What is RGB LED : Circuit and Its Working

A LED (Light Emitting Diode) is a semiconductor device that works on the principle of electro luminous. The term electro luminous was discovered by combining  Silicon Carbide and a Cat whisker detector in the year 1907 by H.J Round of Marconi Lab. The very first usage of commercial LED  was to overcome the drawbacks of incandescent, neon indicator lamps, and a 7 segment display. The main advantage of using these LEDs is that they are small in size, longer lifetime, good switching speed, etc.  Hence by using different semiconductor elements and changing their intensity property we can obtain single color LED in different color LEDs, like Blue and ultraviolent LED, White LED, OLED’s, Other white LEDs. The color of the light can be determined based on the energy gap of the semiconductor. The following article explains about RGB LED which one of the sub-classification of white LED.

What is an RGB LED?

Definition: A white light produce by mixing 3 different colors like RGB- Red, Green, and Blue is an RGB LED. The main purpose of this RGB model is for sensing, representation, and displaying images in the electronic system.


RGB LED Structure

White light can be generated by combining 3 different colors like green, red, blue, or by using phosphor material. This LED consist of 3 terminals (RGB in color) which are present internally and a long lead which is present is either a cathode or an anode as shown below

RGB LED Structure
RGB LED Structure

These 3 LED’s on combining they produce a single color output light, and by changing the intensity of the internal individual LED’s we can obtain any desired output color light. There are 2 types of LED’s, they are common cathode or common anode which are similar to a 7 segment LED.

Structure of Common Anode and Common Cathode LED

The structure of Common Anode and Common Cathode LED consists of 4 terminals, where the first terminal is “R” the second terminal is “Anode +” or “Cathode –“, the third terminal is “G” and the fourth terminal is “B” as shown below

Structure of Common Anode and Common Cathode RGB LED
Structure of Common Anode and Common Cathode RGB LED

In a common anode configuration, the colors can be controlled by applying a low power signal or by grounding the RGB pins and connecting the internal anode to a positive lead of the supply as shown below

PCBWay

Common Anode Configuration
Common Anode Configuration

In common Cathode configuration, the colors can be controlled by applying a high power input to the RGB pins and connecting the internal cathode to a negative lead of the supply as shown below

Common Cathode Configuration
Common Cathode Configuration

The Color Setting of an RGB LED on Interfacing with an Arduino Uno

The desired color output can be obtained from RGB LED using CCR – Constant Current Resource or PWM technique. For a better result, we use PWM and Arduino Uno modules along with an RGB LED circuit.

Components Used

  • Arduino Uno
  • RGB LED with Common Cathode configuration
  • 100Ω Resistors 3 in numbers
  • 1kΩ Potentiometers 3 in numbers
  • Jumper Wires 3 in number.

Arduino Uno PIN Diagram

An Arduino Uno consists of a 14 digital input and output pin, 6 analog input pins, one USB pin, one 16MHz resonator, 16 MHz quartz crystal, a power jack, an ICSP header, and an RST button. Power: The IC is provided up to 12 V of external power,

  • Memory: ATmega 328 microcontroller contains 32KB of memory, and also 2KB SRAM, and 1KB EEPROM
  • Serial Pins: TX 1 and RX 0 pins used for communication for transferring and receiving of data between peripherals.
  • External Interrupt Pins: Pin 2 and Pin3 are external interrupt pins that are activated when the clock goes high or low.
  • PWM Pins: The PWM pins are 3,5,6,9,10 and 11 which gives an 8bit output
  • SPI pins: Pin 10,11,12,13
  • LED pin: pin13, LED glows when this pin goes high
  • TWI Pins: A4 and A5, helps in communication
  • AREF Pin: analog reference pin is the voltage reference pin
  • RST Pin: used for resetting the microcontroller when required.

Schematic Diagram

The 3 potentiometers are shorted with, the pin A0, pin A1, and pin A2 of the ADC channel of Arduino Uno. Where this ADC reads the voltage which is in analog form across potentiometer and depending on the voltage obtained, the PWM signals duty signal can be adjusted using Arduino Uno where RGB LED intensity can be controlled using D9 D10 D11 pins of Arduino Uno. The color setting of this LED when interfaced with Arduino Uno can be constructed in 2 ways, which is either in the common cathode or common anode method as shown below

Common Anode Configuration
Common Anode Configuration

 

Schematic Diagram for Common Anode RGB LED
Schematic Diagram for Common Anode RGB LED

 

Common Cathode Configuration
Common Cathode Configuration

 

Schematic Diagram for Common Cathode RGB LED
Schematic Diagram for Common Cathode RGB LED

In order to understand the working of RGB LED using Arduino Uno, software code is helpful in understanding the circuit. By running the code, we can observe the LED glowing with RGB color.

Advantages of RGB LED

The following are the advantages

  • It occupies less area
  • Small in size
  • Less weight
  • Greater efficiency
  • Toxicity is less
  • Contract and brightness of the light is better compared to other LED
  • Good maintenance of Lumen.

Disadvantages of RGB LED

The following are the disadvantages

  • Cost of manufacturing is high
  • Dispersion of color
  • The shift in color.

Applications of RGB LED

The following are the applications

  • LCD
  • CRT
  • Indoor and Outdoor lighting
  • Automotive industries
  • They are used in mobile applications.

Thus, this is all about an overview of the RGB LED. The LED is a semiconductor device that emits light on supplying external power. It works on the principle of electroluminescence. There are different types of LED’s available like Blue and ultraviolent LED, White LED ( RGB LED or using Phosphor material in LED), OLED’s, Other white LED’s. The mixing 3 different colors like Blue, Green, and Red a white light is generated this kind of LED is called RGB LED. They can be represented in 2 ways Common Anode and Common Cathode method. The main function of RGB LEDs is sensing, representation, and displaying images in the electronic system.

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