White LED, crazy idea... or not?

[Giroud Francois]

the luxeon is like a bulbe, not like a panel, then the field given is smaller, and the intensity very high like bulb, so viewing directly at is painful. these are all advantages you get with panels and we should take care when selecting components.

The best would be to select surface mount led , draw a printed circuit. smd led with high power are luxeon that comes either in modules or in smd elements and golden dragon smd leds.
you can see something like this here
http://www.i2systems.com/services/pcb.htm
or here
http://www.primolite.com.tw/products...24&category=07

it looks ok to do it yourslef
http://www.candlepowerforums.com/ubb...b=5&o=&fpart=1

i already gave this link , you should find anything you need included luxeon module.
http://shop.dotlight.de/shop/

and if you need to know more about luxeon modules
http://ledmuseum.home.att.net/agilent.htm

and people really mad about flashlights...
www.surefire.com

i think i will use the golden dragon smd led over home made printed circuit and use this heatsink http://www.radianstore.com/plate-fin...-hs1591eb.html for the back (to give you an idea of the size).
As they come by pack of five, i will build 1 prototype and 4 lamps.
batteries will be li-ion on a separate pack.
The front of the lamp will be very thin frosted acrylic glass (about 2mm). or thicker (5mm) with kind of lens in it to help diffusion.
i think i can use a hot steel ball to make the "lens".
the total thickness should be about half an inch and all sealed in expoxy (for thermal transfer)
cost for 20 leds is about 120 $ + heatsink 10$ + 10$ for misc.
i hope the total under 150$.
The trick will be to make a very thin print circuit, then drill holes to accept the leds, so the led is looking through the printed circuit. then i will isolate the printed circuit with a layer of epoxy or mylar or both and glu the back of the led on the heatsink.(eventually adding a touch of thermal silicon on each led)
the front of the printed circuit can be covered with a layer of aluminium to make a reflector, then the epoxy over. 6 screws are fixing all the layers together.
This idea is not copyrighted, so go ahead and lets compare.

[Mike Rehmus]

Suggest you use DeltaBond which is a thermally conductive epoxy to fasten the board to the heat sink. Otherwise, the layer of epoxy or plastic will add a thermal barrier between your source and the heat sink.

[Giroud Francois]

Don't know where i can find this but google says it is standard
epoxy with 75-85% of alu. oxide.
found a way to recycle my alu. oxide from my miniDV35 project...

[Mike Rehmus]

Wakefield is the company that makes DeltaBond
http://www.wakefield.com/pdf/accessories.pdf

[Giroud Francois]

I will try this, looks better and cheaper
http://www.xpcgear.com/arsiltherad.html
it is epoxy glu and 65 % of silver.

I could even try to get some copper powder and build my own.

this company is selling everything under atomized/micronized form.
http://www.micronmetals.com/silver.htm
and it is cheap....

[Giroud Francois]

I just receive my leds.
Finally i ordered 16x 1 watt luxeon (hi output model, because there is 2 versions, the other delivering half the light only).
I choose them for first prototype, because they came mounted on a small alu plate that makes them self-cooled. That means the little plate is big enough to dissipate all the heat. Be aware that is not the case for the 3 or 5 watt models that requires additional heatsink.
The good news is that if you aligne them side by side you will just fill a rectangle exactly the size of the heatsink mentinned in my previous post.
Wiring 4 groups of 4, will make a 13.6 volt/ 1.4 Amps module.
The bad news is, that using the 1Watt model on this heatsink, will limit to 16 leds that would be the equivalent of a 20W lamp.
If I use two modules, this could give a decent light.
Iwill test the heat dissipated this way and try either with 16 x 3W luxeon stars or 24x1w luxeon or 30x golden dragon.
I expect that the golden dragon is a lot more difficult to cool properly.
just waiting for the heatsink now

[Giroud Francois]

for info , if you go for the heatsink presented above, note that
http://www.radianstore.com/round-pin...-hs2070db.html (pin model) has a thermal resistance half of the fin model. for thermal resistance, low value ist best.

[Sean McHenry]

On adding diodes to taper off voltage, this is an age old trick. You could read up a bit further and get variable voltage regulators that range from 2 - 37 volts. You have a loss in heat to overcome. That is, you couldn't regulate long at 14v if your input is only 14.4. In fact, that drop probably isn't enough to even make it work. It's been a while since I played with voltage regulators. they come in transistor like packages labeled like LM7805 (5 volts) LM7808 (8 volts) LM 7809 (9 volts), etc.

They create heat and must have an enherent loss to work.

You could use the diodes and put small switches across each one and as the voltage goes in the battery, use a small switch to bypass individual diodes to keep the voltage to the LEDs up.

That's a bit impractical as you now need to add a Volt meter to watch the voltage. Besides, that's basically what a voltage regulator does anyway on it's own.

The best option might be to use the backup lights as they are obviously meant to handle 12 - 14 volts.

Check the actual output of Gel Cells and other battery sources as they are usually a bit over the 12v mark anyway.

As a last alternative, make your own battery packs. You can get the AA sized professional NiMH and NiCad batterys individually. NiCads are 1.2 volts each compared to Alkalines at 1.5 volts each. Rememer to take that difference into account when building packs. Coincidentally, 12 NiCads at 1.2 volts is 14.4 vdc.

You can buy AA battery holders in variuos places for various numbers of cells. Or, you can still get the batteries with solder tabs on them and make an old fashioned belt pack with lumps of soldered batteries in a case.

One quick safety tip. When you start stringing together cells like this, you can get a significant current. Watch for shorts or those little metal cans can get quite hot. In my broadcast engineering days, when you rebuilt a pack of "D" cells, you better remember to check or replace the thermal fuses. A short on those packs can melt lots of things, like clothing, seat covers, carpeting, etc.

Good Luck,

Sean McHenry

[Giroud Francois]

currently , there is a lot of ways to deal with problem.
the resistor solution works well when you got steady voltage from power supply (connected on the main) but is bad with batteries of any kind.
the regulator solution is ok but even with low drop regulator as soon as the voltage goes under the specs, it is bad and if you go too high, you just dissipate heat. So basically regulators have same use than resistances, they are just more precise.
The solution if working on batteries is the current pump, a DCD-DC converter with high efficiency (up to 90%).
It makes a steady high voltage (12V for example) from a 3V cell and is able to sucks evey electron out of the cell (the nyou have to take care if using ni-cad or lead batteries that don't like deep discharge)
Most of these converter are single chip, doing all the work with few of them allowing to frive the final stage with an external transistor, allowing high current.
go to google and type "LED driver PWM", you will find a lot of them.

[Giroud Francois]

I just receive the heatsink, now trying to find a way to glue the led properly.
I can not get the hand on arctic silver epoxy.
I will try a mix with regular epoxy and alu. oxyde from my mini35 project.

[Mike Rehmus]

Finally edited the video I shot with these flashlights. Massive difference between video shot with and without. Even though you cannot see a lot of difference with your eyes, the video makes a great deal of quality out of just a few watts of light from this rig.

I might not have bothered with the MR-16 LED setup had I had time to edit this video before I built the newer rig.

<<<-- Originally posted by Mike Rehmus : OK, flashlight adapter #1.

Go to hardware store, get an 2" L-bracket (Stanley part # 75-6371), 2 x spring-loaded broom holders (Stanley part # 75-2025)for hanging brooms on wall. These are the type witha round spring arm and a plastic pad to grip the object in their jaws. Costco 7-LED flashlights fit in very nicely.

Mount broom holders to the L-bracket (one on each side) with 2 screws. You will have to drill one hole. I used 8-32 screws to fasten the broom holders to the L-bracket

Mount L-bracket on camera shoe adapter that has 1/4-20 stud.

Flashlights are now mounted side by side above the camera without interfering with CAC-12 microphone holder on Sony PD150.

I placed two disks of diffusing material and one disk of CC filter material on backside of lens cover, clamped between LED holder and lens cover. Warm White LEDs would be nicer than these Cool White LEDs.

Works very nicely.

Interesting, the LEDs get quite hot in constant use. Burn your hand on the inside metal power connectors hot. Have to turn them off from time-to-time.

Total cost for flashlights and bracketry - About $50.

Run-time is said to be about 140 hours per each load of 4X AA Cells.

Total weight, 1 Lb., 0.7 Oz.

I'm off to Pennsylvania on Friday to try them out. -->>>

[Dan Euritt]

thanks for the feedback on this light setup, it sounds like it worked out pretty well.

now to figure out how to control the intensity... maybe turn one light off, leave the other one on? and where to get the warm led's.

[Mike Rehmus]

LEDTronics sells warm LEDs.

I placed a diffusing gel and a warming gel inside each light to warm them up since they were daylights and I wanted a more difuse light.

They didn't look like they did much with the naked eye but the video really liked the light.

Of course my subjects were of painted metal, not people. For that the MR-16 lamp does very well.

[Marius Luessi]

Heya,
interesting developments and posts in this thread. I have also designed an on-camera LED video light, which will be available for purchase in about 6 or 7 weeks. The initial design uses 52 x 5mm LEDs, the next one (available in about 5 months) uses the high-flux LEDs; but that will be a bit more expensive, especially as it also will include a battery pack.
We have selected specific LEDs (both for the 'conventional' and high-flux variety) which are binned, meaning we can deliver consistent performance, colour and brightness.

Indeed, as many have mentioned here, LEDs are not 'quite' as fantastic and wonderful as some make them out to be:
- They are NOT "heat free" as many claim. They produce quite a bit of heat in fact.
- Their life expectancy might well be 100'000 as many claim (for non-high flux LEDs), however, as soon as you turn them on, their light-output diminishes. It does depend on the environment in which they operate, but after about 10'000 they may well be under 80% of their original brightness. Still 10'000 is a heck of a long time.
Having said all that though, they do offer many advantages over incandescent lights, also very well mentioned in this thread.

The lights we have designed will be available in different colour temperatures, and beam angles, all of them are dimmable from ~1% to 100%, and use either 9V to 28V (or 16V to 28V respectively for one model).
And unlike some 'other' LED lights, one model of ours can be used quite well for a tight shot of a subject about 20' to 30' away (we call that one the "Paparazzi Light"! ;-)

Prices will start at around $225 for a warm-white (~2900K), which is MSRP.

I'll be glad to answer any questions, technical or otherwise.

[Marius Luessi]

<<<-- Originally posted by moi: - Their life expectancy might well be 100'000 as many claim (for non-high flux LEDs), however, as soon as you turn them on, their light-output diminishes. It does depend on the environment in which they operate, but after about 10'000 they may well be under 80% of their original brightness. Still 10'000 is a heck of a long time. >>>

Err....those numbers were for HOURS of course; I forgot to put "hours" after the numbers, sorry.