LEDs and Forward Voltage | Basic Electronics

[@Jay-fp8iy]

Great channel.

[@CircuitBread]

Thank you so much for the feedback! We're continually trying to improve our content and we always hope that people will like it. 😃 Check out our site CircuitBread.com for written versions of the tutorials, tools, an equation library, and fun extras. 😎

[@Jay-fp8iy]

@@CircuitBread Thanks for the link I most certainly will.

[@FabioSpelta]

Agreed

[@isaacholden3200]

You all prolly dont give a shit but does anybody know of a method to log back into an Instagram account?? I somehow forgot the password. I would love any tips you can offer me.

[@emorytony7486]

@Isaac Holden instablaster :)

[@squidlings]

Was thinking this was a very educationally focused video until you said, "increase the voltage until it explodes, which I hope to do in a minute...." I saw that twinkle in your eye and I knew we could be friends.

[@CircuitBread]

😂

[@adilkanouni5461]

Explode wich i hope so. Caught my attention.and want to comment on that.but then i read this... Guess i join this club😁

[@chopper5371]

Finally, someone explaining in a way I can understand. Super video, and excellent safety tips.

[@Mr.wither_storm]

You're like the Dexter of electricity, the way your aura changes and eyes twinkle at the thought of an explosion ❤️

[@CircuitBread]

😂

[@eclipsen_27]

What an ending, absolutely hilarious! :D

[@Jumphouse2]

Good call on the safety glasses. Always pays to have eye protection whether you think you're going to need it or not.

[@RoshDroz]

I read your comment before finishing the video and was thinking that's quite paranoid to wear safety glasses just for tiny Leds. But then I saw that he's purposely blowing one up. So in that case, yeah, safety glasses were a good call

[@raylow304]

Very detailed explanation, i learn something, cool video!!!

[@CircuitBread]

Awesome, glad to hear it!

[@muhammadbilal2000]

hahah loved the experiment. but what I loved the most was the way you speak. I can listen to you literally for hours :D Anddd subscribed

[@Autotrope]

I like the way you explained this.

[@CircuitBread]

Thanks!

[@aros007z]

Great tutorial I learned a lot, thanks!

[@CircuitBread]

Glad it was helpful! Have a good one!

[@mnada72]

Super cool, I really enjoy watching your videos... have a great day 🙂

[@CircuitBread]

Thanks!

[@soulimanemammar2909]

Great video ! Thanks for sharing

[@eugenevoltage1654]

This is a great video, glad I found your channel. Just starting out with electronics via Arduino starter kit. Looking for extra background info. Thanks for highlighting that LEDs have resistance. I couldn't figure out why my math wasn't matching reality. I have a resistor and LED in series. I see a voltage drop across the LED, therefore it must have resistance. The math in the Arduino book seems to be disregarding LED resistance, perhaps to make simpler for beginners.

[@CircuitBread]

Hi Jarrett, you're exactly right - it's to make things simpler. Their resistance is very non-linear and in most cases, modeling it with no resistance (while on) or only dealing with a set voltage drop is much easier to deal with and "close-enough" for the vast majority of applications/calculations.

[@ddp7240]

Thanks a lot

[@RedSparrow_FREEDOM]

That's funny started work again that's awesome lol! Thanks for nice Video : )

[@CircuitBread]

Thanks! Yeah, that entire demo didn't go at all like I was expecting - part of the fun of working with electronics, I guess!

[@NewShockerGuy]

Great video! I'm trying to understand something and I don't think it's making sense to me. I'm swapping LEDS on a little board. I have two leds that are pretty much the same specs except the following. My one white led says it's 3.4v Vf-forward voltage with a Forward current of 20mA. The other white led I have is also 3.4v Vf-forward voltage with a Forward current of 10mA. Is there a benefit of running one over the other? I even see some LEDS have a forward current of 5mA. I'm confused on the forward current and what that exactly means. I understand if I put more voltage into the LED it will fry... IE: If I don't use the correct resistors and use 9v to power the 3.4v LED it will fry, but why would one choose a forward current of an LED vs another? Or does that not matter as long as I ensure that the forard voltage of the LED is at 3.4v or slightly below?

[@Raptilicus]

I had an infrared LED explode a while ago. It was rated at about 2 V, but I used it on a 3.3 V GPIO pin of my Raspberry Pi without a resistor. This wasn't a problem because it only ever got powered in short bursts to send out an IR signal to my fan. However, a while later, I rebooted my Raspberry Pi and for some reason it completely turned on the GPIO pin. The LED's cap flew across my entire room a few seconds later. I'm glad I didn't sit in front of it while it happened. I didn't try to reproduce it because I don't have too many IR LEDs left. I also killed some LEDs with 5 V in the past, but they all just died immediately with no visible damage.

[@CircuitBread]

It's amazing how far they can fly when they do pop! I'm propose to the team that we just buy a bunch of LEDs and overvolt all of them at the same time and see what happens. Useful? No. Educational? Not really. Fun? Hopefully!

[@pedrotorchio]

such a good video. thank you 🙏

[@vinayakmishra8408]

i was looking for exactly the same thing thanks a lot sir/bro...

[@CircuitBread]

👍 Glad it helped!

[@Ni5ei]

Funny how in English words like odometer, speedometer, calorimeter and dosimeter are all pronounced with the emphasis on the syllable before "meter" but nearly everyone pronounces multimeter with the emphasis on the first syllable. You're the first person I hear it prounouncing like the other words. So which pronunciation is correct?

[@CircuitBread]

I have no idea... I've gotten multiple comments of people saying I pronounce it wrong (or just "different") and I sometimes vary the way I say it. I just don't know anymore. 🤷‍♂️

[@ifell3]

What a creat explanation.

[@newfie-dean5803]

If a 194 size automotive LED bulb specifies the following specs: power = 0.3 W, operating voltage = 9-16V and current @ 13.2 V = 0.035 amps, can you calculate the forward voltage for that bulb using that? V = 0.3/0.035 = 8.6V or would you subtract that number from 12V battery to get 3.4V? Im using an LED license plate bulb but the car turns off the bulb after so long because the Incandescent power draw is like 2.4W whereas the LED needs just 0.3W. So I’m trying to figure out what size resistor I could use to trick the car’s computer. Not sure if I can just take 13.2V and divide by 0.035 amps to get 377 ohms. Then to select the watt rating, use 3.4 V (assuming that’s the forward voltage) and x by 0.035 amps to get 0.12W so you could use a 1/4W resistor with an ohm rating above 377 ohms so a 1/4W, 390-ohm resistor for example. This seems like it should be a simple calculation for someone electrically inclined but even LED bulb specialty vendors have not been able to answer this for me. Do you know if my calculation is correct? Thanks for your time!

[@davidfalconer8913]

LED's make great Zener diodes ( 1v7 to 3 v ) depending on colour .... with the added bonus that they light up when your circuit is functioning correctly ! ..... should you want a higher Zener voltage put some in series , also ( off topic ) the EHT diode from a microwave oven also makes a good 8 to 10 Volt Zener diode ( tried - n - tested ) ...... DAVE™🛑

[@Jaime714Lopez]

Should resistors be in series before LED. I’m just confused when it comes to the seven segment display. I see resistors connected to ground.

[@CircuitBread]

Hi Jaime! It's kind of strange to think about at first, but resistors can be before or after the LED in series - it is electrically equivalent. So, if you see resistors connected to ground, they could just as easily be connected to power on the other side of the LED. As long as there aren't other factors in the circuit that would affect it.

[@scottnathens6377]

I remember the introduction of compact florescent, then said to be "the future." A couple of items you show are good, EG, factors affecting life-span and "directionality" of light emissions. I'd like to believe mass production is responsible for lower-cost LEDs, but "sustainability" remains an unresolved question. For comparison, falling PV costs did not obviate energy inputs needed for production. (If the energy input necessary to produce a PV is subtracted from its life-time production, is it still a good deal, or environmentally friendly?) Given massive subsidies granted for production -- everything from cheap labor to lax environmental regulations -- it's hard to predict if -- this time -- the LED is the future. As for directionality, let's just say it: Structurally, LEDs "leak" out light that must be redirected to mimic what most consumers consider as a light bulb. It's an engineering challenge resolution of which deserves a fair hearing.

[@CircuitBread]

Hey Scott - these are valid points! And while I used to be heavily pro-LED, I'm still pro-LED but with my enthusiasm tempered a bit. I still think LEDs have the large benefit of not requiring mercury like CFLs but the way they're used in arrays make me wonder if their touted lifetimes will never be achieved because the likelihood of one LED in an array failing, rendering the entire array useless, is much higher than a single LED by itself. However, for small embedded projects, while I can actually think of some exceptions, overwhelmingly LEDs will be the right choice.

[@Eroc.48]

So I am trying to understand something. Can a blue led light change in the spectrum value (400nm - 500nm) depending on the voltage? Or is the Spectrum based on the makeup of the light itself and voltage will only increase the intensity of the specific spectrum of the light? For example: a 420nm blue led light at 3 volts will not change and increase to 460nm if the voltage is increased or decreased from its intended rating? Furthermore, if voltage does not have an effect on the spectrum range, what does? And how do they make a 430nm spectrum blue light different from say a 480nm lighter blue light? I see led lights that can be controlled and vary in color, is this due to the wave length of the electric signal, or something else? Also, I understand 2000k 3000k 5000k 6000k 10000k etc etc etc... but how does those ratings relate to certain color of spectrums? From what I understand, "k" ratings is ratings of all colors emitting at once. But it seems that the "k" ratings do have an effect on what spectrum ends up becoming more dominant or visible. For example: 3000k had a yellowish tent to it and 6500k has a white color. How does this "k" ratings change or why does it change the color at different values? I trying to relate this aspect with how they make some led lights with specific spectrum values that are only available to change the intensity of that color, not the color itself.

[@CircuitBread]

Hey Eric, those are some great questions. I'll see if I can address all your questions. First, color is NOT dependent on voltage - you're right that once you pass the forward voltage, modifying the voltage only changes the brightness of the LED. Second, color is dependent on the materials used in manufacturing the LED. We actually created a chart to show this relationship: www.circuitbread.com/tools/led-colors-and-materials-chart Now, the LEDs you're looking at that can vary in color (or have color ratings measured in K) are packaged deals. The LEDs that can vary color are actually RGB LEDs (www.circuitbread.com/tutorials/how-rgb-leds-work-and-how-to-control-color) and there's actually three LEDs in there that can be controlled individually to "fake" the color you want. Finally, the K ratings are actually the way the manufacturers tell you, as the consumer, the color of the light you're planning on buying - if it's more yellow or blue.

[@Eroc.48]

@@CircuitBread thank you for the quick reply. You answered my questions, which leads me to one more question. The link that you sent me for the different color variations was not as specific as I would like. It's the information I was wanting to know but it didn't state the different percentage of materials used to determine a specific color. Do you know of a hyperlink that might be more detailed? For example, what percentage of materials they use to achieve 450nm, or 470nm etc etc etc...? More interested in the specifics instead of the general concept of how it's done. Just want a deeper understanding how they manufacture led lights.

[@mattzee6287]

Hey, I have a question... Would it be possible to safely step down U.S. power on a 100 vac Japanese device, using blue led lights?

[@CircuitBread]

Technically, yes, realistically, no. With the blue LEDs, you'd have to be very careful about how much current ran through them (so your Japanese device would have to consume nearly no power) and, in the negative half cycle of the AC signal, you'd have to make sure you were reverse biasing your diodes so much that they failed. So, while you could technically get something to work, I doubt it would be effective and easy enough to be worth the hassle.

[@s1ovaak]

What's the model name of this power supply unit you using? It's nice and compact...

[@CircuitBread]

Sadly, Sparkfun retired it (www.sparkfun.com/products/retired/9291) but I'm not sure if it's still being manufactured and sold through someone else.. It's not perfect but it does have a nice footprint and works for the majority of applications I've needed.

[@s1ovaak]

@@CircuitBread Thanks for the reply, I will check the internet. Maybe, I will get lucky and find one lol

[@ApexMark2002]

How on earth 1) did that LED not burn out long before it did and 2) how did it come back on?? Mine fry and die with 5v input if I don't use a resistor, and certainly none have ever come back on. I'd like to know your special source. : )

[@CircuitBread]

The key is to publicly try and make it burn out! If I weren't trying to show it burning out, I'm sure it would've exploded in a fiery ruin the moment I gave it any voltage.

[@ApexMark2002]

@@CircuitBread Actually since watching your video I've been testing mine. I find the red ones oddly difficult to fry. They flare out, then nearly die, but return to near original quality despite suffering several times their front voltage which my other colors (esp. white) can't take. Strange. (Just saw a SciAmerican article saying the worst environment offenders are low intensity red LED's, which contain up to 8x the amount of lead while white contain the least. Wonder if it's related).

[@CircuitBread]

That's interesting! I'm trying to remember the color of the LEDs I've seen fail and/or pop. Not something I typically pay attention to. I'll ask some of the other engineers here if they've ever noticed that. I wonder why the red LEDs require 8x the amount of lead. What portion of the LED requires all that lead? If we knew the answer to that, maybe we'd be able to better guess if it is actually related.

[@mightymagnum8811]

I got confused when you had all LEDs connected to your power supply at the beginning, when you were quoting the current that was flowing. If you were reading that direct from your power supply screen, then shouldn't you have been dividing the quoted value accordingly, since you had them wired in parallel? Secondly, even doing some simple division to describe what current was flowing where, wouldn't have been very accurate either, since the different characteristics of each LED would mean more current flowing through one and the other. At 3:44 in the link below, he gives a clear explanation of this. I think it is a good idea to have a separate window showing what is being displayed on your power supply, whilst showing your main DUT in the main window, as I ended up just guessing that you were doing mental division when quoting current flow, but at the end of the day, I still didn't know what current was flowing where. Thanks kzbin.info/www/bejne/a3PSc4GNaNiqpqM

[@needsomehike]

at 1:50 when you said current will flow in through the longer lead (anode - positive) through the LED and out through the shorter lead ( cathode - negtive) were you talking in "conventional" terms? as the current flows from negative to positive and the LED-s are polarized...... isn't it (non-conventional) real life scenario that the current flows from negative to positive, so through the shorter lead and out the longer lead?

[@CircuitBread]

This is where the challenge is. The conventional current notation is that current flows from positive to negative (anode to cathode) but electron flow is opposite (cathode to anode). It isn’t normally an issue, but it confuses people (including me) when going from the semiconductor device level to the circuits level, as that’s where you typically switch from one standard being the norm to the other standard being the norm.

[@needsomehike]

@@CircuitBread yes, i am an absolute beginner and it confuses the shit out of me..... so the answer is, sir........? in real life (like on my little breadboard) current flows in at the shorter leg (neg) through the LED out on the longer leg isn't it? also the diode with the stripe on the positive end .....current flows in at the positive (striped end) through the diode and out on the negative end.....isn't it? please confirm.......I had asked the same question under other videos as well but it seems engineers lie enigmas....barely anybody would give me a straight answer.

[@CircuitBread]

I can sympathize, as it is confusing. I'd recommend these two videos to lay a foundation: kzbin.info/www/bejne/gqeVZGSap5iqa5o and then kzbin.info/www/bejne/qWGtq6GOiq16gsk With that foundation, you can see how electrons will flow from the shorter leg to the longer leg (cathode to anode). BUT as current is semi-arbitrarily considered opposite to the flow of electrons, current flows from the longer leg to the shorter leg (anode to cathode). That will hopefully resolve the contradiction, if not necessarily the frustration.

[@needsomehike]

@@CircuitBread the second one is gold! thank you!

[@charlesklein7232]

the new led for your house dont have a standard voltage! they are not 110 or 220 volts but rather are "RANGES" they are " AC85-265V " between 85 and 265 volts. while this sounds interesting that it will work on any supply i suspect this will effect the wattage ratings and in term its brightness! a 10 watt bulb run on 220 volts i would think would be brighter then one run at 110 volts! unless these can change their amperage ratings? can they change their amperage ratings and stay at the "claimed" wattage ratings? because most LED are in general 220 volts. so for the usa i suspect we get lower wattage ratings.

[@CircuitBread]

Hey Charles - certain LEDs, like power supplies for computers, have driving electronics that can take a wide range of voltages. They're setup so that if there is a greater voltage, there will be less current draw, to keep the power consumption the same (and the light output). Conversely, at the lower voltages you find in the US, you'll have to draw more power. Not all LED bulbs do this, though, and definitely the discrete bulbs discussed in this video could not handle a direct application of even 85V without utter destruction. Even bare, discrete LEDs have different voltage and current ratings - once you add in some electronics to drive the LEDs, the amount of different voltage/current/control options increases dramatically.

[@Muradsahar]

Why it is not possible to make a LED from pure silicon?

[@CircuitBread]

The magic happens when you put two types of doped silicon together. Otherwise, electrons flow through the material like a poor conductor, just generating heat and not much else. I recommend checking out our semiconductor playlist that discusses the lower level aspects of semiconductors in greater detail.

[@Muradsahar]

@@CircuitBread I am going to watch that playlist!, Recently I was corrected when I said that silicon might be used for making an LED in addition to GaAs (Compound-Semiconductors), the explanation I got was, that silicon goes through what is known as "indirect-electronic-transition", which ends up producing phonons (heat) not the photons (light), so if we forced a silicon wafer by applying voltage, it would end up heating silicon wafer, and eventually destroying it. Can you recommend any article with detailed explanation on this topic of discussion.?

[@jesterraj]

Nice what P/S are you using??

[@CircuitBread]

Hey there! I got this power supply from Sparkfun years ago, they don't actually sell it anymore, but here's a link to their "retired" page: www.sparkfun.com/products/retired/9291 For client videos we have a much beefier B&K Precision power supply which is more versatile and can provide a lot more power. But it was quadruple the price, so not something we would've gotten if it weren't for actually paid client work.

[@jesterraj]

@@CircuitBread IS it a linear p/s?

[@CircuitBread]

Nope, it's a switching power supply, not linear.

[@james77011]

😅🤣 u are lucky... when i applied to much current through my L.E.Ds they started to smoke for a short moment... so to make things more fun for me.. i went outside and connected about 300 L.E.Ds in series and got a lot of smoke and a few pops.. 😂

[@CircuitBread]

Maybe we should mix up the content on this channel with component failures... I'll have to think about this.

[@Roman00744]

Very well made video but the info is not very relevant. No 1 uses this kind of leds anymore except for indicators, it would have been much more informative if you talked about and showed the current mostly used 5050, 2830, 3070 and so on kind of leds that have very different voltage and amp ratings. Right now i'm a little stomped trying to lower the current in a new kind of led driver from a 13w tablet lamp, no more easy 2 resistors current setting.

[@CircuitBread]

Hey Roman, thanks for the feedback! Are you referring to those LED packages in discrete configurations or in strips? If it's discrete, we have another video going over the steps for how to figure out the best resistor for an LED - it's pretty generic (though still using the 5mm LED as an example) and is only for using the much easier but less efficient method of driving LEDs with a resistor. But, reading your comment, I imagine you're already way beyond that tutorial. We don't have anything about driving strips, nor any plans to do so, honestly. What exactly are you struggling with your LED driver?

[@Roman00744]

@@CircuitBread Thanks for the answer. Yeah limiting with a resistor is the easiest and it has it's uses but not for limiting modern leds, the simplest "modern" led driver i know is capacitor limiting but it's not great. Best way is with a dedicated cc led driver chip and up until now the chinese used a simple chip that had 2 resistors to set the desired cc. In this new driver there is a new chip that I don't know how to set the cc because i can't find the datasheet.

[@ryanjayryannnicolas8435]

Michael Bay is disappointed

[@CircuitBread]

😂

[@james77011]

well, if u want to show some components explode.. connect some electrolytic capacitors backwards .. 😅🤣😂

[@CircuitBread]

I've done that once (unfortunately, it was on accident) and it was fun but just made a bit of a "pfft" sound, blew the end out, and smoked a touch.

[@james77011]

@@CircuitBread try putting in a larger capacitor backwards and let's see if it can explode 🙈

[@MichaelApproved]

Ahhh the smell of cancer.

[@CircuitBread]

😂