How to Calculate the Correct Resistor for LEDs Light Emitting Diodes
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- เผยแพร่เมื่อ 14 พ.ค. 2024
- This is part of a series of videos about basic electronics. This video shows how to calculate the correct resistor for LEDs using OHMs law. And a few things about parallel and series calculations.
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I have struggled for years! trying to figure this stuff out. You single handedly demonstrated this better than anyone, and simple enough where I now understand it. I have been thunking my head over this so many times, but now I did it one last time because it was so easy to do and makes more sense than ever before. Thank you.
Its simple. Just check the voltage drop of the LED and calculate the resistor value for 10mA current. For indicators even 2 mA current is enough. Even you dont have to be exact, just find nearest value of resistor you calculated.
LOL!
This is like our first physics lesson in 7th grade. My grandpa taught me this when I was about 7 though beacause he was a physics teacher.
Sounds like you are missing the most basic of electronics skills.
You should have bought and read a basic electronics book for $10. Then you would have known in an hour or two and not years.
Eureka!!! It has sunk in.... I wish I could have grasped this 10 years ago. What a great technique you have for teaching folk like me. Thank you.
This is THE BEST tutorial video of this subject! I hope you make more of these! The whiteboard, clearly drawn and written and spoken at a calm pace, the perfect combination! This setup works perfectly for teaching purpose!
I wish I had a teacher like you in school... you broke it down to bare basics... Great JOB!!!! thank you.
Great video. I have a couple small car electrical projects where I wanted to use LED diodes and just didn't know how to properly put them in the circuit. It seemed so difficult to learn, but you broke it down easy to understand.
This took me back to my R.A.F. basic electronics training ... great refresher - thank you !!
You Sir have a gift to teach stuff with such clarity, plus you've covered the topic in its entirety leaving nothing out. Thank you !
Thank you very much for your kind comment.
FINALLY! Someone explaining this clearly. Very much appreciated 🙌
I was struggling with this for 3 years... And now I understand everything... You're amazing bro keep your good work 😉
Mate, you make this process much easier than other videos.
Thanks Sir!
I can’t thank you enough for the math lesson AND lab demonstration. Great Post!
Hands down one of the best explanations I've ever seen... thank you brother! SMJ 23
I would just like to say.....that was the most simple way of explaining the triangle....when I was at trade school doing my electrical apprenticeship...at the start the way this was explained was so SUPER CONFUSING MY HEAD WAS GOING TO EXPLODE...🤯
SO HATS OF TO YOU ON A SIMPLE WAY OF SHOWING A WAY THIS ALL WORKS....I WISH I COULD HAVE BEEN SHOWN THIS BACK IN THE DAY....WELL DONE...👍
Very good show for this 62 year old that’s adding some electronics related improvements to his model railway! You are an excellent instructor, and provide tons of information in an easy to comprehend way! Thanks! Subbed!
Thank you very much Tom. If I had more room I would love to build a model railway but there is not enough room to swing a cat where I live. Best wishes
@@markusfuller “Not enough room to swing a cat!” I love it! Ha!
Exactly the same reason as I am glad I learned this. Indicator lights for a display panel for my HO railway.
cant thank you enough ive asked and read but couldnt take it in you explain so well that ive finally got it thank you from all our beginners we will get there in the end with teachers as good as you are colinxxx
You, Sir, are a great teacher! You made this very easy to understand and apply. Thank you!
What a fantastic video. I have been struggling with wondering if I had to add the total Vf for led's in parallel or series. I found your vid by accident and it has saved my sanity. Thank you for uploading it and you are a great teacher.
Hey, youre so nice and teaching this as simple as possible and taking it slow... it ecourages me, a commoner, to study this. I always thought I would never get it, but now I actually do. Thank you Sir
Glad I can help. best wishes
Brilliant.
You've actually described this issue simply.
Now we understand.!🤔😊
Thank you.
Thank you for this. I'm a novice amateur in electronics and had been wondering how to determine what size resistor to use. Your Examples make perfect sense to me.
This is the best explanation I've ever found on figuring out a resistor for an LED! Well explained!
Good video. Takes me back to my Signal Corps radio school days; we spent a lot of time calculating circuits using Ohms law. This was years before calculators were available- man, they make electronics SO much easier!
Ft Gordon?
Thank you so much for that very clear explanations. I’ve been searching for that for a long time.
Such a great lecture, so informative and professional thank you kindly!!!
Very well explained. I truly left with some very interesting and new information. Great job!
Great tutorial. I had no idea about ohms and resistors. I have learned so much from your video. Thanks.
Thank you for taking the time to make this video, extremely informative.
Bought some 5050 SMD LED's for a project and this was valuable information. Never really got into RGB's that much so I'm learning from videos like this. Thanks for the info, you helped me more than you know.
Thank you, you've explained everything that I needed to know for a small project I'm working on.
Nice video, Markus.
This is the first one of your videos I've ever seen, keep up the good work!
Very fine basic video indeed! Thank you, Markus. Good even for an old hand at this art.
Vary good video. I learned more from your video on LED circuits then other videos I have watched. I was hoping to see more electronics videos but found they're mostly musical instruments.
You are a good teacher.. great job keep it up!
This simple tutorial really helped me understand how to put some electronic components work together in a circuit adhering the best practices as in my case I am a visual learner.
More video like this please.
Very nicely explained and good making of Video. Thank you sir. I am a novice in this area and I loved the way you explained the entire things.
Thank you for producing this educational video.
Sir all the years in college, and you are the only one I understand.
Great and very useful video, a whole series of basic electronics, how too videos wouldn’t go amiss. Maybe you could do a step by step, build a synth tutorial. A CS-80 using modern components may seem ambitious, but don’t let that stop you, or something like an SY-1, a mono synth that someone could use multiple example’s of to make a poly synth.
I just subscribed. Thank you for posting this video. I’m new to electronics and this video will be very helpful for me. I really like your teaching method.
Thankyou Alan
Thank you. This is the most wanted basically calculation.
Beautiful job explaining how to determine resistive voltage drop requirements on how to drive a led. Great job on identifying units in the equations. I think the video could have been better if you explained the equations used to get wattage. Like P=VxI and the other equation variants.
Thanks for your clear explanations.
Splendid, simple instruction. Much appreciated! If I have a higher voltage source, say 12v, will a larger resistor mitigate the potential burn out? Ah! You’re well ahead of me.
Yes. That's the purpose of the resistor. Just perform the calculation for 12v
Thanks man! I always thought the thick part within the LED was always the cathode, until I plugged a yellow LED the other day and went: Uhm... it doesn't work. Turns out I had to connect it "backwards" (the cathode was the thin part in this case). And checking the little cut in the package (thanks to your video) I have now confirmed that was the actual cathode! (I don't tend to rely on the length of the wires).
Thank you ! Crystal clear and simple even for a lazy brain like me 🙂
Wow, this was so helpful!! Thank you!
Great video Mark, thank you👍
pretty simple right? You explain it very clearly, I now get it in one video. My project can roll now!
Perfectly explained!!!
By far, the best hands on demo for this ever. THANK YOU SIR.
First of all english is not my mother language, even that i've fully understood ! Why you was not my teacher 60 years ago?! Thank so much for this clear and fully understandable explanation. Regards from burgundy. ..
Exactly what I was looking for. Graduated electronics tech course nearly 40 years ago and infrequently used the info. Knew what I was looking for to refresh my memory but couldn't find it till now. A near perfect presentation. Thank you. I recognized the Ohm's law triangle and knew where you were going with the power calculations so I could follow but would have liked to see the P - I - E triangle as well just to be sure I was remembering it all correctly. Also, I was a bit confused at 19 min 41 sec into the video I read "This example would be less efficient than the previous example of running the LEDs in parallel". Wasn't the previous example in series? Sincerely not busting your chops, I just need to be sure because I'm easily confused.
Hello. firstly thank you for your kind comment, I must rewatch the video and have a look at what I said at 19min41s . I made this video a while ago and cannot remember what I said but I have made mistakes before in other videos so I may be able to add some text on the video to correct any mistake or if not place it in the about section under the video. thanks for pointing this out to me. best wishes.
There is a typo on the screen. The LEDs are in parallel and each want to take 20mA , whereas the previous series example they were sharing the same 20mA.
LED (indeed all diodes) should not be connected in series like this a fraction of a mV difference is all that is needed for ALL the current to go through ONE LED and cause it to very quickly fail (sometimes dramatically). The better solution is to add a limiting resistor in series with each diode and break the relationship.
Use the series configuration if you have a lot of voltage and the parallel if you are running from a low voltage.
Efficiency of design is also understood by looking at the power wasted by the LED, you obviously want that to be as small as possible
@@deansmith4752 You mean "all diodes should not be connected in _parallel_ like this ..." and that's because whichever diode is taking more current, it will heat up more and its negative temperature coefficient will cause it to draw more of the current, and so on. The power consumed by the LED is fixed for a given brightness, so the efficiency is governed by the power wasted in the dropping resistor (not the LED). To maximise efficiency, you want the supply voltage not too far above the on-voltage of the LED, but that makes the dropping resistor small and can lead to greater variations in current consumed for changes in temperature or variations in samples of the LED.
@@RexxSchneider I'd say you're both right. To summarize it; a series connection *guarantees* that the same amount of current (A) runs through each LED. A parallel connection of LED's *guarantees* that the same voltage potential is applied across them.
LED's are inherently a bit "tricky" in ohm's law, as they don't follow a linear relationship between voltage and current since it's an "active component", being a semiconductor. Since ohm's law doesn't really work on active circuits, we have to use static/idealized values for semiconductors. LEDs, and regular diodes for that matter, are simple enough since when surpassing their forward voltage, (or reverse breakdown voltage), they'll be idealized as essentially having resistance that IS the proportional of voltage and current, and likewise, when below the threshold, we could in a way say the resistance is infinity. But naturally a LED that's ON will heat up, and that's the culprit that makes LEDs so "hard to calculate" with Ohm's law, cause that changes it's forward voltage. The hotter it gets, the lower the forward voltage gets.
So dean is correct in that when LEDs are in series, one single LED with different forward voltage would drop less voltage, allowing more current to pass in total, and also leaving more potential for the next LED. It should be noted that the next LED would then sink more total power, decreasing it's forward voltage faster than the first, and kinda "balancing" it out. The solution proposed isn't in effect changing this fact, but does make it look a lot easier to calculate individual LED in a diagram. I think what Dean meant by "current to go through ONE LED" was that one led would drop all the voltage, in effect "consuming all the current", since the current would be the same across all LED's in series what. (disregarding inductance etc.)
Rexx is absolutely correct that LEDs shouldn't be connected in parallel, but the "like this" doesn't show in the video, since they all have a limiting resistor. But if the LEDs were indeed in parallel, this is when Dean's comment would happen. One LED would be a fraction out (inevitable) of the forward voltage of the others, thereby making it drop less voltage and in turn let more current flow. This is thermal-runaway waiting to happen, as that LED would consume more power, getting hotter, dropping even less voltage but passing even more current. I wouldn't say that "the power consumed is fixed for a given brightness", since brightness tends to get weaker when over-driven (more power used for heat than for producing photons). But I get the idea.
The reason a parallel circuit could be stable a while with very similar LEDs, is that power consumption is equal to voltage times current. A LED is dropping less and less voltage, but taking more and more of the current, making it effectively use close to the same amount of power. But when it drops enough voltage to drag another LED into it's forward voltage threshold, that other LED is drastically affecting the total current in the circuit, since it's basically "turning off" letting all it's current flow through the other LEDs. This is when they'll get over driven and blow. (sometimes dramatically) ^^
So to summarize: use a LED driver to maximize efficiency. It changes voltage in accordance with current drawn, thereby limiting the total current and not exceeding the rating of any LEDs, and use a resistor as a "current limiter" that would account for a certain drop in forward voltage. It's easier, but simplicity has it's tradeoffs.
Wow, sorry for the wall of text... I got on a roll there..
@@arsenic1987 You have a decent grasp of what is happening when diodes are connected in parallel, but underestimate the effect of the exponential relationship between voltage and current. When you say, for example, _"A LED is dropping less and less voltage, but taking more and more of the current, making it effectively use close to the same amount of power"_ you miss the point that a forward voltage increase only needs be around 20mV to produce a doubling of the current through it. That's equivalent to as little as 10°C rise in temperature. That means that the power consumed by the diode (or LED) does increase quite dramatically as its temperature increases; the increase in current is is far greater than the minute change in forward voltage. It definitely does not _"effectively use close to the same amount of power"._
The whole point of the dropper resistor is to stabilise the current against changes in temperature since an increase in current as the diode heats up will cause more voltage to be dropped across the resistor, thus reducing the voltage across the diode and significantly reducing the increase in current because of the exponential relationship.
Nice video, very well done!
I really appreciate you making this video. I'm 70 and just now getting into messing around with LED's and breadboards etc. Much of the I R V triangle is still a bit of a puzzle to me and hopefully this old brain will eventually learn to correctly apply the appropriate formulas where needed. I have no idea how far I'll go with this stuff but it's pure fun for now. Thanks again.
Scott
Good for you, hmmm, um put your finger over the value you want, so if its V then IxR, if it is if you want Current (I) then it's V over R (V/r or V divided by R) because V is over R. Sorry didn't watch the vid maybe he/she says this. Then you have Watts so P Power (at the peak of the triangle) = I x V. Type in Ohm's Law to your browser then go to images and you should find a wheel image that uses more conventional maths. Stops my brain falling apart like a chocolate orange. You'll get the hang of it. :) Many electronics shops have them as a bookmark. Such as I=√P/R..... Hi from Oz.
Love this video, very informative
That was sooo easy to understand, thank you sir!!
Simply Briljant and thanks.
Marvelous. A born instructor.
Very nicely explained.
Bless you!
Thank you
Very insightful thanks a lot for making this video :) !
Hi Mark, you should now continue this article for running a LED on ac with higher voltage as well, with and without a rectifier!
Fantastic video meny thanks you made it so simple and clear Kind regards Mike 😁😁😁😁
Great Video! helped me a lot!
Great video, Markus. 😃🙏🏼
I specially like the triangle. When I got familiar with that at school I used it at many formulas. 😉👍🏼
I only have one critic to say...
Don't put the dot (comma) in the middle of the numbers! Then it can be mistaken for the multiplication sign and is very annoying. 🙈😉
Really good tutorial. I like to use a multimeter to find the Anode and the Cathode of a LED. Put your multi-meter in Diode mode. Connect the lead one direction the diode doen't light and the meter will measure "OL". Connect the leads the oppiste direction and the diode lights (a little dim).
that works for some DVMMs
TOP MAN! THANKS FOR EDUCATING US!!! 👏👏👏👏👏👏👏👏
You helped me a lot on that one! Liked and subscribed
Thankyou very much.
Great explanation. Thank you!
Ty you made this so clear
Thanks for this Markus, really super helpful :)
There is hope yet for my SX-240 flat top LED repair / replacement mod!
Now all I need is someone to step me through continuity/Basic troubleshooting on a dead SQ-80 mainboard (yes I eliminated everything eles).
He says cheekily probably asking for too much help.
Honestly I’d contribute to your patreon if you’d help step me through it.
Thank you...please make one similar video but for capacitors with two three practical examples
Very informative 👍🏼
Nicely explained. Can you please tell be about that circuit board tester you're using & possibly where it can be purchased. Thank You.
So glad I found this guy, he speaks good English 😂❤
Content is king, why don’t you do a step by step build a synth series? A CS-80 using modern components may seem ambitious, but something like an SY-1 would be interesting. Then people could make multiple examples of that mono synth for a poly synth variant. Should give you around two years of content. And then you’d have loads of The Fuller Luv Philtre synths out there. You could also get sponsorship from some parts source outlet where people can get their parts from. A win, win.
Thanks. Very clear! I subscribed!
That is important figuring out current across resistors to determine correct power the resistor can handle before getting too hot I sometimes don't check but must! 👍 LED color choices of red, yellow, green and blue ... Interesting to use different color LEDs if for holiday lighting or for color code uses engineering thoughts overlook also.
Good explanation.
great work!
Very well explained
Thanks a lot for your sharing.
Great video...the only thing I would have done different is plug the two LEDs back to back instead or back to front! I looked like the second LED was already on before you plugged in the resistor. I had to watch it a couple times to see that it was actually dimmer before you added the resistor.
Awesome Explained thanks
Excellent. Very helpful thank you.
perfect lecture😍 love from Pakistan🥰
Great video thank you
This will save me change since I love to play with electronics and have little clue about the value of using LEDs. I pop them in my project and they went dead. Where can I buy that bread board... what's the name.
i learnt more than in did during my 4 years in college in EEE
Fantastic Job ⭐️⭐️⭐️⭐️⭐️
Excellent explanation! I really enjoy learning from people who truly understand what they are teaching!
Question: How do you figure out an LEDs values if you have no literature, like scavenging from used boards or replacing a bad LED etc.?
Thank You
say you have a 5V power supply, connect a LED and a 200 Ohm resistor as done here, Use a multi-meter (20 VDC setting) and measure the voltage across the LED - that gives the Vf
Another way of thinking is that a diode will always stay at almost the same voltage, while the current will adapt according to the resistor. The more difficult question is, how much power can a scavenged diode take? Use 200ohm like suggested and see how long it takes for it to die .. it's a scavenged diode after all ;) Most 'normal' diodes will live "forever" with a 1k resistor, most even with a 100ohm resistor .. the high power diodes are the ones that are more sensitive.
And yet another way of looking at the problem is to consider that almost every LED ever made can take a current of 20mA and will have a forward voltage somewhere between 1V and 3.5V. So get a 12V supply and a 470 ohm 1/2 Watt resistor, hook them up with the LED and measure the voltage across the LED with a voltmeter. You can then calculate the current. If you only have a 5V supply, then use a 180 ohm 1/4 Watt resistor, although that will give more variability in the current depending on the type of LED.
If the LED can't take 20mA, it's not going to be much use to you anyway.
very good tudor..
Great very good>class.
Thank You Tristan
Very good and informative video.
I have a question, how can you work out the resistance value if you do not have a spec sheet on the LED?
Do you set up a circuit and measure the voltage across the LED and also the amps running through the circuit?
Do you set up a circuit and measure the voltage across the LED - yes
brilliant. Thank you!
Thanks very clear.
Great video! Still trying to wrap my head around the fact that series wiring doesn't require more current.
It’s because power is voltage times current (P=UI).
When you have two leds, you need twice the power to get the same brightness. Connecting them in series requires doubling the voltage, which doubles the power as well so you’re good.
When the leds are parallel, the voltage requirement remains the same but you still need twice the power so they draw double the current.
It’s the same with the torque and rpm of car and motorcycle engines: when engine A produces X kW of power at 3000 rpm and engine B produces the same kW at 6000 rpm, we know that the latter is providing half the torque.
@@sauliluolajan-mikkola620 Thanks! That makes sense. Parallel draws more current, and series draws more voltage. Irrespective, the wattage remains the same. The motor analogy helped as well.
Nicely done
Thank you,,more please 🙏
best handwriting on youtube
Thanks. I needed that. ;)
thanks so much maraming salamat sobra
What would the feasibility of just stepping down the supplied current to keep the 1/4w resistor? I mean if it is just drawing 3.2v in parallel, less to burn off?