIO Extension Board x1
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Breadboard x1
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RGBLED x1
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Resistor 220Ω x1
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Jumper M/M x2
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Related knowledge
RGB LED has integrated 3 LEDs that can respectively emit red, green and blue light. And it has 4 pins. The long pin (1) is the common port, that is, 3 LED ‘s positive or negative port. The RGB LED with common positive port and its symbol is shown below. We can make RGB LED emit various colors of light by controlling these 3 LEDs to emit light with different brightness,
Red, green, and blue are known as three primary colors. When you combine these three primary-color lights with different brightness, it can produce almost all kinds of visible lights. Computer screens, single pixel of cell phone screen, neon, and etc. are working under this principle.
If we use three 8-bit PWMs to control the RGB LED, in theory, we can create 28*28*28=16777216 (16 million) colors through different combinations.
Circuit
Schematic diagram |
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Hardware connection |
If you need any support, please feel free to contact us via: support@freenove.com
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Sketch
We need to create three PWM channels and use random duty cycle to make random RGB LED color.
Sketch_05.1_ColorfulLight
With the code downloaded to ESP32-WROVER, RGB LED begins to display random colors.
If you need any support, please feel free to contact us via: support@freenove.com
The following is the program code:
1/**********************************************************************
2 Filename : ColorfulLight
3 Description : Use RGBLED to show random color.
4 Auther : www.freenove.com
5 Modification: 2024/06/18
6**********************************************************************/
7const byte ledPins[] = {4, 2, 15}; //define red, green, blue led pins
8const byte chns[] = {0, 1, 2}; //define the pwm channels
9int red, green, blue;
10void setup() {
11 for (int i = 0; i < 3; i++) { //setup the pwm channels,1KHz,8bit
12 ledcAttachChannel(ledPins[i], 1000, 8, chns[i]);
13 }
14}
15
16void loop() {
17 red = random(0, 256);
18 green = random(0, 256);
19 blue = random(0, 256);
20 setColor(red, green, blue);
21 delay(200);
22}
23
24void setColor(byte r, byte g, byte b) {
25 ledcWrite(ledPins[0], 255 - r); //Common anode LED, low level to turn on the led.
26 ledcWrite(ledPins[1], 255 - g);
27 ledcWrite(ledPins[2], 255 - b);
28}
Define the PWM channel and associate it with the pin connected to RGB LED, and define the variable to hold the color value and initialize it in setup().
1const byte ledPins[] = {4, 2, 15}; //define red, green, blue led pins
2const byte chns[] = {0, 1, 2}; //define the pwm channels
3int red, green, blue;
4void setup() {
5 for (int i = 0; i < 3; i++) { //setup the pwm channels,1KHz,8bit
6 ledcAttachChannel(ledPins[i], 1000, 8, chns[i]);
7 }
8}
In setColor(), this function controls the output color of RGB LED by the given color value. Because the circuit uses a common anode, the LED lights up when the GPIO outputs low power. Therefore, in PWM, low level is the active level, so 255 minus the given value is necessary.
1void setColor(byte r, byte g, byte b) {
2 ledcWrite(ledPins[0], 255 - r); //Common anode LED, low level to turn on the led.
3 ledcWrite(ledPins[1], 255 - g);
4 ledcWrite(ledPins[2], 255 - b);
5}
In loop(), get three random Numbers and set them as color values.
1red = random(0, 256);
2green = random(0, 256);
3blue = random(0, 256);
4setColor(red, green, blue);
5delay(200);
The related function of software PWM can be described as follows:
- long random(min, max);
This function will return a random number(min — max-1).
Project 5.2 Gradient Color Light
In the previous project, we have mastered the usage of RGB LED, but the random display of colors is rather stiff. This project will realize a fashionable light with soft color changes.
Component list and the circuit are exactly the same as the random color light.
Using a color model, the color changes from 0 to 255 as shown below.
In this code, the color model will be implemented and RGB LED will change colors along the model.
Sketch_05.2_SoftColorfulLight
The following is the program code:
1/**********************************************************************
2 Filename : SoftColorfulLight
3 Description : Colorful light with gradually changing color.
4 Auther : www.freenove.com
5 Modification: 2024/06/18
6**********************************************************************/
7const byte ledPins[] = {4, 2, 15}; //define led pins
8const byte chns[] = {0, 1, 2}; //define the pwm channels
9
10void setup() {
11 for (int i = 0; i < 3; i++) { //setup the pwm channels
12 ledcAttachChannel(ledPins[i], 1000, 8, chns[i]);
13 }
14}
15
16void loop() {
17 for (int i = 0; i < 256; i++) {
18 setColor(wheel(i));
19 delay(20);
20 }
21}
22
23void setColor(long rgb) {
24 ledcWrite(ledPins[0], 255 - (rgb >> 16) & 0xFF);
25 ledcWrite(ledPins[1], 255 - (rgb >> 8) & 0xFF);
26 ledcWrite(ledPins[2], 255 - (rgb >> 0) & 0xFF);
27}
28
29long wheel(int pos) {
30 long WheelPos = pos % 0xff;
31 if (WheelPos < 85) {
32 return ((255 - WheelPos * 3) << 16) | ((WheelPos * 3) << 8);
33 } else if (WheelPos < 170) {
34 WheelPos -= 85;
35 return (((255 - WheelPos * 3) << 8) | (WheelPos * 3));
36 } else {
37 WheelPos -= 170;
38 return ((WheelPos * 3) << 16 | (255 - WheelPos * 3));
39 }
40}
In setColor(), a variable represents the value of RGB, and a hexadecimal representation of color is a common representation, such as 0xAABBCC, where AA represents the red value, BB represents the green value, and CC represents the blue value. The use of a variable can make the transmission of parameters more convenient, in the split, only a simple operation can take out the value of each color channel
1void setColor(long rgb) {
2 ledcWrite(ledPins[0], 255 - (rgb >> 16) & 0xFF);
3 ledcWrite(ledPins[1], 255 - (rgb >> 8) & 0xFF);
4 ledcWrite(ledPins[2], 255 - (rgb >> 0) & 0xFF);
5}
The wheel() function is the color selection method for the color model introduced earlier. The pos parameter ranges from 0 to 255 and outputs a color value in hexadecimal.