I'm new in Processing. 

My idea is to detect real-time motion and then write the information hereof to my Arduino causing a led lighting up. I though this peace of code would do it. The image processing part is great, but I can't make the movementSum > 0 turn on ledPin13... It's only blinking for a while and then nothing... Any ideas to how i can make it work will be apreciated :)   

2. import processing.serial.*;
3. import cc.arduino.*;
4. import processing.video.*;
5. 
   
6. Arduino arduino;
7. 
   
8. int ledPin = 13;
9. int numPixels;
10. int[] previousFrame;
11. Capture video;
12. 
    
13. void setup() {
14.   size(640, 480); // Change size to 320 x 240 if too slow at 640 x 480
15.   // Uses the default video input, see the reference if this causes an error
16.   video = new Capture(this, width, height, 24);
17.   numPixels = video.width * video.height;
18.   // Create an array to store the previously captured frame
19.   previousFrame = new int[numPixels];
20.   loadPixels();
21.   
22.   println(Arduino.list());
23.   arduino = new Arduino(this, Serial.list()[1], 57600);
24.   for (int i = 0; i <= 13; i++)
25.     arduino.pinMode(i, Arduino.OUTPUT);
26. }
27. 
    
28. void draw() {
29.   if (video.available()) {
30.     // When using video to manipulate the screen, use video.available() and
31.     // video.read() inside the draw() method so that it's safe to draw to the screen
32.     video.read(); // Read the new frame from the camera
33.     video.loadPixels(); // Make its pixels[] array available
34.     
35.     int movementSum = 0; // Amount of movement in the frame
36.     for (int i = 0; i < numPixels; i++) { // For each pixel in the video frame...
37.       
38.       color currColor = video.pixels[i];
39.       color prevColor = previousFrame[i];
40.       // Extract the red, green, and blue components from current pixel
41.       int currR = (currColor >> 16) & 0xFF; // Like red(), but faster
42.       int currG = (currColor >> 8) & 0xFF;
43.       int currB = currColor & 0xFF;
44.       // Extract red, green, and blue components from previous pixel
45.       int prevR = (prevColor >> 16) & 0xFF;
46.       int prevG = (prevColor >> 8) & 0xFF;
47.       int prevB = prevColor & 0xFF;
48.       // Compute the difference of the red, green, and blue values
49.       int diffR = abs(currR - prevR);
50.       int diffG = abs(currG - prevG);
51.       int diffB = abs(currB - prevB);
52.       // Add these differences to the running tally
53.       movementSum += diffR + diffG + diffB;
54.       // Render the difference image to the screen
55.       pixels[i] = color(diffR, diffG, diffB);
56.       // The following line is much faster, but more confusing to read
57.       //pixels[i] = 0xff000000 | (diffR << 16) | (diffG << 8) | diffB;
58.       // Save the current color into the 'previous' buffer
59.       previousFrame[i] = currColor;
60.     }
61.     // To prevent flicker from frames that are all black (no movement),
62.     // only update the screen if the image has changed.
63.       updatePixels();
64.       println(movementSum); // Print the total amount of movement to the console
65.       
66.       if (movementSum > 0) {
67.  arduino.digitalWrite(ledPin, arduino.HIGH); // turn the LED on
68.  } else {
69.  arduino.digitalWrite(ledPin, arduino.LOW); // Otherwise turn it OFF
70.     }
71.   }
72. }