No, this isn’t a trick project. It actually works. Since the energy source for this flashlight is light and it works just fine at night, it must have a way of storing energy–and it does. However, like commercial solar powered flashlights, which store chemical energy in batteries which then convert this chemical energy to electrical energy, this flashlight stores electrical energy directly in two one-farad super capacitors. Today we use two 1-farad capacitors to store electrical energy to light an LED; tomorrow we will be using a bank of 10K farad capacitors to store electrical energy to power an automobile!
Whenever wiring circuits with insulated wires or leads, make sure you strip off a half to an inch of insulation before connecting them. I often use side cutters to do this although you might want to use a special purpose wire stripper.
The super capacitors have their negative lead marked. Make sure you connect the capacitors, rectifier, and the LED as shown. If you connect any of these three components backwards the flashlight will not work.
A 1K resistor is called for in the parts list. If you want a brighter flashlight you can use a 480 ohm or even a 330 ohm resistor. However, the smaller the resistance of the resistor the shorter the time the LED will light between charges.
Press the Popsicle switch when you want light. A couple of minutes of bright sun will fully charge the capacitors which store enough electrical energy to light the LED for half an hour of continual use.
This project makes use of super capacitors to store electrical energy. It shows in a practical way the superiority that super capacitors have over chemical batteries. What are the advantages that capacitors have over chemical batteries? They last far longer, they can be charged much faster and they don't produce flammable or toxic gases.
For a clear understanding behind how a capacitor can store electrical charge and thus electrical energy see the video http://youtu.be/PAPGTuvHSRo
I've been designing contraptions since I was 12. One early contraption I made was designed to turn a room light on when dark, nearly burned the house down! It also stunk the house up since its selenium rectifier overheated big time which is a real no-no.
I've learned a lot since then...thank God! Since I became interested in electricity about the time I started to crave hot dogs roasted on an open fire, I went to the Illinois Institute of Technology and received a Master of Science in Electrical Engineering. After that I started to turn out the electronic contraption designs and their prototypes at a furious pace. Many of these designs I had published in many electronic magazines such as Popular Electronics, Radio-Electronics, Modern Electronics, etc. etc. etc. and I am still doing it. My aim now is to instill in the viewer an interest in electronics AND knowledge of it as well. I firmly believe interest and motivation comes before knowledge--just look at the movie "October Sky"!