Yes you heard me right! It sounds crazy, and it will be expensive, but I am not paying for it. Dont worry about how it will be done. I have plans and it can be done! I know, I know. I will get so much criticism over this idea since it hasnt been done by many.
My current concern is how to to drive them. Mosfets will take the current, but my knowledge of using them in a circuit is limited. The more powerful HexFETs will reduce the parts count, but I dont know if they are built differently than the standard mosfet and need to be controlled/wired differently.
All I need is a circuit that has two inputs, a HI and LO. The circuit should have a fixed voltage (to protect the LEDs from spikes) and it should have two fixed current levels (like 350mA and 700mA - each should be set by a resistor). If I have a cluster of LED's wired in six parallel banks of four that are connected in series, then I can feed different levels of current to each 14V sets. I need to see how R-binned or even S-binned) K2's are available, but I have untill the end of summer. With these, I can send 2.1A per headlight (350mA per bank) and get 1080lm per headlight (45lm per LED). Then I can send 4.2A per headlight (700mA per bank) and get 1560lm per headlight (65lm per LED). I can even use a cluster of 28 or 29 for more output.
I chose the K2 because I can safely power (within specs) the LED at two separate levels and still maintain a great efficiency (though not close to HID). I could use the U-bin and have fewer LED's and optics, but then I get a bit more heat and it will lack efficiency even further. I can always power them over or under specs to fine tune the output. Also, they are cheap (-ish).
My findings is that most aftermarket 55W Xenon headlight bulbs output 1500lm (Hi beam?), so I figure that the Lo beams are about 1000lm. Older cars only put out 1000lm. HID puts out roughly 3000lm per headlight. I understand that what makes the headlights so bright is the throw (the candlepower), but this project is just for fun. Also, the beams from the Hi and Lo on this will pointing in one direction and the difference will be the brightness (so far). I may have two 7-LED clusters that act as fog-lights to shine light lower to the ground. Possibly I can have a simple motor or cable system to tilt the LED and heatsink assembly a few degrees to make up for the difference in Hi/Lo beam. Hmmm...
The copper heatsink material I plan on using should work well. It is only 60W per headlight at full power, and many processors in your PC today dissipates that much heat. Plus the Lo beams wont require much power and everything should stay relatively cool. Plus I will have a 12V 120mm fan for each heatsink (or two 100mm fans) to keep it cool.
Well, I plan on talking to my friend this weekend to discuss the pattern of the cluster. I was thinking of a simple hexagon shape, but I can put them in different shapes and have a middle bar light up brighter or have two circles each light like an eye. I can go with different LED types depending on the design, but that depends. My friend has an older s-10 painted and fixed up pretty nice (almost not worth LEDs but that is okay). His headlights are the 200mm sealed beam headlights. I found the euro headlight conversion for it and I can cut and modify that to my liking. The dimentions are 200mmX140mm so there is plenty of room for different designs and shapes. I liked the K2's because of how they can handle the current and heat. Plus they are relatively cheap. I know they are still imperfect, but they will do. When you are oncoming traffic or a person getting their mail by the road, the color bin wont cross your minds.
Plus this was always my dream and my friend thought it would be cool. He will be one of the few (if any) that can say his car is lit ENTIRELY by LED's. I get excited everytime I think about this project.
If anyone can post tips and ideas for a driver circuit, that would be of great help! It can be done, it will just take a bit of time and work. Its like fitting a 440 in a pinto. Its been done.