Mag 3D to Luxeon 3 mod

OK, I have the switch out of my Mag 3D, and I have wire, hotlips heatsink, and Luxeon 3watt emitter ready to install for direct drive. I have a piece of mica insulation to prevent electrical conductance between the emitter and the heatsink. But, does anyone know if the emitter base is negative or positive? Lumileds pdf simply says insulation is required because the base is not isolated.

I'll be checking this out, but if the base is negative, is there any reason that I cant't use it for the negative terminal? The body of the maglite is connected to the battery negative normally. I suppose I will need electrically conductive as well as thermally conductive heatsink paste.....Are there any other recommendations? -RussH

RussH,

DO NOT use the mica insulator, you will fry the Luxeon.

The slug is electrically neutral; but has static protection diodes between it and the leads. Artic Alumina or Artic Silver thermal epoxy is best for mounting the emitter to the heatsink.

Best to solder wires on the switch and run to the Luxeon, including the negative. Trying to use the heatsink for a connection can introduce all kinds of problems. Plus, it's supposed to be neutral....

OK, I'm definitely not planning to use the slug as an electrical connection. But I'm still confused. This is from DS45.pdf (page 2) from the Lumileds site:

Notes:
1. The anode side of the device is
denoted by a hole in the lead frame.
Electrical insulation between the case
and the board is required – slug of
device is not electrically neutral. Do not
electrically connect either the anode or
cathode to the slug.

Is my info out of date? Isn't this different from both the 1w & 5W, as I recall? I was planning to use the mica with heatsink compound Like I use on transistors (I know it adds some thermal resistance) Note that I am using the emitter, not the star. It appears that some kind of insulation is required...I don't think I can rely on keeping the hotlips electrically isolated from the body of the flashlight.

Russ, if you are using a white LV or LIII, go ahead and use Artic Silver to attach the emitter directly to the Hotlips. The slug is negative biased. You won't have any problems there. /ubbthreads/images/graemlins/smile.gif

Thanks, Howard, it's a white Lux 3watt. I've got some conductive epoxy (I'm not sure if it's Arctic silver) I wanted to test it outside of the flashlight, but it will be a little difficult since the switch goes into the bottom. I figure the LIII needs to be soldered after I reinstall the switch in order to keep my wires short. I'll glue the LED afterwards, too, just in case I cook it while soldering. I'm doing a D size first, then a C size after I test the first one....

The stars are easy, but this is the first hotlips/emitter I'm trying. I'll be testing my temp control soldering iron with a test piece of wire (18 awg on hand) to see what min. temp I can use for this. Hopefully I can post some results tomorrow. I'm not too concerned about frying one of these (I bought extra) but I like to have all of my ducks in a row before I start. It's more fun when I can just go thru the steps with minimum hassle. _RussH

I would epoxy the emitter first, before soldering wires. It's hard enough to keep the emitter centered while the epoxy sets, let alone keep it centered with wires pulling it in all directions.

Just be careful when you're soldering, pre-tin the leads (1 second max), and make sure to only apply the iron for 1 second. You shouldn't have any problem soldering with 1 second uses.

Ditto what evan said re ASing the emitter first before soldering. Much much easier to manage the entire process.

[ QUOTE ]
lambda said:
DO NOT use the mica insulator, you will fry the Luxeon.


[/ QUOTE ]

No mica? Uh-oh /ubbthreads/images/graemlins/help.gif I'm working on a mod myself and I just epoxied a mica sheet between my HotLips and LS. For my project I can't have the slug connected to ground or positive. Anyone know another way to safely isolate the LS slug?