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LED light unit failed

A couple of things to bear in mind if you replace the damaged/broken LEDs.

- whatever you go for, think about using some thermal adhesive to attach them to the heatsink. The most likely cause of failure was heat damage - and, assuming they were attached with thermal pads - these are the worst option for conducting heat.
- think about replacing a few more than just the broken ones. It's unlikely that you'll get an exact colour/brightness match to the existing LEDs and having just 2 of a different type will likely look a bit strange. If you want to, for example, mix in some warm whites to soften the output a bit - then you'll definitely want to change a few - I'd say at least 1 in 5 and maybe 1 in 3 - and spread them evenly.
- LED lenses are designed for a specific range of LEDs (or sometimes a couple). It's likely that they won't work as well with a different brand of LED - the focus/beam will be different and/or they will reflect less efficiently.

Cheers, Mark
 
sciencefiction said:
The earth wire, do I need to connect a separate earth wire to the earth-in that goes in the driver? And if I connect it via a bolt to the aluminium body, do I need to insulate the part of the bolt that will be on the outside in case I touch it?
Basically from the setup on the diagram above everything is connected by the earth wire that comes out of the driver and leads to the aluminium body.
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If you want to connect an earth wire, it should be bolted to the exposed aluminium anywhere you might touch it. However the LED driver outputs are isolated and low voltage thus you probably don't need an earth connection to the aluminium heatsinks. I would still put the earth to the LED driver though.
 
@ian_m . Thanks. The earth to the LED drivers has always been connected; well, at least since I got the new drivers and followed your instructions, because the old ones didn't have an earth input at all. I am so thick I hadn't even noticed :)

@mark Thanks Mark. The pre-existing setup has some black paste between the star and the aluminium. I am assuming its thermal adhesive. One of the led strips has been working for over 3 years with a few weeks break when the driver failed so the overall design isn't that bad, It's the quality of the components that is the problem .I am going to buy thermal adhesive for sure when I buy the leds. I know as much from fiddling with computer processors... Is there any specific type that is best?

OK. I'll look into buying lenses as well. I am going to try to get star leds with the same size and output as the old ones, just a reliable brand. Is 700mA, 3W leds, star shape all I am looking for or are there any other specific details I should be looking for? What about angle? I am seeing most are 120 degrees? Hopefully they won't look much different appearance but I can come to grips with a bit of a variance as it won't be noticed when they are on. The ones I currently have are 700mA 3W cool white star leds, 2cm in diameter. I need to "warm" the light output a little :)
The current setup has 15x3W leds on each of the strips. What would be the general recommendation if I want to mix in some colour in terms of adding blue/reds? Is it better if I change leds on each strip or perhaps leave one as it is with cool whites and add some colour to the other two strips?


I'll keep you guys informed ones I do it. It may not happen till June or so but I am definitely fixing them because it will be a waste considering I don't want to spend hundreds on new lights.
 
A while ago i came accross a thread on another forum where somebody complained about a prisma effect in his tank. He called it like there is a rainbow in my tank.. It was caused by the lenses he used in his led fixture.. :) I have no idea what the beamangle was or if this is typical for any led lens above water. Just a heads up before you buy something useless. :thumbup:
 
Thanks Mark. The pre-existing setup has some black paste between the star and the aluminium. I am assuming its thermal adhesive. One of the led strips has been working for over 3 years with a few weeks break when the driver failed so the overall design isn't that bad, It's the quality of the components that is the problem .I am going to buy thermal adhesive for sure when I buy the leds. I know as much from fiddling with computer processors... Is there any specific type that is best?

OK. I'll look into buying lenses as well. I am going to try to get star leds with the same size and output as the old ones, just a reliable brand. Is 700mA, 3W leds, star shape all I am looking for or are there any other specific details I should be looking for? What about angle? I am seeing most are 120 degrees? Hopefully they won't look much different appearance but I can come to grips with a bit of a variance as it won't be noticed when they are on. The ones I currently have are 700mA 3W cool white star leds, 2cm in diameter. I need to "warm" the light output a little :)
The current setup has 15x3W leds on each of the strips. What would be the general recommendation if I want to mix in some colour in terms of adding blue/reds? Is it better if I change leds on each strip or perhaps leave one as it is with cool whites and add some colour to the other two strips?
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To be honest, black paste sounds a little more like a heat pad that has degraded a little - especially if that is from one of the failed units.

For the replacement LEDs, you probably want to ignore the 3W bit. The wattage specified is normally the maximum rating for the units - for example, top end CREE XM-L leds are spec'd up to 10watts but most people run them at 3watts - it all depends on the current you give them. If you have any sort of power meter, you could check what your total consumption is currently - I doubt it will be 15x3x3 = 135 watts. As Ian said some time ago, that is a LOT of LED light. My gut feeling would be that they're running at 1w each for a total of about 45watts - though that's just a guess:)

So I suggest you focus on units that can accept the 700ma from your drivers - as you say on 20mm stars. Most will be 120degree spread - though it does vary a bit.

My preference would be to change the same number of leds on each strip - I'd be too worried about getting warm/cold spots (as in colour temperature) if it isn't an even spread.

regards, Mark
 
I see you have those star heatsinks.. :) Why not just drill 2 holes and screw on with some thermal paste.. :) With those epoxies, i guess you need a hammer and a screwdriver to nick them off again if it ever burnes out.. Taping a thread into aluminium aint so difficult, just put the tap in the cordless drill and it runs like going through butter. M3 or M4 thread is all you need. If one ever burns out again you're greatfull you did a bit extra work on it.

Ps, you would need only 1 machine tap.. Not those 3 piece sets of manual tap.
 
markk said:
As Ian said some time ago, that is a LOT of LED light. My gut feeling would be that they're running at 1w each for a total of about 45watts - though that's just a guess
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I think the leds are rated 3W for sure. I don't know what they are running at in practice but they burn holes in plants from 5cm distance. I had to keep them well above my emersed plants.

zozo said:
I see you have those star heatsinks.. :) Why not just drill 2 holes and screw on with some thermal paste.. :) With those epoxies, i guess you need a hammer and a screwdriver to nick them off again if it ever burnes out.. Taping a thread into aluminium aint so difficult, just put the tap in the cordless drill and it runs like going through butter. M3 or M4 thread is all you need. If one ever burns out again you're greatfull you did a bit extra work on it.

Ps, you would need only 1 machine tap.. Not those 3 piece sets of manual tap.
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Zozo, I've no idea what you mean by the above :) Isn't the heatsink the aluminium frame itself? How do I "screw on with thermal paste" ? I agree I don't want to stick on those stars permanently considering their fail rate.....There are holes on the aluminium on both sides of each star through which the cables are threaded. The cables are inside the aluminium frame.
 
Sorry science :) my bad, i meant the star pcb
LT-1721-1287658250.jpg

And drill 2 holes in the heatsink for each pcb for example at the LT side and opposite and screw them on. If you drill a 2,5 mm hole same widht as the holes in the pcb and tape some M3 tap in the holes or M4 what ever fits best. Then you can screw 'm on and off with little M3 or M4 screws and use thermal paste between pcb and heatsink.
Here is a chart for tap drill size. M3 = 2.5mm drill. M4 = 3.3 mm drill.. :) Most predrilled and taped heatsinks for highpower led i've seen had M3 thread.

If you have a cordless drill, they have a reverse, put the tap in the cordless dril and tape the thread in the hole the same like you drilled the hole. Once it is in deep enough, reverse to get the tap out again. Most cordless drills are stepless in speed, this means they go faster the deeper you push the button. Just go easy on the speed with the tap. Use the torc controll setting, if you go to deep you do not break the tap. :)

It's actualy very easy.. But that's maybe easy to say.. Dunno.. Sorry if i'm not explaining clear enough..

Here i found a video :) but the guy is using steel and larger diameter tap.. Aluminium and small diameter tap like M3 is much easier and quicker..
 
Welcome :) and succes.. Hope to see some nice results soon.. :thumbup: SOme red plants would be nice.. :woot:
 
Thanks Marcel. I won't start the project till June or July. So the thread will go into oblivion for another bit. But for me it's been a unique source of help that I could not get from searching the internet for months. I've no knowledge about that kind of stuff.

Thanks again everyone and Ian for persevering with me for so long :)
 
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