Do you know that your computer USB port have stable 5 volt dc voltage? Yes your computer USB is a very useful voltage source to light up a bright white LED which is very useful for many purposes. Many times we want to look in our CPU but due to low light inside we cannot able to
see it clearly and we have to take it to below the room light from its original place. But by this simple USB lamp you can able to easily see inside of CPU or you can also use it for other purposes like you can see keyboard keys in the dark etc. The circuit is so simple uses only one 47 ohms resistor, LED and USB type "A" male plug. The 47 ohms resistor is used to limit the current to 25mA and it is ideal for operating a bright white LED. You can easily connect this circuit to any extra or scrap USB cable you have.