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• TCS3200 color sensor with k-Nearest Neighbor classification algorithm

  M. Bindhammer • 03/03/2019 at 14:14 • 0 comments

  The k-NN (k-nearest neighbors) algorithm is among the simplest of all machine learning algorithms. We will use this algorithm to classify the color of a new object. As our training set of learned colors will only contain one sample per color, k = 1, and the object is simply assigned to the class of that single nearest neighbor. We will work in a 3-dimensional Euclidean space ℝ³. The x-axis represents the ratio of the clear channel frequency to the red channel frequency, the y-axis the ratio of the clear channel frequency to the green channel frequency and the z-axis the ratio of the clear channel frequency to the blue channel frequency (see TCS3200 data sheet for more details).

  The image below illustrates the 3-dimensional Euclidean space, the trained colors (white, orange, yellow, red, green and blue point) and a new sample (black point), which color needs to be classified. The black lines are the so called Euclidean distances from the new sample point to every trained color point. All we need to do is to find the smallest distance.

  Fig. 1 Euclidean distances of RGB values
  

  In general, for an n-dimensional Euclidean space ℝⁿ, the Euclidean distance between two points

  and

  is given by

  Trouble shooting:
  

  • Colored objects shall be non glossy
  • Best work colored paper post-it notes (or sticky notes) with a large surface area of at least 8100 square millimeters
  • Always keep the same distance from the color sensor resp. collimator lens to the object
  • Fix the distance of the collimator lens to the TCS3200 color sensor itself by using Loctite or other glue or a small screw. The distance itself is unproblematic

  Machine learning code:

  #include <SPI.h>
  #include <Wire.h>
  #include <Servo.h>
  #include <Adafruit_GFX.h>
  #include <Adafruit_SSD1306.h>
  #include "musical_notes.h"
  #define SCREEN_WIDTH 128 /* OLED display width */
  #define SCREEN_HEIGHT 64 /* OLED display height */
  
  /* Declaration for an SSD1306 display connected to I2C (SDA, SCL, reset pin) */
  #define OLED_RESET 9 /* Reset pin */
  Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, OLED_RESET);
  
  byte LED = 8, S0 = 7, S1 = 6, S2 = 5, S3 = 4, OUT = 3;
  char* color[] = {"white", "orange", "yellow", "red", "green", "blue", "out of range"};
  char point[] = "Point color sensor to";
  char object[] = " object";
  char submit[] = "Press the push buttonif it's done";
  int learned_colors[3][6];
  int PercentageRed, PercentageGreen, PercentageBlue;
  float OutOfRange;
  int switchPin = 23;
  int debounce = 200;
  /* Speaker connected to digital pin 26 */
  int speakerPin = 26;
  
  void setup() {
    Serial.begin(9600);
    /* Init OLED */
    display.begin(SSD1306_SWITCHCAPVCC, 0x3D);
    /* Clear the buffer */
    display.clearDisplay();
    TCS3200_Setup();
    pinMode(switchPin, INPUT);
    pinMode(speakerPin, OUTPUT); 
  }
  
  void loop() {
    learning_mode();
    while(1) {
      new_sample();
      classify();
    }
  }
  
  void TCS3200_Setup() {
    pinMode(S0,OUTPUT);
    pinMode(S1,OUTPUT);
    pinMode(S2,OUTPUT);
    pinMode(S3,OUTPUT);
    pinMode(LED,OUTPUT);
    pinMode(OUT,INPUT);
  }
  
  void TCS3200_On() {
    digitalWrite(LED,HIGH); // switch LED on
    digitalWrite(S0,HIGH); // output frequency scaling (100%)
    digitalWrite(S1,HIGH);
    delay(5);
  }
  
  void TCS3200_Off() {
    digitalWrite(LED,LOW); // switch LED off
    digitalWrite(S0,LOW); // power off sensor
    digitalWrite(S1,LOW);
  }
  
  void NoFilter() {
    digitalWrite(S2,HIGH); // select no filter
    digitalWrite(S3,LOW);
    delay(5);
  }
  
  void RedFilter() {
    digitalWrite(S2,LOW); // select red filter
    digitalWrite(S3,LOW);
    delay(5);
  }
  
  void GreenFilter() {
    digitalWrite(S2,HIGH); // select green filter
    digitalWrite(S3,HIGH);
    delay(5);
  }
  
  void BlueFilter() {
    digitalWrite(S2,LOW); // select blue filter
    digitalWrite(S3,HIGH);
    delay(5);
  }
  
  void input() {
    while (1) {
      if(digitalRead(switchPin) == 1) {
        squeak();
        break;
      }
    }
  }
  
  void GetColor() {
    float FrequencyClear, FrequencyRed, FrequencyGreen, FrequencyBlue;
    TCS3200_On();
    NoFilter();
    FrequencyClear = float(pulseIn(OUT,LOW,...

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