Who is willing to build me Led Fog lights?

LEDBE
A

Art

Enlightened
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Oct 19, 2008
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Portugal
Hi,
I hope this thread is not against forum rules , if it is please remove.

I need to build some new fog lights for my car but the space I have now is only 4 to 5cm for the optic diameter and more less the same 5 or 6cm for the heat sinking and circuit at the back.

The idea is to run a SSC P7 led or even a SST 90 in a proper heat sink with a lens capable of making a perfect flood. Also add a good regulation board to run it the most efficient way.

The bad part is that I dont know if I have the skills to do this. I can make the piece to install it at the car but I dont think I am able to build a proper light ( remember it needs to be water prof and 200kmh mosquito prof :oops:)

Hope to have some input of you guys.

Regards,
 
Hi Art,

Your project sounds interesting. I am not sure if flood type lighting is what you need though - unless it is really just for "show" and not for "fog use".

IMHO, a fog light needs to be really highly focused and directed to really "cut through" the fog. A flood is likely to bounce back and just blind you.

It might be worth trying out some different ordinary flashlights first with flood and throw to see which ones you like the best for the fog light applications.
 
Only 2.5 inches to work with? What is the real shape of your opening?

How much are you looking to spend?

You could start out with a fog light housing from a retail store and design a heatsink around that maybe.
 
What I am beginning to see are sunglasses with yellow tinted lenses for use day or night. All fog lights are are regular bulbs, halogens, or HID's with a yellow lens in front of them. Wearing these yellow sunglasses are supposed to accomplish the same thing and you don't need to buy fog lights to put on your car. You carry the sunglasses with you and you get the same effect in any car that you drive. I have never been in a car with fog lights so I'm not familiar with how they improve night vision. I'm sure different brands of fog lights focus the light differently than your cars headlights. They might have a narrower more penetrating beam, so the yellow glass may not have same effect as a real fog light. Just thought I would throw out the idea.

Here's an article about fog lights: Fog lights
 
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Yellow light penetrates fog/smoke better. Typical cool white led spectrum just illuminates the hell of the fog, but not the thing hiding underneath it.

So the first tip would be to find some warm LEDs. The second would be to make sure you get it right, or don't do it at all, because fog lights can be annoying as hell and dangerous too, if you blind someone too much at night.
 
Thanks to everyone for the input. Later I will post pics of the spot to install the lights.
Im not very worried about the fog penetration capability , but it is also something that I want to take into account.
My fog lights work also as a "follow me home" system so its also important to have enought light for that.
I also like to use fog lights on mountain roads to see better the corner , and this is probably the most important part for me.
I can run them also as DRLs( day runing lights) if they are build to last.
Sadly I cant find a car that uses fog lights that small that is why I remembered to build some led fog lights.

Since there is no limit(more less) in power what would be the best led to use?
P7 with 2,8A at 3,6v?
SST90 can go up to 2000lumens right?

My biggest problem is that I really don trust myself to build such a light :(

Regards,
 
I´m working on a prototype 6xP7 headlight, driven by two Der Wichtel circuits. They will be sitting in a rectangular housing made out of aluminium, with a sealed plastic window in front.
Not ready to show yet though...
 
Scattergun said:
I´m working on a prototype 6xP7 headlight, driven by two Der Wichtel circuits. They will be sitting in a rectangular housing made out of aluminium, with a sealed plastic window in front.
Not ready to show yet though...
Click to expand...

I only have room for 1xP7 :candle:

Here are the pics I took:

FogSpace.JPG


That is more less 5cm...

FogSpace2.JPG


And here is the same 5cm.

This is the space I have. On the other side there is a bit more space but there is no point on making 2 different lights.

I dont really think that a P7 will have enought like... I just took my M2C4 out to test and I know that the beam is a bit to throwy to use as a fog light but I dont think that if I use like a aspheric lens it will have enought power.

Regards,
 
Light Sabre said:
What I am beginning to see are sunglasses with yellow tinted lenses for use day or night. All fog lights are are regular bulbs, halogens, or HID's with a yellow lens in front of them. Wearing these yellow sunglasses are supposed to accomplish the same thing and you don't need to buy fog lights to put on your car. You carry the sunglasses with you and you get the same effect in any car that you drive. I have never been in a car with fog lights so I'm not familiar with how they improve night vision. I'm sure different brands of fog lights focus the light differently than your cars headlights. They might have a narrower more penetrating beam, so the yellow glass may not have same effect as a real fog light. Just thought I would throw out the idea.

Here's an article about fog lights: Fog lights
Click to expand...

The term "fog lights" gets applied to everything from auxiliary driving lights (think, "extra high beams", and practically the opposite of fog lights) to show-lights having no purpose but to have a yellow, purple. green, etc. light in the empty holes in your body kit, to genuine fog lights.

The number one characteristic of a genuine fog light, IMO, is a low mount and sharp cutoff, to illuminate the road a short ways in front of you without spilling light up and causing backscatter to interfer with your vision "over" the foglight beams. This beam-shape isn't exactly the easiest thing to rig up yourself, but a lens with a rippled back should come decently close (aspheric-style profile vertically, but wide horizontally), or perhaps you could rig something up by adapting a projector unit to LED, if you could find one small enough. Excessive spill will seriously diminish the effectiveness.

Color? You can find many excellent debunkings of the notion of a yellow-filtered blackbody source for greater penetration (unfiltered is as good, and really a bit better due to extra brightness) -- but the notion of using light efficiently generated at yellow (as by a yellow LED) is much less covered, because until recently there were no suitable sources of sufficient power for use in fog lamps. It's not clear to me whether a yellow LED can be scientifically shown more effective at penetrating fog than a white LED at the same power, but it still won't be hugely better -- in the end, beam shape is the number one priority, followed by brightness, and color is mostly optional. Yellow glasses may or may not help, but they can't fix a bad beam pattern or too little light.


Art, the most likely LED for your project seems to me like the SST-50 -- you could probably fit two of them, with some sort of focused vertical/dispersed horizontal optics in that space, and given adequate heatsinking provide 2.5x or so times the light of a P7. Alternatively, you could go with the SST-90, for more efficiency, but worse focus. Whatever you do, I think you'll need to have some sort of thermal throttling to prevent the lights from overheating at a stop -- hit 10mph and they'll probably be fine, but it's just too hard to dump that much heat by natural convection in a confined space near a hot radiator and engine...
 
Hi Art, it is good to see that you are making progress with ideas and parts selection, as that is the hard part (IMHO) and very time consuming.

Driver Board
- I looked at the link, and that driver board looks like it operates by just on/off pulsing. It is ok to do that, but not ideal for such a large voltage drop. (12 volts in vs P7 needs.) The reason I think this is correct is by its general description and a picture with no inductors.
- It also is not auto rated at all, so I have some doubts about its ability to take common auto voltage spikes. This can kill the driver and LEDs in one shot. I cannot read the info on the forum (Its in German) but perhaps there is more info there.
- The only drivers that I have seen with auto use in mind are the ones from taskled.com. The reason, is that George designed even the first one for personal use in a car. There might be others that can hold up to auto use, but I have not seen that built into them.
- There is a hobby builder (der witchel I think) who builds a nice driver for that range. If you do a search using the google link in top of the page it should show up. You can ask him if his driver can withstand auto voltage spike abuse, or perhaps just put a spike clamp on the input.

LEDs
- The P7 is ok, I prefer the Cree MC-E for a 4 die package, but that is somewhat a personal preference.
- I actually have a couple of spare MC-Es I bought for another project that I really don't need. They are a recent buy / high bin (need to look at the specs) They are a nice LED, I just decided on a different direction with that project. (send me a pm if interested)

Optics / Reflector
- For a flood type beam, I would use a ledil boom reflector, which will work with either your P7 or the MC-E
- Phonton fanatic sells these on the forum in his threads and I think at his web site as well.

DX - There are mixed experienced with them, so I hesitate to recommend buying from them. Certainly I would not design something important or time critical using their stuff.

I am really curious about how it comes out - please keep posting ideas / failures / progress. They are all normal. You have no idea how many experiments I have done on LED lighting projects with "mixed" results. :)
 
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This article explains why color does not matter. You have to get to the second part to read about the actual science.
Fog lights work better than headlights for two reasons.
1. The fog at ground level is usually less than a couple feet up so a light will penetrate farther, that's why they are mounted low.
2. The main reason is that they minimize back scatter as has been mentioned.
It the same reason why you see long arms on underwater camera lights.

As for the glasses, our eyes are more sensitive to yellow so things seem brighter but they reduce light overall. They can't let more light in and you can't see farther with them, fog or not.
 
Well I have not forgotten this project Im actually working on it now and I need some help.

I decided Im going to use SST50 leds running at its max. As soon as I got a flashlight with this led I decided its the best for it.

So now the part that is making it difficult for me is not the build of the heat sink and the led on the car , its the connections.

My car has 12v when it is stopped and 14v with the engine running. I can put 2 SST50 on the same circuit and they need 7,2 to 7,4v to work at its maximum power.
Now my doubt is if a simple resistor that would make it go from 14v to 7,4v will work?

I know I can use a driver , but is there any need? The voltage is always 12 or 14v so if it runs at max power at 14v when it gets to 12v it will get lower but no problem , actually it would be perfect like that.

Give me your ideas.

Regards,
 
irv_usc said:
you need a really big resistor and somewhere to mount it. it will dissipate a lot of heat.

best bet is to use a driver.
Click to expand...

+1 to this. A resistor would have to dissipate a good deal more power than the LEDs and would be unable to insulate the LEDs from transients. Transients are also a concern with drivers, but to a slightly lesser extent.

I know that member Steve K is a good man to ask about automotive applications of electronic circuits.
 
I can mont the resistor in a place where to get a lot of air... my concern now is how efficient will it be compared to a driver.

If I used 4 leds I could direct drive them?
 
For a Fog light, you will want to select a LED with a ~3000K color temperature.

Do they have many high powered LED's with this color temperature?
 
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