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LED lighting fail
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Nick
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LED lighting fail

I have been working on an idea to replace the regular CFL bulbs in some light fittings with LEDs. The regular bulbs are quite dim and throw a very ugly light pattern on the walls. The idea is to make a large emitter panel that throws an even light that is twice as bright as the CFL. I just finished this:



The panel is 250 x 234 mm and has 150 LEDs. The dark vertical stripes on the edge of the plate are pieces of Kapton tape to insulate the cut ends of the LED strips.

The huge fail is that the strips are already pulling off the aluminium plate, even before I powered the LEDs up Evil or Very Mad. The strips are supposed to have quality 3M adhesive but in places I can see the tape coming off the back of the PCB as well as the aluminium.

To fix this, I can think of two options: buy some *real* 3M VHB tape and re-stick all the strips. The second option is to cut a matching rectangle of 3 mm clear plastic and screw it down over the LEDs to clamp them in place. What do you think, is there a better solution?

Post Wed Feb 05, 2014 8:20 pm 
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Jaemus
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probably the first option, they do generate a fair bit of heat that you probably want not to insulate with plastic clamped over them
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Post Wed Feb 05, 2014 8:31 pm 
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Nick
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Heat is definitely a worry; the ali plate is there to be a large heatsink for the LEDs. If I add thicker VHB tape, that might be just as bad as as covering the LEDs with a sheet of plastic. If I wire up the strips and then cover half of them with plastic, the thermal camera will quickly show if there is a problem. Thanks for giving me some new ideas!

Post Wed Feb 05, 2014 9:07 pm 
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kato



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Would Arctic Silver, or some of the heat sink adhesives or adhesive tape from RS be appropriate?

Post Thu Feb 06, 2014 6:38 am 
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Nick
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I will look into that, it depends on how expensive the products are. The individual LEDs are not that powerful and don't need to be treated like 5 watt Cree mega LEDs. I have another 3 panels to build so keeping costs down is important.

Update: I just ran a heat test with half a strip covered and there was absolutely no temperature difference between the covered & uncovered LEDs, so I will go with the no-cost option of scrap acrylic sheet covers.

Post Thu Feb 06, 2014 8:13 am 
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Knightrous
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I had similar issues with the LED strips in Farmboy coming off the polycarb, so I just drilled some holes either side of the strips and secured them with a ziptie.
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Post Thu Feb 06, 2014 10:28 am 
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Nick
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The finished panel is working well, this is how it looks:



The white hotspots on the LED strips at about 38 degrees and just happen to be where the strips have unstuck from the aluminium plate. Its using 22 watts of power and if the spec sheet is to be believed, it is putting out 1,425 lumens. That's pretty good, considering that an off-the-shelf Cree 10W LED bulb only puts out around 560 lumens.

Post Thu Feb 06, 2014 3:16 pm 
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miles&Jules
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looks pretty damn cool Nick….we bought a fancy led filming light kit and this one looks just as bright.

Amazing stuff them leds. Very Happy

Now... next version I want to see warm led strips next to these with a mixer to mix daylight colour between them ...and then a dimmer….I know you can do it . Very Happy Very Happy
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Post Thu Feb 06, 2014 4:48 pm 
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Knightrous
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quote:
Originally posted by miles&Jules:
Now... next version I want to see warm led strips next to these with a mixer to mix daylight colour between them ...and then a dimmer….I know you can do it . Very Happy Very Happy


Why not just go RGB LED strips and go any colour you want Very Happy
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Post Thu Feb 06, 2014 4:49 pm 
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Nick
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Don't tempt me! Laughing

Its difficult to get a good white by mixing RGB LEDs and RGB strips are relatively expensive for the amount of lumens you get out of them, but for mood lighting in a lounge, I would definitely think about it, particularly the addressable strips.

This has gotten me wondering why consumer LED lights are so expensive; I definitely didn't get the best deal on this LED strip and these panels only cost me $34 each while emitting more light than two regular LED bulbs costing at least $60. Those pro photographic LED lights are even more expensive per lumen, although you do get extra features.

@ Miles: have you seen these cheapo lights on-line:



http://www.amazon.com/gp/product/B004TJ6JH6/ref=oh_details_o02_s00_i01?ie=UTF8&psc=1

I bought a pair for macro photography and for $28.95 USD, they work really well! They would be plenty bright enough for the sort of video you are doing and appear to be very hackable; I am looking at adding barn-doors and other attachments.

Post Thu Feb 06, 2014 5:59 pm 
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miles&Jules
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yeah the possibilities are amazing….and because they don't use much power you could run them off a big ass lipo and it would last for ages. We bought a couple of little ones that go on our cameras to.

I like the idea of building your own custom ones though. Very Happy


yep those ones look like one of the ones we bought ..but of cause we bought em at a real shop they were at least $100 each... Evil or Very Mad
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Post Thu Feb 06, 2014 9:13 pm 
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DumHed
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I ordered one of these to test:

http://www.ebay.com.au/itm/DC-30-34V-9000-10000LM-High-Power-Warm-White-100W-LED-light-Lamp-SMD-Chip-DIY/360811317782?rt=nc&_trksid=p2047675.m1851&_trkparms=aid%3D222002%26algo%3DSIC.FIT%26ao%3D1%26asc%3D261%26meid%3D4822786964162518047%26pid%3D100005%26prg%3D1088%26rk%3D3%26rkt%3D5%26sd%3D400623150865%26

I have a couple of the 50W ones and they are pretty impressive!
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Post Fri Feb 14, 2014 3:31 pm 
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Nick
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That's an insanely low price! now we just need to find a constant current PSU to drive it for $9 and we can all convert our workshops to LED lighting.

Post Fri Feb 14, 2014 4:06 pm 
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dyrodium
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haha wow you think it's a normal SMD part then you see the photo with it on the hand. Shocked Nuts!
Also I like uses:

Fish tank lighting

Remote Controll toy

Maybe if you want your fish tank or RC heli to look like it's birthing a new star.
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Post Fri Feb 14, 2014 4:23 pm 
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Valen
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if you're going to do it
http://www.ebay.com.au/itm/100W-RGB-LED-Light-Bulb-Lamp-Chips-Red-Green-Blue-DIY-1050LM-2250LM-450LM-/181308731517?pt=AU_B_I_Electrical_Test_Equipment&hash=item2a36d7b07d&_uhb=1

might as well go all the way.

Those could make for some epic room lights, presuming they don't have a chinese lifespan.
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Post Fri Feb 14, 2014 7:09 pm 
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