We see leds every where. what do they do? they light up. well yeah thats their main purpose but not a lot of people know that if you expose them to sunlight it can
produce a small amount of voltage. So in a way it can act as a solar panel. The flashlight I made uses one 10mm white led. The led charges the battery and with a flick of
a switch it allows the led to emit light. It is such a small circuit you can fit it into two pop bottle caps. For this small build I used a 10mm white led, small nickel battery
(20mah size of a super cap. good runtime for one led) a blocking diode and a spdt switch.
I will explain how all the componets go hand in hand in the 1st step.
if you want to see a video of this working please copy and paste this ;link into your browser. I didnt feel like uploading it to youtube just to emmbed it. its such a short
video so I hope you dont mind. here is the link https://www.facebook.com/photo.php?v=10200431925699995¬if_t=video_processed
In the comments section you will see there was a bit of confusion. I take full blame for that confusion. When I first measured the voltage output of the led it read as 1.2 volts. That was the foundation of the confusion. However I was measuring the voltage output when the sun was setting and being blocked by clouds and trees. I meaured it again today in absolute sunlight. And it read as high as 2.7 volts. The battery charged to 2.7. Now that is enough to charge the battery and enough to run the led, however it doesnt live up to its full potential. The led works best at 3 volts. I am sorry for the confusion and I thank everyone who commented and got me interested in taking it apart and re-testing the voltage. I will be making a newer better one in the future. The more leds you use in series the higher voltage output you will get. I plan on making a new instructable in a few days. Sorry for the confusion!
Step 1: How it works/quick brief
This is a small brief on the circuit.
First I recommend using a white led as they produce the most voltage (in my studies) when in sunlight.
The white led I used outputs 2.7 volts when in absolute direct sunlight which is perfect for a slow charge. that being said, the type of battery I used is a very small nickel
based battery. when i first got it I thought it was a super cap. the battery is rated at 20mah and 3.6 volts. once its fully charged it can run one led for a decent amount of
time. it charges best when its in direct sunlight.
in the next step you will see the schematic and even if youre new to electronics you will see its very easy. It revolves around the switch and diode, in one position the
switch allows the led to charge the battery and in the other position it allows the battery to run through the led and emit light. The charge can also be an off position.