An Arduino general purpose detector!

I’ve been spending some time getting acquainted with my new Arduino Uno.

I did the first Blinking LED tutorial which went exactly as expected.  This particular board has a built-in LED connected to pin 13, so I didn’t even need to do any wiring!

Having forced the on-board LED to blink, I decided to get a little more ambitious.  Along with my Arduino, I bought a bag of LEDs which came with the appropriate resistors for building simple circuits with the board I have.  I attached a 2nd LED to a small Bread Board and wired it up to pin 12.  After modifying the program a little bit, I got the two LEDs to alternate blinking.

Not wanting to stop at using only 2 LEDs, I strung up 5 more to the Bread Board and connected each to a corresponding pin from 7 to 11.  With everything wired up, I coded up a simple function that would take a number from 0-6 and light up an appropriate number of LEDs.  0 leds if 0 were passed and 6 if six was passed.  You can see that segment of the code here:

void light(int i) {

  if(i < 0) { i = 0; }
  if (i > 6) {  i = 6; }

  for(int j = 0; j < 6; j++) {
     int reg = 12 - j;
     if (j < i) {
        digitalWrite(reg, HIGH);
     } else {
       digitalWrite(reg, LOW);

The first time running it, I simply cycled through numbers from 0 to 7 which resulted in the LEDs lighting up one at a time then resetting.

Finally, I decided to mess around with the Arduino’s Analog Input capabilities.  The input seems quite sensitive because as I touched the wire that I connected to the input, it immediately began registering a voltage.   In my program’s main loop, I scaled the analog input to the 0-7 range of my LED array.  Now when I touch the wire, the more fingers I touch the wire with… the more LEDs light up!  Here’s the pic!

Here, I was holding the wire with three fingers; my thumb, pointer  and middle finger… four of the LEDs lit up.  Presumably, if I connect up any random sensor (light, sound, etc), the intensity will light up a corresponding set of LEDs.  That aught to be more useful than detecting fingers touching a wire.