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Old 08-12-2012, 05:06 PM   #1
Scooby Newbie
Member#: 263963
Join Date: Nov 2010
Chapter/Region: RMIC
Location: Salt Lake City, UT
2002 Impreza RS 2.5L

Default LED wiring guru's - Please double check me!

I am in the middle of an interior illumination color change for my 02 impreza and I am working on fully populating and illuminating my driver's side Power window/Lock switch. I have been going off of Soccermom's DIY guide, here.

I am pretty new to LEDs, but I have done a lot of homework. Still, I am a little unsure of myself... So I was hoping someone could double check my numbers and make sure I have done everything right.

From what I figure this will work.
The source voltage is 14.4v, when the car is on.
The forward voltage of the LEDs is 2.1v each
They are 20 mA each
So I calculated that I would need 615 Ohm resistor - R = (V1 - V2) / I | so (14.4 - 2.1) / .02 = 615
Since there is no such thing as a 615 Ohm, I will wire three 220 Ohm, 1/4 watt resistors in a series to equal 660 ohms.

TL;DR - Basic set up look good?
I take 5 of these red LEDs wired in a series with three of these 220ohm 1/4 watt resistors in front. So it would go: 14.4v power from car > 3 resistors (in series) > 5 LEDs (in series) > negative cable in car.

Is that right?
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Old 08-12-2012, 11:16 PM   #2
Scooby Specialist
Member#: 266122
Join Date: Dec 2010
Chapter/Region: Tri-State
Location: Patchogue, NY
2007 WRX Limited


No. 20 mA is the maximum current. You want to limit the current to between 10 and 15 mA. Pick a resistor value that will limit the current in that range ( 1 kohm). 1/4 watt is good.
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