What is an LED and how does it work #technology #electronics #engineering #led

[GhostlyMinty]

remember kids, any electronic circuit can emit light, it’s just most can only do it once

[tedrobinson]

It is not voltage that destroys the LED. It is current.

[X_mano]

"the colour is not because of the case"
My brain has been lying to me this whole time

[jonathanm]

You perfectly achieved what you obviously set out to do - complete, basic, logical description in as few words as possible. Beautiful.

[hglankshear]

Love the simplicity of this explanation

[jBKht]

Diodes were designed and used as one way valves. The light was a by product and it wasn't until later people started focusing on the light

[oreo]

The science behind the blue LED is crazy

[dhruv]

This man will taught me Whole Semiconductor Chapter 😂

[blobscott]

An LED will maintain a fixed voltage across its leads, typically .6 volts. If you provide a power source with no current limiting, the LED will draw current up to its max current rating where it will burn out. The resistor limits the current flowing through the circuit, protecting the LED - It's generally referred to as a current limiting resistor. Describing it as a voltage limiter is incorrect.

[gregjones]

The flow of electrons is termed electron current. Electrons flow from the negative terminal to the positive. Conventional current or simply current, behaves as if positive charge carriers cause current flow. Conventional current flows from the positive terminal to the negative.

[julesvandenaker]

Really like the visuals in your explanation! One thing I want to point out is that the resistor is used to limit current through the diode. Diodes have a maximum voltage rating, however the failure of the diode in the video is cause by too much current.

[robertoprestigiacomo]

In a way, the explanation makes sense, or it's more accessible for a bigger audience, but technically it's not a 100% correct answer (and I saw people failing their 'Electronic Devices' exam for giving answers like this... In engineering you can fail exams depending on how you phrase your answer).

Short answer (given by many others already): The resistor limits the current, not the voltage. The voltage across the LED will be practically constant and not so high while it's on.

Long Answer (to explain what we all mean by limiting the current): LEDs are used in direct polarization to light up and in this condition when you apply a voltage to a LED, the voltage across the LED will be fixed at its cut-off voltage of a few volts (depending on the colour or the material it's made of) so you don't need to limit the voltage (on the contrary, you need to be at it's cut-off). On the other hand, at the cut-off voltage the current ramps up to very high values, very quickly, causing the power (V x I) to raise too much above the maximum power rating (the LED will melt and break like in the video due to excessive heat dissipation) and this is because the LED itself doesn't have enough internal resistance due to its chemical composition, size, packaging, etc. The resistor is used to determine a more or less fixed value of the current (knowing the supply voltage and the cutoff voltage across the LED, you know the voltage across the resistor by difference (2nd Kirchhoff's law) and you can choose the resistor value depending on which current you want (Ohm's law)). The current value is chosen so that the product between that current and the LED cut-off voltage stays below the maximum power rating specified in the LED datasheet.

One way you can get around if you want to stick with the voltage limiting point of view is by pointing out that if you want to use a, let's say 5 V supply to a LED than has a cutoff voltage of 2 V, the remaining 3 V must go somewhere (2nd Kirchhoff's Law) so you put a resistor there to "keep those 3 V busy".
It's an absolutely valid and correct answer, but the current limiting answer is better because it takes into account how a LED acually works and can avoid a teacher asking "so why wouldn't I just use 2 V supply directly on the LED and no resistor?".


PS I love this content so I don't mean to be disrespectful with my correction :)

[Nick_]

why the "end at the start" thing... all you're doing is causing confusion just for the sake of using a feature...
other than that, your videos are great!

[mrreemann]

I am of the school that doesn't believe a photon is a particle. Light is a wave of energy.

[farmerab]

Voltage destroy’s incandescent lamps, current destroys LED’s. The resistor is to reduce current so the led isn’t over driven.

[craigathonian]

Fascinating ! LED's each have a different element to emit their color, With purple being the impossible for scientist for many years. Love this technology !

[L-udo]

Leds are driven with constant current.

Thats what resistors do. They limit current flow. Not voltage

[ericbaca]

The length of the wave determines the color, mind boggling ❤

[christianhawkins]

sometimes an led's color is from the case, its dependant on whether or not the assembler wants to use an actual colored led or just white and then use the case to change the color

[StrummerDave]

We use a resistor to limit current not to manage voltage.