First attempt with LED lighting

[lonesouth]

Here is my very poorly made first attempt at an LED housing. The parts are 2 x 3/4" copper end caps, 1 x cree XR-E R2 15943, 1 x 5 mode driver 06190, 1 x 3/4" electrical box plug, 1 x size M power connection.

I put the two caps together with JB Weld mixed with some CPU thermal compound I had laying around. I discovered that it is advisible to rough the caps before apply any adhesive for a stronger bond. The LED is held in place with the same mixture. Everything was rather difficult to drill through and I found I need more experience with the drill press and sharper drill bits. My soldering is fine, spent 2 years soldering circuits down to fine pitch at work, so that's not an issue. It would be good to have some more tips of varying sizes, some flux and better solder.

I did learn a lot in building this, and hope then next one turns out better. I do have some lexan for a cover, but am not going to waste it on this one. The next will be built from some aluminum tubing I had laying around. Hopefully it will have more surface area for cooling, cause this on gets HOT at 1000ma. Not too hot to hold, but hot enough for you to think, wow that's hot.

The output is plenty for my desired goal of replacing my 100w flood lights. I think 5 of these along each side of the house will be ample light. Another thing I like is that I can tune the flood by changing the depth of housing. I tried to get some outside beamshots, but was for not with my lack of camera skills. I hait waiting for the next batch from china, but it will give me time to think of more ways to spend money on lights!

here's the pics:

here's a pic of the multipurpose workbench. I figure if the CPF crowd is anything like every other forum I'm in, you guys love pictures...

 

[blasterman]

Gotta love those copper pipe fittings for ad-hoc heatsinks. Been doing this for awhile, and there's endless configurations you can come up with.

A friend of mine wants to do his landscaping along the same lines, and we've been troubleshooting some of the same things you've run across.

One thing I learned is it takes a pretty good size copper end cap to remove the heat from a Cree driven at even 350mA. At least a 1 1/2" size cap by itself, or a small cap connected to more fittings on the back for additional surface area.

Other ideas I came up: with are

-Spray painting the inside of the cap with metallic paint to increase reflectivity. Obviously doing this *before* mounting the emitter.

-Mounting the end cap onto a cut piece of pipe rather than end cap to end cap. The reason being is that copper end caps (big ones) are expensive, and the same surface area of raw 1" pipe (that you can cut yourself) is much, much cheaper.

I've also thought about using JB weld as an alternative to silver based epoxies because the later are very expensive for such a low metal content. However, I believe that JB Weld contains either Iron or Steel that in such a small quantity does't make much of a difference in terms of heat x-fer either. Depends on who you believe. Consequently, I'm going to try making my own semi-conductive epoxy by mixing it with some aluminum powder I have laying around.

Just one suggestion: the 1000mA you're running the Cree at will eventually shorten it's life. Better off using a lower driven MCE or P7. I've got a couple of the smaller Bridgelux arrays coming that I'm going to also test for potential yard lights.

 

[lonesouth]

one thought on the spray paint. I did notice that copper reflection gave a rather soothing glow in a sort of outer cone of light. It may be worth trying to polish the inside of the cap instead of painting it...just a thought. I'm going to try the next round with some aluminum square tubing I've got. After playing around last night, I also thought these would make some very nice landscape lights.

Last thought. The XR-E, driven at a spec of 700ma has a life expectancy of ~50,000 hours? So driving it at 1000ma would shorten that by how much?

Thanks for the advice!

 

[blasterman]

So driving it at 1000ma would shorten that by how much?

Not sure - depends on other variables such as how hot it's running. The flashlight geeks run stress tests on these kind of things. I've just found that beyond 600-700mA the extra heat doesn't seem to warrant the negligible extra light - IMHO.

 

[purduephotog]

one thought on the spray paint. I did notice that copper reflection gave a rather soothing glow in a sort of outer cone of light. It may be worth trying to polish the inside of the cap instead of painting it...just a thought. I'm going to try the next round with some aluminum square tubing I've got. After playing around last night, I also thought these would make some very nice landscape lights.

Last thought. The XR-E, driven at a spec of 700ma has a life expectancy of ~50,000 hours? So driving it at 1000ma would shorten that by how much?

Thanks for the advice!

I polished the inside of my wine corker (no jokes) with a standard drill and a couple of pieces of tape. You could probably make a polisher by using one of those spindle sanders that are compressible- or just some tape wrapped around the outside of the spindle / pipe.

I wonder if you could find a buffing wheel that fit inside tight.

That leaves the last piece- adhesion- and sealing it water tight.

Crees are advertised at 228lm/1A. I don't know what that does to the lifetime... but for short bursts sure- I'd take the extra 40 lumens any day

 

[lonesouth]

suppose I intentionally burn em faster so as to have a reason to buy better ones two years from now when they have burned out or degraded...even if I burned them 4 hours a day every day of the year, which isn't likely, it would take 7 years to burn 10,000 hours or 1/5th the expected life at 700ma . Planned obscelesence isn't always a bad thing..."but honey, the light is burned out and needs to be replaced..."

 

[blasterman]

Good point

Hey, I got those Bridgelux emitters today, and man, they are insane.

I got a 400 lumen neutral and warm-white for testing, and I plan on showing the neutral-white in a mock-up for my friend who is considering having me build him some nice yard lights. Compared to the neutral white Cree I showed him last this will blow him away.

My cool-white R2s are actually quite a bit brighter than the Bridgelux when viewed direct (the Cree has much greater surface brightness), but the Cree doesn't throw out near the total light.

If you haven't spent your spousal allowance yet you gotta get one of these things.

 

[purduephotog]

Good point

Hey, I got those Bridgelux emitters today, and man, they are insane.

I got a 400 lumen neutral and warm-white for testing, and I plan on showing the neutral-white in a mock-up for my friend who is considering having me build him some nice yard lights. Compared to the neutral white Cree I showed him last this will blow him away.

My cool-white R2s are actually quite a bit brighter than the Bridgelux when viewed direct (the Cree has much greater surface brightness), but the Cree doesn't throw out near the total light.

If you haven't spent your spousal allowance yet you gotta get one of these things.

As always, my favorite question: Driver? Mains?

 

[blasterman]

I don't have a dedicated LED power supply that can handle that current, so right now I'm just using a 12 volt computer PSU and 4ohms worth of power resistors. For final implementation I'm really not sure what to do at the moment.

Further update - I stress tested the warm-white Bridgelux with no heat sink, and I actually burned the solder off the connection lead in a fairly nasty puff of burning smoke. LED was so hot it scorched the wood floor it fell on. LED also continues to work fine, which shows how tough these things are.

Yeah....for outdoor lights...these things will be perfect. If you need a lot of lumens that is. Sorry...not trying to hijack this thread.

 

[lonesouth]

by no means, we are in the same vein of thought...fixed lighting and all that it entails! happy to have learned about the bridgelux, now if only we can find a flux capacitor to power these things...i think mcgizmo has one.

I will probably end up with some xitanium drivers for my lights, but not really sure which one to go with yet. I'd like to see one that can run 10 XR-E at 700ma - 1000ma. So that would be maybe their 24v-1400ma unit with two parallel strings of 5 series LEDS...

Maybe THIS one.

40w
1700ma / 2p = 850ma per string
24v / 3.5 = 6.8

so: 6 LEDs at 3.5 volts = 21 volts
21 volts at 1700ma= 37.5 watts

darnit, now i need to buy more leds!