Team U.tu4pm:

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Alvaro Camacho Guadamuz

Published April 19, 2020

At Last I See the Light

See alll the colors in light through a RGB LED that cycles through colors with a tilt switch. It's brilliant stuff!

BeginnerShowcase (no instructions)1 hour442

Things used in this project

Hardware components

Texas Instruments EK-TM4C123GXL TM4C Tiva LaunchPad

Powerful microprocessor used to compile our code and coordinate the use of the tilt switch with the RGB LED.

Breadboard (generic)

Tilt Switch, SPST

Jumper wires (generic)

Software apps and online services

Texas Instruments Energia

Story

Part One: Defining the Problem

As a team we reviewed the various products that our customer requested for us to design. Our customer had hired other engineering groups to build other designs. Thus, we only had to select one project. One of the first projects that we looked at was one involving a photoresistor with a 7 segment display. This project involved displaying a light at varying intensities depending on the brightness detected by the photoresistor, ideally so that a light would be displayed when in the darkness and no light would display when in the light. Another option that we had was a project involving a buzzer that would have varying output based on the value read by a potentiometer. In addition to this, we had the option of creating a display that counted how many times a button was pressed. Additionally, we could create an RGB LED that would fade between the colors of the rainbow continuously.

Part Two: Brainstorming and Choosing Project...

One of our teammates, Alvarro, remembered that there is already a working RGB LED on our TIVA processor and that we had already worked on projects regarding changing LED colors. Thus, we decided that with our previous experience and the powerful applications of a fading RGB LED, we decided to pursue the fading RGB LED project. We thought it was important to understand how LED displays work because of their versatile applications utilized n almost every sort of mobile device from smartphones, smartwatches, and computer monitors.

Part Three: Develop

We began to build our project using the Launchpad and Energia. We wired up the boards and wrote code in C.

Our customer originally gave us the following hue chart to follow:

Original Color Chart

We developed the product, but upon looking at our product, the customer communicated with us that they wanted a different color pattern. The updated color chart they gave us looked like this:

Final Color Chart

This was our board set-up:

Wiring the Board

Then, our customer let us know that they also wanted the RGB color fade to switch directions in response to a tilt switch. So we added in additional feature, and wired it up! (The schematics of the set-up can be found in the Schematic section...)

Wiring the Breadboard to the Launchpad

Part Four: Testing

Watch our fading RGB LED in action! After much trial and error, the RGB LED finally works! The color fade matches the given color chart and it switches direction in response to the tilt switch!

RGB LED in Action!

Code

RGB Fading Light

#define Cols 8
# define ENABLE 29

/* Defining RGB Colors to fade through */
int colours[Cols][3] = {
  {255,   0,   0}, // Red
  {171,  85,   0}, // Orange
  {171, 171,   0}, // Yellow
  {  0, 255,   0}, // Green
  {  0, 171,  85}, // Aqua
  {  0,   0, 255}, // Blue
  { 85,   0, 171}, // Purple
  {171,   0,  85} // Pink
};

int LED[3] = {RED_LED, GREEN_LED, BLUE_LED};
int steps = 50;
int current_col = 1;
int math;
int bright;
int interval;

/* Function to select the next color. Loops around from pink to red */
int NEXT(int i){
  return (i+1) % Cols;
}


/* Function to interpolate between colors */
int Linear(int col_1, int step_N, int led){
  int math;
  int col_2;
  col_2=NEXT(col_1);
  math=(colours[col_1][led]*(steps-step_N)+colours[col_2][led]*step_N)/steps;
  return math;
}


void setup()  { 

  /* Setting up the LED and the initial conditions */
  for(int i=0; i<3;i++){
    pinMode(LED[i],OUTPUT);
    analogWrite(LED[i],colours[0][i]);
  }

  /* Setting tilt switch pin as input */
  pinMode(ENABLE, INPUT);
} 


  
void loop()  { 
  /* Looping from color to color (i), from interpolation value to interpolation value (j),
   and from LED to LED (k) */
  for (int i=0; i<Cols; i++){
    for (int j=0; j<steps; j++){
       for (int k=0; k<3; k++){

        /* Calculating and applying luminance values */
             bright=Linear(i,j,k);
             analogWrite(LED[k], bright);
           }
           delay(5);

           /* Enters infinite loop while the tilt switch is enabled */
           interval=digitalRead(ENABLE);
           while(interval){
            interval=digitalRead(ENABLE);
           }
    }
  }
}

At Last I See the Light