1000 Lumen 7pcs. XR-E LED Floodlight

Amonra · Nov 8, 2006

For a long time i have been trying to replace the very energy wasting 500W halogen floodlights i have lighting my showroom facade with an LED version but till now LED's were not up to it, until the XR-E arrived, and here are the results:

7 XR-E's AA'ed to a 10cm x 15cm x 1cm aluminium plate

close up Very Underexposed

close up Still Very Underexposed

Actual ( this is a small room )

I have them connected in series to a 24V wallwart type power supply having a max of 1.5A.
So when cool the LED's were getting 3.5V @ 700mA each but after an hour they are getting 3.33V @ 1.05A each. the plate did get hot at 64 deg Celcius after an hour so that might be the culprit but im not complaining as there was an increase in the output

so according to the Cree data sheet and Newbie's study i should be getting 1260 Lumens @ 24.5W but im loosing about 20% due to the junction temp being a bit high so now it should be about 1000 Lumens !!

I'm gonna put this monster inside the housing of a halogen floodlight which will not help with the heat so i have to add some heatsinking and find a way to transfer the heat to the floodlight housing.

This will not directly replace a 500W Halogen floodlight in terms of output but it will be enough light for me as i will be using two of these, plus i will be saving $25 a month in electricity bills.

Thanks for looking.

BentHeadTX · Nov 8, 2006

Amazing flood light and it shows that LEDs have finally jumped high enough in efficiency to become very competitive. Flourescent lights really bite with their flickering, hazardous contents, delicate nature and lower life span than the Crees.

I think I'll build a flood light for a friend of mine that can't stand the 50Hz flicker at work. Now to find that one place online that makes giant heat sinks and run 8 of them at 24V for around 350mA/80 lumens each according to Newbie's charts. 640 lumens will make a great, non-flickering light to make him happy.

It is winter, the XR-E mods are rolling as the weather goes to dookie. Kind of nice how that all fit together. Thanks for your efforts.

Amonra · Nov 8, 2006

BentHeadTX said:
It is winter, the XR-E mods are rolling as the weather goes to dookie. Kind of nice how that all fit together. Thanks for your efforts.

if it gets cold and dark you can always strap this thing to your chest - light up and get warm.

if youre running them @ 350mA i guess a HS similar to the one i used should be enough as it did take an hour to get that hot @ 1.05A.

Christexan · Nov 8, 2006

Just a thought, depending on your housing, you've got plenty of volts and milliamps to spare for a couple of small fans to circulate cold air. Luxeon testing showed that even a flat plate is a fine heatsink with a modest airflow over it, 2 80mm fans blowing/out of the housing (or just over the open plate as pictured), would be 5V/.5A each (in series 10V, .5A)... no stress at all to your wallwart really, but would probably keep the temp way down over what you are seeing.
Also, paint (or much better choice, anodize) the plate black (if painted, scrub the paint off at the LED/plate interface for best heat transfer)... a black plate will radiate heat a lot faster than a silver one will. Just paint it as thinly as possible to minimize the paint material insulation effect.
Option C, buy/scrounge a few modest heatsinks (not hard to find, all old computers from the past 10 years have at least one or two)... and mount those (drill holes and do a metal/metal join, not AA, with as thin a layer of thermal grease between them as possible)... near the LED units (space out however works best)... mouser.com has a wide selection of heatsinks for 10s of cents, 8 or 10 black anodized pentium heatsinks would probably dump a LOT of the heat off that plate with minimal thickness increase (and if used on both sides of the plate, even better)....
Combine this, and all told, a couple of 80mm fans (or even smaller 60mm or whatever will fit), and some black heatsinks well-mounted, might run you $5-$10, but dramatically improve the heat transfer issue.
Heck, for real cheap and simple, just pickup some L-bar aluminum at the hardware store and screw down a few pieces (thermally greased) in a pattern across that plate to add "fins" to it, and you'd see a big improvement
Anyhow, would love to see more beamshots of that, looks great!

tebore · Nov 8, 2006

Christexan said:
Just a thought, depending on your housing, you've got plenty of volts and milliamps to spare for a couple of small fans to circulate cold air. Luxeon testing showed that even a flat plate is a fine heatsink with a modest airflow over it, 2 80mm fans blowing/out of the housing (or just over the open plate as pictured), would be 5V/.5A each (in series 10V, .5A)... no stress at all to your wallwart really, but would probably keep the temp way down over what you are seeing.
Also, paint (or much better choice, anodize) the plate black (if painted, scrub the paint off at the LED/plate interface for best heat transfer)... a black plate will radiate heat a lot faster than a silver one will. Just paint it as thinly as possible to minimize the paint material insulation effect.
Option C, buy/scrounge a few modest heatsinks (not hard to find, all old computers from the past 10 years have at least one or two)... and mount those (drill holes and do a metal/metal join, not AA, with as thin a layer of thermal grease between them as possible)... near the LED units (space out however works best)... mouser.com has a wide selection of heatsinks for 10s of cents, 8 or 10 black anodized pentium heatsinks would probably dump a LOT of the heat off that plate with minimal thickness increase (and if used on both sides of the plate, even better)....
Combine this, and all told, a couple of 80mm fans (or even smaller 60mm or whatever will fit), and some black heatsinks well-mounted, might run you $5-$10, but dramatically improve the heat transfer issue.
Heck, for real cheap and simple, just pickup some L-bar aluminum at the hardware store and screw down a few pieces (thermally greased) in a pattern across that plate to add "fins" to it, and you'd see a big improvement
Anyhow, would love to see more beamshots of that, looks great!

There's 0 proof that a dark surface will make a better heatsink that a plain aluminium surface. A dark surface can absorb more light energy. There's no proof what so ever that a dark surface can radiate heat better.

If he wanted a dark surface paint should NOT be used as it hinders heat transfer greatly. Anodizing is a better choice but again it hinders.

Handlobraesing · Nov 8, 2006

tebore said:
There's 0 proof that a dark surface will make a better heatsink that a plain aluminium surface. A dark surface can absorb more light energy. There's no proof what so ever that a dark surface can radiate heat better.

If he wanted a dark surface paint should NOT be used as it hinders heat transfer greatly. Anodizing is a better choice but again it hinders.

Dark surface can radiate heat MUCH readily. Don't believe me? Heatup a frying pan with blank interior and bare aluminum bottom. Now, bring it close to you with the inside facing you. Do the same with outside facing you. MUCH different.

Handlobraesing · Nov 8, 2006

Amonra said:
so according to the Cree data sheet and Newbie's study i should be getting 1260 Lumens @ 24.5W but im loosing about 20% due to the junction temp being a bit high so now it should be about 1000 Lumens !!

These linear dropper wallwarts are quite inefficient. So, lets see you got 1,000 lumen to 24.5W on DC, then 24.5/70% efficiency = 35W input, negating loss on limiting resistors on output side.

This brings you down to 35lumens per watt.

I have here, a pair of 6500K 26W spiral T3 CFL rated at 1600 lumens and these were $6.50 USD at Wal-Mart. This yields 61.5 lumens per AC outlet watt. Since you're making a flood light, I think CFL is a much much feasible alternative.

Two of these would put out 3200 lumens for 52W (plug power)

tebore · Nov 8, 2006

Handlobraesing said:
Dark surface can radiate heat MUCH readily. Don't believe me? Heatup a frying pan with blank interior and bare aluminum bottom. Now, bring it close to you with the inside facing you. Do the same with outside facing you. MUCH different.

Again no proof. That's a not even a scientific test. You're telling me feel fire. It's warm it has to work. Get me some numbers. Why don't you go do an experiment? Take 2 identical pieces of metal. Leave one bare, the second one you anodize black. Heat them using the same kind of heating system for the same amount of time and let them air cool in the same conditions and keep checking the temps. They will cool at almost the same rate(given the Anodizing coating is not too thick and is doesn't change the co-efficent of the metal).

I'm an Overclocker and we've been throught this in the search for the best cooling for CPUs. Any sort of coating on a heatsink only hinders heat transfer. The test I described above was conducted a few years ago. When Athlons were hitting 100watts and Aluminum heatsinks have been swamped with heat.

Handlobraesing · Nov 8, 2006

tebore said:
Again no proof. That's a not even a scientific test. You're telling me feel fire. It's warm it has to work. Get me some numbers. Why don't you go do an experiment? Take 2 identical pieces of metal. Leave one bare, the second one you anodize black. Heat them using the same kind of heating system for the same amount of time and let them air cool in the same conditions and keep checking the temps. They will cool at almost the same rate(given the Anodizing coating is not too thick and is doesn't change the co-efficent of the metal).

The color has no bearing on conductive heat transfer and CPU heatsink doesn't rely on radiant heat. Color does affect radiant heat.

Go buy one of this and you'll be convinced.
http://www.ap.stmarys.ca/demos/content/thermodynamics/radiometer/radiometer.html

Have you owned a glass thermos? the wall is silver plated much like a mirror. No, it's not silvered to make it look pretty.

I'm an Overclocker and we've been throught this in the search for the best cooling for CPUs. Any sort of coating on a heatsink only hinders heat transfer. The test I described above was conducted a few years ago. When Athlons were hitting 100watts and Aluminum heatsinks have been swamped with heat.

Obviously, coating is going to hinder performance in fluid cooling(be it air, Freon, water, etc)

tebore · Nov 8, 2006

OK that took a while damn "Server busy" msg

Anyway. You're confused by how dark materials can absorb light and allow it to transform in to heat better.

This theory is useless in a heatsink application. Because:

1. It won't make the heatsink radiate the heat any "faster"
2. We're not even talking about IR here because the LED is directly connected and it's not blasting much light towards it. (You didn't mention IR but I figure I'd CMA)
3. The point of a heatsink is to remove heat not get heated up. Which is where a dark coating would help.

Point is a making a heatsink dark is USELESS.

How is a CPU heatsink not dependant on Radiant heat? Heatsinks do nothing but create a larger surface area to radiate heat. As long as something makes heat, a heatsink will radiate it from the source.

Handlobraesing · Nov 8, 2006

tebore said:
How is a CPU heatsink not dependant on Radiant heat? Heatsinks do nothing but create a larger surface area to radiate heat. As long as something makes heat, a heatsink will radiate it from the source.

because the temperature difference between air and CPU heatsink isn't great enough to have much of a radiant emission. Most of heat transfer is directly from metal to air. Radiant heat doesn't need any medium

Morelite · Nov 8, 2006

Handlobraesing said:
Dark surface can radiate heat MUCH readily. Don't believe me? Heatup a frying pan with blank interior and bare aluminum bottom. Now, bring it close to you with the inside facing you. Do the same with outside facing you. MUCH different.

Darker surfaces will absorb more solar heat than an lighter colored surface, That is alot different than radiating heat.

Try your pan with the colors reversed, you'll still find that the inside feels like it is radiating more heat, it is the shape of the pan that causes that effect.

tebore · Nov 8, 2006

Handlobraesing said:
because the temperature difference between air and CPU heatsink isn't great enough to have much of a radiant emission. Most of heat transfer is directly from metal to air. Radiant heat doesn't need any medium

Please expand on your statement.

^^Thank god (morelite) finally someone who has more than a Grade school education.

Handlobraesing · Nov 8, 2006

tebore said:
Please expand on your statement.

^^Thank god (morelite) finally someone who has more than a Grade school education.

http://www.bedford.k12.ny.us/flhs/science/stevek/DLESEworkshop/inquiry_dlese.doc

Get two white coffee mugs and paint one black and fill both with boiling hot water and place both on styrofoam (to minimize conduction loss).

Cover both with a styrofoam lid. check temperatures of both like 10 minutes later. Come back and report back the result.

tebore · Nov 8, 2006

Handlobraesing said:
http://www.bedford.k12.ny.us/flhs/science/stevek/DLESEworkshop/inquiry_dlese.doc

Get two white coffee mugs and paint one black and fill both with boiling hot water and place both on styrofoam (to minimize conduction loss).

Cover both with a styrofoam lid. check temperatures of both like 10 minutes later. Come back and report back the result.

Good link to a highschool experiment and if did it you'll know the answer to it is dark colors DON'T help in the radiation of heat.

The coffee mug experiment is again going to fail.

You're gonna have to google harder to find something concrete.

MAN I'M GETTING PLENTY FRUSTRATED AT THAT DAMN " SERVER BUSY" msg.

Luff · Nov 8, 2006

Let me whip out some ancient concepts. Granted, it's been 30 years since I last sat in physics and thermodynamics classrooms, but heck, the cobwebs aren't that thick yet (but getting there).

This isn't about collecting heat from an external source (solar, etc.) ... it's about moving heat from a metal plate to a medium to cool the plate down.

As I recall, bare metal's ability to transfer heat to a medium (air, water, chocolate, whatever) is directly proportional to the surface area exposed to the medium. That's all there is to it.

Keeping it simple, the reason CPU heatsinks have more fins is because those fins increase the surface area exposed to the medium.

Etching a metal surface (anodizing) creates a porous surface, which can increase surface area (although by a negligible amount) ... but then you get into complexity determining how well the very oxides anodizing creates interface with the medium. Most oxides don't conduct heat as well as bare, clean metal.

Moving air over a heat sink strips away the boundary layer caused by surface tension ... which exposes more surface area to the medium ... which cools the metal.

Common paint deters heat transfer. Not just because it is an insulator, but because it reduces the surface area of the metal exposed to the medium.

But then, maybe it's all just voodoo magic after all.

jur · Nov 8, 2006

http://en.wikipedia.org/wiki/Emissivity

The amount of heat lost through radiation is neglible compared to convection at temperatures where LEDs still operate. So a black heatsink is irrelevant for still working electronics.

Any colour heatsink except shiny will have very similar emissivity to pure black, over 0.9.

chesterqw · Nov 8, 2006

yeap, black surface radiates heat and absorb heat better then white or sliver-ish surfaces.

but if black surface is glossy, it will not absorb that well but will still radiate heat better then the white and silver-ish

Kevin Tan · Nov 9, 2006

question is whats the percentage for black against white? How much surface area are the difference?

NickBose · Nov 9, 2006

Amonra: where did you buy the XR-E LEDs?
Can you post some more pictures of your light (unlit)?

1000 Lumen 7pcs. XR-E LED Floodlight

Enlightened

Flashlight Enthusiast

Enlightened

Enlightened

Flashlight Enthusiast

Banned

Banned

Flashlight Enthusiast

Banned

Flashlight Enthusiast

Banned

Flashlight Enthusiast

Flashlight Enthusiast

Banned

Flashlight Enthusiast

Enlightened

Newly Enlightened

Flashlight Enthusiast

Enlightened

Enlightened

Similar threads