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Leds for meter lights burning out?

Cityboy

Active Member
Dec 25, 2008
123
1
26
I had purchased some LED for replacements for meter lights. I purchased ready to go 12v application meter light replacements and they have been burning out on me. So I took them apart and found they have been putting a 180 series resistor inline to bring it down so it will work. Well doing the math of V = IxR and that most 5mm led run around 20ma + or - .5ma or so. So using the resistor that is being used V = 20max180ohms that would give you a rated voltage of 3.6v. Well they have been advertised as meter replacement for cbs and doing the math it seems the resistor should be more like 510ohms to 680ohms to use in a 12v application and this differs depending on the color of the LED and the current draw. My question is am I correct that this person is selling me LEDs for the wrong application or is he correct. If I don't get satisfaction from him I will reveal whom had sold them to me and I am sure that will cost him some business. If I am wrong I will drop it and appologize. Thanks for any help with this.
 

Your definitely in the ballpark, perhaps his chosen value is relative to job security? Obviously for a more precise choice you can use the exact LED specs and plug them in to a calc.

For
Red & Yellow (2.2v 20 ma or so) use a 560ohm 1/4 watt resistor and for White, Green
& Blue (3.5v 20 ma or so) use a 470ohm 1/4 watt resistor. If you want to find a more
suitable resistor I suggest using a LED Current Limiting Resistor Calculator
and for what its worth I buy all my LEDs from the following link, fair quality, at a decent price, most are in stock, and he ships fairly fast.

Buy LEDs OnLine Home Page
 
Jives with my LED work. Try 470~530 ohm resistor for the 3.2V LEDs.

I usually buy my LEDs on ebay. Variety of good sellers. Anything under the sun.
 
I am wondering why some of the LED have actually lasted; I have a few friends that I have installed in mainly Ranger products and they have yet to burn out. Thanks for the replies. I didn't think I was far off.
 
Before I understood you needed a current limiting resistor with an LED heh....

I bought several for making a little gooseneck light to illuminate a cycle computer I was using as a speedo on my motorcycle and could never figure out why they blew out so quickly.

I would say you are correct, try a bit higher value resistor for those LEDs or change LEDs for a different value.
 

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