Simple USB Lamp Circuit

This circuit shows you how to build a mini nightlight powered by your computers USB port.

All you need is a few basic parts:

A USB plug like the one on the end of your phone charger.

An LED a small light that does not use much power.

A resistor a tiny part that controls the brightness of the LED.

This is a handy little light for power outages or when you need a little extra light in a small space.

Circuit Working:

Parts List:

USB Type A connectors also known as standard A connectors have a flat and rectangular shape.

Type A is the original USB connector and is widely used across various USB versions including USB 3.0, USB 2.0 and USB 1.1.

Primarily designed for host controllers in computers and hubs the USB Type ‘A’ connector is found in every USB version.

The USB A socket is specifically crafted for downstream connections to host controllers and hubs rarely serving as an upstream connector on any device.

This circuit is basic employing only a single 5 ohm 1 watt resistor, LED and a USB Type ‘A’ male plug.

The 5 ohm 1 watt resistor limits the current to 25mA making it ideal for powering a 3.3V 1 watt white LED

You can easily connect this circuit to any spare or unused USB cable you may have.

This USB Lamp Circuit is made to be used with a laptop during unexpected power outages, but it can also be fastened to a portable USB port to provide quick and easy lighting in places where carrying a large emergency light, torch or flashlight is not practical like small fuse boxes or computer motherboards.

Formula:

Ohms Law is absolutely relevant to understanding a USB Lamp Circuit:

R = V / I

where,

• R: stands for resistance, and it expresses an elements resistance in the circuit in ohms Ω.
• Resistance is commonly encountered in a resistor connected in series with the LED in a USB lamp circuit.
• By restricting the amount of electricity that passes through the LED, this resistor shields it from harm.
• V: is the unit of measurement for the voltage across the component.
• The voltage used in a USB light circuit is the same as the voltage provided by the USB port, which is normally 5V.
• I: This stands for the components current flow, expressed in amps A.
• In order to keep the LED from burning out, the current flowing through it must be restricted to a safe amount.

The formula for calculating the resistor value for an LED circuit is based on ohms law:

R = (V_source – V_LED) / I_LED

where,

• R: is the resistors resistance measured in ohms Ω.
• V:The voltage of your power source, which is typically the battery voltage measured in volts.
• V_LED: the LEDs forward voltage drop, expressed in volts V, the datasheet for the LED has this value, for popular LEDs, it is usually between 1.8V and 3.4V.
  I_LED: The intended current through the LED, expressed in amps A, this amount, which is typically between 10mA and 30mA for tiny LEDs, is also mentioned in the datasheet for the LED.

How to use the formula:

Assemble information: From the datasheet, determine the voltage of your power source V_source the forward voltage V_LED and the intended current I_LED of your LED.

Enter the values: Enter the values as replacements in the formula.

Determine the resistance: Find R by solving, the resistance value in ohms required for your resistor will be the outcome.

How to Build:

Building a USB Lamp Circuit is a simple and practical project below are the process:

Identify USB Type ‘A’ Connector:

• Ensure you have a USB Type ‘A’ male plug.
• This is the flat and rectangular connector commonly used in USB cables.

Gather Components:

• Collect the LED (bright white) and the 5 ohm 1 watt resistor.
• Make sure the resistor can handle the power rating of the LED.

Right Resistor:

• The 5 ohm 1 watt resistor is crucial for limiting the current to 25mA ensuring the LED operates correctly.
• If you are using a different LED, check its specifications and adjust the resistor accordingly using ohms Law formula mentioned above.

Connect the Resistor to LED:

• Connect one leg of the resistor to the longer leg anode of the LED.
• The other leg of the resistor connects to the USB Type ‘A’ connectors power Vcc line.

Connect the Shorter Leg of the LED:

• Connect the shorter leg cathode of the LED to the ground line of the USB Type ‘A’ connector.

Assemble the Circuit:

• If you have a PC, you can assemble the circuit on it using jumper wires.
• Connect the components as described in the previous steps.
• If not using, a PCB solder the components together.

Connect to USB Port:

• Plug the USB Type ‘A’ male connector into the USB port of a laptop or any USB power source.

Test the Circuit:

• Once connected the LED should light up, providing emergency lighting.

Usage:

• During a power outage or in tight spaces where conventional emergency lights may not be practical connect the USB Lamp Circuit to a USB port for instant lighting.

Conclusion:

The USB Lamp Circuit is a project that can be a fun and educational introduction to basic electronics for enthusiasts or hobbyists.

It demonstrates the versatility of USB ports beyond data transfer and power charging, showcasing their utility for powering small electronic devices.

References:

USB-Powered PC Lamp