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What Happens to an LED when it is overvolted? Answered




Best Answer 8 years ago

depends on how much severly it will burn the plastic leaving a brown spot. it might also crack the led. funny you should ask i just put 12v in a red 3v led all it did was turn on for a second then go out then you could see the burn filament and it would not turn on. and flickering is a sign of bad connection.

Would there be a possiblity that the bad connection is within the LED itself, because i tryed out some new LEDs with the same spec's and they worked fine... I also found that when the same LED was connected to an almost flat 3v Lithium battery, it was dim by didn't flicker.

 the LED will also heat up a lot and possibly start smoking-- and do all the rest of the stuff on other posts 

I have abused some led's on purpose sometimes... and they seem to get dimmer with slight abuse... and finally have no light output with major abuse.  Try to limit currrent to about 10 milliamps  (.010 amperes) to most led's as a general rule.  To limit current, just place a resistor in series with the LED.  You calculate the proper resistor using OHMS law... Current equals battery volts divided by resistance... or  resistance in OHMS equals battery volts divided by amperes (0.010A).    using a 12 volt battery... divide by 0.10 amps equals 1200 ohms... generally, just add another 100 ohms for each VOLT higher than 12V. 

I've always used this basic  formula

R = (Vin-Vf)/If, where Vin is the supply voltage, Vf is the forward voltage of the LED, and If is the predicted (or desired forward current)

it's not exact, but it's close.

To get a tighter control, especially for LEDs that I have no data for, I use a 1-10K trimmer pot on a breadboard and set the forward current for the brightness I want to achieve, then measure and replace the trimmer with a fixed resistor as close to the set value as I can get.

Flickering is usually an indication of bad connections.

the filiment changes color, then it burns out, and possibly explodes