Udate
 

This coming April will be the 2 year mark since I've put this fixture into service. I'm finally preparing a proper top for the thing. All the LEDs are still going strong but the 27 heatsink fans are becoming a nuisance. They are cheap & I suppose I should have expected the odd failure but it's starting to get old with 5 or 6 failures & many of them are getting a tad noisy. Time for a redesign in that regard.

Larger heatsinks that are supposed to provide adequate cooling of the 10 watt multi chip LEDs without a fan have started showing up on eBay so I ordered a batch of 10. They came in recently & I've redone the center rail of 9 LEDs with them. They come drilled/tapped complete with screws to mount the 10 watt multi-chips. Instead of using angle aluminum I opted for a piece of U-channel I had laying around from my old MH/T5HO Frankenfixture. Drilled a single hole in the back of each heatsink, tapped it & screw mounted with a blob of heatsink compound, making the U-channel an efficient contributor to the cooling process.

https://ojcrhq.dm1.livefilestore.com...01e.JPG?psid=1

Running for about a week now & so far so good. Vewy, vewy quiet! The U-channel gets quite warm but not hot enough to burn fingertips. I had to remount the SMD5050 strips used for supplemental lighting because they'd been attached to the aluminum angle of the original rail. No biggie, but they're a bit higher now, attached to the wood braces of the fixture frame. The new rail weighs only slightly more than the original.

For the cover, I've cut two arc-shaped end pieces out of the same material used for the frame & my idea is to span these with strips of wood, effectively hiding the mess of wiring. Spaces between the wood will allow warm air to vent and I plan to add a couple of larger fans to boost circulation. I have 20 more of the large heatsinks on order to replace the outer rails, so I'm thinking additional flow to keep things cooler will be required.

I've laid some thin pine slats left over from another project on to the end arcs, noting that they sag in the middle due to the 4 foot span. Might have to rethink that & go with very thin plywood that I can bend to shape over the end pieces. Will need to add slots or holes to ventilate. Or I could go with some corner molding, which might hold it's shape a bit better, but not sure I'd like the look of that. Whatever I decide, I'd like to keep it as lightweight as possible. If anyone has ideas, I'd be glad to hear them. I'd like to stick to wood as a material. A couple of coats of finish & the thing should look quite pleasing to the eye.

https://ojcrhq.dm2301.livefilestore....04e.JPG?psid=1

https://ojcrhq.dm2304.livefilestore....05e.JPG?psid=1

Do have suggestions but would love to come see your setup sometime Mike. I also liked those heatsinks so much I bought three myself today. I have 3 10w chips sitting doing nothing so I figure I'll do something with them now.

Hey Mike, can you just cut 2 matching arc shaped pieces of 1/2" ply or something and just stick them in 1/3 of the way from each end, effectively cutting the span of those strips to 16"?

My main display's DIY LED unit using 10w emitters has a big enough Al heatsink that it uses NO fans and stays barely warm to the touch. Should consider upping the heatsink size/mass to dissipate the heat.

Thanks for the suggestion. I have considered an additional support near the center of the fixture, but there's just too much stuff in the way, wiring, terminal strips etc.

I have no idea what an "Al heatsink" is or how many emitters you have attached to it, what your spacing is, so more details as to size, weight etc. would help. I'm trying to keep the weight of the fixture reasonable, so not too keen on adding excessive mass. This is the reason I went with the small heatsinks with individual fans in the outset. The fixture hangs by two anchors in the ceiling (I think one is in a stud, but the other is just in drywall), so I'd rather not take the chance on excessive weight causing my fixture to pull loose & fall. The new heatsinks I've used for the center rail seem to be doing the job without fans, so I'm fairly confident that modifying the remaining two rails with the same hardware with a couple of good quality fans to move some air through the fixture should be more than adequate.

More details on your fixture would be a great help. Do you have an update to your LED build thread?

Sure thing. My setup is pretty modest, but yeah, I'd be happy to let you have a look see some time. My schedule is pretty flexible, I'll shoot you my phone # by pm. I'm in the old part of town on Mission Hill, a few blocks southeast of the hospital. I've been planning an upgrade for years, room divider probably similar to what you've done, but not much progress due to other things in life keeping me busy & drawing on my finances.

Mike instead of a center brace, a half moon, maybe a quarter moon shape in the middle will clear all the wiring, terminal blocks etc.

Al is Aluminum. My lights use Aluminum bars connected into a heatsink. Dissipates heat well.

Small, light-weight heatsinks will have more trouble dissipating the heat from 10w emitters so you'll probably have to continue using fans.

Hmm, half moon, that's an idea. Thanks.