Harvest energy from the USB port of your Laptop or PC to light an LED lamp. It is useful as an Emergency lamp in the event of a power failure or it can help you to use the Key pad in night without disturbing the sleep of others. It is too simple and easy to make it. The USB.2 .0 port available in all laptops and PC gives 5 Volt DC and 200-300 milli ampere current. It is enough to light a High power 1 watt LED. Just plug the light in the USB port and enjoy its light. Cool! it is good enough to read a book also. In the market its costs Rs. 300 and you can make it for just Rs.10.
You need only a few items to build the LED light
Plug it in the USB port and identify the + and – contacts using a multi meter or simply using an LED with 1K series resistor. Mark the + and – contact points.
Remove the Circuit board from the Pen drive and take only the Pin.
Identify the + and – contacts of the 1 watt LED. Then solder the insulated Copper wire to the positive. In the prototype I used 20 SWG enameled copper wire. So that, the light will stand erect nicely. Solder two 1 Ohms resistors in series to the negative terminal of the LED. Since the power from the USB is only 5V and the LED requires around 4 V and 200-300 mA current, the low value 1 ohm resistors were used. It makes 2 ohms series resistor.
Enclose the leads of the LED with the copper wire and resistors connected inside a sleeve.
Solder the USB pin to the LED leads observing correct polarity