Alert others of your presence, and comfort them with your bike lights.

Rather than using a stressful red light, with a robotic and off-putting tempo, this blue light reminds other cyclists of our shared humanity. It reminds fellow cyclists to treat each other well and be aware of pedestrians.

I live in Melbourne, Australia, and my nighttime commute can be dangerous. I bike to and from work. My ride back home is really dark.

The bright headlights and taillights on my path are too similar to driving. I can barely see ahead of me when fellow cyclists zoom by. This light reasserts the wonder of cycling, while still keeping passersby alert of the incoming cyclist.

Note: For this Instructable, I am using my own Recycled printer paper sketchbook, rather than starting from scratch. If any of the steps are unclear, please let me know, and I’ll try to clarify them.

Step 1: Materials and Tools

Materials

Bicycle with a bike rack
Cardboard
Tea box
Plastic bottle, 1 Liter (empty)
Makedo Scrus*
Arduino UNO
AA Battery pack for Arduino
AA Batteries, x4
Blue LED, x1
Tape

* If you aren't sure what Makedo is, they're reusable plastic screws for building with cardboard. Check out Makedo's instructables page.

Tools

Makedo Safe-saw
Makedo Scru-driver
Cutting mat
Ruler
Craft knife

Prep

Clean working surface. Desk, workbench, whatever you’d like!
Stable bike, balanced against a wall or with a stand

Hints and tips

Choosing cardboard: Choose a piece of cardboard that looks beautiful and is reasonably strong. I chose a piece of double-thick cardboard that is hard to bend.
Cutting cardboard: Makedo Safe-saw works best with rigid, un-bruised cardboard. If you have trouble sawing with it, use a craft knife.
If craft knife tip is dull, replace it to make cleaner cuts.
Cut cardboard taking a few passes, following the line you’ve drawn.

Step 2: Start With a Bike Rack

Make sure your bike has a bike rack. My back has a hinge that allows it to clamp things. I use this feature to secure the base of my bike light.

Step 3: Add Base

Grab a piece of cardboard that can wrap around your bike rack. I chose one that could be held down securely by my bike rack. Fold it around a handle, edge, or side, so the cardboard wraps over itself.

Use the Makedo safe-saw to punch a hole into two pieces of cardboard. Use the Makedo scru-driver to add a scru to that hole. Make sure it is held down in enough places so it doesn't fall off.

Step 4: Make Light Holder From Tea Box

Tear off one side of your tea box. The breathing light will sit in here. I unfolded my box to make the label face inwards.

Cut a gap near the edge of your box if you are using a square tea box. This helped my Arduino Uno fit properly. If your box is rectangular, your Arduino may fit without the need of a gap.

Step 5: Add Support

Add cardboard support around your tea box to hold it more firmly to the base. Cut a thin sheet of cardboard that is long enough to wrap on all for sides. Cut it to the height of your tea box. Punch and scru it in on one side. On the opposite side, add a piece of cardboard that joins the support to the base. Punch and scru it in as well.

Step 6: Set Up Arduino Uno

Set up device

Connect you Arduino Uno with a USB Cable. If you haven't already, download the Arduino software from their website here. Open the application and make sure your computer recognizes the device. Follow these steps to configure your device:

Go to Tools in the menu, and configure the following parts:
Board > Arduino Uno.
Port > /dev/cu.usbmodem (there may be extra numbers here. Make sure usbmodem is what you select.

Add code

Next, upload the program into your Arduino. Go to Examples > Basics > Fade.

At the very top, make sure it is written: int led = 9;
Scroll down to the end of the code and change the delay(30); to delay(20);
Choose upload. This button is in the sketch.

This reduces the time between fades. I think that making it slightly faster allows cyclists to see the full effect. Do not make it too slow or too fast. The "breathing" effect is what we are trying to achieve.

Add light!

Wrap some tape around the negative leg of your LED. This leg connects to GND (ground) in your board. LEDs are polarized, so they only work in one direction.

Put the positive leg (usually the long leg) into Pin 9.
Put the negative leg into GND.
The light should immediately begin flashing.

Tip: If you need extra help setting up you Arduino, there is a large community that can help you. Don't be afraid to ask- these things took me forever to understand. Search your question, too!

Step 7: Add Battery Pack

Put 4 AAs into pack and connect to your Arduino. Your device has 2 main plugs: a barrel port for batteries, and a USB port.

Tape it to Arduino. Keep it unplugged when not in use. This light doesn't have a button- that's a great addition for the next version!

Step 8: Make the Lamp

Cut the bottom third of your bottle with the craft knife. Hold it down firmly to prevent it from slipping. Cut a 0.5 inch (1 cm) hole in the bottle the same distance that the scru in your tea box is from the base. The scru will hold on to this hole and prevent your plastic bottle from flying off if you hit a bump

Depending on the size of your bottle, you may have to cut a gap into the bottle to fit the Arduino and battery pack. Hold it down firmly against a surface to prevent it from slipping as you cut.