Looking to build DIY RP Fresnel-style light

B

briankauf

Member
Hello folks,

I wanted to see if anyone had any advice on this before I started ordering parts and tinkering :-)

I am looking to expand my ability to light portably, and as a part of this, I am looking to create a set of battery powered lights.

Typically, I light with a set of homemade kino flos I built with highend ballasts and Kino tubes. These work great, but they won't work in situations where I don't have access to wall power.

I am looking to retrofit some old fresnel enclosures with LED + remote phoshor lights to see if I might be able to make a reasonable fascimile of a tungsten lamp that can be powered by batteries.

I have done some research, and it looks like my best bet is to use remote phosphor sheet from Phosphor Tech (since their brand of RP sheet is thinner and diffuses far less than other panel I have seen), combined with a 100W 455nm (ideally 452nm) LED. I am wondering if anyone has suggestions on brand of LED to look for, and what sort of optics I could use directly on the LED to best approximately a point light for fresnel purposes (I want the light to start as hard as possible, as i can easily modify it to make it soft, but not the other way around).

Advice on ballasts or enclosures are also appreciated :-)

Thanks,

Brian
 
I would forget about trying to modify the LED to make it a near point-source. Doing so would require using some sort of convex lens that would waste away more light than it's worth by giving the LED an even wider beam that's ultimately going to be condensed back down to a narrow beam by the fresnel lens. I think your best bet is to use a larger fixture like an old studio 2k, the large lens on a light like that will be more efficient with an LED of that immense size. This will also give you more room for the monster heat sink that you'll need for a 100w LED.
 
I'd be curious what you come up with here too. Definitely interested in a battery operated LED Fresnel. Don't quite understand how that could be remote phosphor, but I'm all ears. A suggestion I got from RyanT on my quest for a battery operated system was to look at www.litegear.com. They have some very cool and quite cost effective LED ribbon. Not exactly what you're looking for by any means, but definitely an option to create a semblance of light panel effect that weights next to nothing and can be configured or built up anyway you chose. Cheers, Pete
 
The single-array LEDs do produce a decently sharp point source of light. But at 100 and 150 watts, they require a big heat sink and a fan. That may defeat what you are trying to do. A few of us have successfully converted the 100 and 150w Bowens-mount LED lights like the Alzo, RPS, and Nicephoto to be quiet enough for video work. They provide a decently hard light and have many more light modifiers than a Fresnel.

You might take a look at what these manufacturers are doing and perhaps convert one of them to battery power. No, they are not Fresnel, but worth considering.

http://www.dvxuser.com/V6/archive/index.php/t-316956.html
http://www.dvxuser.com/V6/showthread.php?315845-Alzo-300-LED-light
http://www.dvxuser.com/V6/showthrea...-when-used-as-a-backlight-snoot-and-key-light
 
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The reason I was considering RP would be to better control the light quality. I wouldn't actually have been using it in the remote sense. Phosphor Tech makes a much thinner, non-diffusing version of RP that I was looking at, but I did eventually find some higher quality 100 and 150W LEDs to use, so I am going that route. Cree XLamp and Bridgelux BXRA. I will let you know what I design!
 
briankauf said:
The reason I was considering RP would be to better control the light quality. I wouldn't actually have been using it in the remote sense. Phosphor Tech makes a much thinner, non-diffusing version of RP that I was looking at, but I did eventually find some higher quality 100 and 150W LEDs to use, so I am going that route. Cree XLamp and Bridgelux BXRA. I will let you know what I design!
Click to expand...

You may want to check out this Cree http://www.cree.com/LED-Components-and-Modules/Products/XLamp/Arrays-NonDirectional/XLamp-CXA3070

along with this driver http://www.taskled.com/hboost.shtml

This is the setup for DC battery operation it has a very wide Battery voltage input range. It is a BOOST type driver, Nice thing about it is that you can put a dimmer.
 
I'm doing a similar project as you guys and was looking at the CXA2590 too but I can't find them in stock anywhere.
 
It is a new led just out recently. I can just imagine the heat coming out the back of it at full power. That beast will, according to specs have a 10-15K lumen, ( almost a 700w filament).
I knew this sort of performance was inevitable. Now, if they just can make one a wee bit bigger to reach that proverbial 1K filament equivalent. I can see this chip being easily driven with a 14.4 V brick battery with the proper driver. I see possibilities.
 
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