Knagimember
397 posts
Location: Brunswick, Ohio


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


Bassmanmember
95 posts
Location: Austin, TX, USA


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.

tr1blstranger
3 posts


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

tr1blstranger
3 posts


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)

astonSILVER Member
Unofficial Chairperson of Squirrel Defense League
4,061 posts
Location: South Africa


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


tr1blstranger
3 posts


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!

happyinmotionSILVER Member
newbie
42 posts
Location: New Zealand


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.

GeezaGOLD Member
addict
694 posts
Location: Leeds, United Kingdom


Posted:
how does volts and ohms equate to lumens?

happyinmotionSILVER Member
newbie
42 posts
Location: New Zealand


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:
https://led.linear1.org/lumen.wiz

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.