USB powered LED

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 USB cable. I took it from an old digital camera. I used about three feet [36 inches] of this cable. The USB cable has 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 a USB port is 5 Volts. The maximum current for any device connected to the USB cannot be more than 500 mA. Do not build this project 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.

The circuit described is a basic LED lighting solution powered by a USB interface, commonly found on computers and other electronic devices. The schematic consists of a single white LED and a current-limiting resistor. The primary components include a 10,000 mcd white LED, which provides sufficient brightness for illuminating a keyboard, and a resistor that controls the current flowing through the LED to prevent damage.

In this circuit, the LED is connected in series with the resistor. The USB power supply provides a nominal voltage of 5 volts. The choice of resistor value is crucial for determining the current flowing through the LED. For instance, using a 100-ohm resistor results in a current of approximately 15.27 mA, while a 200-ohm resistor reduces the current to about 8 mA. Both values are safely within the USB port's maximum current rating of 500 mA, making this circuit suitable for use without risking damage to the USB port or the LED.

The USB cable used consists of five wires: two for data transfer and two for power, with the remaining wire serving as a ground shield. The red wire typically represents the positive voltage (Vcc), while the black wire serves as the ground (GND). Proper identification and connection of these wires are essential for the successful operation of the circuit.

This LED circuit is not only functional but also versatile, as it can be adapted to use different types of LEDs, such as yellow LEDs, which may also provide adequate illumination. However, it is important to calculate the appropriate resistor value based on the type of LED used and its forward voltage and current specifications.

Overall, this simple LED circuit is an effective and efficient solution for providing localized lighting, enhancing visibility in low-light conditions, such as when working at a computer keyboard 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. 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. 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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