A LED, or Light Emitting Diode, is a type of semiconductor device that emits light when an electric current is passed through it. LEDs are highly efficient, long-lasting, and durable compared to traditional incandescent and fluorescent lights, making them popular for use in a wide range of applications, such as lighting, displays, and signaling. LED lights are available in a variety of colors and sizes, including the widely used 3mm, 5mm and 10mm LEDs. They are made of semiconductor material and have a positive and negative terminal, the positive is the anode and the negative is the cathode. When the electric current flows through the semiconductor material, it generates photons, producing light.
LEDs are popular in a many applications due to their small size, high efficiency, and long lifespan. Some popular usage examples include:
A resistor is typically placed in series with an LED to limit the amount of current flowing through the LED. LEDs are sensitive to excessive current, and too much current can damage or shorten the lifespan of the LED.
To calculate the resistance for a circuit using LEDs, you need to know the forward voltage (Vf) and forward current (If) of the LED, as well as the desired operating current and the voltage source of the circuit.
First, you need to calculate the total circuit voltage (Vtotal) by subtracting the LED's forward voltage (Vf) from the voltage source of the circuit.
Next, you need to calculate the total current (I) flowing through the circuit by dividing the total circuit voltage (Vtotal) by the desired operating current (Io) for the LED.
Finally, you can calculate the resistance (R) for the circuit by dividing the total circuit voltage (Vtotal) by the total current (I) flowing through the circuit.
R = Vtotal / I
This table displays a list of approximate resistor values to use with a single LED at various circuit voltages:
|Resistor Value (Ohms)
It's important to note that all above calculations are based on the assumption of a single LED connected in series with a resistor. When multiple LEDs are connected in series or parallel, the calculations will be different. In series, the forward voltage of the LEDs will add up, and in parallel, the current will be divided among all the LEDs.
The forward voltage and current rating for a 5mm LED can vary depending on the specific type of LED and the manufacturer.
Typically, the forward voltage (Vf) for a LED ranges from 1.8 to 3.5 volts. This refers to the voltage required to forward-bias the LED and make it light up. The forward voltage is mostly depending on the LED color and might have small viariances between suppliers.
Genrally these forward voltages apply for the following LED colors:
|Forward Voltage (Vf)
|3.2V - 3.6V
|3.2V - 3.6V
The typical forward current (If) rating for a LED is around 20-30mA, but it can vary depending on the LED. This refers to the maximum current that the LED can safely handle without damage. The forward current rating is also known as the "operating current" and it is important to not exceed it, otherwise the LED can be damaged or have a shorter lifespan.
It's important to check the specifications provided by the manufacturer or supplier for the specific LED you are using to ensure the correct voltage and current are being used.