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Resistors getting... warm?

Tengis

Tengis

Supreme [H]ardness
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Jun 11, 2003
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Ya... Ive got some lights I have made for my case... the 330ohm 1/2 volt resistors seem to be getting a bit... warm. They are cutting back the 12v for the LEDs... is this normal? They arent going to implode are they?

Just wondering, I havent done much with LEDs/soldering so I want to make sure they are ok.

According to the few LED calculators I just messed with, I am using the correct resistors.

LED info:
supply voltage- 12v

resistor- 330ohm 1/2v

forwardV- 2.5v
forwardcurrent- 30mA
 
You're running about 29mA which will eventually fry your LEDs and is why the resistor is warm. 30mA is the maximum forward current but you don't want that... try using 15mA.
(12 - 2.5) / .015 = 633 ohms, so use 620 ohms
 
Power dissipated by a resistor is IV or I^2*R, which in your case is giving you 0.297 watts. Most of the little resistors are good for 1/4 watt, and you are going .047 watts above that, and thats why they are getting too warm.
 
Well... that sucks. Gotta make another trip to Frys... =/
 
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