Resistors

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=81908
Printed Date: July 04, 2025 at 7:15 AM

Topic: Resistors

Posted By: Focusedonsound
Subject: Resistors
Date Posted: August 22, 2006 at 9:46 AM

Im going to be wiring up some LED's and Blue, Green, RED, White & UV. I have tons and tons of 1/4w resistors is it necessary to use 1/5w or can I use the 1/4 & double up or something?

Thanks for the help
Nick

Replies:

Posted By: djfearny2
Date Posted: August 22, 2006 at 10:58 AM

use 1kohm 1/4 and youll be fine.

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Jon
Installer/Help Technician
---coral springs florida---
mecp certification is not always needed. I have it and it has not helped me out at all. my experience out shines it.

Posted By: Cameronjc
Date Posted: August 23, 2006 at 3:26 PM

1k ohms is over kill. It will work, but you'll be getting much less the output it's capable of.

Anyway you want to use 1/4W resistors minium with the correct ohms for the LED and input voltage you plan to use.

Posted By: KPierson
Date Posted: August 24, 2006 at 1:28 PM

To properly size your resistor you need to multiply resistance by voltage to figure out the power.

For a 5vdc LED with a 470ohm resistor you would be looking at 10.6mA, which equals 0.053 watts.

A 1/8th watt resistor is good for 0.125 watts, so you should be OK with a much smaller resistor.

For a 14.4vdc LED with a 470ohm resistor you would be looking at 30.6mA, which equals 0.44 watts, so a 1/2watt resistor would be needed.

Finally,

For a 14.4vdc LED with a 1000ohm resistor you would be looking at 14.4mA (quite a bit of current for most LEDs), which equals 0.21watts, making the 1/4 watt resistor perfect!

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Kevin Pierson