LED Resistor Calculation
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- čas přidán 24. 10. 2019
- How do you select the right size resistor for an LED? This video will guide you through the calculation to select the proper current-limiting resistor for an LED, given the LED's forward voltage drop, desired current, and the voltage of your power supply. It also covers more complicated scenarios like combining multiple LEDs of different colors in series or parallel, and how to make sure you don't exceed the power rating of your resistors.
Don't have the right resistor value laying around? Check out this video to learn how you can combine resistors in series and parallel to create almost any value you need: • Resistors in Series an...
Don't understand why I said it's OK to put the LED before the resistor? Watch this video for an explanation: • Does the resistor need...
Have a question? Ask in the comments and I'll do my best to get back to you. - Věda a technologie
Finally found someone who knows his stuff and explain it in a very clear way. Thank you!
Thanks!
Dude! Thank you, this was super helpful. I’ve always struggled with this math, and this broke it down a way I could really digest.
This is the first video (of MANY) that I've come across that actually shows how to find the voltage and current for an LED, or actually uses the terms one sees in the data sheets for that matter (forward voltage and forward current). All other videos explaining how to calculate the resistor just say, "...and this LED has a voltage drop of 2V." Thank you for explaining in a practical, applicable way!
Thanks for explicating each of the cases comprehensively, sir. The succinctness of your tutorials is truly appreciable.
Excellent teacher, i love the practical knowledge I used to do this in my GCSEs but never got the application part but you've shown exactly where it would be applied to real life. You are a W guy!
I had electronics in school roughty 25 years ago, so I was a little rusty... I've seen more than a couple of videos to refresh, but this one is by far the best. Thanks!
you nailed it. nice presentation, nice knowledge, nice appearance. you deserve more views
Absolutely awesome education video explaining about the LED's!! Thanks so much!!!
You deserve a lot of subscribers. Great educative video!
Nailed it. Thanks for going through every scenario
Thanks for this, very good examples for someone who is just learning about using leds and a breadboard!
your video is going in my playlist .
well explained !
Wow this was so helpful, thanks.
The explanation was so clear without knots.
Most compehrnsive video on resistor value. Thanks.
Dr. Ben Finio, thank you for the video, you made things easy to understand. I will subscribe and watch more of your videos, they are awesome!
Thank you!
Excellent! You make it very easy to follow... thank you!
Thanks for your help. This is video gives a clear and concise explanation. well done!
Thank you!
Thank you! Answered my question and explained it well. Been too many years since my junior high electronics class I have forgotten everything.
tbh, i was very pleased with the presentation its informative and well, easily understood. i wish they did this when i was in grade school. couldve made things so much different for my life today.
Thank you for this informative video
No joke dude I actually thought you would have thousands of subscribers u deserve it
Well, it took a year, but now I have more than a thousand subscribers!
The best explanation! Very good presentation.
Phenomenal explanation, thank you!
Nicely explained an demonstrated, doc. You’ve got me as a subscriber.
Thanks!
This is exactly what I needed to know. Thank you
Nice video shot, thanks for sharing it with us, well done :)
The world's best teacher thanks sir
Excellent video, thank you.
Thank you for this explanation.
I so needed this tutorial. Spot on buddy.. 👍
Thank you. Clear explanation.
That was as clear as it gets. Thanks!
Very well put together
Wowwww this is very to understand all my question are already answered upon watching this thank you Dr.!
You're welcome!
Brilliant explanation
Thank you verry clear explanation.
Thank you for your work. Finally i get it.❤👍
very well and clearly explained with practical. keep it up. love from INDIA
Thanks, glad it was helpful!
thanx for nice explanation
Thank you, this was so usefull and clear, please make many many more. Greatings from Argentina.
Thanks! If you check out the playlists on my channel you will see many other electronics and Arduino tutorials that I hope you will find useful.
@@BenFinio I have seen and I would love to see many more!!!
This was a great tutorial, but still way over my head. At 55 years of age, I feel I need to go back to school and re-learn the basics of electronics. I feel a real temptation to do so, though, so that's a good reflection on your video.
No need to go back to school when it's all on CZcams! Check out my intro to circuits playlist, you may find this helpful: czcams.com/play/PLKL6KBeCnI3U6KNZEiitdtqvrxkBhpuOp.html
It’s the conventional flow thing, and then calling it current. Call electrons like it is or confuse the watchers who probably understand electron flow theory. Good picture quality and explanation with rated resistors! Thanks for sharing.
Relevant XKCD... xkcd.com/567/
We stick to conventional flow cause we can use right hand rule to find the magnetic fields 😁
wow amazing. you need more susbcribers. amazing explanations.
Thank you! It's been quite a while since I've made a video and I usually make them to go along with something on Instructables www.instructables.com/member/Ben%20Finio/instructables/
I've watched so many video's on LED lighting today that you might as well have been speaking Chinese . Brain overloaded . A great video for sue but I need it in slow motion . You talk faster that I can think ! I need a nap !
If you have a specific question about part of the video, feel free to leave a comment and I'll do my best to answer it.
how can you only have 187 subs with such high quality vids
Haha, thank you - most of these tutorial videos are relatively new and I don't post them that often, so that probably explains it.
Bro has 9k subs now.. And that's what I called the result of dedication
Up to 11.9 now
Thanks,You Are King 👑
Nice, Thanks.
Very nice video. In respect to LEDs themselves, read your datasheet and it should have relative luminosity at a specific current. That way if you're doing RGB stuff, you can figure out what current you want in order to make the relative brightness between each color the same.
Very helpful video thanks it helped me understand my tech hw
Glad you found it helpful!
Very cool 🇧🇷😉👏👏👏👏👏 awesome video !
Good presentation! I'm little lost on resistor power handling...heat dissipation. Like when to use a 1/4 watt instead of a 1/8 watt (example).
I had a project to use LED lights on a golf cart. Cart batteries were 8.43 vdc each.
I had LEDs using 4.5 vdc. Not knowing current draw of LED....I started off with 100 ohm resistor...had 2.7 vdc to LED...was very dim illumination. Then tried 33 ohm (was 1/4 watt)...got 3.2 vdc to LED...was little brighter...then tried a 10 ohm (was a 10 watt)...got 3.9 vdc to LED....was much brighter. By seeing my results I figured to get the 4.5 vdc I would need a ~ 2 ohm resistor (to achieve optimal light illumination of LED...rated as 100 lumens output).
I noticed I could not read actual drop down voltage out of my "circuit" until there was the LED load put on it.
Had fun playing with it....not an "orthodox" way of designing...didn't have the current draw specs of the LED.
Not sure if this is an acceptable way to do it.
😁
Just curious if my estimation of the 2 ohm resistor is correct. And would a 5 watt rating work?
This is amazing
Thank you so much for this information on the green led with a 100 ohm resistor would it make the led last longer instead of to much power to burn the led out
Thanks
thank you!
You're welcome!
Nicely explained. The only thing I did not understand is how the breadboard parrallel connection with your multimeter plugged in at 6:42 works.
Not sure why, but my dyslexia doesn't affect me while learning this from you. Thanks!
Hi, What are the green wires on the circuit board between the LED's and the plus voltage?
I have a car license plate bulb socket that requires a resistor to make an LED bulb work in the socket. If I use an axial resistor and connect one wire end to the left socket contact and the other wire end to the right socket contact and then insert the bulb into the socket is that a series connection? Also, if I calculate a 115 ohm, 1W resistor could I go with a higher power rated resistor like a 5W? I believe I read you can do that. In this case if you chose a 100 ohm resistor would that be close enough or should you be at or above the calculated resistance value? Thanks for your time!
Great video, thank you for making it. How do you figure this out when you don’t know the values of the LEDs you are using?
Hi Michael - the voltages for LEDs are pretty standard based on the color. Just google "LED voltage color chart" and you will find a bunch of them. Almost all of the "regular size" LEDs (the kind you see in this video) are rated at 20mA, so that is usually a good guess to start. To be safe, you can always start with a bigger resistor, measure the current through the LED (assuming you have a multimeter - separate tutorial on that coming soon), and then move down to a smaller resistor if the current is still below 20mA.
Hi, thanks for the great explanation, I have a question for calculating the value of the resistance @ min 10:46 , why did you put 0.02 for the current when we have 2 LED? Isn't that supposed to be 0.04? or that's because we connected the LED in parallel?
Really great video. What’s the purpose of the 0-ohm resistors in your kit?
Good question - honestly I wasn't sure and had to Google it. Apparently the answer to "why not just use a jumper wire?" is that it makes automated assembly of printed circuit boards easier. It's the same size/shape as all the other resistors so the pick-and-place machines can just grab it without needing a separate machine or attachment. So, for a hobbyist kit like this where you're probably putting all the parts in a breadboard by hand, there's no functional difference between the 0 ohm resistor and a jumper wire.
Can connect a 3v led with a resistor and a 12v led to the same 12v battery? Does the resistor limit the 12v as well?
Nice video! The only thing I would have liked to know more about is the construction of the LED and which side to attach the resistor and which side of the LED to attach to + or - of the battery.
Honestly I always get "cathode" and "anode" mixed up and find it easier just to remember that the long lead is the positive one. This diagram is a good one though: qph.fs.quoracdn.net/main-qimg-54791c1af8a06f2051c64b9d0c4d7f55
@@BenFinio Think of it in terms of exam results. (C)athode, (A)node. Scoring a C in the exam would be a negative result, scoring an A a positive result.
@@PetrikNZ Never heard that one before - helpful, thanks!
What resistor could i use if i put together the red and green led on 9v battery?
Really enjoyed this video! Question, if voltage is similar to 'pressure' would sending 5.2v through the first LED which is rated for 3.2V not blow it up in the series circuit?
No because the entire 5.2V is not dropped over the first LED. This new video series might help, particularly video #14: czcams.com/video/eLSoJn__gAc/video.html
@@BenFinio great thank you! I really enjoy learning all of this!
thanks!
(:
Or to put my question a different way: What is the difference between voltage drop and forward voltage?
Very clear and comprehensive with different scenerios, thank you!
I got few questions, in another video it said it is possible to measure forward voltage of an LED diode in multimeter diode mode. And it did work for my red and yellow leds, showing around 1.8 volts, but it doesnt seem to work for my blue or white LEDs,. Any idea what is the problem?
Also is this method applicable for longer LED strips?
Is it possible to figure out ideal current for a given LED too, without risking burning out the LED with trial and error?
I'm quite a newbie, I'm sorry if these are dumb questions, but any help is much appreciated. Cheers.
I noticed in the answers the safe guess approach and lowering the resistance slowly. That's helpful to me. But I still wonder about my questions :/
Hi Emirworks -
First, I'm not that familiar with the diode measurement mode on multimeters. Blue and white LEDs have a higher voltage drop, typically around 3-4V, so maybe your multimeter's diode mode can't measure that high.
The LED strips you can buy usually have built-in resistors so you don't need to worry about adding external ones. You just connect them directly to whatever power supply they come with or say to use.
And yes from your other comment you're correct that the safest thing to do is start high and slowly lower the resistance.
Hope that helps!
@@BenFinio Thank you so much for the reply. I really acknowledge the value of feedback. I subbed :)
Have a nice day!
@@EmirUysal Thanks! If you haven't seen it yet, I have a playlist of other tutorials here that may be useful if you're new to electronics: czcams.com/play/PLKL6KBeCnI3V5XgmKOHv4vKPGBd-qc1QU.html
Good inf
Hi Ben . Lovely video explaining the maths and the valuable point about not making an error of adding up the forward ampage in a LED in series circuit. I have a question ,please. On resistors size my little project works out the power going thru my resistor is 0.029w , does it make any difference if i was to use a 0.125w power rated resistor , to say , using a 0.500w power rated resistor ? Hope you could help. Look forward to hearing from you . Regards Don Codman
Hi Don - as long as they have the same resistance, it doesn't change the math for the current going through the LED. Resistors with bigger power ratings will generally be more expensive so you don't "need" the 0.5W resistor in this case but there's no harm in using it that I'm aware of.
no difference in general a higher wattage resistor is less likely to drift or burn-out
Thank you for the video. What can one do if they don't have info about the voltage drop and current of the led
The voltages for different colors are pretty standard, usually starting around 2V for red up to around 4V for blue or white. So to be safe, you can assume a higher voltage and target a lower current (10mA), and start off with a large resistor (say 1kohm). Take measurements and work your way down to a smaller resistor. If you are using standard 5mm LEDs then from what I've seen the current is almost always 20mA.
@@BenFinio Thank you very much
Great video! I have an LED string with non-removable bulbs and 1/2 of the string is dead. I have found the bad bulb and I want to cut it out of the circuit. I know that I have to replace the bulb with a resistor but, since I have no data on the string of lights, I don't know what value of resistor to use to phase out the dead LED. Suggestions?
not even info is given. if you like try a 330 Ohm resistor ...if too dim, try 220, if too dim try 100, etc
In general if you are in a guess-and-check situation with resistors, it's safer to start with a very high value and work your way down. If you start low you are more likely to burn something out by having too much current.
I have a question 5mm fat led datasheet is missing... How do I find out
This is a really good video, thanks for making it and posting it. It will be helpful for my project.
My only criticism is that it would be more helpful if you included the units (mA, A, V, etc.) next to the numbers to help understand the formulas and calculations.
Will be subscribing to this channel as its so helpful.
This is a good example of "do as I say, not as I do" - you're right, it's always a good idea to write out units in the equation for clarity, not just in the final answer. Sometimes I get lazy about it!
Thank you.
What is the 0.6 or o.7 drop voltage that it is mentionned in many tutorials. Is it the minimum PD between anode and cathode needed by the current to cross the LED ?
I am confused on this point.
Thanks in advance 😀
0.6 or 0.7 is the typical forward voltage drop for a silicon diode when it begins conducting. The voltage drop for LEDs is usually higher, 2-4V depending on the color.
@@BenFinio
Thanks a lot Ben !
You are the only one who answer me.
Thanks my Dear 😀
@@kenzo4Ever once you know the voltage drops or rises across every component except for 1 then you can do kirchoffs voltage law and find that unknown voltage drop, which is what he was doing but he didn’t mention it
Hi sir, just wondering if you can provide credible sources like websites or articles that I can use as reference for this experiment. Need it for the demo paper hehe. Thank you!
I am not sure what your teacher will consider "credible," but if you just google "LED resistor calculation," LED calculator," "LED current limiting resistor" etc. you will find many websites that present the same information.
Ben Eater and and Bean Finio damn ❤️❤️
Could you add a small capacitor between each diode for voltage stabilization
Try it LOL
in an AC Circuit a Cap will smooth out the voltage spikes or ripple that you have
because the difference in charge from one plate to the other will allow current to flow through teh capacitor
HOWEVER..... in DC Circuits
With the capacitor empty
With the capacitor connected to the power supply , Let's assume you have a 5V Supply
and a 10V Capacitor
well....
Your capacitor will charge up to the voltage of the supply and no further
but since it's not AC but DC Current won't flow through it and your LED will turn off
if you wanted to control the voltage you could always put a voltage regulator on the line before the LED, it'd serve the same purpose
Can you do a more complicated network? Gained a subscriber here.
Hi - right now I am mostly doing Zoom tutorials, early next year I will probably do a longer electronics tutorial playlist which will include mesh and node analysis (tools for solving more complicated resistor networks). In general LED networks should not get too "complicated," you should be able to arrange them in combinations of series and/or parallel as shown towards the end of this video.
@@BenFinio Oh. Thanks. The video is a great help. As of right now, I'm doing a simple led project so I'm probably just finding some easier ways to finish it. You've got a great voice for teaching.
@@joshrillo Thank you. If you haven't seen them already you may enjoy my other electronics tutorials then. You can find the playlists here: czcams.com/users/BenFinioplaylists
Im just starting teaching myself. Your the man..
Hi Ben I have 90 LED 2v all individually switched obviously will each have their own resistor what is the lowest and highest power I can run these on and what calculation would I use pleas kind regards John
Sorry I should have said run in parallel
Thanks a lot for great explanation. However, one huge minus is using that marker - when you write on paper with it I got goosebumps (I hate that sound irl)
Could you not also run the different lights from different 'taps' of the battery pack.
This would be equivalent to putting the LEDs in parallel.
What would you recommend for 12 LEDs and a single power source between 9v and 12v? All parallel with a resistor on each, or several LEDs in series and those series in parallel sets with a resistor for each set? Concern over how hot the resistor gets is unique due to the material near the LEDs being very sensitive. Thanks.
To minimize power dissipation (and thus heat generation) in the resistors you want to minimize voltage drop across them. So for example if you combine several LEDs in series and then put sets of those in parallel as you suggested, the voltage drop over the resistor is smaller than if you just put all the LEDs in parallel each with their own resistor. However, note that the LEDs themselves will also heat up (they are not 100% efficient - i.e. they do not convert 100% of electrical energy into visible light) so you may still need to be careful if your application is very temperature sensitive.
@@BenFinio Thanks!
So if I want to run 8 3v multi colored flickering leds off a 12 volt power supply what size resistor would I use
You watch the video and learn to do the calculation yourself :-)
I try drop my reciver voltage from 6 volts to 5.5 volts. I thought it would be 1 or 2 ohm resistor but it took 1M resistor to do it. I am bit confuse why that is 🤔
bookmarked :)
Hi, if I have 3w or 5w led, can I consider the current is 0.8 amp and 1.38amp respectively, based on led forward voltage is 3.6v? Thanks,
Yes, that is reasonable to assume, although it's not clear if that's the typical rating or the maximum rating. The datasheet might say.
If you do not a data sheet for LED's how would calculate the voltage drop ?
The voltage drops are pretty standard for a given color. Just google "LED color voltage" and you will find many general tables with the data. If you're unsure, it's also always safer to start out with a larger resistor. You can then measure the current and gradually decrease the resistance while keeping the current below 20mA (for most regular LEDs like the ones shown in this video).
I realize this is an older video. But no need to look up anything or to find the forward voltage drop to any LED. Merely take the supply voltage and divide by ~20ma or less and WALA, you have the resistor value. No need to look up anything, and too many times you have no idea what type LED you have. So merely pick your resistor for 20ma or less and it will work every time... JMHO!
Yeah I have a question. I have a power supply (coin cell) of 3.7V I need to power 3 LED Filaments that are 3V at 50 - 100 milliamps. Do I need to add more power to run them? How money resistors would I need? And What resistor would I use? I don’t want to overheat anything? Just FYI I have a 6V power supply if I need it.
A coin cell battery may not have enough current to power that many LEDs. You can typically power a single LED with a coin cell battery without needing a resistor, because the current they provide is so small. This video may help, as well as the introduction to circuits playlist on my channel: czcams.com/video/ZdIBle_9Y_4/video.html
I have a 12V LED and a 24V power supply. Would a resistor protect my LED?
If you are referring to a 12V LED strip, those are typically designed to work with a 12V power supply. They consist of sets of 3 LEDs in series and include current limiting resistors in the strip. In theory you could use a single external resistor with a 24V supply but it would be dissipating a LOT of power so you'd need to make sure the resistor could handle the power. It's probably better to just buy an appropriate 12V supply.
Need help. I want a simple led and resistor and diode combination which will glow the led at exact 4.2V. My BMS does not have led indicator to show li-ion battery is fully charged.
Google on "Li-ion battery indicator light circuit" and you will get several circuits. To get a precise voltage point for turn-on, a zener diode or else a voltage-divider of two or more resistors will be needed.
I feel like I almost grasp this.
If you're running 3 red LED in series, you have a combined total of 6v. If you ran this setup on a 6v battery would you use a resistor at all?
Hi Heza - in general you should always still include a resistor, even if it's a very small one. It's a bit of a simplification to say that the voltage drop across an LED is perfectly constant. You can see this if you look at the current vs voltage graph on an LED datasheet. For example see the FORWARD CURRENT VS APPLIED VOLTAGE graph on this one: www.jameco.com/Jameco/Products/ProdDS/333851.pdf. In other words, even if you have an LED with a rated forward voltage of 2V, and you apply 1.9V to it, you're going to get a non-zero amount of current.
why did you subtract 2v from the original 3v? is it because there is another load whose voltage drop is 2v (doesnt have to be an LED)?
There is a 2V drop across the LED.
what if i need 15 LED? what battery and resistor should I use?
Sorry, you'll have to watch the video and figure that out yourself :-)
You can use two or more resistances in parallel to overcome the power limitation problem.
well this adds a new problem, the new resistance of the in parallel resistors
@@zoroco3230 well in that case it is best to use , as you suggested one resistor in series with each led.
The main main advantage of this is that the circuit will always work well. In the case of using one resistance it might not work well at all. The reason being is that not all the led is going to have the same exact value of the barrier potential to overcome to light up. Therefore the one with the lowest will turn on first and all the current will rush through it causing it to be bright and may burn out and cause a chain reaction.
How do I determine how much resistence I need? I assume I look at everything in the circuit and find out how much each invidiual component would require and add resistors between the main power and that component. Do That for every component and I have a safe circuit? So if I am correct I would need to read the data sheet for every component but I'm not sure what I would be looking for in the data sheet? Sorry for all the questions. I have been having a lot of fun but I'm destroying all my components lol. I have been building none stop but my lack of tolerance knowledge has had me going down all kinds of rabbit holes trying to get circuits to work that already do and I just have a bad component... -.- Thanks for any help!
Hi - this is more than I can really answer in a single comment, you may find my intro to circuits series helpful: czcams.com/play/PLKL6KBeCnI3U6KNZEiitdtqvrxkBhpuOp.html
@@IthacaNature Thanks. Can you answer me this then? Is my idea above at all accurate in how one would determine what resistance they would need and where? Or am I completely off?
@@retroguardian4802 Whoops, replied from my other account. It depends on what you mean by "component." This video is only about LEDs. Resistors have many different uses. If you are building circuits with other components, you need to learn what resistors are used for and when you need them (which is a much bigger explanation and why I directed you to my other playlist). If you are building a circuit with multiple LEDs, then yes, you need to make sure the current is limited through each LED. The latter part of this video explains circuits with multiple LEDs.
add resistors between the main power and that component, Main power?????
can i connect fifty 3.2 led which is going to powered by a 24 V system with a single resistor?
It depends on how you connect the LEDs and the power rating of the resistor. If you watch the entire video it will show you how to do the calculation.
@@BenFinio I to want connect 50 rgb in series with a 24v system..
@@jeevabharathir8163 24 volts will not be enough to put 50 LEDs in series. At a minimum of about 2 volts per LED, putting 50 of them in series would require at least 100 volts.
Hey, Thanks for not replying. I was thinking of subscribing but you solved that question for me.
CZcams stopped sending me comment notifications for some reason and I am working through a giant backlog of comments on this channel.