Lifespan of throttled LEDs

Discussion in 'General Electronics Chat' started by cracker, Mar 21, 2008.

  1. cracker

    Thread Starter Member

    Jan 5, 2008
    13
    0
    I know this probably won't make a huge difference in the lifespan of the LEDs since they are installed in a PSX and won't be on 24/7 but it just got me wondering... I am driving the LEDs with a 12F629 and throttling them quickly to dim them down some (because they were pretty bright after the initial resistors still). I am wondering what kind of impact this would have on the LEDs' lifespans?
     
  2. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    As long as current through the individual LED's is kept at or below the stated maximum, then the lifespan should remain in the area of 100,000 hours. Dimming them probably won't make much difference.
     
  3. Søren

    Senior Member

    Sep 2, 2006
    472
    28
    Hi,


    LED's driven at lower than nominal current will have increased life. The 100khour lifespan given for many LED's are just a choice of lifetime vs. current.
    The exact same LED could be sold as a higher intensity, higher current one but with a shorter life time.

    Doubling the current will more than halve their life since it's not a linear relationship.
    The lifetime given is the time until the light intensity is down to 50% of the original, not to zero light.

    If they need to be pulsed to get the light down, when the resistor is allready chosen for under_the_nominal current, they will have increased life.

    The only kind of pulsing that may shorten their light is when they are pulsed with high current (compared to nominal), perhaps with a low duty cycle to give an average current at or lower than nominal (to eg. get more apparent range - won't work with white LED's btw.).
     
  4. mrmeval

    Distinguished Member

    Jun 30, 2006
    833
    2
    What LEDs? If they're that bright I want some. ;) I did find some fantastic water clear ones but they are pricey.
     
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