LED – The Light Emitting Diode that is mostly used in electrical and electronics circuits. the led are mostly used for indication, for used inn decoratiove in decorative lamps, led panels are used for advertising panels.
LED Defination
An LED is a type of Semiconductor device that emits light when an electric current flows through it. The LED will convert the electric current to light with the working principle of electroluminescence.
How an LED is constructed
The LEDs are constructed using the semiconductor materials arranged in a specific pattern that will help to allow light to be emitted when power is applied to them.
The semiconductor materials used in the LED are
- Gallium Arsenide (GaAs)
- Gallium Phosphide (GaP)
- Gallium Nitride (GaN)
The semiconductor materials used for the construction will determine the colour of the LED
P – N junction
The semiconductor use in the construction of the are divided into two regions
- P – type
- N – type
The P-type semiconductor is positive, and it contains the majority of holes. The N – type semiconductor is negative, and it contains the majority of electrons.
These two different types of semiconductor material join together to form a junction, which is called a PN Junction. This is essential for the working of the LED.
The area around the junction is called the active region. When the current flows through the junction, it will emit light from the active region. This process is known as electroluminescence.
When the current passes through the LED, the holes and electrons in the semiconductor material recombine to form a junction, and this will help in emitting light. The electrical energy is converted into light by emitting photons.
The Anode is the positive terminal, which is connected to the P-type, and the Cathode is the negative terminal, which is connected to the N-type.
Why does an LED need a resistor?
An LED needs a resistor because it is not able to handle the flow of high current. When the LED is directly connected to the power supply, high current flows through the led it will damage the LED.
So a resistor is used in the circuit to limit the flow of current and protect the lrd from overheating, burning, and bursting.
What happens when choosing the wrong resistor?
When we choose the wrong resistor for a circuit, it causes several problems, so we need to select the correct value of the resistor
- If the resistor value is too low, a large amount of current flows through the circuit. When high current flows through the LED, it will overheat and cause problems like burning and bursting.
- If the resistor value is too high, it will limit the current flow and allow only a small amount of current, so the LED will not glow brighter.
How to choose the correct resistor for an LED?
We can easily choose the LED resistor with the help of a simple calculation. The formula used for the calculation is,
R is the resistor value to be calculated
VSource – is the voltage of the power source to be connected to the LED
VLED – is the forward voltage of the LED
I is the rated current of the LED
Now we can simply understand the calculation using an example,
For example, an LED consume 20 mA of current with a forward voltage of 2V, which is connected to the power supply of 12V
The required resistance value for the circuit is 500 Ω
I market we have only standard values of the resistor, only available. You can choose the resistor close to this value.
After finding the resistance value, we need to calculate the power rating of the resistor to avoid overheating and failure of the resistor.
We can easily calculate the power rating by using this simple calculation.
P=(Vsource−VLED)×I
for the above,
P=(12−2)×0.02
P=10×0.02
P=0.2W
We need to choose the high-power rating resistor for the calculated rating. It is safer to choose 1.5x or 2x times greater than the calculated power rating.
For this scenario, we can choose the market available resistor of 560 Ω 0.5-watt resistor