LED array layout... which voltage should I use?

Question

Instead of buying a $40 LED stick, I decided to try making my own.  My question is about the resistance.  I used this calculator:
http://led.linear1.org/led.wiz

The LEDs are 3.4-3.6v fwd voltage, 30mA fwd current - 75mA max.  I used 3.5v, 30mA

with a 12v source, it tells me to wire in groups of 3 (series) with a 56 ohm resistor.

If I input 14v, I get 4 in series with a 1 ohm resistor.

My question is, if I do the 14v wiring, will it hurt to run them on 12v (engine off)?

If I wire them according to the 12v layout, will it burn them up at 14-14.4v?

Or should I just go with an average of 13v? (3 in series with 100 ohm resistor)

Anonymous · Accepted Answer

Do them to 13.8-14.4 volts and you'll be fine. It's what I did - http://i81.photobucket.com/albums/j230/sparky3489/subs1.jpg

Anonymous · Answer

No, do not stray, the directions for setting up on a 12 volt system are what you need to follow. There are tollerances and there is room alloted for the increased voltage while the vehicle is running. You will not burn up your LED's by setting it up for a 12 volt system.

LED array layout... which voltage should I use?

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