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This is a simple hack which will enable your calculator to work on solar power but there is a twist in there we are not going to use photovoltaic cells but we are going to use LED's to build a solar cell. The LED's can not only emit light but sense light and produce a voltage which we will be using to build a solar cell. This is a fun to do project  ,  requires minimal parts and is a low cost project.

This instructable will explain how to create a solar powered calculator , experimenting with LED's to produce voltage , build a solar cell using LED's and how to power devices with it.


Step 1: How Does It Work?

An LED can be used for light detection as well as emission . LED is a simple diode which has been adopted to emit light . Therefore if it is inserted into the circuit the same way as the photodiode it will serve the same function of sensing light.

The LEDs will be sensitive to the light which has the wavelength equal to it or lesser than it.

When a LED detects light it produces a voltage and this voltage we are going to use to power our clock.

I started experimenting with LED's of different colours and here are my results:

BRIGHT LIGHT                                                     AMBIENT    
  
Red LED - 1.3v                                                   Red LED - 0.007v
Green LED - 1.4v                                               Green LED - 0.001v
Blue LED - 0.2v                                                  Blue LED - 0v
IR LED - 0.1v                                                      IR LED - 0.01v
Yellow LED - 1.2v                                               Yellow LED - 0.001v
White LED - 0.003v                                            Whit LED - 0v

From the experiments it is clear that Red ,Green and yellow LED's produce the most voltage so we are going to use one of these three colors.

Step 2: Parts & Tools

Parts :
~ 10 x LED's (Red , Green , Yellow) - Sparkfun.com
~ A Clock - General Store
~ Some Wires - Local Electronic Store

Tools :
~ Soldering Iron - Sparkfun .com
~ Solder Wire - Sparkfun.com
~ Screwdriver (Optional) - Sparkfun.com

Step 3: Build the Solar Cell

First we need to make a solar cell to power our clock . We are going to build a solar cell using ten LED's I am using assorted LED's of colors red , greed, , yellow (4 red , 3 green , and 3 yellow ) you could use any of the three . You could solder them in series or in parallel . Connecting them in series will increase the voltage while connecting them in parallel will increase the current . I soldered them in series. The circuit diagrams for the LED's in series have been attached at the end.

Step 4: Hack the Clock

To enable the clock to work on solar power you need to make some changes to it. First turn the clock around and then remove any covering on the battery and then remove the battery ( We will replace the battery with the solar cell ) . Now connect the two wires from the solar cell i.e the positive and the negative , to the positive and negative terminals of the clock respectively . Now take the clock in sunlight or in bright light and the clock will start ticking . You can use this solar cell to power anything that works on 3 volts and if you increase the number of LED's maybe even more . This can be helpful at the time  of emergency.

Step 5: All Done!

I hope this project inspires further experimentation.This is just one of the many applications of LED's. They are incredibly versatile,cheap, and accessible to all hobbyists . Keep pondering for newer projects and applications of LED's . Don't forget to follow mores comming up. For any queries contact me here's my E-mail ID r1398ohit@gmail.com
cool idea, not enough people realize this about leds

About This Instructable

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