19 LED Maglite

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MP80968.jpg

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To see full size pics: http://community.webshots.com/user/chetvaldes
sorry about previous post with defective pictures. This is a plain vanilla conversion with no resistors or electronics.
Chet
 

Steelwolf

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Looks good. Very well done. But some questions need to be answered.

What sized Mag are you using? 3D, 3C? What is the amp draw? What about brightness comparison?

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Thanks.
 

X-CalBR8

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"This is a plain vanilla conversion with no resistors or electronics."

Chet: Have you run into any heat problems or thermal runaway problems yet with not using any resistors? Have you done an amperage reading on it with new batteries to see if it is stabile? BTW, nice conversion. I'm a big fan of aluminum flashlight conversions.
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This is the extremely popular 3-D model.
Previously, I had made a 10 LED conversion which ulilized a drop-in module which simply replaced the existing reflector assembly. I felt that more power was needed, so I made the 19. The 19 produces a light which appears comparable in "brightness" to the original bulb, yet is much whiter and easier on the eyes. More of a narrow flood light pattern or a wide spot. With new batteries (alkaline) it draws about 350 mils, quickly dropping to 300, then to 250 after a couple of hours. Interestingly, the light from the 19 is almost the same as the 10 after the batteries have several hours on them. I work as a mechanic in dark, cramped areas. The light quality is very good for this as it is less contrasty than a bulb. I have never encountered any thermal problems when using 3 cells on these simple curcuit lights. I did notice, however, that when running greater voltage {5 volts) excessive heat was noticed not on the "heatsink" or lenses, but on the leads! In fact, they got too hot to touch. I wonder if there could be a thermal advantage to "potting" the connections- obviously a lot of heat is conducted down the leads. It would need to be a poor electrical conductor obviously, yet a good thermal one. Would epoxy fit the bill? For "high power" LED use, this could a big issue.
Chet
 
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Ohio
Chet, the leads definitely are the major conductors of heat. And the negative gets much hotter than the positive. Heatsinking just the negative leads all together would probably help alot.

If you look closely at the dice of the LED, the negative one is MUCH larger. So. it carries most of the heat away from the reflector in the LED.

I was thinking of using an aluminum disc as the negative conductor. It would have holes in it for the positive leads to go through without contact.

This is essentially what Luxeon did with their huge LEDs that Gransee is talking about in the manufacturer's forum.
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Yes, I think that's a good idea. I used an alumin(i)um disc thinking it would carry heat away from the body of the LEDs, and also for accurate holes for alignment and strenth. However now I see where the majority of the heat is going. Making a backing disc with such accurate lead holes sounds challenging. What about encapsulating the back area with something like silicone oil? If it was designed properly, a water (oil) tight chamber around the backside of the LED holder could be filled with oil, utilising conduction/convection to the aluminum disc or metal torch body.
Thanks for the input.
Chet
 
Joined
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Messages
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Location
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I don't know, I think that making a sealed liquid chamber would be harder than acurately placing the holes.
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I use predrilled PC boards. You could use one as a drill guide over the Aluminum disc. Or, draw out the details on paper and glue it on to the disc as a guide. Use heatshrink tubing on the positive leads to insulate them.

I think the biggest problem will be attaching the negative leads to the aluminum disc. I don't think you can't solder to aluminum.
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Soldering is out of the question if you ask me. Then there is the aluminum oxide problem- aluminum wiring in household wiring is famous for deteriorating and causing fires due to the oxide causing a high resistance, and thus heat. Better go with copper which is a better heat conductor anyway.
Chet
 

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