Overdriven CREE XP-E2 LED Sabers & Fluorescence Enhanced Saber Blades - Part 2 Sabers
Two sabers are to be constructed:
Saber 1 - Quad royal blue CREE XP-E2 LED star driven at 1.5 amps per LED - Intended to drive a green fluorescent saber blade at more practical current levels and heat loads than the 30 amp saber referenced in: [http://www.fx-sabers.com/forum/index.php?topic=46064.0]
Saber 2 - Tri green CREE XP-E2 LED star driven at 1.5 amps per LED - Intended to drive a Vader's Vault double diffused saber blade to act as a brightness reference to compare fluorescent blade sabers with a known high brightness rated conventional blade-LED combo.
Sound card - Plecter Labs Nano Biscotte
V2. The Nano Biscotte board is powered by a voltage regulated 5 volts from a lithium battery stack regulated down from 8 volts using a LT3083 programmable voltage/current regulator IC.
LED Driver - The LED driver is custom designed using Linear Technologies LT3083 programmable low dropout voltage linear current/voltage regulator ICs to individually drive each LED on the CREE LED stars. The four regulators are configured to be switched on and off simultaneously by the Nano Biscotte LED output pad. Each regulator can be independently set for up to 3 amps output current. If you want to drive an SSR-90 type high current single die LED, the regulators can be operated in parallel to sum their current outputs into a single LED.
Saber electronics schematic
Power - The saber is powered by a pair of LG brand high current (up to 35 amps) lithium rechargeable 18650 batteries. A thin wall Kevlar-epoxy tube with spring loaded solid copper rod end contacts holds the batteries and allows them to be rapidly swapped out without tools.In Stock genuine high discharge rate rechargeable cylindrical 18650 Li-Ion
Measured power and equivalent lumens
Ophir model L150C-A optical power measurement head
Tri CREE XP-E2 green LED saber at 4.5 amps (1.5 amps per LED)
1.2 watts optical output power at 520 nm
Electric input to optical output efficiency = 8%
Driving a conventional saber blade = 610 lumens
Quad CREE XP-E2 royal blue LED saber at 6 amps (1.5 amps per LED)
5.0 watts optical output power at 450 nm
Electric input to optical output efficiency = 26%
Driving a conventional saber blade = 130 lumens
Driving a green fluorescent saber blade = 2,200 lumens
Luminous Devices CBT-120 Blue LED driven at 30 amps (50% duty cycle square wave drive, 20 Hz)
Link: 30 Amp LED Sabers & Fluorescence Enhanced Saber Blades (Part 1 - Saber)
7.5 watts average / 15 watts peak power optical output at 462 nm
Electric input to optical output efficiency = 11%
Driving a conventional saber blade = 340 lumens
Driving a green fluorescent saber blade = 3,300 lumens
Driving a conventional saber blade = 680 lumens
Driving a green fluorescent saber blade = 6,700 lumens
Tri-CREE XP-E2 green LED Saber driven at 4.5 amps- Vader's Vault Double Diffused Blade
Quad-CREE XP-E2 royal blue Saber driven at 6 amps - Fluorescent blade
Luminous Devices blue CBT-120 LED Saber driven at 30 amps (50% duty cycle, square wave) - Fluorescent blade
Estimated fluorescent blade luminosity due to sunlight:
Assume that 1/3 of the solar spectrum is in the fluorescein dye excitation band.
Solar Insolation (late afternoon cloudy day and clear day just before sunset) ~ 100-200 watt / square meter
Fluorescein dye pump band to green light conversion efficiency 92%
- cloudy day, late afternoon
- clear day, 1 hour before sunset
Starting fluorescent blade brightness in the green from sunlight alone approximately 400 - 800 lumens.
Blue LED illumination fluorescing the blade adds to this baseline brightness value.
Scattered white light from conventional blade approximately 200 - 500 lumens.
This is the white light level that is competing with the LED to wash out the LED color in conventional blades.
Outdoors, cloudy day, late afternoon.
Outdoors, clear day, 1 hour before sunset.
The optical output power of the 6 amp driven royal blue Quad CREE XP-E2 is just slightly less than the time average power output of the 30 amp Luminous devices CBT-120 LED that has been shown to be able to burn blade diameter holes in trash bags.
A burning capabilities ( and eye hazard ) test is in order for the 6 amp Quad CREE XP-E2 royal blue saber.
The test material here is an 1/8" thick Depron model aircraft foam sheet.
Definitely not something that you want to shine into someone's eyes!
The Quad CREE XP-E2 royal blue LED is surprisingly efficient in converting electrical input power into optical output. The CREE XP-E2 royal blue LED has a measured electrical power to optical power conversion efficiency of 26% at 1.5 amps, and 35% at its officially rated drive limit at 1.0 amp. For driving fluorescent blades, this makes the Quad CREE XP-E2 royal blue LED two and a half times more efficient at converting electrical energy into pump band optical energy than the 30 amp Luminous Devices CBT-120 blue LED which still has the edge for absolute brightness, though at 5 times the drive current.
For making a maximally bright saber blade at a given (reasonable) drive current, a Fluorescein ("day glow green") dyed fluorescent blade, illuminated by an overdriven CREE XP-E2 royal blue LED array seems to be the best option with current technology LEDs (August 2015). The CREE XP-E2 royal blue driven fluorescent blade has triple the brightness of a conventional blade illuminated by the same generation green LEDs.
So far, both the green and the royal blue CREE XP-E2 LED stars are surviving being driven at 1.5 amps per diode.
Fluorescent blades illuminated by over driven Quad CREE XP-E2 royal blue LEDs are adequately bright for non-direct sunlight outdoor daylight conditions for doing illuminated “glow stick” saber demos. They are significantly brighter under these conditions than conventional LED in-hilt sabers. Fluorescent blades have the additional advantage in the a large fraction of the sunlight shining on the blade is converted into the same colored blade light that the LEDs are driving the blade to produce.
While not having the peak brightness capability of the Luminous Devices blue CBT-120 LEDs, the Quad royal blue CREE stars have the advantages of two to three times higher electrical power to optical output conversion efficiencies resulting in far more reasonable drive current requirements, and a much smaller mechanical form factor enabling them to fit into vastly more hilt designs.
Until a source of fluorescent dyed polycarbonate blades are found, the current acrylic fluorescent dyed saber blades are display/demo only blades not suitable for full speed sparring.
Thanks again to LUMINARA for the suggestion to investigate the use of CREE XP-E2 LEDs for my high brightness saber blade experiments.