Texaspyro's Handmade Multi-Emitter DIY Contest Entry

While waiting for the show to begin, first a little mod’ing music:

Life in the Valley Below is good. Fertile fields. Great apple crop every year, the Queen of Light bakes a mean cobbler. Supple maidens cavort in the woods all night. They are always willing to lend a helping hand. Things couldn’t be any better. Except… except for that pesky Dragon of Darkness. Nasty creature. Poops in your garden. Ravages maidens. Farts like a mainiac. Gotta do someting about that critter… not easy. The EPA has banned Dragon Be Gone. Fish and Wildlife has declared it a Threatening Species, you kill one and they take away your birthday.

Oh now, oh now, what do we know about Dragons of Darkness? Not much. Except that sunlight blinds its’ eyes. Merlin is a useless old codger. Nary a sun spell in any of his Grimoires. The old fart can’t even make a single lumen by rubbing two matches together. Gonna have to do this one alone…

Scour the kingdom for something. Something to blind the Dragon of Darkness. Nothing pops up. Gotta build it from scratch. Figure 20,000 lumens ought to do it…

The Cast of Characters:

A Bridgelux C9000 multi-emitter array.
A big honkin’ bowl for a heatsink/reflector
A purpose built custom driver
A couple of 6000 mAh 4S LiPo packs (can do 1000+ amps)
A cooling fan
A handy handle
A 98mm phenolic high power rocket body tube laminated with carbon fiber.
Some missile-anus nuts and bolts and paint and sandpaper and…

Mechanically this build is rather simple. Technically, it is definitely not…

This one turned out to be a lot harder than imagined… it took three attempts and a month of trying to get something that worked.

Plan A:
I bought a 4 quart stainless steel mixing bowl from Blood Bath and Beyond. Very nice, sturdy, light weight, very shiny inside surface. It is made from stamped or spun molded stainless steel sheet. Whatever made it, work hardened the material out the wazoo. It took around 20 hits with an automatic center punch to dent it. Harbor Freight titanium nitride drill bits wouldn’t even scratch it (why am I not surprised). It took cobalt steel and carbide bits to get through. Finally got the emitter mounted. Epic fail! I could only drive it with about 35 watts before it went into thermal shutdown. I want around 200 watts… Stainless steel is a VERY poor conductor of heat. It could be spit sizzlin’ hot behind the emitter, but an inch away it was room temperature.

Plan B:
Well if stainless blows chunks, copper is king. Finding a copper bowl with a flat bottom is rather hard… particularly one made of solid copper. I finally found a nice one on Ebay for $35. When it arrived… phooey! The outside bottom was nice and flat. The inside was curved. Milling the bottom flat would have been a no-no for a hand-built light.

Plan C:
Well, about all that was left was aluminum (aluminium for you foreigners). I located a Mikasa pasta bowl on Ebay (sorry folks, no longer made). It is big (13” in diameter). Heavy (3.3 pounds/1500 grams). Material is over 0.20 inches thick. Nice flat bottom. Nice shiny inside (ok, scratched to hell but polished up nice). The outside has nice ridges to increase the surface area.

Smooth/shiny surfaces are rather poor for shedding heat. Flat black, textured surfaces are good. Just how much difference could it make? See http://www.molalla.net/members/leeper/coatbar.htm

So, what’s a boy to do? Why paint it, of course. Painting aluminum/aluminium is easy. Getting the paint to stick is not. First it got an acetone bath. Next, I roughed up the surface by wire-brushing the outside with a rotary brush in a drill. It had to be a thin wheel to get in the ridges of the bowl. Wet sanded it as best I could. Etched in by weighting it down in a vat of sodium hydroxide. Etched it again in a couple gallons of vinegar.

Masked off the decorative rim. It’s a compound curve and took a zillion small pieces to tape to follow the contours. Sprayed it with Rustoleum Self Etching auto primer. Etch, retch, etch, retch, etch. Finally sprayed it with a flat black Rustoleum Truck Bed paint. It (supposedly) dries to a tough, textured finish. Seems to work.

The results:

The Bridgelux array requires around 30 volts to run. At 5 amps/150 watts in, it puts out over 16,000 lumens. Not many drivers are available to run it. So I build my own driver. It gets it’s own thread: An ultra high power direct drive LED driver

Powering the beast is a 6000 mAh 8S lipo battery pack (actually 2 4S Turnigy Nanotech packs in series). Those batteries can dump over 1000 amps. The driver is a direct drive driver. To control the maximum current that the LED can see, you have to charge the batteries to a certain voltage. 30.4 volts gives around 5 amps. Each 0.5V increase in voltage raises the current around an amp. If the battery voltage is too high, the driver starts backing off the PWM level to help protect the LED. Above another threshold, it won’t even turn on the LED. I’ve driven it at 10 amps… I might eventually go with a 9S LiFePO4 pack.

Edit: I did a better voltage vs current test with the assembled light. At the 5A drive level the emitter array puts out over 110 lumens/watt. At 7A it is around 95 lumens/watt (21,000 lumens):
29.5V - 3.6A - 105 watts
30.0V - 4.5A - 135 watts
30.5V - 5.4A - 165 watts
31.0V - 6.3A - 195 watts
31.5V - 7.0A - 220 watts

The emitter is bolted to the reflector/heatsink/pasta bowl with four M3 screws. Antec Formula 7 diamond thermal paste was used. I usually use my own diamond paste, but wanted to give the Antec stuff a try. Seems to work well.

Getting rid of all that heat needs some assistance. So there is a cooling fan mounted to the bowl. The driver controls the fan based upon the LED temperature. There is an LM35 temperature sensor epoxied to the LED “star” with silicon carbide filled epoxy. At around 80 watts in the fan does not come on (I guess that paint job is doing it’s job). At 160 watts in the fan is at full blow and after around 5 minutes the driver has to start backing off the LED drive level to keep the temperature within the programmed limits.

Here’s the fan tower. That plywood disk gets epoxied in to the flashlight body and supports the reflector. The fan is mounted on stainless steel standoffs to prevent back pressure from reducing the air flow. There are intake and exit holes drilled in the flashlight body. The temperature sensor wires and LED power wires feed though the bowl. Rubber grommets prevent chafing. The temperature sensor and power wires are kept apart so that those hugh current pules when the light is being PWMed don’t corrupt the temperature sensor readings.

Here’s the driver mounted in the tailcap:

The flashlight body is made of 98mm diameter high power rocket phenolic airframe tube laminated with 4 oz 1Kx1K (1000 fibers per bundle) 24x24 (24 bundles per inch) tight weave carbon fiber cloth. West System epoxy was used to do the lamination. I used their “Special Coating Hardener” with the epoxy resin. The Special Coating Hardener is magic stuff. It causes the epoxy to cure to a smooth, self-leveling, optically flat surface.

The tailcap is made of the same material. A piece of phenolic coupler tube (telescopes with the airframe tube) is used to do mount the tailcap. A plywood disk laminated with the same carbon fiber cloth seals the back of the tailcap. The light tailstands just fine. It makes for a dandy candle…

An electrical equipment rack handle is used for the flashlight handle. The handle position was chosen so that the batteries and reflector counterbalance each other. The light is controlled by a small tactile switch mounted on the handle. I’ll probably add attachments for a shoulder strap…

The body parts:

Ok, here’s the finsihed light. It weighs 7.5 pounds (3.4 kg) with the batteries. It balances perfectly at the handle and feels much lighter than 20,000 lumens. Tactile switch is at the top end of the handle. You can see the vent holes for the forced air cooling. Shown with a Sky Ray King cowering in its’ shadow:

And a picture of the LED array in the reflector (before I cleaned up all the finger prints). Temperature sensor is under that grey glob of thermal epoxy.

Beamshot against a very light beige wall. What isn’t obvious is the wall is over 10 feet wide and the light was around 4 feet from it. It was pretty much fully illuminated. The camera makes it look like there was some variation towards the edges. The beam is around 120 degrees wide with a small hotspot. The thing has almost NO throw, all flood… flood of biblical proportions. Enough flood to make Noah despair…

Getting ground based images of the beam of this thing is rather hard. The beam is over 120 degrees wide. It hits the ground near your feet and the foreground gets rather overexposed. Here is a double wide soccer field:

Ok, let’s try something a bit more vertical… how about a five story bank building? Without the light, the thing pretty much photographed as black. How far away was the camera? Try across the street… oh, woe is Noah…

For some strange reason, that streetlight is not on… I could have sworn that it was… J)

Cast of characters:
Bridgelux C9000 array: $55
Mikasa pasta bowl (and two others): $75
Custom driver: $25
Batteries: free from a RC pilot friend… a bit worn out ($135 new)
Wire and connectors: $5
Phenolic tube: $10
1/4” aircraft plywood: $3
Nuts, bolts, washers, standoffs: $5
Diamond paste: $1 (out of a $10 syringe)
Carbon fiber cloth: $10
Epoxy: $5 (out of around $80 cans)
High Density Epoxy Filler: $1
Epoxy squeege: $1
Foam brushes: $3
Sandpaper: $3
Paint and primer: $20
Acetone: $5
Vinegar: $5
Lye: $1

Nut driver
Coping saw
Wire bush
Automatic center punch
Drill and bits (3mm, #6 screw, 1/2”)
Soldering iron (used a butane one to minimize use of power tools)
Ruler, marker, compass

This is a rather useless light unless you want to light up the side of a building/tall tree/canyon or light a playing field/worksite from above. The beam is SOOOO wide, most light is wasted on your feet and the sky. It needs a much more reasonable reflector. It will probably be redone with a commercial copper CPU heatsink and reflector like in: 15,000 Lumen Bridgelux C9000 Light Engine

Speechless. I’m not sure what I just read but wow. Have I just read the ramblings from a freak, poet, mad scientist, genius, creative fool or a light junkie. I reckon theres a bit off all the above mixed together to create this new sun that is about to illuminate the daytime.
I take my hat off to you texaspyro and there is no insult at all intended with the above. I literally stood up and gave you a round off applause. Well done so far. Cheers.

Sorry Texas, no harm meant 

Cant wait to see that driver in use 

edit mrsdnf:

edit: mrsdnf

A little waiting doesn’t hurt, especially with good music! :wink:
I’m quite curious now. :slight_smile:

ok, I'm all eyes, love the intro music already, awaiting the rest...

I should have reserved more posts.

I sense further/impending epicness.

You can't go wrong with Led Zep!

Reserved post for future comments…

EDIT now that the build has been revealed!

That light is just sick!

Something really different. Looking forward to see beamshots!

With the one post per minute limit, it’s really hard to reserve 5 posts without some sneaky person sneaking in a post between them… :wink:

Hehe... Sooooooorry

I’ve seen a hint or two of what you are planning here. So many secrets. I do know that there will be a lot of power involved. :slight_smile:

I was so tempted...

Don't let it kill you baby, don't let it get to you
Don't let 'em kill you baby, don't let 'em get to you
I'll be your breathin' heart, I'll be your cryin' fool
Don't let this go to far, don't let it get to you

The waiting is the hardest part
Every day you see one more card
You take it on faith, you take it to the heart
The waiting is the hardest part

Hey tp, got any reservations about your build?

I reserve the right to be reserved about my reservations…