Night riding and lights - Page 2

[QUOTE=alienator;3914083]

One important thing to consider when buying LED lights of either sort--battery or generator driven--is whether or not that light is overdriving its LED's. It's well known that LED's typically have a long life, but what's not very often discussed is that life can be reduced dramatically by being overdriven (too much amperage, too much voltage,....). They don't get more efficient if they're overdriven. They're limited from the start by their quantum efficiency (how many electrons it takes to produce a photon). Overdriving them will actually cause them to be less efficient, as part of the LED, the junction, heats up. Also, as their overdriven, they shed more heat, thus the cooling fins you see on so many lights. It's better to find a well illuminating light that doesn't need cooling fins. With damage from being overdriven, the LED's will start producing less light, and the time will come when they won't produce switch on at all. For properly driven LED's, that's not a worry. Properly driven LED's can easily have lifespans in excess of 10,000 hours: that's over 416 days of non-stop light production.

As a happy bonus, properly driven LED's get longer burn times out of their batteries, everything else being equal.[/QUOTE


How does your average mortal know if the light they are buying is using overdriven LED's? I'd only be guesing but one review shows a light and motion seca 700 hitting 80+ degrees. Is operating temperature an indicator?

I'd completely forgotten to consider dynamo lights, some of those look pretty good. Are they heavy, that might be a pretty useful back up for the winter? Must be the childhood memories of powering an old tungsten bulb and having to keep up 20mph to see where you were going ;-)

Well, that's a good question. A big hint is that if a light's festooned with cooling fins, it's probably being overdriven. LED's for bicycle illuminating purposes don't run hot. It's not like they're LED lasers which can need active or passive cooling. Operating temperature without cooling fins would be a good indicator.

If you want to know absolutely, then that requires a bit of digging that most people really don't want to do ( and I don't blame them). You'd have find out what the actual LED in use, in the light, is and what it's specs and performance parameters are.

On the upside, LED's keep getting cheaper and batteries keep getting better. I would expect in the next 10 years or so to start seeing small electronic devices powered by fuel cells. When that happens, you'll see lights that run for days without needing a generator (dynamo).

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I'm not an LED expert, so I'm not going to pontificate on the technology. What I can tell you is that the newest LED generator powered lights are out there being "tested" under the most rigorous conditions by long-distance cyclists. That is, they are being ridden through some extreme weather for long hours, rather than used for a couple of hours occasionally.

There are some very good battery-powered lights out there, that's for sure. But I -- and many other marathon cyclists -- prefer not to have the extra hassle and limited lifespan of batteries to deal with. Buy lights and generator and (barring total failure possible with any piece of hi-tech equipment) you're good to go for many years.

Weight: A Schmidt hub weighs between 61Og and 385g, depending on model (i.e. SON 28 or SON 20R)



Let's say you are a weight weenie and choose to go for the SON 20R with the Edelux headlight (85 g). Total weight is 470g (1.03lb). That's less than the battery weight of a L&M Seca 900 Ultra battery (system weight is 686g). Considering that a long-distance rider would likely need to carry an extra ($300) battery, weight we can conclude is not an issue with dynamo lights.

As far as light output, etc. let's just note that not all lumens are created equal so this measurement can be misleading Lumen quotes do not tell us much about the "kind" of light that gets put down the road. All I can say is that the light output from an Edelux light for instance is truly stunning. I can't imagine that that I could benefit from any more light. I can comfortably descend at 50+kph on unlit, narrow winding roads. Motorists will dim their headlights a kilometre away.

The Schmidt hubs produce a regulated 6 volts at 3 watts. Lights incorporate circuitry to prevent the overvoltage of the bulb. The Edelux has a bullt-in heat sink. I can attest that the light body does not heat up even after a full night of riding.

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+ for generator lights. But SON hubs are too expensive to me, i woul'd go with new Shimano dynamo hub (72 or 80) and B&M Cyo headlight.

I do a 35km commute each morning. I used cheap Nightpro halogen lights that just didn't cut the mustard in output and battery life.

So I replaced them with Ayup Lights about 2 months ago. They cost more than I wanted to spend but now I couldn't be happier with their performance.

They are truly brighter than some cars. Drivers give way to you as they don't know whats coming. The battery life exceeds their run time. (We will see how they are going in 12 months). The lights are tiny (about the size of your thumb) and look sexy. The 3 hour batteries are also tiny (about the size of a match box).

The mounting systems are simple, light, bomb proof and effective. Some people complain about the mounts because they are so simple, they want more for the big $$$. I believe in the kiss method. In the kit you get what they call a gheko mount, This is a helmet mount for MTB. They also supply a headband.

Three spreads of light to choose from. I chose one spot and one intermediate. I am happy with this. I would choose the same again. I only road ride so I have both lights on the bars. I put them on an extender. The main reason for this it put them out front and I get no reflection from cables and stuff. The two 3 hour batteries (they supply a 6 hour as well) strap neatly & unobtrusively to each side of the stem. The switch is waterproof, simple and can be used with gloves.

When considering lights, nothing is more important than performance and these perform in spades. I'm sure some HIDs outgun these but they are superb. I can ride totally relaxed with the same confidence as day time. I can see every stone, nut or stick let alone larger obstacles.

If I had to buy more lights would I buy the same again? Without a doubt. If you want photos I will muck around and post them.

Actually, there is nothing at all misleading about "lumens." A lumen is a watt weighted to the photopic response of the human eye. Therefore, a lumen is a measure of power output. Power out is power out. It's cut and dry. There are other factors, though. A big one is the sensitivity of the human eye to the spectral range of the light being used. The human eye's spectral range is centered at a green/yellow wavelength. That's no surprise. Our sun's visible spectrum is basically centered there. What this means is the eye is most sensitive to light that is yellow/green, like the Sun's output. What this means for LED users is that blue white light--that some LED's use--isn't ideal for human's to see by at night. Not only will blue-white at a given frequency seem less intense than yellow-green, it will also yield poorer contrast. Good contrast is essential for night time riding.

As important as power output is, illuminance is even more important. Illuminance is power per unit area. A simple to think about this is to think about a laser. Laser beams are narrow--on the order of 1-2 mm in diameter--so they pack a lot of power into a very small spot on an illuminated surface. A bare lightbulb, however, essentially spreads it's power everywhere, so less power is concentrated, everything else being equal, in a given area.

So, you have to consider power output (lumens), illuminance (lumens/sq. meter, a result of beam pattern), and light center wavelength (color). FWIW, at the center wavelength of the eye's response (555 nm), there are 683 lumens per watt. Be careful using that figure, though, because that conversion factor varies with wavelength in the spectrum.

If a manufacturer gives a power in watts, I tend to shy away, as either they don't firmly grasp how the eye responds to light or they're trying to do a little misdirection by using units that others don't use.

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As I said, I'm no iLUMENati. But I know from actual experience that simple lumen ratings do not tell the whole story. I could quote Wiki articles, etc. without "illuminating" readers.

I know enough to understand that lumens per watt is the important measurement, but what is also important to me is what the lamp does with that. Beam pattern is an integral, not to mention practical, part of the equation.

Regarding spectrum. Indeed the blue spectrum of some LEDs limits their usefulness, especially in wet conditions. Therefore, some randonneurs still prefer the yellow light of halogen (twin Schmidt E-6s are still a good choice). The Edelux however is much more neutral than most LEDs.

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~William Saroyan

Uhm, I wasn't quoting Wiki. Optics is my field, and I was just trying to explain things. By lumens per watt I assume you mean lumens/per watt energy produced by the generator. Otherwise, in optics lumens and watts are two units that are the same in that they're both measures of luminous flux.......er....light power. Lumens/watt of energy produced really doesn't tell you anything except what the efficiency of the light system is in terms of output. Lumens per watt is just a conversion factor.

Otherwise, what I said explained what you felt: that lumens weren't the entire story.

The reason that blue-white light is limited in its usefulness is, again, 'cuz the typical human eye isn't as sensitive to that end of the spectrum as it is to the yellow/green part of the spectrum. That's all.

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Wasn't suggesting you were quoting Wki -- I'd have to to get into a technical treatise.

What I was originally suggesting, again, is I know ratings on a box are not created equal and lights with same rating do not necessarily light the road similarly. My experience is out on the road and from testing and selling the products.

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VeloWeb The bicycle is the noblest invention of mankind.
~William Saroyan

I agree. Rarely does on parameter describe the performance of anything. Luckily, now, riders have access to web pages that show light patterns and stuff like that. It's an extra data point that tells a lot more than a spec or two on a box.

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The Shimano is indeed a decent hub. But for those that can afford it, the SON is without peer.

__________________
VeloWeb The bicycle is the noblest invention of mankind.
~William Saroyan

CygoLite seem to be making some decent stuff. I just ordered a Trion 600 for $280 shipped after Bing discount. Magic Shine also seem to be creating a buzz right now with about the same output as the Trion for $90. I went with the Trion as I prefer the integrated unit as opposed to separate battery and light units.

For being seen something like the Planet Bike 1/2W unit I was using should be fine but those don't light up the road nearly well enough to see where you are going in the darker stretches of my commute and I've hit potholes unexpectedly a few times, not to mention nearly ploughed through several piles of grass clippings.

I got tired of replacing batteries, both regular and the big expensive rechargeable packs, and went with a generator hub (Shimano). They put out more light than the claimed wattage would indicate (lots more). The B&M Lumotec is rated at 6 v 3 watt, and is overvolted to 9 volts and the Shimano is rated at 9v 5watt and is over volted to 12+ volts and throws light like some 10w beams. They never need recharged and my hub is over 5 with 10000 miles and still going strong.
And generator lights, unlike battery powered ones , do not start to lose intensity the moment you turn them on.
Did I mention I can ride over 3 hours without having to carry another heavy battery. I recently acquired a Son dynohub with Spanninga lights, it's fabulous to see with , but i can't speak of the reliability yet, as I've only had it about 6 months.

I ride an obscene amount at night, batteries just aint gonna work.

Just thought I'd bring this thread back to life to ask what people consider a 'baseline' number of lumens for unlit roads?
I have quite an electrical background and I'm looking at making my own front light. At the moment I believe I can produce 540 lumens for approx 5hrs for around £100 and 200g of mass. Is a focused beam of 540 enough for country roads at night when riding 20-25mph?
cheers
rob

Yes.