Handlobraesing
Banned
- Joined
- Feb 14, 2006
- Messages
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This forums has at least a few experts on them, so I've got questions.
The dealer's claim is that its got 200 lumens leaving the lens,
"What's more, the Fenix P3D throws an awesome 200 lumens beam"*3 but I find that a little hard to believe from reading the datasheet for LED. Is this a measured value?
On datasheet, it reads "Cree maintains a tolerance of +/- 7% on flux" and power measurements and all the output is at 25C TJ.*2
The binning sheet says 107-117 lumen for Q5 *1. I'm assuming I can apply the 7% tolerance and 25C TJ given in datasheet.
If I assume 80% Light output ratio for the optics(this is a PURE assumption, could be way too high), the LED has to put out 250 lumens. If I assume the LED has an output at the mean of the range min and max, which is [email protected]. Since realistically, junction temperature is going to be 50-75C, to get 250 lumens, the current would have to be what it takes to get 278 lumen at TJ of 25C.
The output derating factor for temperature I used is 0.9, based on the datasheet graph.
Cree's graph rates the output at 0.35A as 100%, so to get 248% output relative to this point, it would have to be driven beyond 1A, which is the highest point the graph goes to, it seems that you have to drive at 1.2-1.3A to get 278 lumens, but that's going outside the allowed specs.
Is my estimate of Light Output Ratio for the optics way too high?
Are they driving the LEDs out of specs?
Am I estimating the LED's internal temperature junction too high?
HOW are they getting 200 Lumens OUT THE LENS?
1
Cree® XLamp® XR-E and XR-C LED Binning & Labeling. Durham: Cree, 2007.
http://www.cree.com/products/pdf/XLamp7090XR-E_B&L.pdf
2
Cree® XLamp® XR-E LED Datasheet. Durham: Cree, 2007.
http://www.cree.com/products/pdf/XLamp7090XR-E.pdf
3
"Fenix Digital P3D Black Premium Q5." Fenix-Store.Com. 13 Oct. 2007. 9 Nov. 2007 <https://www.fenix-store.com/product_info.php?products_id=358&osCsid=7e7e24ce0a7d40a0f53755bc085188a7>.
The dealer's claim is that its got 200 lumens leaving the lens,
"What's more, the Fenix P3D throws an awesome 200 lumens beam"*3 but I find that a little hard to believe from reading the datasheet for LED. Is this a measured value?
On datasheet, it reads "Cree maintains a tolerance of +/- 7% on flux" and power measurements and all the output is at 25C TJ.*2
The binning sheet says 107-117 lumen for Q5 *1. I'm assuming I can apply the 7% tolerance and 25C TJ given in datasheet.
If I assume 80% Light output ratio for the optics(this is a PURE assumption, could be way too high), the LED has to put out 250 lumens. If I assume the LED has an output at the mean of the range min and max, which is [email protected]. Since realistically, junction temperature is going to be 50-75C, to get 250 lumens, the current would have to be what it takes to get 278 lumen at TJ of 25C.
The output derating factor for temperature I used is 0.9, based on the datasheet graph.
Cree's graph rates the output at 0.35A as 100%, so to get 248% output relative to this point, it would have to be driven beyond 1A, which is the highest point the graph goes to, it seems that you have to drive at 1.2-1.3A to get 278 lumens, but that's going outside the allowed specs.
Is my estimate of Light Output Ratio for the optics way too high?
Are they driving the LEDs out of specs?
Am I estimating the LED's internal temperature junction too high?
HOW are they getting 200 Lumens OUT THE LENS?
1
Cree® XLamp® XR-E and XR-C LED Binning & Labeling. Durham: Cree, 2007.
http://www.cree.com/products/pdf/XLamp7090XR-E_B&L.pdf
2
Cree® XLamp® XR-E LED Datasheet. Durham: Cree, 2007.
http://www.cree.com/products/pdf/XLamp7090XR-E.pdf
3
"Fenix Digital P3D Black Premium Q5." Fenix-Store.Com. 13 Oct. 2007. 9 Nov. 2007 <https://www.fenix-store.com/product_info.php?products_id=358&osCsid=7e7e24ce0a7d40a0f53755bc085188a7>.
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