Renewable Energy Questions/Discussion > Renewable Energy Q&A

Using High Power LEDs to Make Lights

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WooferHound:

--- Quote from: Solarnewbee on November 19, 2018, 11:55:38 am ---Hey Woof!

I have installed and repaired many outdoor 100w led floodlights of the Chinese persuasion and they use the case as a heat sink and use thermal paste under the led and screw it down. The led’s are the same like the 20w you show in the pic. I have used a thermal glue to attach waterproof Dallas temp sensors to my inverter and find it works quite well. I just bed the sensor in a glob of it and masking taped it in place for 24 hours. Not as fast as epoxy but I feel like it conducts heat better. Of course the fixtures I installed had a flaw in that the case had minimal fins on the back and the entire surface area was only 10”X10”. This may be why they failed so often or power surges lightning. I did install a a high quality surge protector on the parking lot lighting system and failures have slowed.

I wonder if you were to epoxy a 100w led to a heat sink that it may begin to melt the epoxy? There are screw holes so maybe consider drilling holes. I designed and built a dump load for my windmill and drilled holes in the heat sink, thermal paste under the resisters and small screws.

Like your projects. Keep on keeping on bud!

SN

--- End quote ---

Those 100w LEDs get scary hot. We have some store-bought LED floodlights in our theater that we use as worklights. Last week I looked at them closely and there were only small ripples on the back for a heatsink. I placed my hand on the back and it was burning hot. I don't see how these can last very long working at a temperature that high. Those high power LED modules that hook directly to the 120vac mains, Flash hugely at 120hz, I would use them outdoors but would never work under them. I have seen a lot of YouTube videos about Construction and Teardown of powerful LED fixtures and I always feel that they don't pay enough attention to the heat.

I have given a lot of thought to the possibility of the Epoxy Glue melting, but I have decided to only use LEDs that are only 10 watts or less because they all work well with 12 volt power using Buck Converters to control the current. The heat is very easy to manage using these LEDs and if I need more light I'll just use multiple  pieces until I get what I need. I have tried a 10w LED on a substantial heatsink before and it still got too hot to hold onto but the glue seemed to be OK. I have a small fan that I will add to it later to make it usable.

Here is a small 10w fixture that I made yesterday afternoon. The LED is glued to a CPU cooler. The fan has an 82ohm resister in series to the 12v side of the buck converter to slow it down and keep it quiet. Then it is all glued to a PVC ring to help control the light and will give me a way to mount & aim it later.



I ran it for a coupla hours and the heatsink stays cool to the touch, not warm at all. The backplate on the LED had a hint of warmness, The electrical connections were warm, but the LED case was too hot to touch in a couple of areas. I was very satisfied with the cooling.
These LEDs put out an amazing amount of light using only 10 watts of electricity, 10 volts at 1 amp. I think they were rated at 1150 lumens.

rossw:
I wonder how some of these high-power LEDs would go with NO heatsink, stuck between two sheets of glass with a decent circulation of some of these "engineered fluids" they use for immersion cooling of electronic components (read: super high density datacentre computing stacks).

In effect, liquid-cooling and being able to make them very small and quite importantly, silent and cool...

solarnewbee:
Hi Ross!

How are ya? I’ve seen guys submerging desktop computers in mineral oil and the Fans actually kept all the components quite cool well under oil. The temps were monitored using an app in windows. They did have to add external cooling pump and cooling heat sink as the tank heated up. Then the aquarium started leaking and that was the end of that. Maybe a frame with double pane glass like you say and a cpu cooler system using mineral oil might work. Hmm wonder.

SN

Pete:
I have used 12 volt LED's for years now as home lighting. The main problem I have found is that the capacitors in the converter circuits die. Mostly in the dicroic lamps. It seems that sending all the heat upwards to where the electronics are is not such a great idea.
It also seems that electrolytic capacitors are not always what they used to be. Some of the capacitors I have come across coming out of China are only half the weight of older better known products.
Oil cooling has been used in power transformers for many years, the tubes on the outside of the tanks are there for convection cooling.
keep having fun Woofer
Pete

rossw:

--- Quote from: Solarnewbee on November 22, 2018, 11:18:07 am ---I’ve seen guys submerging desktop computers in mineral oil and the Fans actually kept all the components quite cool well under oil. The temps were monitored using an app in windows. They did have to add external cooling pump and cooling heat sink as the tank heated up. Then the aquarium started leaking and that was the end of that. Maybe a frame with double pane glass like you say and a cpu cooler system using mineral oil might work. Hmm wonder.

--- End quote ---

Not oil. Certainly not oil. It does a nice job cooling, but it has more downsides than up.

Google Novec, or Novec 1230. Your components come out of Novec clean and dry.

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