Prototyping

Use alligator clips to test the circuit before soldering the components. Lets start with getting the accelerometer to light up the neopixel ring. We can use USB to power the FLORA after we have our components clipped together.

Accelerometer

  • GND to GND
  • SCL to SCL
  • 3V to 3.3V
  • SDA to SDA

NeoPixel Ring

  • IN to D10
  • GND to GND
  • Vcc to VBATT

Arduino Sketch

Copy the code below into your Adafruit Arduino IDE and click Upload. The colors can be specified in the myFavoriteColors array, and the sensitivity to motion can be defined with MOVE_THRESHOLD.
#include <Wire.h>
#include <Adafruit_LSM303.h>
#include <Adafruit_NeoPixel.h>

// Parameter 1 = number of pixels in strip
// Parameter 2 = pin number (most are valid)
// Parameter 3 = pixel type flags, add together as needed:
//   NEO_RGB     Pixels are wired for RGB bitstream
//   NEO_GRB     Pixels are wired for GRB bitstream
//   NEO_KHZ400  400 KHz bitstream (e.g. FLORA pixels)
//   NEO_KHZ800  800 KHz bitstream (e.g. High Density LED strip)
Adafruit_NeoPixel strip = Adafruit_NeoPixel(16, 10, NEO_GRB + NEO_KHZ800);
Adafruit_LSM303 lsm;

// Here is where you can put in your favorite colors that will appear!
// just add new {nnn, nnn, nnn}, lines. They will be picked out randomly
//                                  R   G   B
uint8_t myFavoriteColors[][3] = {{200,   0, 200},   // purple
                                 {0,   117,   255},   // blue 
                                 {200, 200, 200},   // white
                               };
// don't edit the line below
#define FAVCOLORS sizeof(myFavoriteColors) / 3

// mess with this number to adjust TWINklitude :)
// lower number = more sensitive
#define MOVE_THRESHOLD 300

void setup() 
{
  Serial.begin(9600);
  
  // Try to initialise and warn if we couldn't detect the chip
  if (!lsm.begin())
  {
    Serial.println("Oops ... unable to initialize the LSM303. Check your wiring!");
    while (1);
  }
  strip.begin();
  strip.show(); // Initialize all pixels to 'off'
}

void loop() 
{
  // Take a reading of accellerometer data
  lsm.read();
  Serial.print("Accel X: "); Serial.print(lsm.accelData.x); Serial.print(" ");
  Serial.print("Y: "); Serial.print(lsm.accelData.y);       Serial.print(" ");
  Serial.print("Z: "); Serial.print(lsm.accelData.z);     Serial.print(" ");

  // Get the magnitude (length) of the 3 axis vector
  // http://en.wikipedia.org/wiki/Euclidean_vector#Length
  double storedVector = lsm.accelData.x*lsm.accelData.x;
  storedVector += lsm.accelData.y*lsm.accelData.y;
  storedVector += lsm.accelData.z*lsm.accelData.z;
  storedVector = sqrt(storedVector);
  Serial.print("Len: "); Serial.println(storedVector);
  
  // wait a bit
  delay(100);
  
  // get new data!
  lsm.read();
  double newVector = lsm.accelData.x*lsm.accelData.x;
  newVector += lsm.accelData.y*lsm.accelData.y;
  newVector += lsm.accelData.z*lsm.accelData.z;
  newVector = sqrt(newVector);
  Serial.print("New Len: "); Serial.println(newVector);
  
  // are we moving 
  if (abs(newVector - storedVector) > MOVE_THRESHOLD) {
    Serial.println("Twinkle!");
    flashRandom(5, 1);  // first number is 'wait' delay, shorter num == shorter twinkle
    flashRandom(5, 3);  // second number is how many neopixels to simultaneously light up
    flashRandom(5, 2);
  }
}

void flashRandom(int wait, uint8_t howmany) {

  for(uint16_t i=0; i<howmany; i++) {
    // pick a random favorite color!
    int c = random(FAVCOLORS);
    int red = myFavoriteColors[c][0];
    int green = myFavoriteColors[c][1];
    int blue = myFavoriteColors[c][2]; 

    // get a random pixel from the list
    int j = random(strip.numPixels());
    //Serial.print("Lighting up "); Serial.println(j); 
    
    // now we will 'fade' it in 5 steps
    for (int x=0; x < 5; x++) {
      int r = red * (x+1); r /= 5;
      int g = green * (x+1); g /= 5;
      int b = blue * (x+1); b /= 5;
      
      strip.setPixelColor(j, strip.Color(r, g, b));
      strip.show();
      delay(wait);
    }
    // & fade out in 5 steps
    for (int x=5; x >= 0; x--) {
      int r = red * x; r /= 5;
      int g = green * x; g /= 5;
      int b = blue * x; b /= 5;
      
      strip.setPixelColor(j, strip.Color(r, g, b));
      strip.show();
      delay(wait);
    }
  }
  // LEDs will be off when done (they are faded to 0)
}

This guide was first published on Jan 09, 2014. It was last updated on Jan 09, 2014.

This page (Circuit Diagram) was last updated on Apr 17, 2021.

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