For my bike (nothing special, a nice simple road bike bought at a garage sale) I would like to add a bicycle generator and LED lights.
I assume that output voltage of these generators varies with speed. There are some on sale on ebay for not too much, 6v or 12v models, most are 6 watts.
I want to do it in some nice way, such that
1) the LEDs would work across the range of speeds and be protected from overvoltages and such
2) Most power would not be lost on some current limiting resistors, but instead would go into LEDs. I think that 6W spent on LEDs would give me a lot of light.
If there are products like that on the market already, I do not want to "reinvent the wheel" and I would rather buy one, but I am not sure if such a thing is available.
I would prefer LEDs to regular incandescent bulbs for many very obvious reasons (more light and more reliability).
I am moderately handy and built some electronic things before, like a control and inverter for a DC welder.
Back when I rode all the time _the_ mail-order bike place was Bike Nashbar -- I believe they still have a website, and that it's still pretty good. You could also try the REI website (or check if there's an REI near you).
The bees knees would be a Sturmey-Archer dynohub with a switching converter powering the lights, but (a) you'd have to import the hub yourself, (b) you'd have to have a wheel laced with the hub, and (c) you'd have to build the converter.
For anything that involves a generator working against a wheel, you're probably much better off to use LEDs powered by a set of Lithium Polymer batteries.
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On the contrary, almost all bike generators are 6 volts, 3 watts. (That's half an amp.)
Voltage does vary with speed, but these days most generators are well-designed to self-regulate to a max of about 6.5 volts. However, that's assuming that a standard generator headlight bulb (or headlight & taillight) are fitted.
Generators are pretty much constant current devices. If a generator sees more resistance, it still tries its best to pump out half an amp. It does that by producing more voltage. It's not hard to get over 30 volts out of many generators, if the load has high resistance - like, for example, an open circuit.
First, recall that bike generators are AC devices. LEDs are DC.
Red LEDs are much more efficient than incandescent bulbs trying to shine through red plastic lenses, so you could easily gain efficiency in an LED generator taillight. But it's so easy to clip on a battery powered LED blinky that the generator version is probably not worth the trouble.
I think we're just now at the point in time where white LEDs are significantly more efficient than halogen bulbs. (And that's not all white LEDs, but the much more expensive Luxeon creations.) But it requires some serious work to take advantage of that.
The biggest obstacle, I think, is optics. Generator lamps often have excellent, excellent optics, so every lumen goes to a useful place. LEDs put out a fuzzy cone of light, more or less. You want the former.
I once found an article in German where someone had taken a 3 watt Luxeon and found a way to graft it into a commercial bike headlamp unit. IIRC, they needed a big aluminum plate for a heat sink, and they ended up with the LED facing _up_ at the bulb's focus point, slicing the headlamp nearly in half.
Unfortunately, I don't read German; and I'm away from my bookmarks. But that's what I recall.
If you can contact Andreas Oehler (sp?) he can give you all the info you could possibly use. He drops in here occasionally when the talk turns to generators.
Go to Peter White Cycles website and look in the lighting section. He sells a generator driven LED. There is another brand from England he does not sell. I don't recall if he mentions the other brand in his articles or not. The other brand was in a thread on this forum some time ago. Do a Google search on rec.bicycles.tech.
As for LED being preferred over incandescent, no. The only advantage LED has is in battery life and bulb life. Since you are using a generator, battery life is not a consideration. As for bulb life, incandescents are usually $3 each. They run for many, many hours.
There are three ways of coupling the generator to the bike's motion that I've seen in practice:
A toothed wheel that runs on the tire sidewall. These are very draggy.
A generator inside a wheel that runs on the tire tread. These are much lower drag than (1), but the ones I've seen mount on the intersection of the chain stays with the bottom bracket, and they don't last long. They're also not easy to come by.
The Sturmey-Archer dyno hub. I haven't personally used it, but it puts the generator inside the front hub of the wheel. I have a close cousin and friend who _does_ have experience with them, and he speaks highly of them. They're hard to get in the US (if S-A even makes them any more). It's supposed to be very reliable -- the construction certainly _sounds_ bullet proof -- but there's a bit of a weight penalty.
All of these methods suffer from the simple problem that when you stop the light goes out. So you have your choice of inefficient, more efficient but hard to get and breaks, or quite efficient but heavy and unobtainable.
On the other hand batteries enjoy fairly good reliability, availability, and longevity. What's more, they don't drag on the bike _at all_ and you stay visible at intersections, which is where you most want to be seen.
The best of both worlds would be a generator-powered charge controller and battery management system that charges a small battery pack to keep the lights up when you're stopped. With care this could give you a really nice system, but there's a big potential to buy yourself the worst of all possible worlds. Don't rule it out, but count on lots of work getting it working (and when you do get it going I'll buy one).
--
Tim Wescott
Wescott Design Services
http://www.wescottdesign.com
Posting from Google? See http://cfaj.freeshell.org/google/
"Applied Control Theory for Embedded Systems" came out in April.
See details at http://www.wescottdesign.com/actfes/actfes.html
How about mounting several of those LED light generators that you shake back and forth. You can also put one under the seat so you can bounce up and down. Anytime the bike hits a bump your good to go.
Raleigh bicycles (who owned Sturmey-Archer) had this system on some of their products in the 1950s, but there were no rechargeable cells cheap enough in those days, so there was just a (selenium, probably) rectifier to isolate the battery from the lamps when the dynohub was generating.
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Most are 6v and 3W. They generate the 3W from a very low speed. This is because of a German specification for generator performance on bicycles, and Germany is a huge market for such devices, so pretty much everyone supplying Europe makes stuff to the German specification. The convention is to run either a single 3W front lamp, or a 2.4W front and
0.6W rear in parallel (thus creating a 3W load).
The drag and power output of generators varies. To a large extent, you pay more for lower drag and higher efficiency.
If it's a tyre generator, then the tyres need to have side-walls which are strong enough to take the wear. Modern thin "skin wall" tyres found on many race bikes are not really suited. Modern touring tyres are usually fine.
Look at the Busch and Muller website for one supplier. They have LED front and rear lamps, as well as conventional bulb options.
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I think Peter White in the US may import some B&M lamps or some similar items. He also has the expensive (superb) Schmidt SON generator hub. Not sure if he does the "half the price and almost as good" Shimano alternative one (Shimano make several, their top model is the good one).
An expensive, but clever, LED front light (the 1203D) is available from SolidLights in the UK. Designed for use with a hub generator, though should work with side-wall generators. It should be compared with the twin E-6 lamp setup often used by hub dynamos.
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I think the LightSpin generator has an option to include a re-charging circuit which keeps the lamp on full power for a short time when stopped. (If you can't read / translate from Swiss-German, then google for other pages on their products)
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I think Sheldon Brown has pages on generator driven lamps.
I have B&M lamps on a couple of my bikes. The tail lamps are LED, the fronts are conventional bulb. Both front and rear have "stand lights", so stay illuminated when stationary for a few minutes (front illuminated with single LED marker lamp, not glowing your route). I have two different generators: the newer one is a Shimano hub built into a wheel for winter use on my better tourer, and a B&M Dymaotec-6 side-wall generator for my hack bike; cheap enough to not worry about it, and sufficient quality for a 4 mile commuting ride.
- Nigel
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Nigel Cliffe,
Webmaster at http://www.2mm.org.uk/
My enthusiasm for making something of this sort became quite tempered by the simple fact that I cannot possibly make the optical part of it (making sure that LEDs are located in a near perfect spot of a near perfect reflector) nearly good enough.
So it boils down to either buying a ready product, and they seem to be too expensive, or just going with a cheaper light that takes four rechargeable AA batteries.
As my use of the bycicle includes commute to a train station, I am averse to buying very expensive components.
So, I decided to go with a cheaper 4AA light and bought an item similar to this in all respects:
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I hope that it provides enough illumination, but if not, the loss is not huge. I will rarely run in complete darkness, I hope.
The current issue of the Audax UK magazine (*) has an article on AA battery performance in cycle lights. The conclusion was that NiMH rechargeables of 2700mAh were best performance/price option, and some no-brand names were as good as branded items costing three or four times as much. The NiMH cells kept the test-lamp running at "usable" brightness much longer than disposable AA's (Duracell), and nearly as good as much more expensive Lithium cells.
Keep NiMH cells charged regularly, as they can discharge whilst standing still. Turn off the lamp as soon as the output dims significantly to avoid damaging the cells (ie. don't run them down to totally dead).
(* Audax UK is a club for very long distance cycle riding. Many Audax riders ride long distances at night, some events require through the night stages, so interest in effective lighting systems is high. )
I can understand that, though my choice for my bike which is left at station was a modest price generator and lamps on the grounds that they are bolted to the bike and always ready to turn on.
If you don't mind carrying the battery lamps with you, and can keep the batteries charged up, they are effective.
- Nigel
--
Nigel Cliffe,
Webmaster at http://www.2mm.org.uk/
A good place to start getting familiar with generator stuff is peter white cycle's home page, I think peterwhitecycles.com. The generator-powered LED he sells are Inoled, one of the few brands currently available.
I recently set up an Inoled 20+ on a bike I built up for a friend, and we've done a fair amount of riding side by side together. We both have Schmidt hubs and my lights are a dual E6 setup. The Inoled is cheaper, not as well designed (it has a design issue where it's rubber switch button cover can get pushed into the body of the light, and it generally doesn't fit very well - how good of a job it's doing at keeping water out is yet to be seen, but it's probably fine). The amount of light it puts out is pretty good and usable, but less than the E6's by a fair amount. E6's are still quite a bit better for going fast in the dark. Not having to replace bulbs is pretty nice, but it's not a major issue on halogen lights either. However, one thing that the Inoled does that halogens can't match is reach full brightness at low speeds. Peter White's site says it's full brightness at 4.5 miles an hour, compared to like 11 for the dual E6's. Also, it has a standlight that's perfectly functional for reading maps or being seen while you're stopped.
There have been credible reports that some of them are *fakes* (the generator part does nothing) and they just run off of primary cells button cells for a while.
Best regards, Spehro Pefhany
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you'd presumably want white low dome stars with optics at $14.80 each
My own experiments are documented at
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but [gasp] the schematic isn't up-to-date; there's now an LED taillight as well. Drop me a note if you're interested and I'll try to fix the diagram. No standlights, however. That's less than ideal.
The system used on my father's Breezer Uptown 8 is a remarkably nice setup: good halogen headlight, LED standlights front and rear with a Shimano hub dyanamo. Unfortunately it does not seem inexpensive to buy the dynamo in the US, and the cost of lacing a wheel is not appealling unless you need one for other reasons. Roller dynamos work and are both cheap and easy.
Drop me a note or post any questions you might have.
I got them on Ebay. 50 for 99 cents plus $18 'shipping'. Thats basically 50 for $20. They are 10mm (big) and have a 10 degree angle, which runs up the mcd spec. I also bought 50 UV LEDs for $10 plus free shipping - they work great too.
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