What resistor and method should I use to string 12 led's in parallel from a 5v source?

I'm trying to figure out what resistor I should use to string 12 blue led's in a ring from a 5v source (like this except instead of 8, using 12: http://www.llamma.com/xbox/Mods/xbox_jewel_led_mod.htm). The specs that I have on the packaging of the led's are: MCD 4000~6000 and VF: 3.0v~3.2v. I read 2 different ways to do this, one (the easier way which I was leaning towards) was to use one resistor for the entire parallel series. The other way was to use an individual resistor for each led. What do you recommend. Can I get away with doing it the easy way, and if so, what resistor (ohms, wattage, and tolerance) should I use? Thank you.

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If the diodes are well matched, from the same batch and "identical", you MIGHT get away with a single resistor. I really don't like parallel driving LEDs but even some of the driver chip makers use it sometimes.

Steve
gmxx7 years ago
you're going to need 12  resistors. 100ohms each
karnuvap7 years ago
Unfortunately you cannot do it the easy way. When connected in parallel the LED behaves in a strange way (related to the fact that they are current driven devices and not voltage dependant ones) - One of the LEDs will suck all the current and the others won't hardly light.
lemonie7 years ago
If they're 20mA each, you'd need a 0.240mA supply roughly 2V over the resistor(s).
One would need to handle ~0.5 W, 12 ~0.04W (smaller)
For a 2V drop: 8Ohm for 1, 100ohm for 12

L
Re-design7 years ago
Use this site that was listed in the link that you gave to figure it out for yourself.