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Knagi


member
Location: Brunswick, Ohio

Total posts: 397
Posted:I went out today set on making some led poi and well I've collected everything on the list except for one small problem I wasn't able to find it exactly right so here's my question.I have some 10-ohm 1/2 watt and some 22-ohm 1/2 watt resistors and 3 volts of power to light up some 2.1 volt 30Ma yellow leds and 1.7 volt 20ma red leds anyone know what combo of resistors to use for each?

We are all in the cosmic movie. That means the day you die you watch your whole life repeating for eternity. So you'd better have some good things happen in there and have a fitting climax. --Jim MorrisonIt's going to come from a direction you didn't predict at a moment of chaos which you didn't see coming. -- NYC

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Bassman


member
Location: Austin, TX, USA

Total posts: 95
Posted:You want about 30 ohms for the yellow LEDs and 65 ohms for the red LEDs. For the red LEDs, if you combine 3 22 ohm resistors in series, that will give you 66 ohms (close enough). A 22 ohm resistor in series with a 10 ohm resistor, or three 10 ohms in series will work for the yellow LED.

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tr1bl


stranger


Total posts: 3
Posted:so how do you get those numbers? i have some led bulbs (green 20mA 1.9v, pink 30mA 3.5v, UV 20mA 3.3v) and some 10hm/33ohm 1/2 watt resistors but dont really understand the math of it all. i would like to know how all this works because im planning on getting more bits and pieces ro put together so i would really appreciate some help im kinda lost. THANKS!
tr1bl


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tr1bl


stranger


Total posts: 3
Posted:i was figuring id use AAAs?? im not sure ive never really done any of this but i catch on quick i just wish there was more out there on making your own LED poi because i know poi is getting real popular around this area (dc/bmore/va/pa)

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aston
SILVER Member since Dec 2007

aston

Unofficial Chairperson of Squirrel Defense League
Location: South Africa

Total posts: 4061
Posted:The easiest way would be ask someone who has done electronics at almost any level.

'We're all mad here. I'm mad, you're mad." [said the Cat.]
"How do you know I'm mad?" said Alice.
"You must be," said the Cat, "Or you wouldn't have come here."
- Lewis Carroll, Alice's Adventures In Wonderland

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tr1bl


stranger


Total posts: 3
Posted:yea im learning ive been doing more research im thinking about making it usb rechargable but first i need a working prototype. i wish they had rechargable button batteries!

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happyinmotion
SILVER Member since May 2007

newbie
Location: , New Zealand

Total posts: 42
Posted:You may well want to have a play with the LED resistance calculator. Just chuck your numbers in that and it'll tell you what resistor to use.

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Geeza
GOLD Member since May 2006

Geeza

addict
Location: Leeds, United Kingdom

Total posts: 694
Posted:how does volts and ohms equate to lumens?

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happyinmotion
SILVER Member since May 2007

newbie
Location: , New Zealand

Total posts: 42
Posted:It's a bit complicated to find out the lumen output from an LED. You need to know the brightness in millicandela (mcd) and the beam angle, then you can use this calculator:
http://led.linear1.org/lumen.wiz
br>
But simply, any LED running off 20 milliAmps is going to be ok, and more will be brighter, but you really just have to try it. (Any LED running off more than that will be bright, but will require lots of special circuitry to run it.) The Mitochondrion glowstaff runs off forty 20 mA LEDs, and that's plenty bright for most uses.


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