l.e.d

Printed From: the12volt.com
Forum Name: Lights, Neon, LEDs, HIDs
Forum Discription: Under Car Lighting, Strobe Lights, Fog Lights, Headlights, HIDs, DRL, Tail Lights, Brake Lights, Dashboard Lights, WigWag, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=29710
Printed Date: July 01, 2025 at 7:26 AM

Topic: l.e.d

Posted By: Legrones
Subject: l.e.d
Date Posted: April 05, 2004 at 10:27 AM

what size resistor do u use on a led with a 12 volt car source ?

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Dale / Cory

Replies:

Posted By: markcars
Date Posted: April 05, 2004 at 2:18 PM

Here's one of the basic electricity formulae that helps me always.

V = I X R
or
Voltage = Amps times Ohms(Resistance)
9v = LED's amperage * R

Get the amperage of your LED from its specs and put the values in the formula above.
Also I assumed your LED runs on 3v, so I used 12-3 to get 9v.

Do the math for R, you'll get the value or your resistor.
Just make sure to convert the Amperage of the LED into Amps from milliamps, because they usually are described in milliamps.

Hope this helps.
Mark

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