3 ms·

The descriptions on Transcend's website make me feel uneasy. I presume they have a solid product, but it feels like it's being oversold. Each of our remote ph

by nkurz 11y ago

The descriptions on Transcend's website make me feel uneasy. I presume they have a solid product, but it feels like it's being oversold. Each of our remote phosphor fixtures are rated to last for 96,000 hours to 90% output. That's over 10 years of 24/7 use. How has this been tested? And if it is true, why is there a 5 year warranty rather than a 10 year? And what level of decline in output is covered by the 5 year warranty? Efficiency: >2.0 μmoles per watt Presuming you mean "per joule" rather than "per watt", this is very close to the claimed efficiency of the underlying Royal Blue LED, and (I think) much higher than any white LED. While I can believe there is some benefit from the lower temperature of the remote phosphor, this would be a remarkably high number for a full spectrum light. How has this been measured?

Havoc 11y ago
>remarkably high number for a full spectrum light. I don't think growing lights are full spec
- nkurz 11y ago
  Some are, some aren't. I was going by Transcend's web site which says that they are full spectrum: "The fixture emits full-spectrum PAR light for 96,000 hours (10 years of 24/7 use)." In theory, you can get a significant gain in efficiency by choosing specific wavelengths. In practice, it's difficult figure out exactly what these wavelengths should be, and to match them to existing high efficiency emitters.
TranscendL 11y ago
Yes, it has been tested. The industry standar LM-80 lifetime testing of the LED shows an L70 lifetime of ~300,000 hours. We are operating the LEDs at a lower temperature meaning they should theoretically last even longer. This is how we specify the 96,000 hour operating time to 90% The Royal Blue LEDs we use have a ~55% EQE (external quantum efficiency). This gives a μmoles per joule a fair amount above 2.0. We lose a few photons during the conversion process and that drops us down to about 2.0. We have a ~30% efficiency improvement over standard white LEDs because the phosphor is remote. The gain is 100% due to to the recycling cavity and omnidirectional nature of phosphors.
- ewang1 11y ago
  The LM80 will show a much higher number, but in reality, it's usually the drivers that fail much sooner.
- nkurz 11y ago
  I'm still surprised at the level of efficiency, but glad to hear that you can back it up. I wasn't doubting that an underdriven LED would last that long, rather I was surprised that the remote phosphors would last that long without decrease in output. But reading more elsewhere, I now see that the lifespan of the remote phosphors can be excellent: http://www.digikey.com/en/articles/techzone/2014/apr/developing-a-standard-test-for-remote-phosphor-lifetime-and-color-maintenance http://www.digikey.com/en/articles/techzone/2014/apr/develop... For others who are interested, here's another interesting link on the remote phosphor approach: http://www.ledsmagazine.com/articles/print/volume-9/issue-7/features/fair-comparison-of-white-leds-and-remote-phosphor-guides-design-choice-magazine.html http://www.ledsmagazine.com/articles/print/volume-9/issue-7/... And a nice overview of the efficiencies of white LED's, and where the losses usually are: http://www.sandia.gov/~jytsao/SSL_Trajectories_Proc_IEEE.pdf http://www.sandia.gov/~jytsao/SSL_Trajectories_Proc_IEEE.pdf The exact figure in the last are already somewhat out of date, but if you plug in the specs for the newer LED's, presumably the underlying physics hasn't changed.

by nkurz 11y ago

Havoc 11y ago

>remarkably high number for a full spectrum light. I don't think growing lights are full spec

nkurz 11y ago
Some are, some aren't. I was going by Transcend's web site which says that they are full spectrum: "The fixture emits full-spectrum PAR light for 96,000 hours (10 years of 24/7 use)." In theory, you can get a significant gain in efficiency by choosing specific wavelengths. In practice, it's difficult figure out exactly what these wavelengths should be, and to match them to existing high efficiency emitters.

TranscendL 11y ago

Yes, it has been tested. The industry standar LM-80 lifetime testing of the LED shows an L70 lifetime of ~300,000 hours. We are operating the LEDs at a lower temperature meaning they should theoretically last even longer. This is how we specify the 96,000 hour operating time to 90% The Royal Blue LEDs we use have a ~55% EQE (external quantum efficiency). This gives a μmoles per joule a fair amount above 2.0. We lose a few photons during the conversion process and that drops us down to about 2.0. We have a ~30% efficiency improvement over standard white LEDs because the phosphor is remote. The gain is 100% due to to the recycling cavity and omnidirectional nature of phosphors.

ewang1 11y ago
The LM80 will show a much higher number, but in reality, it's usually the drivers that fail much sooner.
nkurz 11y ago
I'm still surprised at the level of efficiency, but glad to hear that you can back it up. I wasn't doubting that an underdriven LED would last that long, rather I was surprised that the remote phosphors would last that long without decrease in output. But reading more elsewhere, I now see that the lifespan of the remote phosphors can be excellent: http://www.digikey.com/en/articles/techzone/2014/apr/developing-a-standard-test-for-remote-phosphor-lifetime-and-color-maintenance http://www.digikey.com/en/articles/techzone/2014/apr/develop... For others who are interested, here's another interesting link on the remote phosphor approach: http://www.ledsmagazine.com/articles/print/volume-9/issue-7/features/fair-comparison-of-white-leds-and-remote-phosphor-guides-design-choice-magazine.html http://www.ledsmagazine.com/articles/print/volume-9/issue-7/... And a nice overview of the efficiencies of white LED's, and where the losses usually are: http://www.sandia.gov/~jytsao/SSL_Trajectories_Proc_IEEE.pdf http://www.sandia.gov/~jytsao/SSL_Trajectories_Proc_IEEE.pdf The exact figure in the last are already somewhat out of date, but if you plug in the specs for the newer LED's, presumably the underlying physics hasn't changed.