Help designing LED-based floodlight

Daravon

Newly Enlightened
Joined
Nov 27, 2005
Messages
164
I know a guy who needs some portable floodlights for videography and lighting a DJ booth. He wants me to design a LED based floodlight so that they don't generate so much heat. Battery life is not that important because he can use lead-acid batteries, but 12v would be nice. This is what he initially wanted:

http://www.bigclive.com/flud.htm
http://i280.photobucket.com/albums/kk164/bigclivedotcom/flud13.jpg

Note that he does NOT need RGB capabilities, but he does want white, 5-6kish output, and he wants them to fit in the floodlamp housings.

That design uses halogen floodlight housings. It uses 54 leds and has no heatsink, so it looks like pretty much pre-luxeon technology. I'm thinking a better route would be to glue some modern LEDs to a piece of aluminum, more like this:

http://www.textklick.demon.co.uk/54leds.jpg

I think a chunk of 1/4" aluminum with some modern LEDS glued/screwed too it would be the way to do this nowadays, either with a resistor or LM317 for current regulation.

What white emitters would be good to use to cheaply get as many lumens as possible on the lowest budget possible? I think if it was as bright as a 100-200W incandescent he would be happy.
 

LukeA

Flashlight Enthusiast
Joined
Jun 3, 2007
Messages
4,399
Location
near Pittsburgh
Cree XR-E Qn (n= 2-5) are pretty cheap. Check the datasheet (cree.com) to figure out what bin you want. Probably WC or 3A or whatever they split the warm bins into. Best to get them on MCPCBs for easier mounting and soldering.

100W-200W incandescent is pretty easy. 12 XR-Es at ~700mA will give ~2000 lumens and require ~36W or power input. A 100W incandescent bulb puts out about 1700 lumens, emitted over a sphere. The LED's light is emitted in half a sphere, so with LEDs you will get just about twice the intensity of a bare incandescent bulb, given the same luminous flux for each.

For the heatsink, a 1000- or 2000-series aluminum alloy is best for thermal conductivity, but 6000-series are usually easier to find and are less expensive. Paint the aluminum black. It will operate at a lower temperature. The effects of emissivity are significant.

I would use either this or this 2024-alloy aluminum.

Which would be better: 12V lead acid battery or wall power? It'd be a pretty simple matter to get a PC power supply to operate a couple of these proposed lights. Maybe use the right connector and be able to switch between on-grid and off-grid operation.

Hope some of the above helps.
 
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