Resistor value needed to dim ultra bright blue LED?

[decsnspace]

Just finished building a bacon bits booster pedal. I usually use green LEDs with my pedal builds but I only had some Ultra bright blues on hand that I picked up on the cheap from Tayda. I was contemplating just ordering some new greens and replacing it, but I seem to recall reading somewhere that increasing the value of the LED resistor can dim the brightness. I'm currently using the standard 4.7k that madbeans suggests, anyone had any luck with dimming these ultra bright blue LEDs and if so what higher resistor value works well in accomplishing this?

Here's the specs of the ultra blues from Tayda:
Emitting color: Blue
Diameter: 3mm
Lens color: Water clear
Usage voltage(V): 3.2-3.4
Current(MA): 20
View angle: 20 - 25
Luminous intensity(MCD): 18,000

[Thomas_H]

Something between 10k and 33k should work. try 22k and hold it to a 9V battery to try it out.

[Mike B.]

What Thomas said. Or, if you want a specific brightness, just use lugs 1 & 2 of a 50K pot and 9v battery and adjust to taste. Then measure the resistance you ended up with and match it with a fixed resistor. Just be careful not to start with the pot set too low.

[decsnspace]

Something between 10k and 33k should work. try 22k and hold it to a 9V battery to try it out.

Thanks Thomas, I have resistor values on had in that range I will give them a try.

What Thomas said. Or, if you want a specific brightness, just use lugs 1 & 2 of a 50K pot and 9v battery and adjust to taste. Then measure the resistance you ended up with and match it with a fixed resistor. Just be careful not to start with the pot set too low.

Great additional info Mike! I think I may have a 50k pot around here somewhere, that should give me a good idea of what value I'll need so I don't go blind here!

Thanks to both you guys for the assistance. My soldering experience is top notch, but sadly my overall electronics knowledge is a bit lacking... Everyday I'm learning something new and today is no exception, thanks again!

[muddyfox]

I have this tiny contraption permanently plugged in my breadboard which contains two led positions and two B100k pots (what I had no use for at the time).
I use it not only to find the appropriate CLR value for any particular led (as the chinese bulk ones vary wildly in brightness), I also use it for brightness matching when the pedal calls for two (or more, or different color) leds. Comes in quite handy and doesn't take much space.

[decsnspace]

I have this tiny contraption permanently plugged in my breadboard which contains two led positions and two B100k pots (what I had no use for at the time).
I use it not only to find the appropriate CLR value for any particular led (as the chinese bulk ones vary wildly in brightness), I also use it for brightness matching when the pedal calls for two (or more, or different color) leds. Comes in quite handy and doesn't take much space.

That is another great idea. I didn't realize these LEDs varied so much.
I just tested one of the ultra blues using Mike's suggestion with a 50k pot, and the value I came up with that didn't burn the back of my retina was @ 33k. Your idea takes it a step further for matching LED intensities.
Awesome, thanks to all again! Great info!

[jkokura]

I use trim pots on a breadboard if I need to. Usually, I do it with a couple out of the bag when I first get them. I usually aim for about 4.7K and see what that looks like. If it's fine, I leave the bag alone as the 4.7K is my default. If it's too bright or dim, I find a better value and write that value on the bag.

Jacob

[davent]

Mark Hammers idea, rotary switch and a few resister. Twenty four steps 510Ω- 18k pretty much covers it although i have some greens i've put upwards of 50k on.

From stuff i had lying around.