It's really great to see somebody actually talking about this. So many LED tutorials completely gloss over this issue, or worse yet even actually tell people that you can wire LEDs in parallel with a single resistor. And the truth is that if you have all the same LEDs from the same manufacturer, usually they're close enough that it appears to work fine, at first. And then maybe a week, or a month, or 6 months down the line just mysteriously fails. One other thing to note is that the forward voltage of LEDs also _depends on their temperature._ If one LED starts out taking even a tiny tiny bit more current than the others, that will cause it to heat up ever so slightly more than the others, and when LEDs heat up, their forward voltage goes _down,_ which means that LED then starts taking _more current,_ which makes it heat up more, which makes it take more current, etc, etc. It's basically a "runaway" scenario waiting to happen. This is why even if you manage to match your LEDs extremely precisely, you really still can't guarantee that this sort of thing won't happen, because it only takes the slightest imbalance anywhere at any time to make it potentially all spiral out of control.
@@joshp7477 Individual resistors fixes the issue of a single failure that cascades inexorably into failure of all LEDS. But any LED can begin to go into thermal runaway (without affecting the other LEDs) if its resistor value is set to allow the max current through the LED (for max. brightness) and the cooling of the LED is inadequate, e.g. the cooling fan breaks down or the ambient air temperature becomes higher than expected. As the LED starts to overheat its voltage drops and more current flows but the increased current flow causes a larger voltage drop across the resistor which reduces the voltage across the LED. This auto stabilization may be enough to stop the thermal runaway from proceeding to the blowout stage, especially if the LED cooling is restored quickly enough, but the LED operated at a higher current and temperature than it was designed for, and its operational life has been permanently reduced. By how much? It depends on its design and by how much it was abused, i.e. by how much was the normal max current limit exceeded, how close did it come to the absolute max. current (blowout) value, for how long, at what temperature, how much abuse had it endured previously, etc.
I've got an LED flood light with LEDs coupled (tripled?) by 3 and then triplets connected in series to make a strip powered by 40V or so. I found it out during an autopsy, 'cos supid thing died in very predictable way: one LED of one triplet died in a way you just described, then the other 2 took all the current intended for 3 (it has a constant current driver, of course). I think the guy who designed It intended to do a good thing: if one LED fails, the whole floodlight won't.
I saw the whiteboard and was skeptical and then I kept watching and almost cried cos no one else has been able to explain this in a way I can actually understand it and be able to apply it. THANK YOU SO MUCH.
Great explanation. Failure mode analysis is not always the first thing on a hobbyist’s mind. The “what-if” scenarios really help complete the explanation.
i literally just made a parallel LED circuit the other day for my mech model. did the math on it and everything to pick the best resistor for the job. it looked almost exactly like what you had drawn on the white board, 1 resistor > 3 LED's in parallel. and you basically explained exactly what is happening to my LEDs at this time. they arent popping, but one is definitely getting all the juice it needs. now i know why. love the video. im a subscriber now
he got straight into it and didnt feel the need to say like and subscribe like every other tuber , i normally dont subscribe after one video but i can make an exception for this guy looks like i got some vids to watch!
As said previously by others, best explanation I've seen regarding this as opposed to the usual 'oh an led needs a resistor' and leave it at that! Cheers, will be watching more of your stuff, subbed!
I'm a programmer making a toy for my son. Don't ask. Son doesn't speak but likes bright lights. Found your video, doublechecked my logic, seemed sane. Thanks, @SimplyPut!
"It's just a fact of life" Well said, thanks for making this and the rest of your videos. Your content has been a great resource for my Son and I while working on his science project.
Great Explanation!!! There is a small detail to add: the LED drop voltage is temperature dependent (inverse), as hotter as the LED gets, the small is the voltage drop. When you associate LEDs in parallel, one of the LEDs gets mode current (the LED with lowest drop), and since it gets more current, it lights brighter and gets hotter, which lowers the voltage drop, and unbalance it more and gets more current... So it is an "unbalanced" association that tends to be more unbalanced as time goes by.
Was about to create a project with 4 parallel sets of LEDs in series with each parallel set having 6 LEDs and I was planning on powering all of it with a single resistor. This video may have just saved me from the suffering of extreme disappointment. Much appreciated video 👍
I'll have to watch this 15 times to fully understand, but thank you. You kept it in the realms of my understanding, things clicked into place throughout the video. Thanks
I'm learning electronics (just barely managed to wrap my head around basic DC concepts and components like resistors, leds, capacitors and inductors) and found your channel by complete accident. I knew that connecting leds in parallel would require dedicated resistors and roughly understood why (the different forward voltage drop causes a big difference in how they conduct current) but since I know basicly nothing about diodes didn't really grasp it. Not only you managed to explain that perfectly (but I have to watch the video another time taking notes and drawing the circuits as you explain to "get the feel), you also managed to make my brain click about how a diode works and illuminated me (ahah because of leds, ahahaha) about a detail regarding Kirchoff's voltage law (mainly the concept of loop, which I understand but overlooked something). You truly are "Simply put" and I would add "Absolute amazing", I'm very glad the Algorithm decided to popped one of your video on my home page!
I'm just getting into electronics and I didn't understand the whole video but this is such a down to earth explanation that answered alot of my confusions about voltage vs current. Maybe if I watch it 5 more times I'll understand everything.....
You should try to understand voltage and current and resistance and the relationships between them and how they affect each other and depend on each other… first, instead of trying to reverse engineer an understanding of them from this video. Otherwise your understanding of both basic electricity as well as semiconductor electronics operation will likely be warped even though it may make sense, and you won't realize that your understanding is wrong until you apply it and get unexpected results. That is one of the dangers of learning something complex on your own without a teacher's guidance that you can interrupt by raising your hand to say "I didn't understand what happened in the previous step" or being unable to provide feedback by doing in-class practice examples immediately after the explanation or homework, which the teacher checks to see if you have understood it correctly or not. Replaying the video again and again is often not helpful at all. It is not the same as a teacher re-explaining it a different way, using different words and pausing at each step to see exactly which part you are having difficulty understanding. Unlearning a wrong understanding is difficult especially if it has had time to settle down and become embedded, so start learning the right way, by learning things in the proper sequence. You don't learn algebra first and then try to use that understanding to figure out what addition and subtraction are all about, do you? 🙂
Wow, this is really good to know why it wasn't possible. I was thinking in a perfect system, but the natural imperfections begin to snowball over time. It may work on day one, and week one, but it is a fragile system on one resistor and will be prone to failure.
I keep running into your videos. I really appreciate the way you explain things. Even if I am very familiar with a subject, I still manage to learn something from you every time. Keep up the excellent work!
Thanks for the simple explanation. I don’t know much about electronics, but I’m interested, so I watched your video and I finally understand this concept.
Wow, even with knowing all this already but this explanation was TOP! I will bookmark this for sending to people who ask about LEDs and you, sir, gained a subscriber.
Wow! excellent explanation. I wish that my first EEE teacher/Prof had been as clear as you are. It was a joy to watch. Definitely will recommend your channel.
Man, this is great! It is the first time that i really understand what is happening in a circuit like this. VERY well explained, thank you! edit: For videos like this, just straight to the facts, with no ads and no introductory blah blah to pleaaaaase subscribe or like the internet was intended to be. Without question, ofc i did like and subscribe immediately.
I made a toy for my nephew, bunch of buttons and leds mixed. My first electronic project. And I did what you say to not do lol, I mixed colors in parallels, but devided sub parallels by single resistor for identical led colors. Everything works, but as you said, they all doesn't bright the same amount, because I actually mixed identical colors but different manufacturer. Oh well, I thought I was smart ! Next time each led has a dedicated resistor, veru well, thank you so much for your explanation
I just finished installing 22 led beads (in parallel) to light up inside a scale model building, was wondering how to power them to last 4 hours a night every night without any problem, you just gave me the answer I was looking for, i'll just add a resistor to each led and be done with it. thank you for the perfect answer.
Thank you that was excellent. At first I was like this is going to be too complicated, but I kept watching and before long it made perfect sense. I really appreciate you taking the time to do that!
This is really good. Would be helpful if you did a couple calculations to figure out how much the resistor should be when you put one on each LED. Thanks for putting this together.
To do that, you need to know what the maximum current of the LED you want to drive is. Let's say you've got a red LED, rated for 20 mA. A red LED typically has a forward voltage drop of ~1.7 volts. Now, let's say, you're using a 5 volt power supply, a common voltage used for logic circuits. Subtract 1.7 from 5. (5-1.7=3.3) now, divide 3.3 by the amperage. (20mA=.02 amps) 3.3/.02=165. You need a 165 Ohm resistor, to run the LED at full brightness, using a 5 volt supply source. If you don't know the forward voltage drop of the LED, the safe thing to do is calculate the current through the resistor at the full 5 volts, and set for only 10mA. 5/.01=500 Ohms. Connect the LED, and simply measure the voltage across the terminals of the LED, to see what it's forward voltage drop is. Subtract that number from the supply voltage, then divide that number by the current rating of the LED. Keep in mind, if the LED is being used as an indicator, rather than for illumination, you may not want full rated power. It might be too bright to look directly at. It's never a sin to run an LED far below its rated maximum, if you don't need that much light.
Thanks! I'm running my 7 year old through some beginner electricity experiments so that I'm forced to play with all the components I've collected and let sit around. We were wondering why we couldn't get all our LEDs to light up on the parallel circuit. I guess it's a good thing we picked a big enough resistor doing it the wrong way.
You're exactly right about differences when paralleling LED's, except, it's worse! All diodes, including light emitting diodes, are NEGATIVE temperature coefficient. If one LED takes the bulk of the current, it will get hot. that lowers the forward voltage drop of that diode, making it take an even larger percentage of the current available through the single ballast resistor. When you first turn it on, you may see all three LED's light. After a while, you will see one brighten up, while the others go dim. The hottest LED will continue to get hotter, making it conduct more, until it is taking all of the available current. If you try this, be sure to size the resistor to avoid exceeding the absolute maximum current rating of a single LED.
Thank you. D.Ccurrent walking up the pins one voltage in two voltage out batteries. Three power out where loads or circuits are calculated Kirtland laws and four will be neutral or return, whereas rated time will play effects of usage, the Leds are accounted for to which transformers can adjust voltage then breaking it down to the right value the count of resistance to each led thank you I learnt some new things in here to thank you
Correct, but incorrect. The higher power LEDs have a wider Vf over it's current range, EG, take a 1W led, the Vf range for a green led maybe 2.8v to 3.1v, yes 300mV variance or more.
I have some results you may like to comment or analyze: I'm not an expert or really knowledgeable on these matters and in fact I'm just a noob. Here is my 'case': # a parallel circuit with two amber LEDs 20mAh/3.0V and two red Leds 20mAh/1.8V. # power source is coming from a 3.3V controller board's jumper. # following the theory you so clearly expounded here I opted to place a Resistor on each LED resulting with two 15 Ohm on the amber LEDs and two 68 Ohm on the red LEDs. It did not work as only the red LEDs were fully lighting up, but I did notice that a 1K Ohm on the reds resulted in all four LEDs lighted although the amber were dim well below their potential. While trying to figure out a solution to bright up the amber ones I've studied the case where you also had mixed colors LEDs with red and blue (1.8V + 3.0V): there the case was on a different parallel circuit where they tried to make it work using a single resistor, and in fact the answers were suggesting to use resistors calculated for each Led. In one of the comments I read that the blue were not lighting up since from their position the red were short circuiting the current flowing to the lesser Voltage. Without fully understanding the implications (I hope you may comment on this!) it dawned on me that to let the current flow to the amber I had to increase the resistance on the red instead of lowering it: I already had the 1K Ohm resistors showing me some low current was finally dimming up the amber ones. # after some trials I've found a sweet spot using 2.2K Resistors on each of the red LEDs that now are a little dimmer but still quite bright, and the amber LEDs are almost as bright as if I plug off the red ones from the circuit... Case solved? Yes, or so it seems: to me it looks as if I was going against the logic of the Law, but as I said I'm not that knowledgeable on the electrons' race. I will be thankful if someone will explain me what this is all about... Cheers
Ok So… I connected 12 green leds to a 4.4.volt supply, each pair in 6 series. They got very hot. Then I connected a 47 ohm resistor and the heat was gone. Even the simple resistor seems fine. I still got one question after this… What if i connect many resistors (idk like 6) BUT in parallel?
Yeah, although in some applications I did use a common resister in the path to ground: I connected multiple MCU pins to a respective (random colored) led, and then all the leds back to gnd. If it's just for blinking shortly, I figured that it will be able to handle the access power that an led would have to dissipate due to a too low resistance on part of the resistor, and thus the too high current flowing through the led. (And in my setup, I also saved space by doing that.) But, if I'd have to design some filming light with a few power LEDs, I'd want each LED to have an own resistor as well. Anyway, good job!
Good points! If you're lighting only one LED at a time, it's actually perfectly fine since the resistor is only associated with one LED anyway, and if you're just blinking them on and off, they'll handle the current just fine. (In fact, that's an actual technique: Rapidly blinking an LED (faster than the eye can detect) allows you to over-current it without significantly reducing its lifespan, therefore making it brighter.) The only issue is if you try to blink two LEDs at the same time that have large differences in their voltage drops, because the one with the bigger drop might not blink on.
simply put: great video. okay, here's a scenario for you - a real world scenario I have. I have a 12volt DC supply through a regular step-down transformer/wall-wart. I have white and green LED's with an advertised fwd voltage drops of 3 volts. I have 5 arrays of 8 individual LED's, 2p4s configuration for each array. Every 4s LED string has a 120ohm resistor in series. 3 of the arrays use green LED's, and 2 have white LED's. Same fwd voltage drop ratings on all from same manufacturer, and 120ohm resistor used for every 4 x LED in series. I run the green LED arrays and as I turn them on or off, the other green arrays operate perfectly normally as if no circuit interference caused by the other LED arrays in parallel operation. HOWEVER, when I turn on the white LED arrays, they work fine by themselves, but as I switch on the green arrays, one by one, the white LED arrays dim and dim, even though they're operating in parallel. What am I missing? The transformer is rated for like 6 watts (500mA on 12v) so it's not like I have a power supply issue ... or do I?
5 arrays with 4 strings in each array should be 25mA per string before resistance if everything's even, so that shouldn't be your problem, because otherwise I'd expect everything to dim, not just one color. Run your strings and use a multimeter to measure the voltage drops across each of the resistors (both when all LEDs are working and when some are dimmed) and make sure your LEDs are actually fully turning on. If every string has its own resistor (so 20 resistors total here), then it can't be the issue described in this video......IF the LEDs are actually leaving any voltage for the resistor to drop. But rated 3V *4 with a 12V supply is running smack against that limit, so you might very well be needing more voltage. I bet you'd not experience the issue if you had the same number of LEDs but only 3 in each string, or if you used ones with smaller voltage drops. If you have a bench power supply, try a 13V supply (or even a 14V) and see if the issue goes away.
@@simplyput2796 cool. Thanks for the answer. It was 5 arrays in 2p4s with 10 resistors overall and 40 LED's. I was thinking about wiring the setup as 5 arrays of 9 LED's at 3p3s with 45 LED's and 15 resistors, which as you say would leave some voltage to drop across the resistor. I was just confused as to how circuits which are technically isolated from each other in parrallel - thus using their own lines of current from the exact same source voltage - could effect each other in that way.
Remember that the stuff we use, like Kirchhoff's voltage and current laws and the component model, are approximations that work great as long as we stick within their conditions. According to the component model, circuit elements in parallel are isolated from each other...until they aren't. In reality, nothing is ever isolated, and an entire circuit is actually inductively coupled with itself (in addition to numerous other unpleasantnesses). You could also try measuring the maximum voltage drop of each of the LEDs in one of the strings that dims, add them together, and see if your power supply voltage is sufficient.
0:42, I'm sorry for very beginner question, as it is series, current is the same for all. If each LED would require different current (let say 20mA, 25mA and 35mA), what current would be there?
Hi, nicely explained. Thanks I want to make aquarium LED light With 36LEDs each 3W. I have power supply driver of 30v -42v 1700ma. How to make circuit to suit that LED requirements. Any help is appreciated. Thank you
hey bud, quick Q. about Samsung F-series LT-FB24B 4' strips wondering if i had 4 of these wired up with a Mean well HLG-480H-48A, do i have to concern my self with current hogging per each of the 4 modules, or the actual wiring complexity of the LED PCB module itself(mix of series and parallel)? with that driver used at C.C and C.V will i need current limiting resistors and if so does this video apply in theory? thanks if u can answer, dope vid.
Even if you could measure the junction they could fluctuate overtime due to temperature. Other source are inductive differences in the wiring change in the instantaneous current though the diodes.
Good point: I hadn't considered temperature, because higher temperature increases semiconductor conductivity because of greater electron kinetic energy so they can bounce through the doping faster.
@@simplyput2796 I think you miss my second point which could make an interesting video additionally. When you are introduced to high frequency circuits the length of conductors becomes critical to the functioning of the system as they opperate close to transmission line. The components see different voltage as result across the length of the parallel circuit.
how to calculate for each Resistor value as above case if we LED have difference value ? for examble : Red led ( Vf = 1.7V ; If =10mA ) Green led ( 2.3V ; 10mA ) VCC = 3.3V
Just a simple question: when you have a packed SMD LED (3 LEDS with same color, packed in single 6 pin SMD component) would that lower variance and thermal contact between them make it suitable to use in parallel with one resistor?
Loved your video. You explained a lot. I just have one question. Would that last diagram still work if the resistors [500 ohm] were pre-installed on the negative side of led? I have about 75 5mm 12v leds 20mA that I'm using for an address sign. Looking for the right way to wire it . Any help would be greatly appreciated. Thanks
I completely agree with you and the math is correct, but I regularly run yellow, green, blue, and white LEDs on the same voltage (usually 5 or 6V with 100 ohm resistors) and have no issue. Granted they each have their own resistor, but they are the same value. Can you comment on this? I am doing a project soon and need to know if this is okay or not.
I actually found this video after I tried to connect 3 LEDs in parallel with one resistor. Only one led would light. I'm very new and what I've been doing lately is making circuits on my breadboard then trying to figure out why they don't work or why I'm not getting what I think the results should be when I take various readings. They are really simple circuits and the mistakes are stupid but I still get a feeling of accomplishment when I figure out what I've done wrong.
I routinely wire LEDs in parallel with a shared resistor and never have a problem. I don't worry about individual parts not being perfectly equal. That's just a fact of life; no two objects will be precisely the same. But things that have only a tiny difference in construction will give results that are only a tiny bit away from perfect. Also, adding resistors won't erase the individual differences among the LEDs, plus the resistors also have a tolerance range that affects the brightness of the LEDs. By including resistors for each LED you nearly double the chances of there being a current mismatch.
But.... I don't do that anymore; It's not worth the problems that it might lead to. I now feel it's just plain bad practice to put parallel LEDs on a single resister.
It's really great to see somebody actually talking about this. So many LED tutorials completely gloss over this issue, or worse yet even actually tell people that you can wire LEDs in parallel with a single resistor. And the truth is that if you have all the same LEDs from the same manufacturer, usually they're close enough that it appears to work fine, at first. And then maybe a week, or a month, or 6 months down the line just mysteriously fails.
One other thing to note is that the forward voltage of LEDs also _depends on their temperature._ If one LED starts out taking even a tiny tiny bit more current than the others, that will cause it to heat up ever so slightly more than the others, and when LEDs heat up, their forward voltage goes _down,_ which means that LED then starts taking _more current,_ which makes it heat up more, which makes it take more current, etc, etc. It's basically a "runaway" scenario waiting to happen. This is why even if you manage to match your LEDs extremely precisely, you really still can't guarantee that this sort of thing won't happen, because it only takes the slightest imbalance anywhere at any time to make it potentially all spiral out of control.
Does adding individual resistors not fix this temperature issue?
@@joshp7477 Individual resistors fixes the issue of a single failure that cascades inexorably into failure of all LEDS. But any LED can begin to go into thermal runaway (without affecting the other LEDs) if its resistor value is set to allow the max current through the LED (for max. brightness) and the cooling of the LED is inadequate, e.g. the cooling fan breaks down or the ambient air temperature becomes higher than expected. As the LED starts to overheat its voltage drops and more current flows but the increased current flow causes a larger voltage drop across the resistor which reduces the voltage across the LED. This auto stabilization may be enough to stop the thermal runaway from proceeding to the blowout stage, especially if the LED cooling is restored quickly enough, but the LED operated at a higher current and temperature than it was designed for, and its operational life has been permanently reduced. By how much? It depends on its design and by how much it was abused, i.e. by how much was the normal max current limit exceeded, how close did it come to the absolute max. current (blowout) value, for how long, at what temperature, how much abuse had it endured previously, etc.
I've got an LED flood light with LEDs coupled (tripled?) by 3 and then triplets connected in series to make a strip powered by 40V or so. I found it out during an autopsy, 'cos supid thing died in very predictable way: one LED of one triplet died in a way you just described, then the other 2 took all the current intended for 3 (it has a constant current driver, of course). I think the guy who designed It intended to do a good thing: if one LED fails, the whole floodlight won't.
I saw the whiteboard and was skeptical and then I kept watching and almost cried cos no one else has been able to explain this in a way I can actually understand it and be able to apply it. THANK YOU SO MUCH.
Exactly, I thought who is this guy, but he was so clear 😊
the best, most to the point explanation for LEDs in parallel. excellent.
Clear as mud….
gangsta - best explanation on any topic ever
Edit: just noticed you haven't posted for a long time - come back man. You really know your stuff.
Great explanation. Failure mode analysis is not always the first thing on a hobbyist’s mind. The “what-if” scenarios really help complete the explanation.
i literally just made a parallel LED circuit the other day for my mech model. did the math on it and everything to pick the best resistor for the job. it looked almost exactly like what you had drawn on the white board, 1 resistor > 3 LED's in parallel. and you basically explained exactly what is happening to my LEDs at this time. they arent popping, but one is definitely getting all the juice it needs. now i know why. love the video. im a subscriber now
he got straight into it and didnt feel the need to say like and subscribe like every other tuber , i normally dont subscribe after one video but i can make an exception for this guy looks like i got some vids to watch!
The ability to explain something so well is a gift. Thank you.
As said previously by others, best explanation I've seen regarding this as opposed to the usual 'oh an led needs a resistor' and leave it at that! Cheers, will be watching more of your stuff, subbed!
I'm a programmer making a toy for my son. Don't ask. Son doesn't speak but likes bright lights. Found your video, doublechecked my logic, seemed sane. Thanks, @SimplyPut!
"It's just a fact of life" Well said, thanks for making this and the rest of your videos. Your content has been a great resource for my Son and I while working on his science project.
Great Explanation!!! There is a small detail to add: the LED drop voltage is temperature dependent (inverse), as hotter as the LED gets, the small is the voltage drop. When you associate LEDs in parallel, one of the LEDs gets mode current (the LED with lowest drop), and since it gets more current, it lights brighter and gets hotter, which lowers the voltage drop, and unbalance it more and gets more current... So it is an "unbalanced" association that tends to be more unbalanced as time goes by.
That is the same reason why you can't put 2 diodes in parallel expecting it to double the current limits
Was about to create a project with 4 parallel sets of LEDs in series with each parallel set having 6 LEDs and I was planning on powering all of it with a single resistor.
This video may have just saved me from the suffering of extreme disappointment. Much appreciated video 👍
I'll have to watch this 15 times to fully understand, but thank you. You kept it in the realms of my understanding, things clicked into place throughout the video. Thanks
I'm learning electronics (just barely managed to wrap my head around basic DC concepts and components like resistors, leds, capacitors and inductors) and found your channel by complete accident.
I knew that connecting leds in parallel would require dedicated resistors and roughly understood why (the different forward voltage drop causes a big difference in how they conduct current) but since I know basicly nothing about diodes didn't really grasp it.
Not only you managed to explain that perfectly (but I have to watch the video another time taking notes and drawing the circuits as you explain to "get the feel), you also managed to make my brain click about how a diode works and illuminated me (ahah because of leds, ahahaha) about a detail regarding Kirchoff's voltage law (mainly the concept of loop, which I understand but overlooked something).
You truly are "Simply put" and I would add "Absolute amazing", I'm very glad the Algorithm decided to popped one of your video on my home page!
I'm just getting into electronics and I didn't understand the whole video but this is such a down to earth explanation that answered alot of my confusions about voltage vs current. Maybe if I watch it 5 more times I'll understand everything.....
You should try to understand voltage and current and resistance and the relationships between them and how they affect each other and depend on each other… first, instead of trying to reverse engineer an understanding of them from this video. Otherwise your understanding of both basic electricity as well as semiconductor electronics operation will likely be warped even though it may make sense, and you won't realize that your understanding is wrong until you apply it and get unexpected results. That is one of the dangers of learning something complex on your own without a teacher's guidance that you can interrupt by raising your hand to say "I didn't understand what happened in the previous step" or being unable to provide feedback by doing in-class practice examples immediately after the explanation or homework, which the teacher checks to see if you have understood it correctly or not. Replaying the video again and again is often not helpful at all. It is not the same as a teacher re-explaining it a different way, using different words and pausing at each step to see exactly which part you are having difficulty understanding. Unlearning a wrong understanding is difficult especially if it has had time to settle down and become embedded, so start learning the right way, by learning things in the proper sequence. You don't learn algebra first and then try to use that understanding to figure out what addition and subtraction are all about, do you? 🙂
"It's a good thing they're so cheap"!!!! I love it. Great job with this explanation!!
Wow, this is really good to know why it wasn't possible. I was thinking in a perfect system, but the natural imperfections begin to snowball over time. It may work on day one, and week one, but it is a fragile system on one resistor and will be prone to failure.
I keep running into your videos. I really appreciate the way you explain things. Even if I am very familiar with a subject, I still manage to learn something from you every time. Keep up the excellent work!
Thanks for the simple explanation. I don’t know much about electronics, but I’m interested, so I watched your video and I finally understand this concept.
Wow, even with knowing all this already but this explanation was TOP! I will bookmark this for sending to people who ask about LEDs and you, sir, gained a subscriber.
It’s the best explanation I have come cross so far.
Genius! The best dope I came across trying to understand LEDs circuits... Thanks! B)
Wow! excellent explanation. I wish that my first EEE teacher/Prof had been as clear as you are. It was a joy to watch. Definitely will recommend your channel.
You, my friend, are a fantastic teacher.
Why doesn't this have more views? thank you for this, so pleased to have found your page. keep going please!
Man, this is great! It is the first time that i really understand what is happening in a circuit like this. VERY well explained, thank you!
edit: For videos like this, just straight to the facts, with no ads and no introductory blah blah to pleaaaaase subscribe or like the internet was intended to be. Without question, ofc i did like and subscribe immediately.
I made a toy for my nephew, bunch of buttons and leds mixed. My first electronic project. And I did what you say to not do lol, I mixed colors in parallels, but devided sub parallels by single resistor for identical led colors. Everything works, but as you said, they all doesn't bright the same amount, because I actually mixed identical colors but different manufacturer. Oh well, I thought I was smart ! Next time each led has a dedicated resistor, veru well, thank you so much for your explanation
I can't close the video without subscribing man... You won
Thank you, I love learning from people who really KNOW their craft! You absolute legend!
finally, a simple and clear explanation! Thnx
I love your mic!!!! Thank you for the knowledge sir.
I just finished installing 22 led beads (in parallel) to light up inside a scale model building, was wondering how to power them to last 4 hours a night every night without any problem, you just gave me the answer I was looking for, i'll just add a resistor to each led and be done with it. thank you for the perfect answer.
Thank you that was excellent. At first I was like this is going to be too complicated, but I kept watching and before long it made perfect sense. I really appreciate you taking the time to do that!
thank you so much! Ive been looking online for so long to understand how to connect my leds in a row. such clear cut explanation! have a good day sir.
Say no more. Brilliantly explained!
That was an excellent explanation why its not a good idea to wire led's in parallel with a single resistor. Thank you!
really liked this video. direct to the point but not boring and going through most cases.
What an excellent explanation of parallel LED's. Thank you for sharing, you have a new subscriber 🙂
As always...another great explanation.
Excellent video man! Well explained.
Thank you! Your explanation really helped me understand this topic. I guess I'll be adding resistors to all my LEDs.
Absolutely superb explanation!
Excellent visual tutorial. Thank you.
A little bit hand-wavy, and a whole lot of densely informational XD Thank you for this!!
What a great explanation! I have been puzzling this. Subscribed!
Brilliant, that's exactly what I wanted to know and explained in a way I understand. Thankyou.👍
Your videos are awesome and greatly appreciated. Keep up the great work.
Wow, such a great explanation. Thanks a lot!
you sir has helped me open up my mind, thank you!
How do you go about calculating what level resistor you need for each led?
a great video - explaining the topic brilliantly
Thank you very much. This was an enjoyable refresher! You're a very good communicator!
You earned my subscription.
ohhhhhhh, thank you. Needed this!
This describes the issue perfectly, thank you
This is really good. Would be helpful if you did a couple calculations to figure out how much the resistor should be when you put one on each LED. Thanks for putting this together.
To do that, you need to know what the maximum current of the LED you want to drive is. Let's say you've got a red LED, rated for 20 mA. A red LED typically has a forward voltage drop of ~1.7 volts. Now, let's say, you're using a 5 volt power supply, a common voltage used for logic circuits. Subtract 1.7 from 5. (5-1.7=3.3) now, divide 3.3 by the amperage. (20mA=.02 amps) 3.3/.02=165. You need a 165 Ohm resistor, to run the LED at full brightness, using a 5 volt supply source.
If you don't know the forward voltage drop of the LED, the safe thing to do is calculate the current through the resistor at the full 5 volts, and set for only 10mA. 5/.01=500 Ohms. Connect the LED, and simply measure the voltage across the terminals of the LED, to see what it's forward voltage drop is. Subtract that number from the supply voltage, then divide that number by the current rating of the LED. Keep in mind, if the LED is being used as an indicator, rather than for illumination, you may not want full rated power. It might be too bright to look directly at. It's never a sin to run an LED far below its rated maximum, if you don't need that much light.
@@vincentrobinette1507 So you just do Ohms law for each individual LED in the parallel chain disregarding the others as if they're not there?
Yes@@joshp7477
Fantastic. Well explained.
Thanks! I'm running my 7 year old through some beginner electricity experiments so that I'm forced to play with all the components I've collected and let sit around. We were wondering why we couldn't get all our LEDs to light up on the parallel circuit. I guess it's a good thing we picked a big enough resistor doing it the wrong way.
Cool stuff, it's easy to take the basics for granted👍😄
You're exactly right about differences when paralleling LED's, except, it's worse! All diodes, including light emitting diodes, are NEGATIVE temperature coefficient. If one LED takes the bulk of the current, it will get hot. that lowers the forward voltage drop of that diode, making it take an even larger percentage of the current available through the single ballast resistor. When you first turn it on, you may see all three LED's light. After a while, you will see one brighten up, while the others go dim. The hottest LED will continue to get hotter, making it conduct more, until it is taking all of the available current. If you try this, be sure to size the resistor to avoid exceeding the absolute maximum current rating of a single LED.
That was super helpful. Thanks man!
Awesome explanation. Thanks.
this was super helpful. thanks!
Thank you. D.Ccurrent walking up the pins one voltage in two voltage out batteries. Three power out where loads or circuits are calculated Kirtland laws and four will be neutral or return, whereas rated time will play effects of usage, the Leds are accounted for to which transformers can adjust voltage then breaking it down to the right value the count of resistance to each led thank you I learnt some new things in here to thank you
Nicely explained, simple to understand 👏😊👍
clean and detailed explanation....thank you so much.
The best explanation I have seen Great.
If i have 4 led with a FV of 3V, do i still need a resister if I am supplying 12V?
Excellent tutorial!
Correct, but incorrect. The higher power LEDs have a wider Vf over it's current range, EG, take a 1W led, the Vf range for a green led maybe 2.8v to 3.1v, yes 300mV variance or more.
If i have 5v and want to make 2.5v/2.5v how can i measure what resistor to use
Really well done video. Thanks.
I have some results you may like to comment or analyze: I'm not an expert or really knowledgeable on these matters and in fact I'm just a noob. Here is my 'case':
# a parallel circuit with two amber LEDs 20mAh/3.0V and two red Leds 20mAh/1.8V.
# power source is coming from a 3.3V controller board's jumper.
# following the theory you so clearly expounded here I opted to place a Resistor on each LED resulting with two 15 Ohm on the amber LEDs and two 68 Ohm on the red LEDs.
It did not work as only the red LEDs were fully lighting up, but I did notice that a 1K Ohm on the reds resulted in all four LEDs lighted although the amber were dim well below their potential. While trying to figure out a solution to bright up the amber ones I've studied the case where you also had mixed colors LEDs with red and blue (1.8V + 3.0V): there the case was on a different parallel circuit where they tried to make it work using a single resistor, and in fact the answers were suggesting to use resistors calculated for each Led. In one of the comments I read that the blue were not lighting up since from their position the red were short circuiting the current flowing to the lesser Voltage.
Without fully understanding the implications (I hope you may comment on this!) it dawned on me that to let the current flow to the amber I had to increase the resistance on the red instead of lowering it: I already had the 1K Ohm resistors showing me some low current was finally dimming up the amber ones.
# after some trials I've found a sweet spot using 2.2K Resistors on each of the red LEDs that now are a little dimmer but still quite bright, and the amber LEDs are almost as bright as if I plug off the red ones from the circuit...
Case solved? Yes, or so it seems: to me it looks as if I was going against the logic of the Law, but as I said I'm not that knowledgeable on the electrons' race. I will be thankful if someone will explain me what this is all about...
Cheers
Great video really appreciate your simple explanation. (I’ve been blowing LED’s oops). Thanks again
If voltage is high, LED can be connected in series, only 1or no resistor scene also there. LEDs are in series in decorative LED strings.
Ok
So…
I connected 12 green leds to a 4.4.volt supply, each pair in 6 series. They got very hot. Then I connected a 47 ohm resistor and the heat was gone. Even the simple resistor seems fine.
I still got one question after this…
What if i connect many resistors (idk like 6) BUT in parallel?
I absolutely loved your explanation of LEDS in this video but I have to ask what's up with the headphones?
Yeah, although in some applications I did use a common resister in the path to ground: I connected multiple MCU pins to a respective (random colored) led, and then all the leds back to gnd.
If it's just for blinking shortly, I figured that it will be able to handle the access power that an led would have to dissipate due to a too low resistance on part of the resistor, and thus the too high current flowing through the led.
(And in my setup, I also saved space by doing that.)
But, if I'd have to design some filming light with a few power LEDs, I'd want each LED to have an own resistor as well.
Anyway, good job!
Good points! If you're lighting only one LED at a time, it's actually perfectly fine since the resistor is only associated with one LED anyway, and if you're just blinking them on and off, they'll handle the current just fine. (In fact, that's an actual technique: Rapidly blinking an LED (faster than the eye can detect) allows you to over-current it without significantly reducing its lifespan, therefore making it brighter.) The only issue is if you try to blink two LEDs at the same time that have large differences in their voltage drops, because the one with the bigger drop might not blink on.
Finally.... I get it! Thank you😀
Excellent stuff !
Excellent explanation! Subscribed
This man actually helped me by the title lol
Great sound quality headset you have there sir!
simply put: great video.
okay, here's a scenario for you - a real world scenario I have.
I have a 12volt DC supply through a regular step-down transformer/wall-wart.
I have white and green LED's with an advertised fwd voltage drops of 3 volts.
I have 5 arrays of 8 individual LED's, 2p4s configuration for each array. Every 4s LED string has a 120ohm resistor in series.
3 of the arrays use green LED's, and 2 have white LED's. Same fwd voltage drop ratings on all from same manufacturer, and 120ohm resistor used for every 4 x LED in series.
I run the green LED arrays and as I turn them on or off, the other green arrays operate perfectly normally as if no circuit interference caused by the other LED arrays in parallel operation.
HOWEVER, when I turn on the white LED arrays, they work fine by themselves, but as I switch on the green arrays, one by one, the white LED arrays dim and dim, even though they're operating in parallel.
What am I missing? The transformer is rated for like 6 watts (500mA on 12v) so it's not like I have a power supply issue ... or do I?
5 arrays with 4 strings in each array should be 25mA per string before resistance if everything's even, so that shouldn't be your problem, because otherwise I'd expect everything to dim, not just one color. Run your strings and use a multimeter to measure the voltage drops across each of the resistors (both when all LEDs are working and when some are dimmed) and make sure your LEDs are actually fully turning on. If every string has its own resistor (so 20 resistors total here), then it can't be the issue described in this video......IF the LEDs are actually leaving any voltage for the resistor to drop. But rated 3V *4 with a 12V supply is running smack against that limit, so you might very well be needing more voltage. I bet you'd not experience the issue if you had the same number of LEDs but only 3 in each string, or if you used ones with smaller voltage drops. If you have a bench power supply, try a 13V supply (or even a 14V) and see if the issue goes away.
@@simplyput2796 cool. Thanks for the answer.
It was 5 arrays in 2p4s with 10 resistors overall and 40 LED's. I was thinking about wiring the setup as 5 arrays of 9 LED's at 3p3s with 45 LED's and 15 resistors, which as you say would leave some voltage to drop across the resistor.
I was just confused as to how circuits which are technically isolated from each other in parrallel - thus using their own lines of current from the exact same source voltage - could effect each other in that way.
Remember that the stuff we use, like Kirchhoff's voltage and current laws and the component model, are approximations that work great as long as we stick within their conditions. According to the component model, circuit elements in parallel are isolated from each other...until they aren't. In reality, nothing is ever isolated, and an entire circuit is actually inductively coupled with itself (in addition to numerous other unpleasantnesses). You could also try measuring the maximum voltage drop of each of the LEDs in one of the strings that dims, add them together, and see if your power supply voltage is sufficient.
0:42, I'm sorry for very beginner question, as it is series, current is the same for all. If each LED would require different current (let say 20mA, 25mA and 35mA), what current would be there?
your premise is wrong. current is 20mA
Dang 😳 you did it. You my brain is growing.
Hi, nicely explained. Thanks
I want to make aquarium LED light With 36LEDs each 3W. I have power supply driver of 30v -42v 1700ma. How to make circuit to suit that LED requirements.
Any help is appreciated. Thank you
very well put. thanks.
Brilliant video, thank you.
hey bud, quick Q. about Samsung F-series LT-FB24B 4' strips
wondering if i had 4 of these wired up with a Mean well HLG-480H-48A, do i have to concern my self with current hogging per each of the 4 modules, or the actual wiring complexity of the LED PCB module itself(mix of series and parallel)? with that driver used at C.C and C.V will i need current limiting resistors and if so does this video apply in theory? thanks if u can answer, dope vid.
Even if you could measure the junction they could fluctuate overtime due to temperature. Other source are inductive differences in the wiring change in the instantaneous current though the diodes.
Good point: I hadn't considered temperature, because higher temperature increases semiconductor conductivity because of greater electron kinetic energy so they can bounce through the doping faster.
@@simplyput2796 The digial temperature sensors are build arround diodes because resistors are difficult to put in ICs
And you just gave me a video idea.
@@simplyput2796 I think you miss my second point which could make an interesting video additionally. When you are introduced to high frequency circuits the length of conductors becomes critical to the functioning of the system as they opperate close to transmission line. The components see different voltage as result across the length of the parallel circuit.
how to calculate for each Resistor value as above case if we LED have difference value ?
for examble : Red led ( Vf = 1.7V ; If =10mA )
Green led ( 2.3V ; 10mA )
VCC = 3.3V
Just a simple question: when you have a packed SMD LED (3 LEDS with same color, packed in single 6 pin SMD component) would that lower variance and thermal contact between them make it suitable to use in parallel with one resistor?
Loved your video. You explained a lot. I just have one question. Would that last diagram still work if the resistors [500 ohm] were pre-installed on the negative side of led? I have about 75 5mm 12v leds 20mA that I'm using for an address sign. Looking for the right way to wire it . Any help would be greatly appreciated. Thanks
thanks for this explanation
I completely agree with you and the math is correct, but I regularly run yellow, green, blue, and white LEDs on the same voltage (usually 5 or 6V with 100 ohm resistors) and have no issue. Granted they each have their own resistor, but they are the same value. Can you comment on this? I am doing a project soon and need to know if this is okay or not.
So its fine if the current is 20 mA for the leds combined
I actually found this video after I tried to connect 3 LEDs in parallel with one resistor. Only one led would light.
I'm very new and what I've been doing lately is making circuits on my breadboard then trying to figure out why they don't work or why I'm not getting what I think the results should be when I take various readings. They are really simple circuits and the mistakes are stupid but I still get a feeling of accomplishment when I figure out what I've done wrong.
I routinely wire LEDs in parallel with a shared resistor and never have a problem. I don't worry about individual parts not being perfectly equal. That's just a fact of life; no two objects will be precisely the same. But things that have only a tiny difference in construction will give results that are only a tiny bit away from perfect.
Also, adding resistors won't erase the individual differences among the LEDs, plus the resistors also have a tolerance range that affects the brightness of the LEDs. By including resistors for each LED you nearly double the chances of there being a current mismatch.
But.... I don't do that anymore; It's not worth the problems that it might lead to. I now feel it's just plain bad practice to put parallel LEDs on a single resister.