LED resistor value question (red diffused vs bright blue)

[nothing]

(Sorry for my english, I am from Argentina).

Hi, this is the first time I write a new topic on Madbean. I don't usually write stuff, I'm more of a reader. I've built like 10 pedals, half are from Tonepad and half are from Madbean.

I have a simple question: every time I build a pedal I usually use a standard 5mm red diffused led and a 4.7k resistor, and it's great and clear, and it doesn't burn my eyes. Now I wanna use a bright blue 5mm led, but every time I use one of these it's always very bright because I don't know which resistor to use. I tried 4.7k, 10k resistor. The last time I used a blue led i used a 15k resistor and it was very annoying.

To sum up, my question is: Which resistor value is the best for a bright 5mm blue led that can look like the brightness of a red diffused 5mm led with a 4.7k? I want the blue led to shine as a red diffused led with a 4.7k resistor.

Anyway, Madbean rules!! It's an amazing site!! I've learned a lot. Thank you very much to Brian aka Madbean for creating such a great site and for posting so many projects! Greetings from Buenos Aires, Argentina!

Juan.

[rullywowr]

This site is awesome, and the people who frequent it are awesome too. I've learned a ton, and still am always learning.

As far as the resistor for the LED goes, blue will be brighter than diffused red so you need to use a higher value. Which value is up to you. I suggest experimenting with different values until you find one that works for you. You can do this easily with a breadboard, a 9v battery/power source, some resistors, and the led you want to use. Try different resistors until you find one that gives the brightness you are after.

If you have $10 or so, a "resistor decade box" is invaluable. You can find them on ebay. This allows you to try different resistors quickly just by moving a jumper/shunt. I use this all the time when tweaking.

A capacitor decade box is great too, especially when dialing in tone filters.

[Gledison]

Ola Argentino!
You could also use a breadboard and as he said, try different resistors untill you find the good for you! I would start in this case with 20 K!
Saludos!

[muddyfox]

Here's my half a nickel on the subject, fwiw... What I do is I have a small breadboard like so

I have two 100k pots (only because I had nothing smaller at the time of construction  ), a battery clip and two positions marked for leds. It serves two purposes:
- I can do what you describe, plug in one led, turn the pot to get the desired brightness and read the clr value off the pot and
- building mostly dual pedals, i can match two leds of different colors for intensity. I don't know where you do your led shopping but bulk leds from China can really differ in mcd output, even from the same bag. So I just plug in the two leds I'm actually going to use in a pedal and turn the pots until I like what I see

So I basically do clr on a single-case basis, never a fixed value like 1k or 4k7 or whatnot. Because sometimes I build for someone who's mostly gonna play in the sunlight and he specifically asks for a bat-signal, retina-scorching deal and sometimes I build for a bedroom noodler who wants to skip taping the led over because it turns his room into a shady Amsterdam district. 
Having said that, when I build for myself, those superbrights usually get anything from 15k-40k depending on the color, on rare occasion even more.

[davent]

I made a decade LED Tester from parts i had around, a rotary switch, a slider switch and a bunch of resistors etc. Plug in the LED and pick the best resistance. LED's vary widely, I've ended up using everything from as low as 500 ohms up to 50k.



dave

[Gledison]

I made a decade LED Tester from parts i had around, a rotary switch, a slider switch and a bunch of resistors etc. Plug in the LED and pick the best resistance. LED's vary widely, I've ended up using everything from as low as 500 ohms up to 50k.



dave

This is veryyyyyyyyyy  coooool!!!
its your idea or is a clone of a commercial available ones.?
simply great!

[davent]

Hello, An idea put forward by Mark Hammer over diystompboxes. The slider just adds a 10k resistor in series with the rotary switch.

dave