How would you build a R/O Luxeon sandwich?

Thinking of building a red/orange Luxeon sandwich to complement my existing TV1K sandwich. The thing I like most is the modularity of this system, not happy? Switch the sandwich for whatever purposes you can imagine.

In a traditional sandwich, there is of course the LED, emitter board, two connectors, and the converter with epoxy in the center. With a R/O Luxeon, I'd have to put a resistor in the middle to control the current from 2AA alkalines, but what am I supposed to use as the 'converter' board? I realize I can't just make it a conductive slab of metal.

What would you use?

Kevin,

I think the easiest is to buy a couple emitter boards and sandwich them. You can exacto/dremel away any unwanted circuit traces, improvise a + batt contact and add your resistor between the boards.

Larry

Um - be careful - the sandwich puts the slug of the luxeon in contact with the body tube of the flashlight, which is tied to the "-" of the battery. The R/O slug is electrically tied to positive. So, if you were to do this, you'd create a short that would burn open the positive bond wire.

You must be sure that when the emitter is attached to the emitter board, that it is completely electrically isolated from the board, otherwise you will end up destroying the luxeon the first time you try to power it up.

Red/Orange LEDs have lower Vf. You will need a buck converter, not a boost converter, for this purpose.

I would set the drive current at a much lower level than you would with a white luxeon with equivalent heatsinking. The R-O reaches the point of falling output with increasing current at much lower drive current than than the white ones do. If you are building the classic dat2zip MM style sandwich, the thermal resistance from the emitter to the flashlight body is pretty high. I wouldn't go over around 200mA with a R-O in this setup. BTW, a layer of scotch tape under the emitter slug provides adequate isolation.

Thanks for all the tips /ubbthreads/images/graemlins/smile.gif

I see thermal management is always an issue with these little beasts. 200mA of drive current would give me around 25+ lumens of R/O light, not that much. I was hoping for a 400mA retina-searing 55 lumen blaster due to the phenomenal efficiencies of the R/O Luxeons (~50lm/W, LumiLEDs datasheet DS25). Maybe I might give it a miss.

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KevinL said:
Thanks for all the tips /ubbthreads/images/graemlins/smile.gif

I see thermal management is always an issue with these little beasts. 200mA of drive current would give me around 25+ lumens of R/O light, not that much. I was hoping for a 400mA retina-searing 55 lumen blaster due to the phenomenal efficiencies of the R/O Luxeons (~50lm/W, LumiLEDs datasheet DS25). Maybe I might give it a miss.

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Well if you only need those retina searing level for short bursts, you can get them by closely [thermally] coupling the emitter to some aluminum or copper mass. One gram of aluminum takes about one watt-sec to raise its temperature one degree C.