LEDS need help on resistors.

[FuNwaGoN]

Well my LEDS finally arrived from Hong kong but the company was of no help getting me the right resistors to run these off of a 12v power supply. Looks like I am going to Radio Shack after work. But I need to know what resistors specs I need for these LEDS. Here are the specs:

SPECIFICATIONS:
SOURCE MATERIAL:InGaN
EMITTING COLOUR:White
LENS TYPE:WATER CLEAR
LUMINOUS INTENSITY-MCD:5000 TYPICAL/6000MAX
REVERSE VOLTAGE:5.0 V
DC FORWARD VOLTAGE:3.3V TYPICAL
DC FORWARD CURRENT:20~30mA
VIEWING ANGLE: 10
LEAD SOLDERING TEMP:260oC for 5 seconds

Let me know what I need to buy. thought i had this all worked out but I just want to make sure cause I know that some of you guys know alot more than me in this subject. thanks in advance for the help.

 

[Dexter]

here, i love using this calculator whenever i need to figure this out:

http://www.linear1.org/ckts/led.php

 

[1sty]

Not being 100% up on LEDs why not just use 4 in series?
All the resistor does is split the voltage over 2 paths to keep the LED from getting to much. A series circuit of LEDs, since you have multiple will also split up the voltage. The Impedance of the LEDs seems to be about 132 each so with 4 LEDs in series that will split the voltage to about 3 volts each and the overall resistance of 528 will limit the 12 volt supply to 25 milliamps.

I am not big into LEDs but this makes sense to me.

 

[FuNwaGoN]

thanks dexter, that should help out a lot. BTW congrats on getting your car back....enjoy

 

[FuNwaGoN]

hhmmmmm now that you mention it that does make sense MP3.... Will have to talk to the guy at radio shack about that. I am really trying to ensure longevity of the LEDS while trying to get the most light out of it. Because it would really suck to have to open up the headlights to change a led.

 

[1sty]

Did you plan to series all the LED in each headlight?
How are these ehings usualy wired. I would think the best way not to waste current over a resistor especialy ona 3:1 ratio is to wire them in series sets of 4 and then parallel all the sets together but I doubt that can be done neatly in a head lamp.

 

[ToLowMP5]

i don't know what resistor to use but i do know you need one it is used to limited the amount of current going to the LED So You Wont Fry Them

 

[Kimo]

wire in parallel using a 1k.ohm resistor in series on either the neg. leg or pos. leg.