USB powered LED


Posted on Oct 2, 2012

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. 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.


USB powered LED
Click here to download the full size of the above Circuit.

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. 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. 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.





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