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LED burnout Answered

I've been having trouble with LEDs. I'm running 18 blue ultrabright in parallel. The specs for volts and amperage are as follows: 3.6v typ 4.5v max 20ma typ 30ma max Each LED has a 220 ohm resistor which was calculated for a 9v source with each LED at 4v, 25ma. This seems well within their range. But, in about a year and a half's time, I've had about 25% burnout. Most of the others are showing signs of intensity and spectrum degradation. Any thoughts as to the cause of this?

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Super_Dave (author)2010-04-02

If it was me, I'd run 9 banks of 2 LEDs and a 90 ohm resistor for each bank.  (9v-7.2v)/.02 = 90 ohms

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Goodhart (author)2007-10-31

Is your power source a batter, or is it a power supply? There is a possibility that you are getting rippleif from a PS, and that reverse voltage is lessening the life of your LEDs. Just a shot in the dark....

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NachoMahma (author)2007-10-28

. Two guesses: a bad batch of LEDS or there's more current flowing than you think. Takes some measurements and make sure the volts and current are in spec. . Oh yeah! Your power source may be putting out a spike when you turn it on or off.

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hexedene (author)NachoMahma2007-10-30

I have max readings of 9.58v. That keeps me in a safe zone. The current, though, don't they just draw whatever they need? Maybe it was just a bad batch. Have you any preferred sources you utilize?

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NachoMahma (author)hexedene2007-10-30

. If the voltage is right, then, as you say, the current should be right. . When I need an LED, I rob it from something in the junk box. There have been several posts with recommendations for suppliers - search for LED over on the left side of the page. For the first search, I'd check all the boxes. If you get too many hits, start unchecking items.

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gmoon (author)2007-10-28

If the specs are detailed, I'd look closely. Sometimes the max is for intermittent current and voltage, for instance 100 milliseconds (pulsed.)

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