Advice needed on project

rob85635 · Aug 18, 2008

I am working on fabricating my own off road led lightbar for my off road vehicle. There are currently two companies I know of that make led off road lightbars. The one I am looking at for comparison is http://www.holderoffroad.com/.

I am soliciting input on what LED would be best suited for this custom made project. I have looked at luxeon k2s, and found them to be to expensive. Cree makes an LED that might suit the need and is supposed to be cheaper.

The reason for this project is simple. I want to save money. To buy from a vendor, that particular lightbar in the size I want is about $1500. I want to but the leds, drivers, and all other needed items and make one myself. I have a source locally to fabricate the outter shell (it will likely be aluminum) but any advice on LED Brand, LED Prices, best brightness for the buck and what led is currently new enough to give off lots of light but not so new it will break the bank.

I plan on using 30-50 leds in this lightbar. I am in the beginning phases and would love to hear from the real experts.

Thanks,

Rob85635

mds82 · Aug 18, 2008

Cree XR-E's are a great LED to start with, they are fairly inexpensive ( depending where you get them). Here is what i would recomend -

Buy your LED's from LEDLightingSupply.com as well as the optics.
- LED's Cree XR-E, Q5 or R2 binned
- Optics - you have a choice of spot, wide angle, oval, etc. Depending on the beam pattern you are looking for, you can get a few different options.

get the CCHIPO driver (http://www.taskled.com/cchipo.html)
- you can run about 10 LED's in series, so you would need 3-4 of these depending on how many LED's you want.

lets say you wanted to run 40 LED's, - 4 drivers, 40 led's all at 1000ma
40(leds) * est 250 lumen = 10,000 lumen. thats a lot of light.

rob85635 · Aug 21, 2008

Cree XR-E's are a great LED to start with, they are fairly inexpensive

In your opinion would this be the best suited led in terms of brightness for the buck in the next 6 months or maybe longer? I will not be buying the LEDs until as far into the project as I can in hopes that prices will drop on whatever LED I go with or perhaps a newer technology might come out that would better suit this project.

Also, the website shows three different white LEDs (White Leds in cool at 107 lm, neutral at 93.9 lm and warm at 87.4 lm),which of the three is best suited for nightime off road use? I would hope the cool would be since it has the best brightness, but perhaps I am wrong.

Rob85635

LukeA · Aug 21, 2008

rob85635 said:
In your opinion would this be the best suited led in terms of brightness for the buck in the next 6 months or maybe longer? I will not be buying the LEDs until as far into the project as I can in hopes that prices will drop on whatever LED I go with or perhaps a newer technology might come out that would better suit this project.

Also, the website shows three different white LEDs (White Leds in cool at 107 lm, neutral at 93.9 lm and warm at 87.4 lm),which of the three is best suited for nightime off road use? I would hope the cool would be since it has the best brightness, but perhaps I am wrong.

Rob85635

Warm is better.

rob85635 · Aug 21, 2008

Warm is better.

As a novice, can you explain further why this is true. Do you think the manufacturer of this particular light found at http://www.holderoffroad.com uses "warm" leds? It would seem to me this particular product would use the brightest type of led available simply to make it as bright as possible. What are your thoughts?

Thanks,

Rob85635

R33E8 · Aug 21, 2008

rob85635 said:
As a novice, can you explain further why this is true. Do you think the manufacturer of this particular light found at http://www.holderoffroad.com uses "warm" leds? It would seem to me this particular product would use the brightest type of led available simply to make it as bright as possible. What are your thoughts?

Thanks,

Rob85635

Well I think that with warm white's you will get slightly better depth perception.. I would personally go with the cool whites which is what that brand as well as others seem to be using...

LukeA · Aug 21, 2008

rob85635 said:
As a novice, can you explain further why this is true. Do you think the manufacturer of this particular light found at http://www.holderoffroad.com uses "warm" leds? It would seem to me this particular product would use the brightest type of led available simply to make it as bright as possible. What are your thoughts?

Thanks,

Rob85635

Cool nets a higher number of lumens, but warm is better to see by. The LEDs in that bar are SSCs, and so are cool. If they were warm SSCs, the page would say so because warm SSCs are very uncommon. Also, the phosphor SSC uses to make their warm LEDs results in a huge lumen penalty, i.e. 50lm@350mA for warm as opposed to 120lm@350mA with cool.

Cree's phosphor isn't so bad in terms of lumen penalty. As opposed to 114lm@350mA in cool, you can get 87lm@350mA in warm and above 90lm@50mA in neutral.

You might like neutral Crees.

The main point is that seeing brown is important for offroading, and warmer LEDs light brown things better than cool ones.

Warm LEDs really aren't common; I think that's why most people use cool LEDs. Really there's no reason to use cool LEDs for offroading other than unfamiliarity with warm ones.

mds82 · Aug 22, 2008

warm color LED's will help you see much better if it is a bit foggy out.

Basically for the color difference, compare the headlights of an older car with incandescant headlights to a newer car with xenon headlights.

In my car personally i have 6000k xenon bulbs and i have never noticed a problem with the light output / color rendition.

If you can get a led that is close to 5000k that would be ideal i think because it will still be the high lumen output, and will still be able to see well.

if they made yellow LED's then that would be great, but they dont

LukeA · Aug 22, 2008

mds82 said:
if they made yellow LED's then that would be great, but they dont

Yes they do. There are both nearly monochromatic yellow LEDs and LEDs with the tint of incandescent bulbs. The latter is what I recommend.

RyanA · Aug 22, 2008

I'm not sure where your budget is at but it might also be good to check out the HID part of the forums. Not for a kit, but someone may be able to point you towards good ballasts lamps and housings.

2xTrinity · Aug 22, 2008

I would recommend Neutral white LEDs, these are around 4000k, or roughly between incandescent and street-legal HIDs, for reference. Outdoors they provide MUCH better depth perception and color rendition than brighter cool-white LEDs. In fact, I prefer them over the warm white for that matter.

The reason for this is fairly simple: off road, most of what you will be looking at is dirt and grass. Neither of those reflect blue light at all, which means that even though the cool white LEDs have more lumens, since they are more heavily weighted toward the blue end of the spectrum, less will be reflected off of the surfaces you're interested in. Warm or neutral colors on the other hand will give you better contrast and depth perception lumen-for-lumen.

Finally, in a foggy situation, although the most important factor is position of the lamp (low is best for fog), low color temperature is advantageous for the following reason: fog reflects all colors equally, but the target you're trying to light up mostly reflects red and green. A cooler or more bluish light will generate brighter backscatter relative to the surface you're trying to see, or worse contrast. Also, glare from cooler white light is more irritating to others, and yourself (in the case of fog).

http://www.dealextreme.com/details.dx/sku.12501 -- these DX dropins include Q2 5A Neutral white LEDs. They're $11. If you wanted to, you could buy 30-50 of these, mount them in some sort of extruded aluminum chassis with a lot of mass and a lot of surface area for heatsinking, then run them all in parallel directly off your car battery. Each module includes a regulator.

For around $500 You will get much much better results with that than you would with that hoffer $1500 product, which has unknown LEDs (possibly previous generation) and no posted specs -- leading me to suspect the worst.

mudman cj · Aug 22, 2008

mds82 said:
warm color LED's will help you see much better if it is a bit foggy out.

Basically for the color difference, compare the headlights of an older car with incandescant headlights to a newer car with xenon headlights.

In my car personally i have 6000k xenon bulbs and i have never noticed a problem with the light output / color rendition.

If you can get a led that is close to 5000k that would be ideal i think because it will still be the high lumen output, and will still be able to see well.

if they made yellow LED's then that would be great, but they dont

I too am of the opinion that warm or neutral LEDs would be the better choice for this application. Keep in mind that color temperature is only a part of the story here. The spectral output of a 6000k xenon bulb is not the same as that of any LED. Cool white LEDs in particular have much more output in the blue part of the spectrum. It is this blue light that causes issues with perception (depth and otherwise) and scatters in fog, blinding the driver.

clg0159 · Aug 22, 2008

+1 for warm white (I am converting all my lights to WW for outdoor use), or if you want neutral white Cutter has some nice Q3 3A's in stock!

rob85635 · Aug 22, 2008

It is this blue light that causes issues with perception (depth and otherwise) and scatters in fog, blinding the driver.

Well, I just fired off an email to the company requesting specific technical info on color temperature as well as brand/make/model of the LED used in their product. I hope they answer me but I have a feeling from your posts here that they use an LED more on the blue side.

Since this is a fairly new product I am guessing they just went for brightness not considering what you all know in here. I didn't consider color temperature in this product but now I am very curious. I will post what they reply (if they do).

Rob85635

matrixshaman · Aug 22, 2008

2xTrinity said:
I would recommend Neutral white LEDs, these are around 4000k, or roughly between incandescent and street-legal HIDs, for reference. Outdoors they provide MUCH better depth perception and color rendition than brighter cool-white LEDs. In fact, I prefer them over the warm white for that matter.

The reason for this is fairly simple: off road, most of what you will be looking at is dirt and grass. Neither of those reflect blue light at all, which means that even though the cool white LEDs have more lumens, since they are more heavily weighted toward the blue end of the spectrum, less will be reflected off of the surfaces you're interested in. Warm or neutral colors on the other hand will give you better contrast and depth perception lumen-for-lumen.

Finally, in a foggy situation, although the most important factor is position of the lamp (low is best for fog), low color temperature is advantageous for the following reason: fog reflects all colors equally, but the target you're trying to light up mostly reflects red and green. A cooler or more bluish light will generate brighter backscatter relative to the surface you're trying to see, or worse contrast. Also, glare from cooler white light is more irritating to others, and yourself (in the case of fog).

http://www.dealextreme.com/details.dx/sku.12501 -- these DX dropins include Q2 5A Neutral white LEDs. They're $11. If you wanted to, you could buy 30-50 of these, mount them in some sort of extruded aluminum chassis with a lot of mass and a lot of surface area for heatsinking, then run them all in parallel directly off your car battery. Each module includes a regulator.

For around $500 You will get much much better results with that than you would with that hoffer $1500 product, which has unknown LEDs (possibly previous generation) and no posted specs -- leading me to suspect the worst.

I got to agree with our very knowledgeable 2xTrinity on most everything EXCEPT the DX unit mentioned above. I'm afraid it probably is rated for a maximum of 12.0 volts and since most car batteries and car battery/alternator running voltage is closer to 13.8 volts you'd probably fry these in short order. However if you could find a high current regulator to drop you down to under 12 volts it would likely be a blazing bright deal.

LukeA · Aug 23, 2008

matrixshaman said:
I got to agree with our very knowledgeable 2xTrinity on most everything EXCEPT the DX unit mentioned above. I'm afraid it probably is rated for a maximum of 12.0 volts and since most car batteries and car battery/alternator running voltage is closer to 13.8 volts you'd probably fry these in short order. However if you could find a high current regulator to drop you down to under 12 volts it would likely be a blazing bright deal.

Buckpucks + emitters from Cutter is the way to go here.

rob85635 · Aug 23, 2008

Buckpucks + emitters from Cutter is the way to go here.

Care to elaborate on which Buckpucks? I think those are the "drivers" right?

Rob85635

2xTrinity · Aug 23, 2008

matrixshaman said:
I got to agree with our very knowledgeable 2xTrinity on most everything EXCEPT the DX unit mentioned above. I'm afraid it probably is rated for a maximum of 12.0 volts and since most car batteries and car battery/alternator running voltage is closer to 13.8 volts you'd probably fry these in short order. However if you could find a high current regulator to drop you down to under 12 volts it would likely be a blazing bright deal.

You bring up a good point. I had forgotten about the voltage limit on these as I personally cannibalized the modules to use the drivers, reflectors, and LEDs all separately.

If you go with a 12V linear pre-regulator, you will end up wasting a fair amount of power on top of the inherent driver inefficiency.

I do not have the drivers onhand. However, I do know they will not immediately fry if driven higher than 12V. I have driven them as high as 16.8V from a bench supply for short periods without problem and they don't "instaflash". The buck regulator chip, the PT4105, is the same as the Kennan driver at Kaidomain, and is rated to 20V. The only possible issue is with the capacitors' voltage ceiling, which I don't remember of the top of my head. Generally one will want a lot of headroom on input capacitor voltage, approaching the limit will cause expected lifespan of the driver to increase, even if it doesn't burn out immediately. It may be the case that the voltage limit posted is over conservative. I have seen a fair share of oddities in the specs at DX, but I wouldn't count on it.

It may be possible to modify these to work. If I find anything out, I'll post it.

or if you want neutral white Cutter has some nice Q3 3A's in stock!

FYI these are around 5000k, the very high end of the neutral white color temperatures. They actually overlap with the WH bin, though the 3A neutral LEDs should have better white balance, where WH's tend to run green.

LukeA · Aug 24, 2008

rob85635 said:
Care to elaborate on which Buckpucks? I think those are the "drivers" right?

Rob85635

This one does what you want. You can run 4 LEDs with each one, IIRC.

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