Brightest LEDs on the planet?

[Um...Me123]

What has everyone found for the brightest LEDs out there?
For white I know PhlatLight has one pushing 6000lm and LedEngin will have a 40 watt RGB approaching 2000lm.  Anyone know of brighter ones?

 

[audioguru2]

You can buy extremely bright LEDs on E-Bay.
The Chinese discovered that a dim old LED chip is extremely bright when its case focusses the light in a very small angle. But then it cannot be seen if it is not pointing directly at you.

Light bulbs shine all around. Good LEDs shine almost all around. Some Good LEDs are fairly bright.

 

[Um...Me123]

I did notice that Phlatlight had a RGBW (perfect for my app) that is brighter than the 40W but its $200.  yaouch

My idea is to use these on my car as fog lights.  Already have regular halogen ones so it would replace the bulb only, using the stock reflector.  I would be able to precisely color match my HIDs and have a bazillion other options to fit whatever situation.  My only worry is cooling.  The brightest led I've worked with is a 1watt so I'm not sure how to approach it.  All application notes have all these equations and junk but I need to see practical examples.   My space and availability to mount and secure a giant heat sink is limited so I was thinking of using a peltier and maybe a small fan on the hot sink but I have zero experience with those as well.  Tinkering is out of the question because of part cost so planning is vital.  Has anyone ever worked with these super leds?  If anyone knows of links to projects (videos/pictures/instructs) using 15+ watt leds that shows the cooling process that would be great.  
I'm still in the "is this possible?" stage of this one.
Thanks

 

[Hero999]

In my opinion a Peltier cooler is not an option due to the excessive power required.

Rather than a fan, is it possible to rely on the fact that the car is moving through the aire anyway?

I imagine that using the car's chassis as a heatsink is probably the best option. You could probably dump quite a lot of heat into the chassis and hardly get any temperature rise at all.

How are you gong to power the LED?

I wouldn't recommend a resistor due to the excessive power dissipation. High power LEDs also often have quite a high voltage drop because they're actually composed of many smaller LEDs connected in series and parallel. For both reasons you really need a switched mode constant current power supply.

As far as monitoring the temperature is concerned, I've noticed that the forward voltage drops with temperature which might in itself help guard against overheating if a constant current supply is used, if not you could cut the power if the voltage drop is too low.

Usable lamp life is something you need to consider because LEDs get dimmer with age. I'd recommend underrating the LED slightly because not only does it make LEDs last longer, they're also more efficient at lower currents: running at 80% of the current rating does not normally reduce the brightness to 80% of the full rating, it's normally closer to 90%, see the datasheet to be sure.

 

[Um...Me123]

Some very good things to think about on the last posts.  Thanks   My reasoning for the peltier is because I don't think a fan would be reliable enough because of dust/rain and I know peltier use a ton of power but I don't see too much of a problem there as long as the car is running, right?  Some of the leds have a thermistor built right in so that would help and I could PWM the peltiers accordingly to save power as well.   I just have no general idea of how big the heat sink needs to be so my vision is that heat sink only is out of the question.  The fogs are mounted in what would be better called the bumper cover so there isn't much to work with except plastic but it's been a few months since I had it apart.

Found something very helpful: "http://www.luminus.com/stuff/contentmgr/files/0/0179ad38a075ca3c31f708ed19392fa3/miscdocs/960031_rev_a_dk_414n_and_dk314n_development_kit_manual.pdf
User manual for the dev kit for the RGBW led...it can approach 120W!!!  $850 though
Sink = 82 mm x 65 mm x 38mm plus fan

 

[Hero999]

Without seeing the fitting it's difficult to say.

If one of the reasons for using LEDs is for the efficiency then you're defeating it with a Peltier cooler.

CPUs normally use around 100W so a CPU heatsink plus a decent fan should do the job, even then you could use a thermostatic control so the fan doesn't need to run continuously.

I think you should do some experiments before you decide for sure.

 

[Um...Me123]

Does anyone know of white leds at 8000k or are they all <6500k?

 

[audioguru2]

It depends on the viewing angle. Cheap Chinese LEDs have a high brightness number because the case focusses the beam into a very narrow angle. Good LEDs are very bright over a wide angle.

 

[Hero999]

Does anyone know of white leds at 8000k or are they all <6500k?

Why do you want 8000k? That's blue.

If you get a RGB LED you can alter the current to each LED to get any colour you desire.

 

[Um...Me123]

My HIDs are 8000k.  So the idea was that if I decided on not doing the RGBs for financial and flux reasons then I want something to match.  Do color temps differ between types of light sources?--> would 8000k on a LED be more blue than a 8000k xeon arc?  My HIDs are blue-white...mostly white. 

 

[audioguru2]

My compact fluorescent bulbs have 3000k colour temperature and are pure white.
2700k is warm-white (yellowish-orange like incandescent) and 3500k is cool-white (bluish).
Very blue ones are called "daylight" but I don't know their colour temperature because I hate them.

Corrected colour temperatures are in red.

 

[Alex Tsekenis]

Daylight bulbs are amazing, a pure bliss to the eye in an electronics lab. The only issue is that the eye is not so sensitive to that light so maybe you need a few more tubes. If I have daylight tubes on and then change to warm white my eyes hurt. I think they are great, you should try them maybe on a bigger scale. I even convinced Intel Corp. to change the ones in my area. 

 

[Hero999]

Colour temperature is the equivalent to the light emitted by a black body at that temperature. The filament of a typical incandescent bulb is around about 2700K, a halogen filament is hotter about 3000K.

It's a matter of opinion, I hate daylight bulbs, they don't emit daylight but a horrible bluish grey coloured light, give me 2700K any day.

 

[Um...Me123]

I know this is getting a little off topic but while I have you all here...
An led I'm considering is the Luminus Devices CST-90.  It seems to be the best balance between $s and lumens.  $45@2700lm with a perk of having a thermistor.
Question:  It runs at 3.2-3.7V @ 1-13A
With a car as the source what is the best method of power supply which has the following qualities:  cheap, easy, full dimming, and doesn't destroy led in 2 days?

 

[Alex Tsekenis]

You could use a normal constant current source which will be quite inefficient, you could use a hysteretic driver much more efficient or you could use very specialised ICs based on hysteresis again like the new LT3743 or the MAX16818. These are in order of increased complexity.

But I am sure there must be a ready product that meets these specs. That is where I would start.

 

[Hero999]

An SMPs can be made using fairly common components.

The first shows how it can be done using diecrete components and the second shows a comparator. If a comparator with a push-pull output is used Q1, D1 R4 and R5 can be eliminated.

View attachment 40764

View attachment 40765

 

[Um...Me123]

I'm new to SMPs but see that is definitely my way to go.  For benefit of learning, what would be wrong with just PWMing a mosfet and putting a cap across the output?  I can see that there could be fluctuations in output when the input changes but besides that is there any reason one couldn't do such a thing?
Thanks,
A

 

[Alex Tsekenis]

No, no reason why you couldn't do that. But do you want to do that?
Once the transistor is ON, your output will shoot to 12 V (assume car battery) and there is nothing you can do about it by changing the duty cycle. When the transistor is OFF your output volatge will fall depending on component values. You can't regulate this system.

Anyway, constant voltage drive is not suitable for power LEDs. You need constant current drive (see suggestions below).

Attached is a waveform of the output voltage of your proposed system to illustrate my point.

Also, see what I came across:

http://www.amazon.co.uk/gp/product/0750683414/ref=sib_rdr_dp

Prob. an overkill.

View attachment 40771

 

[Hero999]

I'm new to SMPs but see that is definitely my way to go.  For benefit of learning, what would be wrong with just PWMing a mosfet and putting a cap across the output?  I can see that there could be fluctuations in output when the input changes but besides that is there any reason one couldn't do such a thing?
Thanks,
A

You're half way there.

You need an inductor, not a capacitor if you're going to do that. The value will depend on the switching frequency, input voltage, LED voltage, current and maximum acceptable current ripple.

It's true that the current will vary depending on the input voltage but that might not be a problem. This circuit is the switch mode equivalent of just using a resistor but it's well worth it as it's much more efficient.View attachment 40773