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Automotive LEDs...

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bb040:
sounds like you had a bad led

Sinner:

--- Quote from: bb040 on February 06, 2006, 12:41:50 pm ---sounds like you had a bad led

--- End quote ---
Maybe, but I searched around this site, and seems like some people have had the same problem...most of the suggestions I've found say to put a resistor in there...could be a bad batch, or could be that the LEDs I bought were not rated for the power I was putting into them...
I'll give them a try with 100ohm and see if they last...I could kick myself for not checking the package for specs...I fugured it would just be a given that they would be there...

Toonces:
The thing with the LED that burnt out is that the 100Ohm resistor may not be the correct one to use. Current is a draw, not a push. The LED will draw whatever current it needs. The Power Supply doesn't push current through. To properly size the resistor you need to know what current the LED is rated for and the voltage it needs. Depending on the color and intensity it was designed to run at, the LED could be rated for ~2.5-3.5V and ~20-30ma. So a 100Ohm resistor may not be the right choice for that particular LED. With a 5V supply, it's probably a good ballpark but is the LED rated for 20 or 30ma? if the resistor is too low you could be giving it 3.5V and 30ma when it's really rated for 2.5V@20ma and you'd be overdriving it. LEDs typically have different ratings per color, even at the same MCD rating. You best bet is to use an LED calulator to make sure you are using the right resistor. Google LED Calculator and choose your favorite. I usually use the one at http://led.linear1.org/1led.wiz as they have calculators for series/parallel and multiples and even a wizard type calculator.

Basically, you may be overdriving the LED because the resistor is not the right one for your LED.

Toonces

Sinner:

--- Quote from: Toonces on February 06, 2006, 01:12:32 pm ---The thing with the LED that burnt out is that the 100Ohm resistor may not be the correct one to use. Current is a draw, not a push. The LED will draw whatever current it needs. The Power Supply doesn't push current through. To properly size the resistor you need to know what current the LED is rated for and the voltage it needs. Depending on the color and intensity it was designed to run at, the LED could be rated for ~2.5-3.5V and ~20-30ma. So a 100Ohm resistor may not be the right choice for that particular LED. With a 5V supply, it's probably a good ballpark but is the LED rated for 20 or 30ma? if the resistor is too low you could be giving it 3.5V and 30ma when it's really rated for 2.5V@20ma and you'd be overdriving it. LEDs typically have different ratings per color, even at the same MCD rating. You best bet is to use an LED calulator to make sure you are using the right resistor. Google LED Calculator and choose your favorite. I usually use the one at http://led.linear1.org/1led.wiz as they have calculators for series/parallel and multiples and even a wizard type calculator.

Basically, you may be overdriving the LED because the resistor is not the right one for your LED.

Toonces

--- End quote ---
Unfortunately, all I know is that they are superbright, automotive (12V) clear LED lamps (not individual LEDs)...
The 100 ohm resitir I used before, was on a single superbright LED...
Without all the information, I guess it's just a matter of trial and error...
Thanks for the info...

whammoed:
A single led is likely not meant for 5 volts, so you need a resistor for it.  Those 12volt automotive leds already have a resistor built into them, so you just plug them in to any 12 volt source.

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