Bicycle headlights?

I'm looking into constructing my own bicycle headlights.

Typically 10W-15W halogen lamps are used which offer about 30 lumens per watt. I've been looking at LEDs which are supposedly more efficient, but at first look they don't seem to be. For example the highest watt version is rated 120 lumens at 5 watts which doesn't sound terribly impressive (although I don't have one here in my hands to test). Ideally I'd like to use a 3.6V NiMH versapak which probably has a capacity of 3 amp-hours. I wouldn't mind soldering two dozen LEDs together if that's more efficient.

Anybody have any thoughts?

PS: I'm good at soldering. I solder electrics and SMT electronics.

Hi strobe, and welcome to CPF.
I think the general concesus is that LEDs rule the roost for low powered lights (5 watts and under), with halogen or HIDs getting more lumens per watt in higher powered lights. Of course, this will most likely change in time, as LED technology improves.
Having said that, there are a few members here who DO use LED lighting for their bikes.

I think 120 lumens should be enough for a road bike, if it has a narrow beam. I have a Lupine Stuby on my lowracer, wich is 120 lumens, but with a very wide beam. At 40km/h on a dark and rainy night is is *barely* enough. A Fraen Tri-lens might be just the ticket.

If I may interject a comment here.....

When I see 120 lumens mentioned in relation to 5W LED's I am suspicious that this figure is being taken from Lumiled's spec sheet and not a measurement from a real flashlight that's available for purchase. Of course if all Lumens stated for other light sources are from the lamp manufacturers and not real world "net" values, it may be more of a fair comparison.

I think SureFire is getting good flux bin 5W's and check out their stated luminous output on the KL4. It's a dang sight short of 120 lumens.

Of coure getting the photons out is the first challenge. Getting them to go where you need them is the next!

Oh yeah, welcome Strobe! /ubbthreads/images/graemlins/grin.gif

- Don

I'm in the process of doing the same thing.


Using a philips masterline MR16 20 watt for the bar. They use an IR reflecting coating that is supposed to make them more energy efficient. They say 20 W can replace a 35. I tested them at 20 watts and found they are brighter than their normal counterparts (equal power and beam angle) although you won't get twice the visable distance due to the inverse square law. The bulb is quite large though and I'm mulling over mr11 or mr8 for the helmet.

I wouldn't mind using a bunch of LEDs at once, it doesn't have to come from one emitter.

I also wouldn't mind using a non-white LED like cyan. (human eyes are more sensitive to green anyway).

The 5W LEDs are expensive and don't seem to be very efficient. Perhaps using a handful of lower watt LEDs would be better.

What about that?

That MR16 looks interesting.

I've read that to drive a 12V halogen I should use a voltage regulator because halogen bulbs lose efficiency at lower voltages.

I just remembered I have 14.4 Dewalt battery packs.

Hrm, anybody have a good 12v voltage regulator design? |-)

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strobe said:

I also wouldn't mind using a non-white LED like cyan. (human eyes are more sensitive to green anyway).



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Even though the pro and cons of monochromatic lighting have been covered ad nauseam in other threads, I would like to take this opportunity to interject something here. As human beings, we ascertain the identity and therefore the potential threat of objects by three means; color, shape and movement. We are also conditioned by past experience, and for the most of us these are daylight, full-spectrum experiences. So the next time you're charging down a piece of single track (or a poorly lit street) at night doing 30+ mph (45+ ft./sec.) ask yourself this: Do you want your reaction time (and therefore your skin) compromised by using a light frequency that you have minimal experience with? Just a little food for thought.

Dan

Hi Strobe, and welcome.

I'll tell you what: You make a nice form-factor LED headlight that is *regulated* and provides a beam like the L4, and I'll be the first in line with my checkbook. As much as I like the beam from my L4, I'd rather have a real headlight mounted on my handlebars.

[ QUOTE ]
strobe said:

Typically 10W-15W halogen lamps are used which offer about 30 lumens per watt. I've been looking at LEDs which are supposedly more efficient, but at first look they don't seem to be. For example the highest watt version is rated 120 lumens at 5 watts which doesn't sound terribly impressive (although I don't have one here in my hands to test). Ideally I'd like to use a 3.6V NiMH versapak which probably has a capacity of 3 amp-hours. I wouldn't mind soldering two dozen LEDs together if that's more efficient.

Anybody have any thoughts?

[/ QUOTE ]

Unfortunately, for now, halogen lamps are more efficient than LEDS when looking above the 5W category. The subset of high-pressure xenon lamps are even more efficient. And then there are the HID (high-intensity-discharge) lights which are, again, even more efficient.

So if halogen and HID are more efficient at higher wattage, why use LEDs in that range? Only if you're looking for robustness and simplicity. HID and halogen lights can blow if subjected to shock. HID lights need more support electronics (ballast, etc.), halogen loses efficiency as the powersource dies.

I still use halogen as my headlight (I still won't switch to HID because of weight, cost and complexity) and work on ensuring I have enough juice to keep the light working within the efficient range. LEDs, even the 5W still can't quite compare, especially since I also need the throw, which comes naturally to filament lights in a good reflector, but not to LEDs, even with a good lens.

You are going in the right direction with the NiMH pack since NiMH, NiCad and lithiums have a relatively flat discharge curve. You can forget about fancy electronics and go for direct drive. The NiMH will help keep the light output even for as long as possible. If you're going for 5W LS, you're going to need 7V instead of the 3.6V pack you were planning to use. Couple 2 in series.

Best of luck.

It sure is nice to find so many fellow cyclists here!

I'm in need of Better Bike Light(tm) too: long run time (4 hours would be nice), indestructible (LEDs!) and long throw (avg.speed 28kmh, top speed 42).
I'm wondering if a Fraen Tri-lens with 3x3Watt would fill the bill. It would need some means of switching on 1,2, or 3 LEDs, to keep runtime up (1 LED in town, 2 LEDs most of the time, 3 Leds when blinded by oncoming traffic). Preferably running on 7.2V (have a Nimh Accupack with a very nice lightweight charger), or better yet, on anything between 6 and 12 V. A remote switch would be nice too (there's three ft. between lamp bracket and handlebars)
For housing, a shortened Tri-Star (with just enough space for the electronics and mounting hardware) should be just the ticket. Only problem: I know next to nothing about electronics, AND I'm all thumbs /ubbthreads/images/graemlins/frown.gif so I'll have to find someone to design it and someone to build it (for the latter I can probably find someone locally).
Any comments? Would more people want such a light? Could we get Wayne to build us a couple? /ubbthreads/images/graemlins/bowdown.gif
Or I'll just buy a state-of-the-art dimmable 16V xenon light for €160, and always carry my 26-LED headlight as backup. Much the easier option, but more expensive in the long run (replacement bulbs cost €30!)and not so flashaholic either...

an interesting link for those interested by bike lights:

http://www.audax.uk.net/lights/#li