Quad CREE Royal Blue XT-E LED Overdrive Tests and Sabers

[Photonic Bladesmith]

Quad CREE Royal Blue XT-E LED Overdrive Tests and Sabers

Last October I posted some overdrive tests on the CREE Royal Blue XP-E2 LED.  The Blue XP-E2 was then the most powerful source of blue light to drive Photon Blades that could be configured into a conventional LED Star.

Overdriven CREE XP-E2 LED Sabers & Fluorescence Enhanced Saber Blades

There is now a more powerful Royal Blue CREE LED, the XT-E, that is rated at having a maximum drive current of 1.5 amps vs. the 1.0 maximum rated drive current of the XP-E2. 

The Royal Blue CREE XT-E LED can be purchased in quad star configuration from ledsupply.com :

Cree XPE - QuadPod 4-Up Royal-Blue High Power LED
Order this item.  Then, during checkout, leave a note in the "Comments" field stating you would like the QuadPod built with CREE Royal Blue XT-E LEDs.  They typically take 7-10 days to fill an order for custom parts.

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Overdrive test of this new Royal Blue CREE XT-E LED.




Four QuadPod CREE Royal Blue XT-E LED stars with the matched collimating optics were purchased from LEDSupply.com for these tests.





The LED star with the quad collimating lens was attached to an 8 inch long, 1 inch diameter copper rod heat sink using Arctic Silver thermal conductive epoxy.   Aluminum heat sink stands and a cooling fan helped to keep the LED array temperature within reason during sustained high current tests.  The LED drive was increased at 0.1 amp increments at currents above the 1.5 amp rated  maximum current.   Each of these overdrive level tests were done for four hours or until LED failure was observed.   

An Ophir model L150C-A    optical power measurement head was used to measure the LED optical output power.  A pair of Fluke digital volt meters simultaneously measured the LED voltage and current.




Drive current vs. optical output power for: Royal Blue CREE XT-E, Royal Blue CREE XP-E2, Green CREE XP-E2.
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Results:

With an adequate heat sink, the royal blue CREE XT-E LED can be safely operated overdriven at 2.5 amps producing an optical power output of 2.1 watts per diode.

This overdriven optical power output is 40% greater than the 1.5 watts that it emits at its rated output at 1.5 amps and twice that of a royal blue CREE XP-E2 driven at its rated drive current of 1 amp.

The estimated brightness of a green Photon Blade illuminated by a quad royal blue CREE XT-E star driven at 2.5 amps per diode (10 amps total) is around 4,000 lumens.  In contrast, an over driven tri-CREE Green XP-E2 star only puts out about 800 Lumens.

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Next, a pair of sabers to test out this new high output quad Royal Blue CREE XT-E LED array need to be built:

To simplify the electronics and make current regulation heat removal less of an issue, the quad LEDs are to be wired in series and driven by a stack of four rechargeable 18350 lithium batteries, with a low drop out voltage current regulator keeping the current through the LEDs constant at 2.5 amps.






The rechargeable lithium Efest IMR18350 has a peak current output rating of 10 amps and currently costs about $5.00




The current regulator electronics and the Nano Biscotte sound card and its voltage regulator are mounted on a copper strip bolted to the 2 inch long, 1 inch diameter solid copper rod used as the heat sink for the LED star.  Arctic silver thermal conductive epoxy was used to glue the LED star to the copper rod and glue the current regulator IC to the copper heat transfer strip.



 
Since the operating time per battery charge is on the order of ten minutes, the ability to do rapid battery swaps is a necessary part of the lightsaber design.  To facilitate rapid battery exchanges, the batteries are held in a home cast thin wall Kevlar-epoxy tube with custom machined end caps.



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Build Log:








































A finished pair of 10 amp drive quad CREE XT-E LED sabers.




The Covertec cylinder rotates to clamp and retain/release the speaker housing / battery tube access end cap.




A plastic O-ring friction retained cap covers the main power switch.




In order that this saber be loud as well as bright, the largest high performance speaker that would reasonably fit was installed.  A traditional compact saber speaker is shown to the right.








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Daytime Outdoor Tests:

Since the principle reason for constructing high brightness sabers is for their use in outdoor daylight and brightly illuminated con environments, some daylight outdoor tests need to be performed.




This comparative test of the new saber driving a green Photon Blade, next to a green Tri Cree LED star illuminating a conventional blade was done outdoors under overcast skies in a late summer afternoon.

The left side blade is a Vader's Vault Dual Diffused Blade illuminated by a Tri-Green CREE XP-E2 star driven at 2 amps by a Nano Biscotte.

The Saber on the right has a green Photon Blade illuminated by a Quad Royal Blue CREE XT-E star driven at 10 amps.


The two videos of the new saber driving a green Photon Blade were taken outdoors under light overcast skies with the Sun partially shining through the clouds.

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Finally, a caution warning video dramatically showing why one should not stare into the blade holder of a high brightness saber when the saber is on, and that high luminous output power sabers are not to be considered children's toys!

[Sethski]

Great to see you pushing this further forward and thanks for sharing!

I was looking through the data sheets for the XP-E2 and XT-E (http://www.cree.com/~/media/Files/Cree/LED-Components-and-Modules/XLamp/Data-and-Binning/XLampXPE2.pdf http://www.cree.com/~/media/Files/Cree/LED-Components-and-Modules/XLamp/Data-and-Binning/XLampXTE.pdf) and was pleasingly surprised at the results, as the XP-E2 looks better on paper as far as I can see, with brightest binned XP-E2 rated as 675-700mW @ 350mA (p22) and brightest binned XL-E rated as 600mW @ 350mA (p20) as far as I could make out. I also noticed that, although white XLO-Es are rated as max 1.5A, the rB is rated as max 1.0A, same as the XP-E2?

This isn't picking apart your methods and results, just (respectfully) wanting to understand them bit better - you seem to be thorough and meticulous in your process and it's hugely appreciated you sharing this in clarity and detail enough that plebs like myself can get a handle on it  ...and I put more stock in physical tests than on-paper specs.

The big surprise to me is the extent to which the XL-E will stand being overdriven compared to the XP-E2 in tests, which I guess is what clinches it for the XT-E?

Another point of curiosity for me is Blue vs Royal Blue (for the XP-E2 as the XL-E only comes in royal blue and white): info online seems to consistently point to maximum absorption/exitation wavelength for fluorescein in the range of blue rather than royal blue, so I wondered if the reason for choosing royal blue over blue was that the royal blue is more efficient, emitting more energy/photons than blue (even if most of this isn't visible to the eye, and as one's rated in mW and the other lm) and so offering a net brighter result with a fluorescent blade, even if the wavelength isn't optimal?

[Photonic Bladesmith]

Another point of curiosity for me is Blue vs Royal Blue (for the XP-E2 as the XL-E only comes in royal blue and white): info online seems to consistently point to maximum absorption/exitation wavelength for fluorescein in the range of blue rather than royal blue, so I wondered if the reason for choosing royal blue over blue was that the royal blue is more efficient, emitting more energy/photons than blue (even if most of this isn't visible to the eye, and as one's rated in mW and the other lm) and so offering a net brighter result with a fluorescent blade, even if the wavelength isn't optimal?

The emission and absorption curves for fluorescein is highly dependent upon the media it is embedded in.  Most of the online data is for fluorescein in aqueous media since one of the primary scientific uses for fluorescein is as a tag for bio molecules in research.

I actually measured the emission and transmission (inverse of absorption) spectra of fluorescein in polycarbonate by taking measurements in optical spectrometers of cut sections of Custom Saber Shop green Photon Blade tubes. 
The data is presented in:  Photon Blade: Tests, Measurements and Physics

It turns out that for the thick wall blade the absorption of the pump light is over 99% for both the blue and royal blue colors.

For the thin wall blade, which is thin enough that the abosrption does not saturate out, the difference in absorption throughout the range of blue light is only on the order of a few percent.

A secondary issue, though it is also only a small few percent factor, is that shorter wavelengths have been measured to have higher quantum yield (number of photons emitted vs. number of photon absorbed) than longer pump wavelengths.

The conclusion is that if you want to choose a blue color solely to drive a Photon Blade, optical output power (quantity of photons) is the most important factor.

However if the output power of the blue and royal blue were equal between the LEDs you are selecting between, I would choose the longest blue wavelength since it would look subjectively brighter at the same power to the human eye when used with a regular non-fluorescent blade.

[Sethski]

Thanks for reply and clarification. I only spotted the other thread you link to after reading here - still processing that...

[PhoenixJedi]

Would love to know the direct flux measurement of these at Other ratings are.. Compared to XPE-2.. 350mA, 700mA, 1000ma and 1200mA (for all) (Single Die)