My red flashing led rear bike light has never let me down. But what do you do when you have a great bike headlight and are a couple of miles from home when the battery dies? I decided to reposition a $5.00 solar garden light into a light-weight portable "be seen" solar bike light that I could hang on my backpack. Now, in the event of a dead headlight battery, pedestrians and drivers can spot a me and my bobbing white light when I am biking on the road after dark. During the day, ride with the panel facing out. Once it is dark, flip the box over, and the white led brightly shines.
The rules of the game for making the be seen solar bike light were that I could only use things I could find in my kitchen, except for the solar garden light, which was in the living room. (They make very nice mood lights.) I had to make it relatively quickly, have fun, and be able to use it bike riding when I was done. You can certainly make yours snazzier, neater, and more weatherproof. But I was in my PJ's on a Sunday morning feeling lazy. The tools and supplies I used for the $5 be seen solar bike light are as follows:
- An old kitchen knife, a pair of scissors, a corkscrew, a wooden cutting board, a ballpoint pen, a Sharpie, a nail file.
- A solar garden light, a small wooden match, an old postal envelope,a twisty tie, a Newman's Own Organic Ginger Mint metal box. The images on Newman's mint boxes are really cool. I used the ginger dragon. But I have a cinnamon tiger tin waiting for another project. (I thought of making it with a cassette tape case, since the clear plastic will allow more light to escape. But the tape cases are made of plastic that tends to shatter. I've dropped my be seen solar bike light a couple of times, and it has survived.)
Directions to make the $5 be seen solar bike light are after the jump.
1. A very brief overview of how solar garden lights work: Solar garden lights have circuits that takes directions from a photoresistor, which you can think of as a "light sensor" if you are not an electronic type. If the light sensor senses light from the sun or other light source, it tells the circuit to not turn on the led, and instead store the electricity made by the solar panel in the rechargeable battery. When it gets dark, and the light sensor no longer senses light, the circuit knows to go directly to the rechargeable battery, and use the stored power in the battery to make the led shine. You can read more detailed info about solar garden lamps here. (But I got 4 solar garden lights for $19.99. So, my guess is that since this linked article was written, the prices have dropped.)
2. Do not be wicked and "borrow" your neighbor's solar garden light without asking. You want to try to get a solar garden light that has the light sensor built right into the solar panel. In the first photo, the solar garden light on the left is the one I used. It has a silver light sensor strip built into the solar panel. The type on the right, the same one that the finger points to, has a separate light sensor. To make this type of light work for this project, you have to make sure to transfer the sensor, or the circuit won't know when to turn off or on the led. If you have the choice, pick the solar garden light that has the silver strip and not the one with what looks like a white button.
3. Turn the light over; turn the little screws that hold the piece on the bottom to the left to unscrew them. Remove the screws, and carefully remove the black plastic bottom piece.
4. Remember, you have a rechargeable nickel cadmium "Nicad" battery in this light. So, make sure that down the line, when it no longer will store a charge, you dispose of it according to the rules.
5. Take a sharp kitchen knife, and carefully cut out the solar panel and the circuit. Make sure you don't crack the panel by pressing down hard on it. Take your time. Don't slice through anything important. Go slowly, and keep checking to make sure you are not destroying anything that is connected to the panel.
6. Position the panel and circuit battery side up in the tin box. Take a moment to look at the graphic art on the front. Try to line up the led when the lid is closed with the design in such a way it doesn't wreck the graphic image on the lid. (The led in the dragon's eye would have obscured the image.) Flip over your normal kitchen wooden cutting board, so you don't get metal bits in the side you use to make sandwiches. Take the kitchen knife and make a bunch of little perferations in the tin. Don't use your best knife. Use an old one. Metal on metal is a bad idea for good knives. Then, snip the tin with the scissor. This can leave very sharp edges, so take the nail file and gently smooth the edges. You can also cover the edges in bits of cardboard and packing tape if they are really sharp.I didn't have any tape in my kitchen. Remember that tape can get sticky and gooey if left in the full sunlight regularly. Make sure that the hole you create allows for the silver strip light sensor in the solar panel to be exposed and not covered by the box.
7. To make a liner for the tin, place the tin on the old envelope and trace the shape of the back including the hole in the tin. Double the material, and at the same time, cut out two exact copies of the shape. I did this because I did not measure and cut the tin precisely while being a Sunday lazy slug. So, the hole was a bit big for the panel. However, it is better to make it too big than too small, since you have to make sure the light sensor strip is exposed and not covered by the tin box.
8. Put the liner in the box. Put the circuit in the box. Cut the head off of a wooden match, wedge the circuit into place with the matchstick. I didn't have epoxy or silicon caulk in my kitchen. A matchstick works fine. Plus you can easily take the panel and circuit out of the box at a later date and reuse it for another project. Use a Sharpie to blacken the frame around the panel. We want to absorb light.
9. Close the box part way, and line up the led, so you get a sense of where you want to hole for the led to be. Check to make sure you have a clear idea which part of the graphic on the front you are going to remove. Turn the middle part of the corkscrew slowly to the right, and drill the hole in the image side, so that the sharp edges will be inside the box. Then, take the twisty tie, and make a hanger by bending it into an upside down "U". Place it in the middle of the tin, so it is not touching any wires or parts of the circuit, and shut the lid on it. The pressure of the lid will hold it. Take extra care to not mash the led connections to the circuit board when you are putting the led into the drilled hole. Make sure you stash some emergench cash in your be seen solar bike light, in case you want a slice of pie and a cup of tea one night and don't have any money in your pockets.
10. Give it a test. When the back solar panel is covered, it led shines. When the back solar panel is sensing light, the led doesn't shine. And there you have it, a $5 be seen solar bike light.
