Hes right if u wanna absolutely calculate, but what I did all my life is learned the hard way that most standard LED's are 3V MAX and some older Reds, Oranges are 2.3-2.4V MAX. I never calculated such things for my projects, but what I do is I take an any adjustable resistor, connect it with LED in series and the source could be like 3.3V, 5V, 12V, 19V... and what I do is slowly decrease (adjust) resistor till I start to see LED shining and then (by monitoring LED voltage with multimeter) I slowly increase till I reach 3V if I want LED to shine absolutely brightest as it can shine without burning. And I can leave it on this max brightness if I want to, it will work for a loooong time and not burn. Always works. I can even do this with like 10 LED's in parallel and one adjustable resistor (potentiometer). I guess what happens, the current gets adjusted automatically and I can get absolute MAX brightness, if you are gonna use this calculated resistor, you wont get max brightness if you need that for ur project, because it always will be a "safer" value but not of what LED can actually deliver.
All details are very useful,bro. Thanks so much. So, I can't connect my smd RGB led directly to 5v and you're right, It drops the voltage for my motor :( R = 2.2v / 0.0.2A = 110 ohm - based on the RGB datasheet. So, I need 110 Ohm) I understand now Thanks again. May God bless you, bro.
Thank you so much, I have seen so many videos and they all gloss over what the actual math is for figuring out anything, it's just always "we have 9 volts and the led uses 3 so that means we need at least 300 ohms resistance" ok buy why? Yes. thanks to your video I could actually understand this and why and made a working LED lit booknook for my mother!
Thanks for reminding me I forgot to purchase some resistors for my project. Keep the tutorials coming. Sometimes I wonder if you put the videos out just for me. Lol. I have directed several people towards your website so they can learn about electronics and not be intimidated by the content. You make it simple and easy understanding for them. I can fill in some of the blanks for them. Thanks
It’s amazing when a person constructs their first circuit and then board lights up, I like to watch their face because of the smile and amazement they show with success. Hopefully they take interest and build from there. With the creation of the Arduino & Raspberry modules I hope this brings in young and older people’s interest into the world of systems design. Just look at the young lady of 14 years of age that just created the automobile “A” pillar camera system to show blind spots. I am truly amazed at what any age minds can think of!! Truly!
Missed opportunity. Instead of repeating the same stuff everyone always says about selecting a resistor for an LED, how about addressing the real-world problem of someone who needs to determine a resistor value for an LED without having the LED specs? In other words, tell us how to find the voltage drop as well as some clues about typical current values for various colors (a red LED with a clear lens is going to be more modern than a red LED with a red lens).
Usually between 2v~3.3v First hookup 1.5v AA battery, if it doesn't light up, try two 1.5v in series, some SMD LEDs have a forward voltage of 18v, yes, I was surprised too. Just gradually increase the voltage, and you should expect a maximum 1w per single LED.
That's a super easy way to look at it. In case anyone wants to finish the numbers in the circuit your LED has an internal resistance of 100 ohms (r=2/.02).
Sorry, that's not correct. A diode does not obey Ohm's law where voltage is proportional to current. It has an inherent voltage drop of 2V caused by the semiconductor junction, and that voltage does not change greatly as current varies. At 1mA, the voltage is a little smaller, but still around 2V.
@Epi Endless don't be sorry. I'd love to learn more. Maybe it's like a light bulb. When they are turned off they have a way different resistance then when they get hot and turn on.
What will get hotter? A 100 ohm 2W resistor or a 120 ohm 2W resistor? I thought that the 100 ohm resistor should get hotter because it allows more current through but I have seen some articles that say the 120 ohm resistor would get hotter.
Hello and thanks for a great tutorial. I have a question please. I have some colour changing led,s that are only 2 pin, how would I calculate the correct resistor for this type of led ? Thanks John 👍
how might this be achieved is the requirement is to dim an indicator LED on a device that was built / provided by somebody else, and the specs are not published?
You can replace the existing resistor with a larger one or simply add another resistor between the original resistor and the LED. I'd recommend starting with a 1k ohm and moving up from there
As usual, glosses over the fact that the test current may actually be far too bright for your application. The classic resistor calculator worked well a few decades ago, but these days most of the 20mA LEDs I use are perfectly usable as indicators at 1mA, and dazzling at 20mA. In this case I'd stick in around 2-3kohm, and see what it looks like. And driving an LED at 1mA is far more reasonable when connecting it straight to a microcontroller.
I really appreciate you taking the time to do the math, you made it more simple than most videos I watched
Hes right if u wanna absolutely calculate, but what I did all my life is learned the hard way that most standard LED's are 3V MAX and some older Reds, Oranges are 2.3-2.4V MAX.
I never calculated such things for my projects, but what I do is I take an any adjustable resistor, connect it with LED in series and the source could be like 3.3V, 5V, 12V, 19V... and what I do is slowly decrease (adjust) resistor till I start to see LED shining and then (by monitoring LED voltage with multimeter) I slowly increase till I reach 3V if I want LED to shine absolutely brightest as it can shine without burning. And I can leave it on this max brightness if I want to, it will work for a loooong time and not burn. Always works.
I can even do this with like 10 LED's in parallel and one adjustable resistor (potentiometer). I guess what happens, the current gets adjusted automatically and I can get absolute MAX brightness, if you are gonna use this calculated resistor, you wont get max brightness if you need that for ur project, because it always will be a "safer" value but not of what LED can actually deliver.
All details are very useful,bro. Thanks so much. So, I can't connect my smd RGB led directly to 5v and you're right, It drops the voltage for my motor :( R = 2.2v / 0.0.2A = 110 ohm - based on the RGB datasheet. So, I need 110 Ohm) I understand now Thanks again. May God bless you, bro.
Thank you so much, I have seen so many videos and they all gloss over what the actual math is for figuring out anything, it's just always "we have 9 volts and the led uses 3 so that means we need at least 300 ohms resistance" ok buy why? Yes. thanks to your video I could actually understand this and why and made a working LED lit booknook for my mother!
Thanks for reminding me I forgot to purchase some resistors for my project. Keep the tutorials coming. Sometimes I wonder if you put the videos out just for me. Lol. I have directed several people towards your website so they can learn about electronics and not be intimidated by the content. You make it simple and easy understanding for them. I can fill in some of the blanks for them. Thanks
Thank you for the positive feedback!
It’s amazing when a person constructs their first circuit and then board lights up, I like to watch their face because of the smile and amazement they show with success. Hopefully they take interest and build from there. With the creation of the Arduino & Raspberry modules I hope this brings in young and older people’s interest into the world of systems design. Just look at the young lady of 14 years of age that just created the automobile “A” pillar camera system to show blind spots. I am truly amazed at what any age minds can think of!! Truly!
After so much research, this was the video I needed. Thank you!
Very good explanation
Missed opportunity. Instead of repeating the same stuff everyone always says about selecting a resistor for an LED, how about addressing the real-world problem of someone who needs to determine a resistor value for an LED without having the LED specs? In other words, tell us how to find the voltage drop as well as some clues about typical current values for various colors (a red LED with a clear lens is going to be more modern than a red LED with a red lens).
Emmett Turner that’s exactly what I need to know
Do IR LED have the same resistor requirements?
yes
Nice intro xD really nice one :)
What if I do not know the LED's forward voltage?
On internet it is available
You need to contact the supplier.
@@janszreniawski What if I just have a pile of random LEDs?
Usually between 2v~3.3v First hookup 1.5v AA battery, if it doesn't light up, try two 1.5v in series, some SMD LEDs have a forward voltage of 18v, yes, I was surprised too.
Just gradually increase the voltage, and you should expect a maximum 1w per single LED.
@@michaelkrug same problem
Thank you
That's a super easy way to look at it.
In case anyone wants to finish the numbers in the circuit your LED has an internal resistance of 100 ohms (r=2/.02).
Sorry, that's not correct. A diode does not obey Ohm's law where voltage is proportional to current. It has an inherent voltage drop of 2V caused by the semiconductor junction, and that voltage does not change greatly as current varies. At 1mA, the voltage is a little smaller, but still around 2V.
@Epi Endless don't be sorry. I'd love to learn more. Maybe it's like a light bulb. When they are turned off they have a way different resistance then when they get hot and turn on.
Instructions unclear. I died. But it's okay.
What will get hotter? A 100 ohm 2W resistor or a 120 ohm 2W resistor? I thought that the 100 ohm resistor should get hotter because it allows more current through but I have seen some articles that say the 120 ohm resistor would get hotter.
Hello and thanks for a great tutorial. I have a question please. I have some colour changing led,s that are only 2 pin, how would I calculate the correct resistor for this type of led ?
Thanks John 👍
how might this be achieved is the requirement is to dim an indicator LED on a device that was built / provided by somebody else, and the specs are not published?
You can replace the existing resistor with a larger one or simply add another resistor between the original resistor and the LED. I'd recommend starting with a 1k ohm and moving up from there
Can u use 1 resistor for 6 led lights because I got 6 resistors on all 6 my led lights are 3v with a 1k resistor im using a 7.4v batterie
As usual, glosses over the fact that the test current may actually be far too bright for your application. The classic resistor calculator worked well a few decades ago, but these days most of the 20mA LEDs I use are perfectly usable as indicators at 1mA, and dazzling at 20mA. In this case I'd stick in around 2-3kohm, and see what it looks like. And driving an LED at 1mA is far more reasonable when connecting it straight to a microcontroller.
Gud job!
Or on the bench use a variable resistor and increase to desired specs, measure resistance across variable resistor... Voilà... Peak performance
When was Ohm’s law no longer E=IR? You know, electromotive force, shown with E.
It's taught as E=IR and V=IR, so that's also correct!
Music is too loud.