10 watt LED board

Hello, never posted here but need some advice. I am an electronic tweaker but have not messed with many high power LED's.
I am needing to make some LED flood lights to replace 55 watt incandescent flood lights on an offroad only vehicle. The vehicle is a rock crawler and we use lights mounted under the vehicle that illuminate the ground on the sides of the vehicle for off roading at night. We also use driving lights in the front but the beam throw is usually to long with most driving lights for what we do (slow driving but need lots of light)
I was thinking of using something like this
http://www.dealextreme.com/details.dx/sku.5862
to make flood lights under the side of the vehicle, I have plenty of heatsink and the knowledge of mounting items to all sizes of heatsinks. I tinker with high power RF amplifiers.
My first question is, would these LED's work with the vehicles 14 volt system or should I use a resistor to decrease the voltage a tad?? I do not mind shortening the life span a tad to get a little brighter light.

Also I want to make some front flood / driving lights using cree's and the reflectors available. I will more than likely run them in series and then maybe that in parallel to be able to use more LED's. I have all types of heatsinks from flat to tubular to u-shape extrusions so heatsink is not an issue. I plan on possibly mounting some of this either in large incandescent used housings or using the u-shape heatsink and making lexan lens.
My main concern is my lack of knowledge with these LED's. Any suggestions will be greatly appreciated.

Thanks a million.

-=PEAKABOO=-

Another question. I am not familiar with the thermal epoxy as I normally bolt devices to a heatsink. Is this stuff adequate for mounting and transferring heat from the mounted device??

TIA

For high power LEDs (say Luxeon I, III, V, K2, Seoul, Cree, etc) it is almost imperative to use thermal epoxy in between the LED board base and the heat sink mount to get optimal thermal management, other wise there will probably be more heat sticking around on the LED board, and of course we all know that heat and LED life span don't mix well. If you are going to use these in a car, you will need to regulate, because when you first start up, you spike forward voltage to around ~14 to 15 volts. The 10W LED needs 12 volts. The best thermal solution for you is to both thermal epoxy and screw down the LED emitter board to the heat sink.

Lightingguy321 said:

For high power LEDs (say Luxeon I, III, V, K2, Seoul, Cree, etc) it is almost imperative to use thermal epoxy in between the LED board base and the heat sink mount to get optimal thermal management, other wise there will probably be more heat sticking around on the LED board, and of course we all know that heat and LED life span don't mix well. If you are going to use these in a car, you will need to regulate, because when you first start up, you spike forward voltage to around ~14 to 15 volts. The 10W LED needs 12 volts. The best thermal solution for you is to both thermal epoxy and screw down the LED emitter board to the heat sink.

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can I just decrease the voltage using a high wattage resistor?? I have bins full of various resistors ranging from .5 ohm and up and in wattage ratings as high as 25 watts. The larger resistors are made to bolt to a heatsink. I also use only silver clad teflon wire.

10W of LED is still gona be dimmer than 55W of incan, so you'll need to make quite a few of them for your rock lights. In the end it sounds like too much trouble to go through, were the incan flood inadequet as rock lights?

decreasing the output by using a resisot is less efficient in the long run, I really suggest that you look into regulator boards to buy. Also even if the large resistance resistors are made to bolt to heatsinks, you still need to use thermal expoxy because the bolt is just their as an ancor not as the primary transistion zone for heat. The thermal paste is the transistion zone and the bolt keeps it in place. Also reading your initial post again, if you are using 10 watt LEDs you will need several to actually equal the output of a 55watt incan, therefore you most definetaly need a regulator.

I would suggest using more efficient emitters such as Cree Q5 or Seoul SSC P4. Either of these will produce around 250 lumens @1A. Mount a few of them on a heat sink and use a constant current regulator like georges80's CCHIPO http://www.taskled.com/techcchipo.html so as not to worry about over/underdriving the emitters. The CCHIPO is a "boost" converter so you will need a series string of emitters that has a total emitter voltage that is higher than the input voltage (vehicle 12-14 volts) to keep them in regulation. Using thermal epoxy is not necessary, but using some kind of thermal compound is. If you are going to bolt the emitters the the sink, get emitters on a star that will have small mounting tabs and put a little compound between the star and sink.

jzmtl said:

10W of LED is still gona be dimmer than 55W of incan, so you'll need to make quite a few of them for your rock lights. In the end it sounds like too much trouble to go through, were the incan flood inadequet as rock lights?

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No the autozone 55 watt incan's were adequate I just wanted something more efficient. I have seen some of the 1 watts used for rock lights and they were pretty dim compaired to 55 watt incan's. My main concern is that on my crawler there is not room very a very large alternator and I just like LED's.
I want to build something similar to this for the front.
http://www.visionxoffroad.com/Products/LED/XmitterBar/
They do not need to look the same just work in a similar fashion, maybe more flood.

You are gona need a battery of them to get enough light, and some sort of driver too since you want efficiency. It's gona get expensive, but not nearly as expensive as the parts you already got on your crawler.

How about strapping lost of Cree/Seoul lights to the bottom of your crawler.

Well, 2 Cree XR-E Q5 LEDs driven at 1 amp each will have more lumen then the 9watt LED thing(350 lumen vs 450 lumen) and the two LED together would be a bit more then 7 watt so they are also more efficient. Thermal paste/epoxy would be a must.

There might be a few prebuilt drivers that can do what you are think of so if you get those, all you will need to do is wire the LEDs up, attach them to a heatsink, and make sure they won't get crushed by anything.

A 3.6-9 volt power adaptor brick and three or four of these (with the reflectors and springs removed) behind a mild diffuser would be great. ~12W (for 3), scalable, cheap, already regulated.

LukeA said:

A 3.6-9 volt power adaptor brick and three or four of these (with the reflectors and springs removed) behind a mild diffuser would be great. ~12W (for 3), scalable, cheap, already regulated.

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I was looking very closely at these.

-=PEAKABOO=- said:

I was looking very closely at these.

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I somehow missed the phrase "on an offroad vehicle". You could get some (6) Crees and a pair of these boards from Kaidomain which run the LEDs at 750mA each (3 in series) and can run direct from vehicle power.

I have seen LED backup lights and general lighting spotlights for Semi trucks and trailers. I know nothing about them other than they exist, but it would be worth a trip to a truck supply place. They are all set up, just wire it in.

Alex

LukeA said:

I somehow missed the phrase "on an offroad vehicle". You could get some (6) Crees and a pair of these boards from Kaidomain which run the LEDs at 750mA each (3 in series) and can run direct from vehicle power.

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Man those are kick ***.
I have a plan that is starting to come together.
Thanks for the link

This is an older post I realize, but I have a very similar project in mind. I have 4 lights (15mmx9mm) or 3.5 inchesx 6 inches that go on a tractor for Off Road use. These currently use halogen sealed beams but I am eager to change to LED using the same housings if possible. Would it be feasible to make a board with several Cree 3 watts with spot sharp angle optics, and mount the board in the plastic light housing and cut a plexi/ acrylic lense cover to protect the board, LEDs, and Optic lense. i would like to know if anyone has ever heard of this, or similar done before as this post relates to....Thanks, Greg

-=PEAKABOO=- said:

http://www.dealextreme.com/details.dx/sku.5862

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LEDs are current operated devices and some of the comments on the link above hint at this. What are these guys thinking?