midnight

I have some LEDs I would like to hook up but am not sure which resistors I need. Below is the info. I will just be running them off a 12V source. The lady at Radio Shack didn't really know what she was talking about and sold me .5 watt, 220k Ohm resistors and the LED just barely lit up. Also what resistor would I need if I hooked up the circuit to one resistor and then out to say four LEDs.

Features
SUPER LUMINOSITY BLUE LED(InGaN / Sapphire)
STANDARD T1 3/4 LED
I.C COMPATIBLE
LOW POWER CONSUMPTION
WATER CLEAR PACKAGE
Specification

Emitting Color: Blue

Luminous Intensity: 3000mcd@20mA TYP

Viewing Angles: +/- 15 degree ( See it from the pictures! 30 degree's 3000mcd = 20 degree's 4500mcd!! )

DC Forward Current: 30mA Max

DC Forward Voltage: 2.8-3.8V

Wavelength: 460-465nm

Reverse Voltage: 5V

Soldering Temperature: 260°C for 5 seconds


Thanks for your help.

D Love

A 510 Ohm resistor should work well.

midnight

Is that .5 or .25 watt?

midnight

Is 510 for one LED or four?

D Love

Sorry, I was dodging the four LED question cuz I didn't feel like thinking. For the four LED's get something in the 91-100 Ohm range. That one should definitely be 1/2W The resistor for a single LED could be either 1/4W or 1/2W, it doesn't really matter. 1/2W would be a safer bet, but not necessary.