Dead centering a Cree XR-E, tower module too.

After viewing David's (CPF Anglepoise) lathe tailstock centering fixture for leds, I've had the thought of that neat fixture, in the back of my mind for quite some time now.

Anyway...The Cree has a perfect, built in centering device. The metal ring that the dome resides in is perfect for chucking in a normal drill chuck (use caution, lightly hand tighten only)

I use the weight of the tailstock to squish out the excess epoxy, just don't lock the tailstock to the bed...

I've had great results with this method, and if you have a batch to run, this makes quick work of the job...and no error...

I did have one XR-E star that I bought, knowing the emitter was off center (this was disclosed at the time of sale) and using this centering method, the fact that the emitter was off center, didn't make a difference. I just went ahead and epoxied it to the heatsink, and when the epoxy was hardened, I rechucked the whole assembly and turned the tiny bit off star overhang, equal with the diameter of the heatsink, emitter was dead centered, the star was off center...but it didn't make any difference.



I have more ideas on this same subject...

TB

Re: Dead centering a Cree XR-E

This is my other thought on the centering thing...Yes it's very possible, there is enough room for the wires, and it will fit the bore if the SFTH, after the corners are turned.

If your interested in this project, and want more info on DIY...reply to this thread.

A lux V version with adjustable focus...

That's 24 gage wire, 24 would be a difficult build with the XR-E...I'm just showing this module as food for thought...Even with 24 gage wire, soldered straight up, as shown...the fit to the SFTH bore is no problem. The solder joints are clean and bright silver, just shadow from the photo is making them look dark.

God bless lathes, eh

TB
Great idea. I also have found that the 'ring' is very well attached, strong and won't collapse when gripped in the chuck.

In my centralizing tool, I have found the powerfull spring to help in squeezing out excess adhesive and keeping a constant pressure in the critical 10 minutes till it sets up.

I have settled down to gluing my Crees with AA directly to a 7mm post that is sticking up 1/8th" from the base or whatever. Then I solder from the bottom to each ground down edge.Fiddly, time consuming when compared to a LuxIII, but works great.

I guess eventually everyone would like to see a CREE SFTH; I believe the output won't trample a Lux V (X-bin esp), since the latter is a 4-die after all, and I'm not sure what's the max Amps the Cree can be pushed. But runtime should be spectacular while still maintaining a LuxV similar output.

Not sure if the beam scatter pattern is focused well by the Turbohead though. Might end up poorly focused like some have reported on a mag (haven't seen any for myself though so I might be missing something )

TB, does the Cree led need to be raised to get the optimal focus?

thx,
ernest

vacuum3d said:

TB, does the Cree led need to be raised to get the optimal focus?

thx,
ernest

Click to expand...

I was planning to sacrifice one emitter to find optimal focus. I want to make a long post, epoxy the emitter on, turn the corners so it will fit the bore of the SFTH...then wire it up, and find the sweet spot.

The pedestal in the photo is a just a blank, the driver board cavity hasn't been bored, and the lead wire channels haven't been drilled.

TB

I have just ONE question about this mod. How is the heat removed from the die? There's a fair amount of gap between the turbohead and the module to facilitate removal and this air gap is a huge thermal resistance in the path from the die to the body. Not to mention the shock isolation itself presents another very large thermal resistance. While it's a cool concept, I don't think it's practical.










Where's Newbie when I need him :thinking:

CM said:

I have just ONE question about this mod. How is the heat removed from the die? There's a fair amount of gap between the turbohead and the module to facilitate removal and this air gap is a huge thermal resistance in the path from the die to the body. Not to mention the shock isolation itself presents another very large thermal resistance. While it's a cool concept, I don't think it's practical.










Where's Newbie when I need him :thinking:

Click to expand...

For a less the $10 led, and some fun experimenting...I really don't care if it's toast in 1 hour, 100 hours, or 100,000 hours.

Is there a difference with the Lux V, sitting on a TM pedestal, as far as heat removal is concerned?

TB

TranquillityBase said:

Click to expand...

I need a 6-Jaw chuck! :naughty:

TB ... heat removal in a Tower Set-Up is critical, IMHO, which is why I opted for a 700mA drice current in my LuxV module, and I am still not really comfortable with it.

Should you use it in the KT4 shock-isolated head I see real problems coming your way. I only use it in the KT1 and KT2, and as the TM is a tight fit, there should be some heat transfer going on. If it is enough on the long run ... I dunno.

I think the problem is worse with the LuxV.

bernie

Thx TB. Guess I'll wait for your findings before proceeding. I have an empty Tower Module waiting for this mod.

ernest

Bernie, my SFTH's are the KT1 version...If the heat is more of an issue with Lux V, then I think the XR-E will be fine. And if not...at least I gave it a shot.

TB

TranquillityBase said:

For a less the $10 led, and some fun experimenting...I really don't care if it's toast in 1 hour, 100 hours, or 100,000 hours.

Is there a difference with the Lux V, sitting on a TM pedestal, as far as heat removal is concerned?

TB

Click to expand...

Lux V is the worst (4W to 5W). With a Cree, you're still talking about two and a half watts of power which *has* to go somewhere. Don't get me wrong, I'm not knocking the "experiment" part of it. But in all the mods that are similar to this, no one seems to address the heat issue which is very critical in LED's since die temp directly affects the output. Carry on.

From my experiences in centering a Cree with a tailstock chuck, definitely don't tighten the chuck too much even though the metal ring is attached on the board quite well.

When the metal ring is dislodged, sometimes slices of air bubble are introduced into the "goo" under the emitter dome. I'm not sure the kind of effect it has on reflectorized Cree's, but in a no-reflector-pure-flood situation even the slightest bubble can be projected into the beam.

-YC

CM said:

Lux V is the worst (4W to 5W). With a Cree, you're still talking about two and a half watts of power which *has* to go somewhere. Don't get me wrong, I'm not knocking the "experiment" part of it. But in all the mods that are similar to this, no one seems to address the heat issue which is very critical in LED's since die temp directly affects the output. Carry on.

Click to expand...

As mentioned above, I believe if the module is a snug fit with the Turbohead, the heat transfer is adequate. Add some thermal paste on the pedestal for extra security. (Not sure if the shock isolated SFTH's are good for transferring heat)

My runtime test with the SFTH module seems to indicate a very consistent output, which in addition to the good regulation circuit, prob indicates little output loss due to heat.

https://www.candlepowerforums.com/posts/1225635&postcount=59

I've had another failed LuxV mod burn out in 10-20 secs due to improper heatsinking, so I guess the SFTH module is doing just fine since it has seen a total of about 3-4 hours use so far, with a couple of runtime tests.

CM said:

Lux V is the worst (4W to 5W). With a Cree, you're still talking about two and a half watts of power which *has* to go somewhere. Don't get me wrong, I'm not knocking the "experiment" part of it. But in all the mods that are similar to this, no one seems to address the heat issue which is very critical in LED's since die temp directly affects the output. Carry on.

Click to expand...

I'm flying by the seat of my pants, with most of this stuff...so I'm not even partially qualified to answer the heat problem.

My Lux V TM heats the entire KT1 head, I've turn it on for an extended period of time just to see if the heat would transfer to the head, and how long it would take, and it does warm up the entire KT1 head...I don't know if this has any value, or not.

TB

TranquillityBase said:

I'm flying by the seat of my pants, with most of this stuff...so I'm not even partially qualified to answer the heat problem.

My Lux V TM heats the entire KT1 head, I've turn it on for an extended period of time just to see if the heat would transfer to the head, and how long it would take, and it does warm up the entire KT1 head...I don't know if this has any value, or not.

TB

Click to expand...

Is the KT1 shock isolated? If it isn't then it's a better host for one of these. The shock isolation serves to isolate everything mechanical (including heat) One good test is to measure drop off of light like LEDcandle mentioned. If the output drops significantly, then there's a heat transfer problem. If on the other hand, the output drops less than 10%, then I would say that the heat sinking is *adequate*. Not optimum but adequate.

CM said:

Is the KT1 shock isolated? If it isn't then it's a better host for one of these. The shock isolation serves to isolate everything mechanical (including heat) One good test is to measure drop off of light like LEDcandle mentioned. If the output drops significantly, then there's a heat transfer problem. If on the other hand, the output drops less than 10%, then I would say that the heat sinking is *adequate*. Not optimum but adequate.

Click to expand...

No, just the regular KT1.

I'm a flashaholic that doesn't own a light meter...I guess it's about time I buy one...

I'm very curious to see what the XR-E can do in the SFTH, maybe it will suck...heat issues aside, maybe it will be excellent...

Don't give me s--- about not owning a light meter...

TB