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300,000 hours

My son and my nephew were recently handed novelty light pens to amuse them during a trip to a local pub. The pens were cool enough — standard promotional items that would make we want to buy a stapler, or a bed pan, or consulting, or something, from some company or another (boy, does that corporate strategy work or what?). The thing that raised my eyebrows was the claim written on the side that the lights would work for “300,000 hours.” 300,000 hours. That’s 34 and a quarter years. How do they know this?

5 thoughts on “300,000 hours”

  1. HareTrinity says:

    Well, I doubt they’ve tested. Probably an estimate based on the materials used and such.

    Still; let’s test that theory. Everyone got their year 2039 calendars ready?

  2. John Stracke says:

    I think materials science can answer this sort of thing. For example, if you know that conductor X will last four times as long with half as much voltage running through it, then you run it with 16 times the voltage you’re actually going to use, time how long it lasts, and multiply by 256.

    It’s pretty approximate, of course, but it’s not like you’re going to come back and complain that a freebie light only lasted 250,000 hours.

  3. mondopercipient says:

    John Stracke has the right concept, just wrong on a few details. For clarification, you don’t run “voltage” “through” something. “Current” is what runs through it, although there is of course a relationship.

    The relationship on life versus stress is not at all linear, but he has the right concept. It is “proven” statistically, based on confidence levels.

    Also, it doesn’t say that the 300,000 hours is continuous. It might last less if it ran continuously, which would tend to heat it up more. Most normal usage for something like this is occasional playing around, not continuous. Lowering the duty cycle increases the life even further.

  4. HareTrinity says:

    Current (I) through and voltage (V) across. Now let’s change the subject, I took my AS Electronics exam less than 12 hrs ago.

  5. mondopercipient says:

    Yes, but do you know how to measure the phase angle on this?

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