How to select resistor values for LEDs | Basic Electronics

[@DogsOnAcid]

How does this channel have so little views/subscribers? This should be. 100k+ sub channel, the hell is wrong with this algorithm? You've got yourself a subscriber.

[@CircuitBread]

Thanks! We're growing slowly but surely - we're not going anywhere, so hopefully all of our content continues to be helpful. 🤞

[@kabandajamir9844]

The world's best teacher

[@tonyfunguy]

Subscribed!! Need to learn more of these for upcoming projects...

[@adama4356]

thanks for the calculator, it's a good video keep up guys.

[@CircuitBread]

Thanks for the feedback! Let us know if there are any other calculators you'd like that we can put together.

[@braedenplant4400]

Thanks for the calculator really helpful

[@CircuitBread]

Awesome, great to hear!

[@braedenplant4400]

@Makaia Grant-Fargie hi

[@raids1474]

@@braedenplant4400 Nice

[@PrayagSanjay]

Thanks , that is exactly I was looking for. Thanks.

[@umarshaheen6382]

Thanks so mch, helpfull topic, keep up....

[@tattooedstranger]

Ace thank you sir

[@lipinghe40]

Thank you and GOD bless.

[@Yash-Gaikwad]

1- Is maximum current and forward current the dame thing? 2- is it ok that supply voltage is higher than desire or needed 3 volt for led?

[@CircuitBread]

Hey Yash! For #1, it is different. Forward current is generally considered the target current for the advertised brightness whereas maximum current is the point after which the LED will most likely be damaged. #2 - yep, that's totally fine. If the supply voltage is higher, then you just need to modify the value of your resistor to get the correct current through the LED. We actually made a tool so this can be super simple for you: www.circuitbread.com/tools/led-resistor-calculator

[@capistor1]

Thank you

[@Chillandrelax2475]

Hi, I want test PD with oscilloscope, how to select resistor values for photodiode (S1223-01) ?

[@adonisalberto1462]

How about I have 40pcs 5730LEDs 3.4v .15Amps , I connect in parallel with the power supply of 12v, What resistor that I need?

[@adamnasher944]

Good evening sir. My name is adam and i have a question for you if i may. Today i was up grade a security system and some zones had resistor in the felid and the reading is 2.2 k and the new system im installing use 1.9 k . Is it a problem . I tied the zones with 2.2 k and it works. Please advice thank you very much

[@CircuitBread]

Hi Adam! While I can't give you a definitive answer on whether or not this resistor value will put your system outside of the required specifications, my guess is that it is not a problem. It's around a 15% difference and low quality resistors can have tolerances of +/- 15% or more. So, likely, you're fine. But I recommend reaching out to the manufacturer for an official answer if you're concerned!

[@ProfessorStories]

Sir,why didn't you use the kirchoff's law?

[@CircuitBread]

It didn't seem complicated enough to warrant it, that's all. Both of Kirchoff's laws are extremely useful in nearly every circuit.

[@kenzo4Ever]

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 😀

[@CircuitBread]

In any diode (including an LED) there's a junction where you have two semiconductors touching each other. For the electrons to cross in one direction at that junction where they meet, they need a certain amount of energy. This is the forward voltage or voltage drop that you're hearing about. To learn more about it in much, much more detail, we did a trilogy talking about how diodes work at the semiconductor level, starting with this one: kzbin.info/www/bejne/mKWyeneHmrKlg8k

[@kenzo4Ever]

@@CircuitBread Thanks my Dear 😀

[@anichhatre]

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

[@CircuitBread]

What is the forward voltage of your individual LEDs or portions of the LED string? And each LED is 3W, with a total of 36 LEDs? So 108 watts total? That seems very high and would require more power than your power supply is able to provide. My guess is that the entire string is actually 3W, is that correct?

[@RiazAhmad-yg8cy]

Dear Which resistor is better for 1738 sensor using 5v+ current

[@CircuitBread]

Working with suppliers and distributors on the client side, I've found that nearly everyone puts a lot of effort into giving their users as much information as possible with example circuits, recommended values, common challenges, etc. While I'm pretty sure 1K is the ideal resistor for the 1738 sensor, my recommendation would be to look at the specific data sheet for your part and see if they have any ideas of what would work best. And this advice is not just for the 1738 but any IC you want to work with. The people who understand their product best typically have already created simple circuits with values that will make your life a lot easier. And if they haven't, usually there's a competitor product that has.

[@nickwright9429]

Help!! I have a lighting issue. Thought I had a solution but I fried the LED in 30 minutes.

[@CircuitBread]

Hey Nick - just barely saw your comment here. Glad you got it fixed and don't hesitate to reach out again if there are any further issues!

[@marcelloink8454]

can you power 20 LED diodes using one resistor lets say 12v input into a resistor to power 20 3v led diodes? or do i need 19 resistors one in between each LED? they are connected in a row from one led to the other.

[@CircuitBread]

If they're in series, you can use a single resistor. Though your math is off, as 20 3V LEDs would require a minimum of a 60V power source. If you put them in parallel, you can technically do that but there are some challenges (discussed here - the principle stands even though its talking about RGB LEDs: www.circuitbread.com/tutorials/why-cant-i-share-a-resistor-on-the-common-anode-or-cathode-of-my-rgb-led). And when you put a bunch of LEDs in series like that, it gets a bit tricky if there are any variations in their forward voltages. This is why you usually use a constant current power supply in those cases.

[@marcelloink8454]

@@CircuitBread ok its a car led tail light that i want to make. 12V power in i have 20 leds with 3 terminlas one terminal is red led 2v and the second terminal is white led 3v, can the power go into the first LED then from that first LED to the 2nd and 2nd to third ext..... i can run one resistor for the 2v side and one for the 3v side right at the power source? correct? but i have to do the math?

[@CircuitBread]

Sorry for the delay but unfortunately, it doesn't sound like this solution would work. If you have the LEDs in series, their forward voltage adds. So, in the ideal scenario, with a 12V battery, you could only put 6 2V red LEDs in series before they would no longer have enough forward voltage to turn on. However, it's possible that you could put 5 2V LEDs in series but then in parallel with another 5 2V LEDs, with a resistor in series with each set to control the current. And I'd recommend five instead of six LEDs to give yourself a bit more head room. And yes, there is a bit of math involved but nothing too intense. We also have a calculator on CircuitBread.com to help. KZbin doesn't notify us of follow up comments (only the initial comments) so if you have more questions and I don't respond, I'd recommend jumping onto our CircuitBread Discord channel as that's more actively monitored.

[@marcelloink8454]

@@CircuitBread Thank you!!

[@henrygutierrez7289]

For these little LEDs the resistors are fine, but I was wondering if that applies to a 5w led also, I have some 696-LXL99UWC-TR5 High Power LEDs and I would really like to use them with a USB power bank (5v, 2.1A output). I have seen many time people writing about using only "drivers" for these high power LEDs. What do you think?

[@CircuitBread]

Yeah, you'll want specific drivers for those high power LEDs. They're more efficient and give you better control. Those drivers are ubiquitous enough that, while not something you'll have lying around like a pile of resistors, you can get what you need pretty easily and inexpensively. That being said - with your 5V output and the LED forward voltage of 4.5V, you might get away with a direct drive from your USB power bank. I would be careful, though, as you could easily destroy the LED while messing with it.

[@henrygutierrez7289]

@@CircuitBread Thanks! When you said: "your 5V output and the LED forward voltage of 4.5V, you might get away with a direct drive from your USB power bank. I would be careful, though, as you could easily destroy the LED while messing with it" So, I should assume that try to connect it directly and see what happens? Or maybe is a good idea to add a resistor? What kind? Thanks again for any help

[@CircuitBread]

Hi Henry! As LEDs are typically inexpensive and if you have one, you usually have a lot of them, I think it wouldn't be an issue to direct drive an LED, but if you only have only one, then you may not want to risk it. There are LED resistor calculators out there (we even have one - www.circuitbread.com/tools/led-resistor-calculator) that should give you a good idea of the type of resistor you should use, given your LED and your power source.

[@J2A61]

This is like a cam install 😂

[@CircuitBread]

I've done a cam install with my brother in law once - I had fun but I think I'll stick with electrical engineering! Engine repair is too hard for me 😬

[@IronBalls007]

Very interesting, also, your teeth are perfect :D Well done

[@CircuitBread]

Haha, thanks! Well, thanks to my parents paying for braces when I was a kid...