Cree Q5 -> SSC U-bin

[Fallingwater]

I have a flashlight with a single Cree Q5 LED which I'd like to Seoul-ify.
I unsoldered one of the wires going to the emitter and connected multimeters: voltage at maximum power is 3.65, current draw is about 950mA.

Would it be OK to do a straight emitter swap with this, or is there overdrive risk?

Thanks.

 

[KrisP]

It depends of the circuitry is voltage or current regulated. If it's current regulated, whatever LED you put there will receive 950mA. If it's voltage regulated, whatever LED you put there will receive 3.65V... This won't be the best for a LED with a low forward voltage.

You can put the Seoul in it's place and briefly turn it on to measure the current, if it measures under or around 1A, it should be fine.

 

[yellow]

there is no gain,
imho You worsen the light, but I dont like Seouls.

When swapping You have to isolate the slug of the Seoul, so that there is no short-circuit.
The slug is positive on Seouls, while most often the mounting plate is on negative ground.

 

[Bigsy]

I run a SSC at about 1.4a with a voltage regulated driver (+5v), I know people say not to go over 1a and frown on voltage regulation...thermal runaway blah blah blah... but I can't see any harm if its well sinked, well I have been running this light like this for months and there are no problems, simple as.

If your driver is voltage regulated then your it might drive the led a little harder than 950ma, not much more though as I can't see the vf of a SSC at ~1a being a lot lower than 3.65v.

IMO there is very much a gain if you like a smooth floody beam, if the light is well sinked I can't see an issue myself.

And just use some thermal epoxy to isolate the slug.

 

[Fallingwater]

Hmm. I don't have any thermal epoxy, just paste. Do I necessarily have to buy any or can I make do with something else? I'm trying to think about something that is 1) thin, 2) electrically not conductive, 3) thermally conductive and 4) generally available, but I can't come up with anything.

 

[Bigsy]

Best I can think is a small thin piece of paper soaked in thermal paste.

Still how are you going to keep the led centred?

 

[Al Combs]

You can make the equivalent of Arctic Alumina thermal epoxy by putting some 5 or 12 micron aluminum oxide powder in regular epoxy. Of course that might be as hard to come by as the real thing.

You can probably buy some from a local glass store. It's a fine grinding compound. You might be able to buy it as a lapping compound from the local hardware store. Sometimes they sell it as a powder that's not already suspended in oil.

 

[Al Combs]

I forgot to mention that aluminum oxide is non-conductive. If the particle size used is large enough, it will take into account irregularities in the emitter slug. You could conceivable epoxy an LED onto a bare aluminum heat sink with no worries of a short.

 

[Fallingwater]

Best I can think is a small thin piece of paper soaked in thermal paste.

Hmm. Not a bad idea.

Still how are you going to keep the led centred?

I was thinking of heatsinking/insulating the base, splatting the whole thing on the metal base of the flashlight, centering it by hand, cleaning the residue and applying two part epoxy to the LED's base once the correct position is achieved. How does this sound?

 

[yellow]

I stopped typing about Arctic, because everyone is sooo impressed, but in reality its just very expensive 2-component epoxy glue.
Normal heat transfer paste (the kind one uses to mount computer die) is way better: MUCH better thermal capabilities, cheaper, does not harden

So when using paste on the slug, You can place the led and check if it is centered, if not, move it a bit into the right direction, check again, ..., without any timeline when the Arctic were cured.
Then, when placed perfectly, use normal 2-way epoxy around the emitter to glue it in.
Cheaper and much better working than thermal glue.

for isolation, there is a "crazy way": do the same as above, but place 2 hair into the paste. Now there is no way the slug touches the sink, but still almost no distance between them.
Glue in around emitter with epoxy again. Till today works on any Seoul I have done.

 

[CampingLED]

Leave the Q5 in the flashlight. Reasons are:
- You may not gain any higher light output
- You may need to change the driver (unlikely though since most SSC and CREE drivers are compatible and current regulated)
- Chances are 90% that the current reflector is not compatible with the SSC

 

[Bigsy]

Leave the Q5 in the flashlight. Reasons are:
- You may not gain any higher light output
- You may need to change the driver (unlikely though since most SSC and CREE drivers are compatible and current regulated)
- Chances are 90% that the current reflector is not compatible with the SSC

- He probably realises this, I suspect the swap is about beam quality, not output. As well as a less ringy beam he could also have a nicer tint P4 he wants to use?
- As you say he won't.
- The current reflector will be absolutely fine as he is mounting the SSC without a base meaning die height will be roughly the same as the cree. In fact he may even want it a little unfocused for more flood.

To add...I'm liking yellows' hair idea a lot, think I'll give this ago myself next time instead of using thermal epoxy.

 

[Fallingwater]

Leave the Q5 in the flashlight. Reasons are:
- You may not gain any higher light output

Higher output is not my first priority.

- You may need to change the driver (unlikely though since most SSC and CREE drivers are compatible and current regulated)

As you say, unlikely.

- Chances are 90% that the current reflector is not compatible with the SSC

Actually it gives a far better beam with the SSC than with the Cree. See here.

Yellow: are you actually suggesting I use hair from my head? Did I get this right?

 

[dom]

Yellow: are you actually suggesting I use hair from my head? Did I get this right?

Yes -don't use dog hair as it is much thicker

EDIT This might be of interest
http://www.candlepowerforums.com/vb/showthread.php?t=175600

 

[mudman cj]

Thermal greases can have conductivities as high as 9.0 W/m*K as seen in this link that compares some common products. Sorry yellow, thermal epoxies are not necessarily worse than greases. Arctic Silver Thermal Epoxy is over 7.5 W/m*k for example, and therefore not far behind Arctic Silver III. The best I have yet seen is QMI5030 from Henkel corporation, which is actually an adhesive. Here is the data sheet showing its conductivity of 25 W/m*k.

 

[yellow]

I use hair from my arm, these are thinner than the ones on my head
(and since I am in lights and not in knives anymore, there are hair there)

 

[Fallingwater]

I'm giving a go to the hair method, but until I measure zero electrical conductance a part of me is thinking you're pulling my leg.

 

[darkzero]

I stopped typing about Arctic, because everyone is sooo impressed, but in reality its just very expensive 2-component epoxy glue.

:laughing: I've stopped using the epoxy a couple years ago. My tubes are so old one of them has dried up. Don't know why I still have them. :thinking:
I still use Artic Silver 5 grease though.

 

[Fallingwater]

The hair method worked hard to believe, but it worked thanks Yellow!

 

[yellow]

dont loose Your "haired" light to some Voodoo-guy