Removing the abs() call should take care of the problem. With it in, the delta from light to dark and dark to light are always positive and greater than TRIGGER_THRESHHOLD, so each transition causes a trigger.

Code:

if (abs(newLightningVal - lightningVal) > TRIGGER_THRESHHOLD)

will become

Code:

if ((newLightningVal - lightningVal) > TRIGGER_THRESHHOLD)

I'm making a assumption that the analog value for light is greater than the value for dark. If it's the opposite, just swap the values in the equation to this:

Code:

if ((lightningVal - newLightningVal) > TRIGGER_THRESHHOLD)

Select the application file in the Finder and then Get Info on it by either selecting "Get Info" in the File menu, or hitting cmd-I. In the info window, check the, "Open in 32 Bit Mode" checkbox and close the window. Now it should work.

The buffer needs to be large enough to hold the trailing NULL that is the end-of-character marker for the string. If the String contains "123" the whole String will not be copied into buffer by toCharArray, if buffer is only 3 elements long.

Oops! Forgot about the NULL.

The docs for toCharArray() are incorrect. I think this should take care of it for you,

Code:

int Str2int (String Str_value)
{
  char buffer[3]; //max length is three units
  Str_value.toCharArray(buffer, 3);
  int int_value = atoi(buffer);
  return int_value;
}

though I haven't actually tried it.

The other thing I noticed is that

Code:

if(temperature = 90)

should be

Code:

if(temperature == 90)

Check the documentation here, http://arduino.cc/en/Reference/Random. The max value should be one more the largest random value you want.

Forgot about map(). Definitely the way to go.

Assuming angle contains a value between 0 and 359:

Code:

char* directions[]={"N", "NE", "E", "SE", "S", "SW", "W", "NW"};

Serial.println(directions[((angle+22)/45)%8]);

Beware, though, I haven't been able to actually try it.

I can see a couple of problems, but the reason the loop never gets repeated after the LEDs are turned off by the tilt sensor, is the value of i is now equal to num_pins or 4. When you repress the push button, it tries to turn on pins[4] then pin[5], etc.. The variable i needs to get reset. Also, the initialization of the pins to LOW, should go in setup since it only needs to happen once. Here's some code that should work. Be aware I haven't actually tried it yet, so I could have easily made a mistake.

Code:

void setup()
{
  // add this to the setup
  for(int i = 0; i < num_pins; i++)
    digitalWrite(pins[i], LOW); // initialises state of the led at the i array position.
}

void loop()
{
   val = digitalRead(inPin);            // read input value of push button
  val2 = digitalRead(inPin2);            // read input value of tilt switch
  int i;

  if(val == LOW)  // following code is executed if button is pressed
  {
    for(i = 0; i < num_pins; i++)      // turn on LEDs one by one
    {
      digitalWrite(pins[i], HIGH);
      delay(200);            // wait
    }
  }
  
  if(val2 == 1)   // following code is executed if tilt switch is moved
  {
    for(int i = 0; i< num_pins; i++)
    digitalWrite(pins[i], LOW);      // turns LED off
  }
}

I played around with the Polar Heart Rate Module - RMCM01 interfaced to an Arduino. It was fairly easy to get working, but haven't (yet) done anything more than sending data to the Serial Monitor.

TechShop <http://techshop.ws> just opened a branch in downtown San Francisco, and they offer a couple of basic Arduino classes.

It's happening at exactly the same time as the Laser meetup @ TechShop.  

Check out the Arduino classes available at the TechShop http://techshop.ws/take_classes.html