I think you need a zoomy or a headlamp, flood wood be better than throw. I was inspecting some paintwork in a dark garage on the weekend using a zoomable xml
wow - thanks once again for the warm welcome and great information.
Is there a:
i. headlamp
ii. works with a 18650 battery
iii. accepts this T6 drop-in
iv. has a zoom function (optional at this point)
I think it might be THE one for me (for now, lol).
hmm, I read the calculations behind the scene - source: http://hyperphysics.phy-astr.gsu.edu/hbase/vision/lumpow.html & http://hyperphysics.phy-astr.gsu.edu/hbase/vision/bright.html#c2 & http://hyperphysics.phy-astr.gsu.edu/hbase/vision/efficacy.html#c1
and tried to make a connection to Cree data sheets: http://www.cree.com/products/pdf/xlamp7090xr-e_b&l.pdf & http://www.cree.com/products/pdf/XLamp7090XR-Esheet.pdf
now, I don't know whether XR-E is the latest technology (compared to XR-C, XP-C, XP-E, XP-G, MCE, XML); but, I think I want a led in the vicinity of 5000-5500K color temperature with medium luminious flux (250 lumens) on my dark reddish nissan.
If you look at the page 12 of the above Cree datasheet, P4 group - Kit Number:00901 has the desired chromaticity value, though I don't understand the correspondent 80.6 lumens value at 350mA. What is the total lumens then?
According to formula, luminous flux (lumens) = power use (in watts) x 683 lumen/watts x luminous efficacy (based on wavelength). Assuming my dark red color car has 660nm wavelength with 0.061 luminous efficacy, then what would be the total lumens (luminous flux = power use (??? - does this depend on the battery or the led) * 683 * 0.061)?
Sorry for the potentially stupid question but I am trying to digest!
Thanks.
There is a maximum current an emitter can stand, usually 700mA for older 3W leds, 1A for XR-E and XP-E series, 1.5A for XP-G and 3A for XM-L. The calculation seems simple, if 80lm for 350mA should be 2.5-3 x 80 = 200 - 240 for 1Amps. But still there should be some curve for the emitter bin (P4-Q2-Q5, etc), lumens, current and temperature.
alright, it is great to know the limits of the leds. I think I am not understanding the "1A" part - is that the current that the led drains from the battery? Also, I believe the total lumen calculation that was done (3 * 80 lumens = 240 lumens per amp) is a very rough estimation.
For the more accurate results, can we use the "luminous flux (lumens) = power use (in watts) x 683 lumen/watts x luminous efficacy" formula?
And if we use this formula, for my surface (my car) the luminous efficacy would be around 0.061, but I am not sure about the "power use (in watts)" section... If it was a 100w bulb, then the luminous flux would be 100x683x0.061 = 4166 lumens - which is ridiciously high :)
EDIT: also, is the luminous efficacy factor of the source or the color of the object that source will be reflecting on?
Luminous efficacy (let's call it eta) is a light source's luminous flux F divided by used power P, measured in lumen per watt, thus eta = F / P. It already includes the human spectral sensitivity and the source's spectrum (and those 683 lm/W).
Rearranging that formula just gives F = eta * P, i.e. flux = efficacy * power
A 100W incan delivers 100 W * 13 lm/W = 1300 lm.
Efficacy is a physical quantity for light sources.
. I think I am not understanding the "1A" part - is that the current that the led drains from the battery?
No, that's the current through the emitter. Also note from cree's graph the emitter gets less efficient with more current/power.
You might also want to look up the emission pattern and optics and figure out what light hits which parts.
http://flashlight-wiki.com/Brightness_Bins works quite nicely as a quick referrence for the relative brightness at diffrent currents.
"1A" refers to the chromaticity bin, which specifies the color temperature (and a bit more). 1A is cool white. See here.
Edit: Oops. You meant 1 Ampere maximum current for the XR-E. Pushing higher currents through it may kill it (depends how high the current is and how well the LED is cooled).
I'm pretty sure Kokopelli was talking about 1 amp.
Oops, sorry, should have re-read the thread...
I do like the look of that Maglite……which model is it? I don’t seem to be able to find it listed, hard to tell what size it is but it looks a small.
Cheers
Steve