# Recommend a white LED for super bright bicycle headlight?



## nleahcim (Nov 4, 2008)

Hi there - it's getting darker and darker here in Boston and drivers are becoming dumber and dumber. Today a clueless driver just about killed me because, I guess, he didn't see me (he pulled out in front of me when I was going about 25-30 MPH on a downhill, even though I have a bright white LED headlight and a flashing red taillight).

I've reached a breaking point. It's time to step up my lighting. I want to crank the volume of my headlights up to 11. :twothumbs

So - I've stumbled into a supply of 6.6Ah Li-poly cells. I rescued them from trash at work - and they're all fine. Some were slightly out of balance, but otherwise they're fine. Currently they're built up in packs of 4 (in series), but I can do whatever with them. That gives me enough energy to, well, have a really, really freakishly bright lighting system. I want something bright enough that nobody can miss me. My plan is something like this: one super bright white LED (or a cluster) aimed forward. Circling the one white LED will be a long line of RGB LEDs. Everything will be controlled by an AVR (microcontroller). Every LED will be individually addressable and individually PWMed.

I'm planning on running various patterns on the RGB LEDs. The idea behind that is to just attract attention. It should also look cool as hell though.

So I can handle all of the electronics - I mean I design electronics for a living, so this shouldn't be too difficult. The heat management will make things a good deal more interesting - I'm thinking I'll probably use some sort of metal core PCB to make things easier.

But I'm not sure about the LED choices. Does anybody have a suggestion for this? Also - what sort of optics (if any) do I need for the main LED as well as the smaller RGB LEDs?

I should mention - price is not a big consideration here. Safety is.

Thanks everybody!!!


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## spencer (Nov 4, 2008)

For RGB you could get Rebels mounted on a tri-star. For the white one, I would go with the new Cree MCE in a warm or neutral white colour (in warm and neutral you take a hit in lumen output (like 15%) but you get MUCH better colour rendering).


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## TigerhawkT3 (Nov 4, 2008)

First, you might want to look into the legality of using lights in colors other than white on a vehicle's headlights (yes, I know it's a bike's headlights) on a public road in your area.

Second, have you considered HID? It might be more effective.


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## qwertyydude (Nov 4, 2008)

4S-6.6 aH? You could keep them in series and run 4 P7 leds in a light for 700x4=2800 lumen headlight. That's brighter than most cars regular headlights! You'll probably blind them since you'll be running plain reflectors, so maybe just one P7 ought to do, if it's gonna be just one you could put all cells in parallel and have a 26.4 aH pack for extremely long runtimes.


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## nleahcim (Nov 5, 2008)

TigerhawkT3 said:


> First, you might want to look into the legality of using lights in colors other than white on a vehicle's headlights (yes, I know it's a bike's headlights) on a public road in your area.
> 
> Second, have you considered HID? It might be more effective.


My understanding is that you can't use blue on vehicles on the road. I think red, white, and green are all OK though. The reason they don't want you using blue is because that color is reserved for cops. Since there are plenty of cars with red lights I'm fairly sure red is OK, and I don't think I've seen any vehicles with green lights.

Are HID lamps more efficient than LEDs? They're more complicated to drive as I understand it - but that's not a terrible worry. Can HIDs be dimmed? I really want the ability to dim this headlight.


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## nleahcim (Nov 5, 2008)

qwertyydude said:


> 4S-6.6 aH? You could keep them in series and run 4 P7 leds in a light for 700x4=2800 lumen headlight. That's brighter than most cars regular headlights! You'll probably blind them since you'll be running plain reflectors, so maybe just one P7 ought to do, if it's gonna be just one you could put all cells in parallel and have a 26.4 aH pack for extremely long runtimes.


Heh or I could just add all the cells I have (100 or so) and have a pretty much infinite life headlight 

That's gonna start getting pretty darn heavy though - so maybe not.

How is the color of the P7? (and I'm assuming the P7 is this guy: http://www.dealextreme.com/details.dx/sku.11809) I'm really hoping for the really pretty white that some car headlights have - not the more yellowish white that most car headlights have.


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## nleahcim (Nov 5, 2008)

spencer said:


> For RGB you could get Rebels mounted on a tri-star. For the white one, I would go with the new Cree MCE in a warm or neutral white colour (in warm and neutral you take a hit in lumen output (like 15%) but you get MUCH better colour rendering).


I'm looking more for smaller RGB LEDs. I'm thinking I'll have something like 20-30 of them - In order to keep the size down I'll want to use smaller LEDs - maybe a quarter watt or so each. They're more for just attracting attention than providing illumination.

So what does better color rendering mean exactly? I just want a really bright, brilliant white. Like that that you see coming from a lot of luxury car headlights.


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## spencer (Nov 5, 2008)

This post shows better colour rendering. The first shot shows an LED that is considered cool white but it is on the warm side.
This post also shows some difference. The second picture in this post is almost exactly the same tint as the first picture in the first thread.
As I said before, I would go with a warmer tint despite the slight lumen loss.


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## Gunner12 (Nov 5, 2008)

Better color rendering means you can see different colors better. Most white LEDs don't produce a lot of red and make things appear "flat".

The white car headlamps should be 4300K(color tempreature) HID bulbs. The sun is around 5500-6000 K and most white LEDs are 5500-7000 K. IIRC it is not recommended to overdrive or under drive a HID bulb so you shouldn't dim it.


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## gillestugan (Nov 5, 2008)

regarding the heatsinking:
You can do as Trout and use the stem and handlebar as a heatsink. I find this very innovative. This light has 3xMCE and is really crazy. https://www.candlepowerforums.com/threads/209991


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## gillestugan (Nov 5, 2008)

When riding on roads the light is mostly for others to see you.Not for you to see the road, as you can usually see it anyway.

A problem then biking in traffic is that most bikelight put the light in front of you. As you wrote: "he pulled out in front of me" and probably didn't see you. I have this problem especially when I ride my racing bike where the hands will block the light to the sides. 

Maybe a good side emitting light is more important for safety than a strong beam in front? 
I've been thinking about mounting an emitter without any reflector, but have not decided the best place to put it.


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## Oznog (Nov 5, 2008)

HID is more efficient than the best LEDs in the LARGE lights, like car HIDs.

They make some smaller heads with ballasts for bikes. They sell on eBay and online for under $200. A lot more for heads WITH li-ion pack and charger. However, the lumen/w output is not as good as the big HIDs. It may not even be able to compete with the high end LED tech. But they are certainly bright and focus well and don't need a large heatsink.

HID cannot be dimmed.

HID cannot be started and stopped quickly. This kills the idea of using it as a "high beam" and turning it off and switching to a lower power LED or halogen when some's approaching so you won't blind them. The power-on cycle takes like a minute or two to fully complete (dim at first, and the color is off) and I'm pretty sure it damages the expensive lamp to keep turning it on and off.


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## qwertyydude (Nov 5, 2008)

P7's have a very good neutral white light and from the way it distributes it into a reflector, makes a really good beam. Slightly warmer beam with a cool white spill, and lots of spill at that when used with the available reflectors. It's very similar to the light from those fancy HID's.


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## gentlegreen (Nov 7, 2008)

I envy you those lovely batteries.

I, too am more concerned with being seen, than seeing where I'm going - so all these triple LED designs, though very neat, simply aren't the best use of my 3.3AH NiMH battery.

I went to 12 volts many years ago - I used to use a 21 watt car lamp front and rear powered from a 12 volt, 7AH lead acid.
A basic requirement for me was to have none of those annoying flashing LEDs.

But I got fed up with replacing batteries every 1 1/2 winters...

Newer battery technologies being that more expensive, I had to reduce my wattage, so I perversely replaced the 21 watt incandescent in my front lamp with a modified 9 watt minispiral CFL on the basis that though poorly focussed, it chucked out so much light that a decent amount of it would go in the right direction - and importantly, sideways ...

Fluorescents were hopeless for the back - a theatrical gel in front of a 10 watt 2D lamp chucked out a pathetic amount of red light.







I considered trying a red CFL, but they didn't come in low wattages, so I finally relented and went for LEDs - 60 of them... including 5 on each side.

This has been the setup for the past 2 winters :-






Having been so impressed by the usefulness of those bodged-up 12 LED front lights (more useful than the 20 watt Halogen MR16), this year I'm going ALL LED - starting with this modified camping lantern I paid £3.99 for in Wilkinsons Hardware which does a pretty good job with only 4 watts.







I have just finished ordering the rest of my armoury :-







The 21 LED MR16s should hopefully cast a beam a little way ahead (and behind) - plus boost the intensity for cars approaching from a distance. The 15 degree, 5 watt CREE MR16, should enable me to keep up a decent speed on unlit paths. If I did a lot of that sort of thing, doubtless I would end up with an additional CREE spot with a wider beam pattern.

A pity the "UFO lights" don't actually come in red .. hopefully I'll find something creative to do with the LEDs I take out of the housing ...


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## SemiMan (Nov 7, 2008)

You can not use red lights on the front or blue. You become a hazard and at the point may get a higher chance of being hit because people do not know where you are going.

I have a 650 lumen front light on my bike. I have designed it such that it throws some side spill. There is no way no one is not going to see it and in general I get a wide birth. It would be highly visible in a rear view mirror. I have considered adding yellow side marker lights front and back. I have a relatively bright flashing light in back. Again, no chance no one is not going to see from behind. Both my red back and front white have some side spill as noted, but perhaps not as much as I would like. I think I will go yellor markers in the front and perhaps some red to the side. That will make me more visible when people are passing and have lost concentration.


Semiman


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