Tired of barely being able to see while biking at night? Want to be safer about where you are going while at the same time getting maker experience? This post will show you exactly how to put together your own bike light that recharges using solar cells!

Supplies

The supplies needed for this would be:

Soldering Iron (or really high quality electrical tape)
2 Solar Cells
A pack of 2 AA batteries with a case
A single pole single throw switch
6 3Watt LED's
Thin wires
Wire cutters
A small LED that can act as a diode (see blue LED in picture)
Laser Cutter for the box (or make your own encasing)
Glue

Solar cells: https://www.amazon.com/gp/product/B082LVLTTV/ref=ppx_yo_dt_b_asin_title_o03_s00?ie=UTF8&psc=1

SVG File for the Laser cutting: https://climbers.net/sbc/make-laser-cut-case-elastic-clips/

If using electrical tape instead of solder, make sure that every electrical connection made throughout the project is properly sealed and there is obviously contact between both objects.

Step 1: Understand the Circuit

This circuit shows how everything will be connected in the end product. It is important to look back at the picture quite often to avoid making any mistakes. Make sure to how positive and negatives are oriented. If you swap them on accident, the circuit will not work.

A: Two solar cells connected in series

B: The battery pack with positive and negative wire coming out of the box

C: The six LED's connected in parallel with everything else in the circuit. Make sure you have all of their orientations correct

D: The switch that will ultimately turn the LED's on and off when desired

E: LED diode that controls current flow direction. Also is very crucial to pay attention which side is positive and negative. The longer leg of it is positive and the shorter leg is negative.

How much wire you use is ultimately up to you. Using less wire will make the whole circuit more compact but often harder to assemble. Using more wire would take up more space, but it is much easier to make the electrical connections.

Step 2: Electrically Connect Solar Cells, Battery Pack, Diode, and Switch

It is time to begin assembling the easier and bigger pieces. Use the circuit in the previous step and the picture above for as much assistance as needed. Ignore the 3W LEDS for now.

Take a wire and make an electrical connection with either or solder or electrical tape to the positive end of a solar cell.
Take the other end of this wire and electrically connect it to the negative end of the LED diode
Taking another piece of wire, make a connection to the positive end of the LED diode and a second connection to the positive wire (red) of the battery pack. Make sure there is room in this connection to add another wire.
Take another wire, and make a connection to the part connecting the battery pack and the wire that leads to the LED. This should create a sort of "T" shaped intersection for wires. Leave the other end of this wire untouched for now
Take your other solar cell and attach a wire between the positive end of this cell and the negative end of the cell that already has wires connected to it.
With a different wire, connect one end to the second solar cell's negative end and connect it with the negative wire of the battery pack, allowing room to make another "T" shape.
With a different wire, connect one end to the "T" intersection and the other end to either end of the single pole single throw switch.
With one more wire, connect one end to the oppositive end of the switch and leave the other end of the wire untouched for now.

Step 3: 3W LED Set Up Part 1

Before electrically connecting any of the 3W LED's, it is important to keep track of how you want to wire them and how their position will be of use. These LED's are what will act as the "bike light", so make sure to think cleverly about where to glue them onto. Make sure to keep track of the circuit for these in order to allow plenty of room to make connections with a lot of wires. Feel free to use the image above as inspiration for what to expect in Part 2.

If using the laser cut box, make sure that your orientation with the box is correct based on where you want light shining from. In the picture above, one side of the cube was chosen for the LED's and they were hot glued onto this side and left for soldering when the glue dried up. The link provides information on box assembly and cutting.

Step 4: 3W LED Part 2

Implement the very last part of the circuit that we have left out. This includes taking your 6 3W LED's and connecting them in parallel with the rest of the circuit. Make sure that the wire end from the positive side of the battery pack leads into all the negative ends of the LED's and the wire end that leads to the switch connections with all the positive sides of the LED's. This step can vary depending on your decision for the LED set up and where you chose to encase them in. As long as you can trace your wires exactly like how the circuit picture above, the current should be able to flow properly.