USB LED Light. A simply and easy-to-make circuit, useful when working with the computer at night

This is a simple LED circuit that takes power from the USB port. I needed this USB light since long time ago but, finally; I was able to build it. Here is how I made it.

The circuit schematic is so simple: Just one resistor and one White LED. I did use a 10,000mcd white LED. It illuminates perfectly the keyboard of my computer. In fact; it is so bright that, I can use it to read. 

I did use an old USD cable. I took it from an old digital camera (Purchased for $19.99 USD. I remember the big soap opera that my ex-wife made just because I purchased that camera. Precious moments!) Anyway, I used about three feet [36 inches] of this cable. 

The USB cable have five wires: Two are used for data and two for power. The additional one is the grounded shield. The black one is the NEGATIVE, the red one is the POSITIVE. The voltage from an USB port is 5 Volts. The maximun current for any device connected to the USB cannot be more than 500 mA. Do not build this projects if you don't know what you are doing.

Before doing this project, I need to be sure how much current will be used. It is only 15.27 mA using a 100 ohms resistor. That is not a problem for the USB port. Using a 200 ohms resistor, this circuit uses only 8 mA.

Using some heat shrink tubes, I verified that there is no short circuit. Three sizes of shrink tubes were used.

Testing the USB LED light. It works perfect. 

The last step is to attach a clip with hot glue that allows to use it at the computer. I used a paper clip. This one easily can be purchased at office supply stores.

Another way to attach the light is using a piece of velcro.

My USB LED light is ready.

My home-made USB light attached to my computer screen. 

It works perfectly and I can see the keys on my keyboard without problems. I can work at night without turning the light on. I even can read with this light. Yellow LEDs may also work fine.

Update: Some IBM computers (lenovo models) Have an integrated light. The light on IBM computers are activated using a key sequence. I'm planning to create something like that using a fotoresistor to detect when is dark and activate the led automatically. I have to find a way to put the led inside the display.

Source : http://josepino.com/