LilyPad Arduino Blinking Bike Safety Patch

I made this embroidered patch in a different instructable, but here I'll show you how to add flashing LEDs to your backpack for fun and safety. I used a LilyPad Arduino with a rechargeable lithium-polymer battery for flatness and re-usability. The LEDs blink in a marquee pattern, two at a time, in patriotic red, white and blue.

To keep up with what I'm working on, follow me on YouTube, Instagram, Twitter, Pinterest, and subscribe to my newsletter.

Here's the Arduino code! Load it on your LilyPad by hooking up your programmer and USB cable (or FTDI cable if you have a newer LilyPad). For more info about getting the code onto the Lilypad, check out this page at the Arduino website: http://web.media.mit.edu/~leah/LilyPad/04_lights.html

--begin code

int timer = 100; // The higher the number, the slower the timing.
int pins[] = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12 }; // an array of pin numbers
int num_pins = 12; // the number of pins (i.e. the length of the array)

void setup()
{
int i;

for (i = 0; i < num_pins; i++) // the array elements are numbered from 0 to num_pins - 1
pinMode(pins[i], OUTPUT); // set each pin as an output
}

void loop()
{
int i;

for (i = 0; i < num_pins/2; i++) { // loop through each pin state (there are six)
digitalWrite(pins[i], HIGH); // turn one LED on,
digitalWrite(pins[i+num_pins/2], HIGH); //then turn its opposite LED on (six positions away)

//now turn the previous LEDs off:

if (i == 0){ //turn the last LED off from the previous go 'round
digitalWrite(pins[num_pins-1], LOW); //
} else{
digitalWrite(pins[i-1], LOW); // turn off each previous LED
}
digitalWrite(pins[(i+num_pins/2)-1], LOW);

delay(timer); // pausing

}

}