Introduction: The LED

About: Electronics Engineer | Build, Automate, Innovate | I'm a Maker :-)

LED is a type of P-n junction diode. It is always used in the Forward-Biased mode.

'LED' stands for - " Light Emitting Diode " , which means that it's a Diode which emits light .

This is the main difference between an ordinary diode and a LED.

More information about the LED and its theoretical concepts are mentioned in the further steps.

This instructable teaches you the basics of LED, about it's operation, and certain uses.

You can also refer the short video above, for understanding it easily in a simple way or by checking it here -

Step 1: Let's Understand It ...!!!

LED is a type of P-N junction diode which emits light when used in forward-biased mode.

It's a device in which the electric energy is converted into light energy.

It is two- terminal device with the terminals - Anode (positive) & Cathode (negative).

The Cathode is marked with a flat side on the LED. And the other one is the Anode. Refer the above image.

LED works on the same principle as a diode does.... just the main difference is that it emits light (photons) when in Forward mode.

LED cannot operate in reverse biased mode as a diode. As it gets damaged very easily, when done so.

The forward voltage of a LED is much higher than a normal P-N junction diode. It ranges from approx 1.8V to 4V depending on which color it emits.

The forward current of LED is very less than a normal P-N junction diode. It varies from 10mA to 400mA (or more) normally as per the power ratings of a LED.

The normal LEDs generally have a maximum current rating of 20mA.

LED are available in different sizes, colors, and shapes. ( Refer the images above )

There are many important points that must be considered while using a LED. You will learn about it in the further steps.

Step 2: Turning ON a LED...!!!

**Note --- A LED should never be connected to a Battery / Power supply directly...!!!!

A LED is connected in Forward biased mode in a circuit.
That is, Anode is connected to the positive/higher potential of battery/in the circuit whereas the Cathode is connected to the Negative/Ground/ lower potential of the battery/ in the circuit, respectively.

If a LED is directly connected to the battery or power supply, a large amount of forward current flows through the LED and it blows out...!!!

So, in order to protect it from this damage a 'Resistor' is connected in series with the LED.

This Resistor limits the current that flows through the LED, hence protects it from excessive current.

The value of this Resistor is calculated by a simple formula ----

R = [ Vs - Vf ] \ IL
R = Resistance value required (in ohms)
Vs = Supply Voltage (in volts)
Vf = Forward voltage drop of LED (in volts)
IL = Current through the LED (in Milli-Amperes)

The size of the resistor is needed to be determined according to the power it dissipates ( Refer the instructable : THE RESISTOR)

You can try out glowing a LED, on breadboard if you have the required components. (Breadboard, Several LEDs, connecting wires, Resistors with different values [330ohms to 1Kohms].

Similarly, LEDs are also connected in various different series and parallel combinations as per the user requirements......

In series combination, the Voltage drop of each individual LED gets added, while the Forward current remains the same through each LED.

In parallel combination, the Voltage drop remains the same across each LED, while the Forward current is the addition of individual current through each LED connected in parallel.

Step 3: Uses and Types of LED

Today, LEDs are been widely used in various types of applications.

They are used as Indicators, Displays, in Toys, in various electronics devices, etc.

Some of them are as follows --

1) Different colors of LEDs are used as indicator signals in many devices.
For example -
Red color LEDs indicates Alert / Danger / Stop signals
whereas ,
Green color LEDs indicates Safe/ OK / Go signals.

2) Displays are formed using many LEDs together.
For example -
(Seven/multi)-segment displays and Alphanumeric displays made up of LEDs are used to display digits and other text.

Also there are various types of LEDs available in the market.
They differ in different shapes, colours and sizes.

Colors --- They are available in various different colurs [ Red, Green, Blue, Orange, White, Yellow, and many more ]

Shapes --- They are available in various shapes according to the fittings/holder in which they are fitted.

Sizes --- They are available in various sizes ranging from the smallest SMD (Surface mount devices) types to the big ones... ( General purposes sizes are 3mm and 5mm LEDs ) ( Refer above images )

Power LEDs are a type of LED which have high output power. The emit light at a very high intensity.
The sizes of these LEDs differ as per as their output.
Power output ranges from ( 1 Watts to 1000 watts and more...!!! )

Step 4: Finishing It...!!!

Well, that was all about the basics of a LED.

If you plan to get more knowledge about the LEDs, search it over the internet.

Thanks for watching it out ....!!!

Check out the other instructables too:

The Resistor -

The Diode -

The capacitor -

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    4 Discussions


    2 years ago

    I am a very very basic beginner - more interested in e-textiles but trying to to grasp the basic principles. I have looked at a lot on Instructables relating to breadboards but have found yours to be some of the most helpful...just the information I was looking for clearly explained well illustrated! Thank you!


    4 years ago

    This is a great ible thank you.. John :) ....


    Reply 4 years ago

    thanks for checking out....!!!