LED burnout
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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Apr 2, 2010. 2:56 PMSuper_Dave
says:
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
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....
. 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.
Oct 30, 2007. 5:44 PMhexedene (author)
says:
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?
. 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.
Oct 28, 2007. 2:56 PMgmoon
says:
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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