4 emitter mag mod - help me find circuitry

[copperfox]

I am building a C-cell mag with 2x AW "C" cells.
I plan to use four SSC emitters, but that is not set in stone. I could be persuaded to use three or maybe switch to Crees depending on ease of fitment into maglite head.

This is what I've figured out so far, tell me if it is correct:

Two Li-ion cells put out 8.4v fully charged and ~7.2 at cutoff.
SSC U-bin has a Vf of 3 to 3.25v
...so four SSC emitters have a Vf of of 12 to 13v.
Since my cells put out 8.4v at most, and I need at least 12v to power the emitters, I need a driver that increases voltage.

Here is where I need the help. I'm totally clueless when it comes to what circuitry I need. I've heard terms thrown around like "shark" and "downboy" and the like, but I'm more or less clueless. I would like multiple modes, but I don't have a preference as to the power output or number of modes. I would like the maximum mode to run each emitter at or about 1a. It would be awesome if I could drill and tap the body to install some kind of position switch or rheostat instead of having to use the stock switch to change modes. However, if it's cheaper, or lots less trouble, I will stick with the stock switch. Somebody please point me in the right direction.

Also, what would be the best heatsink for four SSCs into a C head? Also, after looking at other builds, it seems that 19mm or 20mm a good size for each reflector -- what are my options?

I have fine soldering skills, so I am confident that if somebody explains it to me I can do it. Thanks in advance.

copperfox

 

[Gunner12]

The Shark is a useful boost driver that is meant to drive multiple LEDs in series. Sounds like something you would want for this mod.

The downboy is a buck driver that takes the higher voltage of the source and lowers it to the right voltage for the LED.

The Seoul driven at 1 amp would have a Vf of around 3.6-3.7v.

Don't forget a heatsink.

Maybe this thread and this thread would help.

 

[Mirage_Man]

If you want multiple levels I would highly recommend the "Maxflex" from TaskLED. It would require the mod and use of the stock switch but the UI is very simple to use and change levels.

If you really want a pot to adjust the level then the Shark would be a good suggestion.

Lastly do a search for "quad" and or "Tri".

 

[LED Zeppelin]

Here is my build of a light you describe.

It is easier to use Crees, McR19XR, and MirageMan centering rings since the Crees can withstand the lateral loads of a reflector. The SSC dome can easily be sheared off, so you need to prevent the refector from touching the dome.

 

[CampingLED]

The reflectors that I can recommend can be found here. I received mine a few days ago and they are designed for Cree emitters. These are typically the ones that you find in the AA flashlights and have the same thread on the outside.

They are made of aluminium and you need to keep your soldering points on a star very small. A textured version is also available (possibly also designed for Cree emitters, but I cannot confirm it).

 

[copperfox]

Thanks for the replies gentlemen. Clearly I have a lot more to research before I commit to anything. It's funny how compared to a layperson I'm quite knowledgeable about LEDs and modern flashlights, but when it comes to this kind of modding I'm a total noob. I have some mechanical and electrical experience under my belt, but the most difficult flashlight related mod I've done so far is swap a luxeon for a SSC.

LED Zep I checked out your thread and your work looks top notch. Very nice.

What are the pros and cons of a bare Cree versus the emitter on a star? Is one easier to work with?

 

[LED Zeppelin]

What are the pros and cons of a bare Cree versus the emitter on a star? Is one easier to work with?

The star is much easier to solder to, but adds thickness and a larger footprint. Depending on the sink and reflectors, the thickness could cause the reflectors to protrude too far above the edge of the head creating a gap between the bezel and head when assembled.

The emitters need to be pre-tinned. Sometimes bench soldering is easier since when mounted on a sink, the sink sucks the heat away. Too much heat and you'll separate the silicone goo under the dome and get bubbles.

Also with emitters, you'll need to isolate the bottom contact strips. A common method is to clip the corners where there is a tiny visible via connecting the top and bottom pads. Or you can use some Kapton tape strips as a mechanical spacer, but this adds to the thickness of the epoxy.

If the reflectors sit below the edge of the head, you will need to use a 2.84 mm thick lens so the bezel O-ring can seat against the lens before the bezel bottoms out on the head since there is no pressure from the reflectors.

Ideally the reflectors will be against the lens, the lens tight against the O-ring, and the bezel nearly bottomed out on the head with minimal gap.