General > General Technical Chat
Video on planned obsolescence.
David Hess:
Operating life ratings for LED bulbs are disingenuous at best. The operating life of the LEDs is 10s of thousands of hours to half brightness but failure is complete when the ballast fails, which in my experience often happens before an incandescent bulb would fail.
So how much energy is saved by using a bulb which costs more in energy to manufacturer (as measured by cost which is a good proxy), when it does not last as long? None. NONE!
SilverSolder:
--- Quote from: wraper on April 04, 2021, 04:54:51 pm ---
--- Quote from: SilverSolder on April 04, 2021, 04:52:07 pm ---
--- Quote from: wraper on April 04, 2021, 03:36:36 pm ---
--- Quote from: madires on April 04, 2021, 03:30:22 pm ---Have you noticed that after the Phoebus cartel was shut down standard incandescent bulbs are still rated for only 1000h? Business as usual - it doesn't need a cartel.
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If you increase longevity, you will decrease lumens per consumed power, as I already mentioned. You will make more durable product but much worse overall.
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I don't understand the science behind that assertion - why would increased lifetime correlate with light output as a percentage of power consumed?
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--- Quote from: wraper on April 04, 2021, 03:51:58 am ---As you decrease filament temperature to increase it's lifetime, bulb becomes less efficient as it's spectrum shifts more towards IR, thus more energy is spent on heating ambient rather than usable light. And light no longer will be "white" and will have a strong yellow/red tint.
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OK but there is an unspoken assumption here - that lowering the filament temperature is the only way to improve bulb life. It is one way, and it is an easy way - but is it really the only way? For example, you could make the filament thicker, so it could withstand "boiling off its surface" for longer?
james_s:
--- Quote from: SilverSolder on April 04, 2021, 04:52:07 pm ---I don't understand the science behind that assertion - why would increased lifetime correlate with light output as a percentage of power consumed?
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Lifespan is determined largely by filament temperature. The hotter the filament, the more rapidly tungsten evaporates off it and the sooner it fails. The ratio of visible light to IR (heat) produced by the filament is also determined by temperature, the cooler the filament, the more of its radiation occurs as heat instead of visible light. There is a sweet spot right around 700-1000 hours where the lamp delivers reasonably good efficiency (in incandescent terms) while lasting an acceptable lifespan.
There are some extreme examples, like photoflood lamps that produce a very bright white light around 3200k and are quite efficient, but this is accomplished by overdriving the filament and the result is a rated life of 6 hours. Lifespan decreases exponentially as voltage is increased.
SilverSolder:
--- Quote from: David Hess on April 04, 2021, 05:04:01 pm ---Operating life ratings for LED bulbs are disingenuous at best. The operating life of the LEDs is 10s of thousands of hours to half brightness but failure is complete when the ballast fails, which in my experience often happens before an incandescent bulb would fail.
So how much energy is saved by using a bulb which costs more in energy to manufacturer (as measured by cost which is a good proxy), when it does not last as long? None. NONE!
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The switch to more advanced bulbs that have less "real world" life and at higher cost might be considered related to Planned Obsolescence: basically, needlessly increase the complexity of a product so you can charge more for it.
This works best of all if you can lobby to have laws passed that bans the simple and inexpensive solution that you don't think is making you enough money... especially if you think the public would not accept price rises on the existing, simpler product!
SilverSolder:
--- Quote from: james_s on April 04, 2021, 05:09:02 pm ---
--- Quote from: SilverSolder on April 04, 2021, 04:52:07 pm ---I don't understand the science behind that assertion - why would increased lifetime correlate with light output as a percentage of power consumed?
--- End quote ---
Lifespan is determined largely by filament temperature. The hotter the filament, the more rapidly tungsten evaporates off it and the sooner it fails. The ratio of visible light to IR (heat) produced by the filament is also determined by temperature, the cooler the filament, the more of its radiation occurs as heat instead of visible light. There is a sweet spot right around 700-1000 hours where the lamp delivers reasonably good efficiency (in incandescent terms) while lasting an acceptable lifespan.
There are some extreme examples, like photoflood lamps that produce a very bright white light around 3200k and are quite efficient, but this is accomplished by overdriving the filament and the result is a rated life of 6 hours. Lifespan decreases exponentially as voltage is increased.
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Understood. What happens if we make a thicker and longer filament to maintain the same resistance - will it burn longer before it breaks?
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