So as I hinted at in my intro thread, Im building a pretty ambitious set of driving lights. Ive picked out the LEDs, the number of LEDs and my OTF lumens requirement. Im still searching for the right optics and drivers. Ill me designing and machining my own heatsinks that will double as the main bodies of the lights.
The design will use 5 Cree XM-L-2 in neutral white, nominally driven at ~2000mA each. Im hoping to get 3000-4000lm per light out of these.
Ive tried a few spot and elliptical optics from Carlclo but nothing has really impressed me. Im planning to buy a few different reflectors and see if those give a more controlled beam.
Taskled has a few drivers that seem like theyll work. Ill need to use a boost type driver to account for the forward voltage of all five LEDs in each light.
Im open to suggestions for drivers and optics. Any critique on the concept?
It seems like it should be a fun project, and your lumen goal is attainable. However, I would suggest that you look into the laws in your area in regards to car headlights, atleast in the US this type of thing is not particularly legal. :(
You won't even get 3000lm from an MT-G2.
I hope you mean 4K lumens total.
My opinion would be to individually drive each LED, so you don't get total failure if something goes wrong. There's plenty of single mode 3A drivers around if you look. Intl-outdoor has a lot of triple XM-L drivers.
What you need to consider is input voltage from your vehicle to the driver and the voltage ranges concerning each one.
As for optics, if you have five, I would make three small angle (throwy) and two large angle (floody). Try different combinations. If you use a multi-emitter driver from intl-out you could even put the floods and throws on separate circuits.
I looked into the taskled hyperboost driver which really seems like the best bet Ive seen. The total vf is 17.5v with 5 xm-l-2 @ 2A. This is pretty much right where the hyperboost is made to operate. This will come to about 3.5A per side.
Im not so worried about total failure modes. If it breaks it breaks, whether they all do out or just one, it needs to be rebuilt. They wont be the primary beam, I have projector headlights already, so these will just be high beam/driving lights.
For those worried about legality, they will only be used on back roads with no other traffic. No different than any other driving light. No more or less legal than anything people buy at autozone or walmart. Ive gone to great lengths to make my lighting system as safe as possible and would rather avoid an argument over the percieved morality of retrofits, headlight modifications, etc. Thats not why Im here.
With optics, it does look like Ill end up with a hybrid setup. The main reason for doing this is that the beam pattern of my stock high beams is horrible. There is way too much foreground lighting and it severely reduces my distance vision. The projectors are bi xenon so they have a rather wide high beam anyway. What I really need is more throw.
more throw than bi-xenons with LEDs will be very hard. I’d recommend looking into fewer LEDs and much bigger reflectors - at least 35mm, if not 60 or 80mm+. A 6v MT-G2 either side with a buck driver in each (or 2x 12V MT-G2 with a boost) in 80mm reflectors will get you a good amount of throw, although you’ll still get plenty of foreground illumination. Another option would be to stick with XM-Ls and have a couple each side behind some decent aspheric lenses. If I were to make some driving lights, I’d make each pod with 2 XM-Ls in series, one behind an aspheric, the other behind an optic of some sort (elliptical on the driver’s side, narrow on the passenger, most likely).
Also, from a practical point of view (and not moral), it wouldn’t hurt to check with your local inspection station to see what would or wouldn’t pass inspection. If you’re in the States, I’m pretty sure that supplemental driving lights are ok, but different states vary in whether or not they must be high beam only, on with low too or whatever. I don’t know about you, but I’d find it a hassle having to remove the lights each year when the car needs to be inspected if they would prevent the car passing.
The Hyperboost will not live in a automotive environment. I have talked with George (TaskLed) about it. It was a while ago. Maybe it will work now. He has a H3CC which is made for automotive use but it is 2.8A. You could run two of those, 3 on one driver and 2 on the other. That would give you almost 4500 Lumens running LT6 Leds. I only recommend running 5000k leds or less for automotive use for better color rendering and eye fatigue. To my knowledge there is no DIY automotive spec driver. Flashlight drivers will not live very long in a automotive environment. They do not have components rated for high voltage spikes you see in A automobile. 26.5mm Carclos are good optics to use. If you want a lot of throw use C8 reflectors, still smallish 42mm, but throw decent.
Why only run the leds at 2A? You have plenty of airflow in a car. Crank them up to 3A.
Here is a pic of my 6 xml light bar running 4 Carclo spots and 2 ellipticals. 5100 lumens.
The inspection thing isn’t an issue. No inspections. If there were I’d have to take outmy headlights anyway because of the retrofitted projectors.
Even with the airflow in front of thecar, I worry a great deal about heat. These would be in place of my high beams and would be subject to underhood heat. I would like to use a driver with automatic thermal throttling if I can find one that will drive these.
I have about 3X3.5 inches of frontal area for optics, so the practical limit on reflector size would probably be about 40mm. If I do 4, there not much to loose by doing one more in the middle. I’m also going off the idea that more leds at lower current withh be more reliable, longer lasting and easier to keep cool. If I can get away with more, I’ll go for it but I want to be able to test it first.
Asherics do seem like a good way to go. I have one sitting around from a cheap flashlight and it pretty much just shines an image of the die which isn’t pretty but it gets light out where I want it. I can’t find a source for them however.
ah, no inspections definitely makes life a bit easier from the design front.
Heat is definitely something to consider, although if these are wired in as high beams presumably you can switch to low beam when you come to a stop? The only drivers I’ve used with thermal throttling (Taskled ones) drop light output considerably to protect the driver (e.g. from 3A to ~900mA) which would give me the absolute shits on the road if that happened. I think it would be a better idea to work out how to get the most surface area and airflow possible and then work out the worst case scenarios of output and airflow. Then you can work backwards and see how much total LED power you have to work with. More LEDs at a lower drive current will be more efficient, but it sounds like you have some space limits to work within.
You can get aspherics from a bunch of places, plenty of people on here use them so just stick up a “where do I get … from?” thread. You can also focus them to project a more or less focused die image, so if you have multiples then you can set them up with different focal lengths to get the beam you want. I vaguely remember seeing a technical diagram for a LExus LED headlight, which used multiple LEDs with different optics to get the beam they wanted.
Oh, and a picture of the space you need to fit them in would help.
If the driver throttled down I’d still have the full use of my bixenon projectors, so it wouldn’t be a safety problem, just annoying as all get out. If all else fails, I can wire a thermocouple into one of my gauges and set it up to flash a warning light when it reads too hot.
I’ll post up some pics of the space I have when I get a chance. The car is in the garage at home getting lots of other mods.
Here’s the car. Lots has changed since these pics though.
Or maybe just the one pic will do. Photobuckets mobile ap is garbage.
You are overthinking the heat thing. My 6 xml light bar running 3A each led only needs a few mph of air to cool. At freeway speeds it is not even warm to the touch. Even with engine temps high I would not worry abou it unless you were stopped for extended period of time.
