How LED Works - Unravel the Mysteries of How LEDs Work!

Summary

This video script delves into the workings of LEDs, explaining how these light-emitting diodes produce various colors by manipulating the semiconductor material inside. It covers the fundamental principles behind diodes and LEDs, their energy efficiency compared to incandescent lights, and the different types and applications of LEDs, including multi-color and high-powered LEDs. The script also touches on the importance of resistors in protecting LEDs from excessive current and introduces the concept of PN junctions in semiconductors, which are key to the color of light emitted. Additionally, it discusses the role of data brokers and the use of Incogni for privacy protection.

Takeaways

• 🚀 LEDs, or light-emitting diodes, emit light when a voltage is applied across them due to the semiconductor material inside.
• 🔍 Shining light onto an LED can reverse the process, producing a small voltage, demonstrating the dual nature of LEDs as light and electricity converters.
• 🌈 The color of the light produced by an LED is determined by the semiconductor material used, with different materials emitting different wavelengths of light within the visible spectrum.
• 🔆 LEDs are more energy-efficient than incandescent lights because they do not require heat to produce light, reducing energy consumption and heat generation.
• 🔌 The polarity of an LED is crucial; it only illuminates when the anode is connected to the positive side and the cathode to the negative.
• 🔍 The flat edge on an LED casing typically indicates the cathode side, helping to identify the correct connection polarity.
• 💡 There are various types of LEDs, including through-hole, surface-mount devices (SMD), high-powered, and multi-color LEDs, each suited for different applications.
• 🛠️ LEDs require a current-limiting resistor to prevent damage from excessive current, with the brightness controlled by varying the current or voltage.
• 🔄 Bi-directional and RGB LEDs can change colors or mix colors to produce a range of hues, including white light, by controlling the current to individual diodes within the unit.
• 🔬 The semiconductor material in LEDs is made by combining elements like gallium and arsenic, with impurities added to create n-type and p-type layers, which determine the emitted light color.
• 🌐 The development of LED technology has led to the creation of energy-efficient lighting solutions, such as LED bulbs, which are now widely used.

Q & A

What is the basic principle behind the light emission of an LED?

An LED emits light when a voltage is applied across it, causing electrons in the semiconductor material to recombine with holes, which releases energy in the form of photons.

How does an LED symbol differ from a standard diode symbol in engineering drawings?

An LED symbol is similar to a diode symbol but includes arrows that indicate light emission, distinguishing it from a standard diode which does not emit light.

What is the range of wavelengths for visible light to human eyes?

Visible light to human eyes has a wavelength range of approximately 400 to 700 nanometers.

Why do standard diodes become hot, unlike LEDs?

Standard diodes become hot because they produce photons in the near-infrared range, which are absorbed by the casing and converted to heat. LEDs, on the other hand, produce very little heat due to their different semiconductor materials and photon emission range.

What is the typical wavelength of the infrared light emitted by an LED in a TV remote?

The typical wavelength of the infrared light emitted by an LED in a TV remote is around 940 nanometers, which is outside the visible spectrum for humans.

What is the main reason LEDs are more energy efficient compared to traditional incandescent lights?

LEDs are more energy efficient because they do not need to produce heat to emit light, unlike incandescent lights which generate a lot of heat through the collisions of electrons with atoms in the filament.

What does the flat edge on one side of a through-hole LED indicate?

The flat edge on one side of a through-hole LED indicates the cathode side of the LED, helping to identify the correct polarity for connection.

What is the purpose of the yellow phosphorus layer over a blue LED in some light bulbs?

The yellow phosphorus layer over a blue LED in some light bulbs is used to combine with the blue light to produce a white light, as the mixture of yellow and blue light appears white to the human eye.

How can the color of an LED be changed by altering its semiconductor material?

The color of an LED can be changed by altering the semiconductor material used in its construction. Different materials and their mixtures produce different band gaps, resulting in photons of different wavelengths and thus different colors of light.

What is the role of a resistor in an LED circuit?

A resistor in an LED circuit is used to limit the current flow and protect the LED from being destroyed by an excessive amount of current. It also helps to control the brightness of the LED by varying the current.

How can the brightness of an LED be controlled?

The brightness of an LED can be controlled by varying the current supplied to it. This can be achieved by using a resistor to set the current in the circuit or by using an LED driver that provides a constant current.

Outlines

00:00

🔌 Understanding LEDs and Their Applications

This paragraph delves into the functioning of Light Emitting Diodes (LEDs), explaining how they emit light when a voltage is applied across them due to the semiconductor material inside. It contrasts LEDs with standard diodes, highlighting the visible light emission of LEDs within the human-visible spectrum of 400 to 700 nanometers. The script also touches on the use of LEDs in various applications, such as TV remotes emitting infrared light, and the energy efficiency of LEDs compared to incandescent lights. The paragraph introduces different types of LEDs, including through-hole and surface mount devices (SMD), and discusses the significance of the flat edge on LEDs, which indicates the cathode side.

05:00

💡 Exploring LED Colors, Polarity, and Circuitry

The second paragraph focuses on the different colors of light emitted by LEDs, which are determined by the semiconductor material rather than the color of the LED case. It explains the importance of connecting the anode and cathode correctly to illuminate the LED and provides tips for identifying the polarity of an LED when the leads are trimmed or not easily distinguishable. The paragraph also covers various types of LEDs, such as bi-color and RGB LEDs, which can produce a spectrum of colors by controlling the voltage and current to each LED. Additionally, it discusses the use of resistors to protect LEDs from high currents and the role of LED drivers in ensuring stable operation.

10:04

🔍 The Inner Workings of LEDs and Semiconductors

This paragraph provides an in-depth look at the internal structure of LEDs, including the anode and cathode leads, the epoxy resin casing, and the semiconductor layers that produce light. It explains the concept of a PN junction and how it forms a barrier that prevents the flow of electrons until a sufficient voltage is applied. The script also discusses the process of creating semiconductors by adding impurities to silicon to form n-type and p-type layers, and how the energy levels and band gaps of these materials determine the color of light emitted by the LED. It further explains how different semiconductor materials, such as gallium arsenide and gallium phosphide, can be combined to produce a range of colors, including white light, which has led to the widespread use of LED bulbs.

15:06

🌐 The Science Behind Semiconductors and Color Production

The final paragraph explores the atomic structure and energy levels that underpin semiconductor behavior, explaining how electrons move between the valence and conduction bands. It details how different semiconductor materials, such as silicon, gallium arsenide, and gallium phosphide, have varying band gaps that affect the wavelength and color of the emitted light. The paragraph concludes by illustrating how mixing different ratios of these materials can produce a wide range of colors, including the primary colors red, green, and blue, which can be combined to create any color, including white light. It also mentions the use of incogni for data privacy and encourages viewers to continue learning about electronics through provided links and social media channels.

Keywords

💡LED

LED stands for Light Emitting Diode. It is a semiconductor device that emits light when an electrical current passes through it. In the video, LEDs are the central theme, with various types and applications being discussed, such as through-hole LEDs, SMD LEDs, and RGB LEDs.

💡Semiconductor

A semiconductor is a material that has electrical conductivity between that of a conductor and an insulator. In the context of the video, semiconductor material is used in LEDs to produce light through the recombination of electrons and holes, which emit photons.

💡Photon

A photon is a quantum of light and other electromagnetic radiation. The script explains that LEDs emit photons in the visible light spectrum, which is why we can see the light they produce.

💡Wavelength

Wavelength is the distance between two successive points in a wave that are in phase with each other. The video discusses how different wavelengths of photons correspond to different colors in the visible light spectrum, which is how LEDs of various colors are made.

💡PN Junction

A PN Junction is a boundary or interface between two types of semiconductor material, p-type and n-type, which join together to form a diode. In the video, the PN Junction is where the recombination of electrons and holes occurs, resulting in the emission of light in LEDs.

💡Diode

A diode is a two-terminal electronic component that allows current to flow primarily in one direction. The video script contrasts LEDs with standard diodes, noting that while both are made from semiconductors, LEDs are designed to emit light in the visible spectrum.

💡Visible Spectrum

The visible spectrum refers to the range of wavelengths of light that are visible to the human eye, typically from 400 to 700 nanometers. The video explains how LEDs emit light within this range, allowing us to see different colors.

💡Infrared Light

Infrared light is a type of electromagnetic radiation with wavelengths longer than visible light, typically around 940 nanometers as mentioned in the script. It is used in applications like TV remotes, which emit infrared light that is invisible to the human eye but can be detected by cameras.

💡SMD

SMD stands for Surface Mount Device. It is a type of LED, as well as other electronic components, that are mounted directly onto the surface of a circuit board. The video mentions SMD LEDs as being smaller and used in compact designs, such as in light bulbs.

💡RGB LED

An RGB LED is a type of LED that contains red, green, and blue LEDs within a single package. The video explains how these can be controlled to produce a wide range of colors, including white, by mixing the light from the individual colored LEDs.

💡Resistor

A resistor is a passive electronic component that opposes the flow of electric current in a circuit. In the context of the video, resistors are used to limit the current flowing through LEDs, preventing them from being damaged by excessive current.

Highlights

LEDs produce light through a semiconductor material that emits energy as photons when voltage is applied.

LEDs and diodes operate on the principle of semiconductor materials, but LEDs emit visible light photons for humans.

The visible light spectrum for humans ranges from 400 to 700 nanometers, which produces different colors.

LEDs are used in various applications, including TV remotes that emit infrared light with a wavelength of around 940 nanometers.

Standard diodes produce near-infrared photons absorbed by the casing and converted to heat, unlike LEDs which are cooler.

Incandescent lights generate a lot of heat, while LEDs are more energy efficient as they don't need to produce heat to emit light.

Different types of LEDs include through-hole, SMD, high-powered, and bi-color LEDs for various applications.

LEDs with color lenses or transparent versions emit different colors based on the semiconductor material, not the case color.

LEDs illuminate when connected correctly with the anode to positive and cathode to negative, and polarity can be identified by the flat edge on the LED case.

Resistors are used to protect LEDs by reducing current and turning electrical energy into heat.

LEDs can be manually flashed or automated with circuits involving resistors, capacitors, and transistors.

RGB LEDs contain red, green, and blue LEDs that can be mixed to create any color, including white light.

LEDs require a specific voltage and current to operate without damage, which can be controlled with LED drivers.

LEDs are made of semiconductor materials with a PN junction that emits photons of specific wavelengths when powered.

Different semiconductor materials like gallium arsenide and gallium phosphide are used to produce a range of visible light colors in LEDs.

The color of the LED light is determined by the wavelength of the emitted photon, which depends on the semiconductor material used.

By mixing different semiconductor materials, any color of light, including white, can be produced in LEDs.

Transcripts

sponsored by incopy why does this led

produce a red light but this one

produces a blue line when we apply a

voltage across an LED it produces light

it all comes from a tiny piece of

semiconductor material inside which is

emitting energy as photons but if we

shine a light onto the LED then we are

firing photons back into it so the

process reverses and it will also

produce a small voltage

80ds look something like this they come

in different shapes colors and sizes for

different applications LED stands for

light emitting diode we use this symbol

in engineering drawings for LEDs notice

it looks very similar to a diode symbol

except it has these arrows that indicate

that light is being emitted LEDs and

diodes both work on the same principle

it's just a semiconductor material in

the middle of some electrical connectors

they both emit photons but only the LED

emits photons in the range visible to

humans and that's when the photon has a

wavelength of around 400 to 700

nanometers we've received different

colors depending on the wavelength of

the photon in this range

FM radio signal is also a photon wave

but it's around 3 meters

Wi-Fi signal is smaller at around six

centimeters and a medical x-ray is Tiny

at around

0.01 nanometers but we can't see any of

these because they are outside of our

visible spectrum have you ever noticed

there's an LED in your TV remote

this emits infrared light the photon has

a wavelength typically around

940 nanometers so humans can't see it

however you can see it on the camera of

your phone

inside the semiconductor we just have

electrons combining with holes and

releasing photons in the process we will

learn how it works in more detail later

on in this video now a standard diode

uses different materials in its

semiconductor layer which produce

photons in the near infrared range these

are absorbed by the casing and converted

to heat so dodes become hot but LEDs

produce very little heat unlike

traditional incandescent lights which

generate a lot of heat in this design

the electrons collide with atoms in the

filament and these collisions produce

heat the filament heats up so much it

produces visible light

LEDs don't need to produce heat to

produce light and so they are much more

energy efficient most of you will

recognize this type of LED the five

millimeter through hole type but have

you ever noticed one side has a flat

Edge

tell me what you think this is for in

the comment section and I'll give you

the answer later on in this video

through-hole LEDs are perfect for

learning electronics we can buy them in

bulk very cheaply and I'll leave a link

for you in the video description for

where you can buy them these can be

inserted into test boards or even

soldered into printed circuit boards we

can get smaller three millimeter

versions or even larger 10 millimeter

versions typically they are Dome shaped

but there are other shapes available

like this square one we also get SMD

type which stands for surface mount

device these are soldered to circuit

boards to allow compact designs these

versions are much smaller some like this

one are so small you would need a

microscope to solder them we usually

find SMD LEDs used in our light bulbs

this one is actually a blue LED it just

has a layer of yellow phosphorus over it

and that's because the yellow and blue

light combined makes a white light we

can also get these very high powered

LEDs which are basically just lots of

LEDs packed tightly together and are

often used for torches and also flood

lights

LEDs can produce such Bright Lights

though we can see them from a great

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below LEDs come in various different

color lenses but we can also get

transparent versions which emit

different color light bytes too the

cases are only colored to make it easy

for us to tell what color light will be

produced is actually just the material

inside the semiconductor layer that

produces the different colors of light

and not the color of the case we will

learn how that works later on in this

video LEDs only illuminate when we

connect the anode lead to the positive

and the cathode to the negative take a

blue LED and a 3 volt coin battery

notice it only illuminates when

connected a certain way it's easy to

identify the correct polarity because

the longest lead of the LED is the anode

but what if the LED leads have been

trimmed well don't worry because one

side of the LED's case has a flat Edge

and this indicates the cathode side

additionally inside we can notice that

there are two metal plates the larger

plate is the cathode with snd LEDs we

find a small dot on the top sometimes

this is used to indicate the anode other

times this is for the cathode so you'll

have to check the manufacturer's

datasheet or test it yourself in this

example the LED illuminates when the

positive is connected to the dot side on

the back we find a marking but this

again could mean either the anode or

cathode here we can see the LED

illuminates when connected like this

we can manually flash LEDs by using a

switch or we can use a simple circuit

like this resistor capacitor and

transistor circuit to automate this and

here is the schematic for that circuit

but these blinking LEDs will turn on and

off by themselves automatically at a

certain frequency there's also these

type which change color by themselves in

a fast or slow transition

inside is a tiny controller that sets

the frequency and here is the schematic

for that circuit then we have

bi-directional LEDs these can change

between two colors inside there are two

LEDs connected in opposite ways so when

current flows this way one LED turns on

and when current flows the other way the

other LED turns on only one LED can be

turned on at a time however we can get

these three pin bio color type we can

manually switch them between one color

the other color or both colors together

these have two LEDs inside but they

share a terminal

then we have four pin RGB LEDs these

have three separate LEDs inside a red a

green and a blue and these all share a

terminal we can't activate them

separately two at a time to mix the

colors or all three to make a white

light we can control the voltage and

current to each led to make any color we

wish and here is the schematic for that

circuit now if you look closely at your

monitor you can see the same thing is

happening here too lots of tiny

multi-color LEDs by the way I've left

links for these LEDs in the video

description down below but where have

you seen these LEDs used or where could

you use them let me know in the comment

section down below if we try to connect

this led to this nine volt battery it

will instantly be destroyed inside the

LED is a thin wire the battery will try

to push so many electrons through this

wire that it just breaks

so we use a resistor to reduce the

current of electrons and you can watch

my video on how resistors work to learn

more the resistor removes energy from

the circuit to protect the LED it is

literally turning the electrical energy

into heat to remove it the battery is

providing 9 volts the resistor removes

around 7 volts and the LED will remove

the remaining two volts

the resistor is setting the current for

the circuit we can vary the current to

control the brightness of the LED but

when we vary the voltage Supply the

current will also vary the

manufacturer's datasheet will tell us

the rated voltage and current this led

is rated for 20 milliamps but we can go

slightly above or below this and it will

work fine the lower we go the dimmer the

LED will shine but if we go too high the

LED will be destroyed that's why we find

LED drivers inside light bulbs and also

dedicated units powering strip lighting

this lamp runs off of 230 volts the

rectifier is changing the alternating

current into direct current and the

capacitor is smoothing this out this

chip is providing a constant current to

the LEDs so that they don't flicker this

USB light strip is incredibly simple the

USB port provides a 5 volt Rail and a

ground Rail between them is just a

resistor and an LED each set is

connected in parallel which means we can

cut this to almost any length the more

LEDs we remove the lower the current

will be when we look at an LED we notice

there are two metal leads which connect

to the main body the longest lead is the

anode and the shortest lead is the

cathode the body is molded from an epoxy

resin these are often colored just to

make it easier to tell what color the

LED light will be on the side of the

case is a flat Edge this indicates the

cathode side looking inside the LED case

we see that both the anode and the

cathode leads each have a metal plate at

the end and these are separated by small

Gap the plates stop the knees from

turning the larger plate also indicates

the cathode side on the cathode plate we

typically find a cone shape within the

cone we find a small p piece of

semiconductor material made from a layer

of n-type material with a layer of

p-type material on top of this this

forms a p n Junction

a thin wire then runs between the ano

terminal and the p-type material to

complete the circuit when the LED is

powered photons are emitted from the PN

Junction of the semiconductor which

produces the colored light the cone

shape helps reflect the light out of the

top of the LED case

the color of the light depends on the

wavelength of the photon being emitted

from the semiconductor and that depends

on the material being used electricity

is the flow of electrons electrons flow

easily through conductors like copper

but they can't flow very easily through

insulators like rubber the n-type layer

has lots of free electrons and the

p-type layer is missing some electrons

but it has lots of holes that electrons

can go and sit in

electrons are negatively charged so the

letter N just lets us know which side

has a negative charge as electrons are

negative we consider the holes to be

positive and so we use the letter P to

make the semiconductor for a normal

diode we just use silicon this has four

electrons in its valence shell the atoms

will share these to become stable so

where do the electrons and holes come

from well we add some impurities like

phosphorus which has five electrons in

its valence shell these are shared with

the Silicon atoms but it will leave one

electron spare

this electron is free to move to other

atoms and so this is our n-type layer

for the p-type layer we add some

aluminum which only has three electrons

in the valence shell it doesn't have

enough to share with all of its

neighboring atoms so there will be a

hole where an electron can move too we

now have a layer with two many electrons

and also a layer with not enough

electrons this joins to form the PN

Junction

at this Junction we get a depletion

region

some of the electrons move across to

fill the holes and some of the holes

move across but this will create a

barrier with a slightly positively

charged region and a slightly negatively

charged region

this creates an electric field which

prevents more electrons moving across

when we connect a battery electrons will

flow and we call this a forward bias but

if the voltage is too small then we

can't break this barrier

with a normal diode we can see the

barrier is around 0.5 to 0.7 volts this

is the minimum voltage required for

current to flow but with a red LED it's

much higher around 1.7 volts the

manufacturer will provide a chart like

this which shows the forward current at

a certain forward voltage we can see

that it starts at around 1.7 volts

and we can see that at 2 volts we should

see around 20 milliamps of current

in this example that's exactly what we

see

now looking at a simple ball model of an

atom we have the nucleus at the center

which contains all the protons and

neutrons

then we have a number of orbital shells

where electrons can sit

each shell can hold a certain number of

electrons and an electron needs to have

a certain energy to be accepted into

that shell the further the distance of

the shell the more energy is required

the outermost shell is the valence band

just beyond this is the conduction band

electrons that reach this band can break

free from the atom in a conductor like

copper the conduction band is very close

so the electrons can easily move but in

an insulator like rubber the conduction

band is too far away so the electrons

can't escape but with a semiconductor

like Silicon the conduction band is just

a short distance away so it will act

like an insulator but when we apply a

voltage the electron in the valence

shell can break free

in the Silicon semiconductor like a

diode the electron is jumping from the

n-type conduction band to the p-type

valence band the valence band has less

energy than the conduction band so the

electron needs to lose some energy to be

accepted into this lower band it does

that by releasing a photon in Silicon it

needs to lose around 1.1 electron volts

to be accepted the energy of this photon

is equal to a wavelength of around

1127 nanometers and I'll show you how to

calculate that in just a moment that

means the Silicon diodes emit near

infrared light which humans can't see

so instead of silicon scientists mix

gallium and arsenic to form the

semiconductor

then they add some impurities to this to

form the n-type and the p-type layers

this semiconductor has a larger band gap

of around

1.424 electron volts and this produces

an 870 nanometer wavelength which is

better but still too high then they

tried gallium phosphide which has a band

gap of 2.26 electron volts and this

results in a wavelength of 548

nanometers which is perfect because the

human eye can see this and we see this

as green

so then scientists realize that by

blending the mixture of gallium arsenic

with gallium phosphide

they could achieve any color between

these two points

so if we mixed 60 gallium arsenic with

40 gallium phosphide we would get around

1.7 electron volts

we can convert that to a wavelength

using this formula so we drop these

numbers in to get this equation and this

gives us a wavelength of around 705

nanometers which produces a red light so

if we mixed 15 gallium arsenic with 85

gallium phosphide then this would give

us 2.13 electron volts which is a

wavelength of 580 nanometers and this

would give us yellow

so by mixing different materials

together to form the semiconductor this

will create different colored lights

once red green and blue could be

produced we can mix these colors to

produce any color we need including

white light and when white light was

possible LED bulbs became widely used

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