DynoHubs: What light bulbs/LED emitters?



Per [email protected]:
>How's the battery life? (And with what kind of battery?)

Two C cells.

Dunno yet - except that I accidentally left it on for one or two
days once and it was still putting out light. Only about as
much as a normal flashlight, and I replaced the batteries right
away... but it was still tickin' and it definitely doesn't chew
up batteries right and left.

--
PeteCresswell
 
bob prohaska's usenet account wrote:
> SMS <[email protected]> wrote:
>> You can't reverse bias the LEDs, at least according to the data sheets.
>> You might get away with it for a while, but you'll greatly shorten the
>> service life. For example, the Cree LED specifies a maximum reverse
>> voltage of 5 volts, while Luxeon just says 'don't do it.' While it's
>> true that if you string three together in series you'll probably not go
>> under -15V, the LEDs will only be forward biased and be on half the time
>> (actually less) compared to a filament bulb. You're better off taking
>> the 20% hit of the bridge rectifier than connecting them directly to the
>> dynamo.
> Ahh, but you're missing the whole point: Use a pair of LEDs wired inverse
> parallel, and drive the common point with AC.

Argh, please don't do this. It's extremely annoying.
 
Per SMS:
>Alas, not sure it's still available.

I bought a half-dozen for gifts last week at a Lowe's in the
Philadelphia area. Hopefully it wasn't the last of them.


>BTW, how did you fasten it to the handlebars?

I went low tech: http://tinyurl.com/26ng7t

For my kind of night riding, it's actually quite useful.
With a bracket, the light's direction is fixed. OTOH, I want to
flip it from side to side sometimes to make sure there aren't any
eye-level tree branches.
--
PeteCresswell
 
Peter Cole wrote:
> [email protected] wrote:
>
>> In a bike lighting system, the efficiency of an incandescent bulb -
>> even a halogen one - is terrible. About 90% of the input energy goes
>> to heat, rather than light. If your emitter does a lot better than
>> that, you can afford to feed it through a 75% efficient component.
>> You'll still come out ahead overall.
>
> All this is true, but the typical bike generators today are designed for
> incandescents. With a few design changes they would be much better
> (smaller, lighter, cheaper) for driving LEDs.

It's not just "a few design changes," either. It's a significant change.
It's been done (or at least designed). See
"http://www.wipo.int/pctdb/en/wo.jsp?wo=2006016397". Actual production,
is far in the future, if ever. It's almost chicken and egg though.
Self-powered lighting continues to decrease in popularity around the
world because newer battery powered lighting is so much more efficient,
yet if there were good (and cheap) DC generators available that could
power LEDs properly then self-powered lighting would become more viable.

> My ideal bike light would be a sidewall bottle with an
> integrated/matched 3W LED. Something like that ought to cost $50 and put
> out 300 lumens.

You won't see a single 3W LED on a dynamo for now for reasons that have
already been explained.

But see "http://www.kmc-drrider.com/product_info.php?id=70"

There's another option as well. If you could design a dynamo with a
higher frequency output you could design a custom switching regulator
that didn't first have to convert the AC to DC. At the current time
you're stuck with the losses of rectifying the AC to DC, and the
additional losses of a switching regulator (as used in the high end LED
lights which is converting the DC to AC internally then back to DC), and
as was used in the LightSpin (I believe). Eliminate one conversion and
you could boost the efficiency from what's currently around 50%, up to
70-80%.
 
(PeteCresswell) wrote:

> For my kind of night riding, it's actually quite useful.
> With a bracket, the light's direction is fixed. OTOH, I want to
> flip it from side to side sometimes to make sure there aren't any
> eye-level tree branches.

Actually, with this bracket I made
("http://nordicgroup.us/s78/images/barbracketcree.jpg") the light
direction is adjustable both up and down, and side to side). Using the
rail clamp in the later design, it's adjustable side to side, and if you
don't tighten it too much, up and down as well.

I should have used an acorn lock nut and a shorter bolt to make it look
better, but the acorn lock nuts have to be special ordered from McMaster.
 
On Mar 20, 2:44 am, bob prohaska's usenet account <[email protected]>
wrote:
>
>
> Ahh, but you're missing the whole point: Use a pair of LEDs wired inverse
> parallel, and drive the common point with AC. The reverse bias is never
> more than the forward drop, which presents no problems. Peak current can
> be increased so long as average current is not exceeded. Series pairs
> allow increased voltage with no per-diode increase in reverse voltage.

About the "peak current:" When LED data sheets show a maximum
current, they're referring to DC current. If (as I believe) they're
really trying to limit thermal problems at the junction, then RMS
current would be the appropriate measurement for an AC source like a
bike generator.

But since your (i.e. Bob's) wiring scheme puts only half the AC wave
through a given LED, your RMS current is only half of what's normal
for AC. IOW, you should have even fewer problems with heat sinking,
etc. I like it.

Not sure why Scharf says your design is "very annoying."

- Frank Krygowski
 
SMS wrote:

>> My ideal bike light would be a sidewall bottle with an
>> integrated/matched 3W LED. Something like that ought to cost $50 and
>> put out 300 lumens.
>
> You won't see a single 3W LED on a dynamo for now for reasons that have
> already been explained.

The only thing that has been explained is the inefficiency of the
current generators with a single LED.

> But see "http://www.kmc-drrider.com/product_info.php?id=70"
>
> There's another option as well. If you could design a dynamo with a
> higher frequency output you could design a custom switching regulator
> that didn't first have to convert the AC to DC. At the current time
> you're stuck with the losses of rectifying the AC to DC, and the
> additional losses of a switching regulator (as used in the high end LED
> lights which is converting the DC to AC internally then back to DC), and
> as was used in the LightSpin (I believe). Eliminate one conversion and
> you could boost the efficiency from what's currently around 50%, up to
> 70-80%.

I agree with Andreas in that I don't see the need for a regulator if the
generator is matched to the load. I don't even see the problem with a
multiple emitter stack if the optics are integrated into a single
housing (as the example you show). 3 of the available high efficiency
LEDs would provide 300 lumens with 1 amp from the generator. If the
generators simply reduced the winding turns, they would raise the short
circuit current and lower the resistance enough to make it work much
better with a single LED.
 
Just to be clear about these terms...

On Thu, 20 Mar 2008, [email protected] wrote:

[snip]

> About the "peak current:" When LED data sheets show a maximum
> current, they're referring to DC current.

No, this refers to an "instantaneous" current level - which is independent
of waveform. Of course, operating near an absolute maximum typically
reduces the lifetime/reliability of a given device.

> If (as I believe) they're
> really trying to limit thermal problems at the junction, then RMS
> current would be the appropriate measurement for an AC source like a
> bike generator.
[snip]

Absolutely! In fact, many high quality RMS voltmeters used the heating
effect of the voltage to make that measurement.

-f (E.E.)
 
Peter Cole wrote:
> SMS wrote:
>
>>> My ideal bike light would be a sidewall bottle with an
>>> integrated/matched 3W LED. Something like that ought to cost $50 and
>>> put out 300 lumens.
>>
>> You won't see a single 3W LED on a dynamo for now for reasons that
>> have already been explained.
>
> The only thing that has been explained is the inefficiency of the
> current generators with a single LED.
>
>> But see "http://www.kmc-drrider.com/product_info.php?id=70"
>>
>> There's another option as well. If you could design a dynamo with a
>> higher frequency output you could design a custom switching regulator
>> that didn't first have to convert the AC to DC. At the current time
>> you're stuck with the losses of rectifying the AC to DC, and the
>> additional losses of a switching regulator (as used in the high end
>> LED lights which is converting the DC to AC internally then back to
>> DC), and as was used in the LightSpin (I believe). Eliminate one
>> conversion and you could boost the efficiency from what's currently
>> around 50%, up to 70-80%.
>
> I agree with Andreas in that I don't see the need for a regulator if the
> generator is matched to the load.

Very difficult to do this with no regulation.

I don't even see the problem with a
> multiple emitter stack if the optics are integrated into a single
> housing (as the example you show). 3 of the available high efficiency
> LEDs would provide 300 lumens with 1 amp from the generator.

Yes it might be sufficient. However it is less efficient than a single
LED in terms of lumens/watt.

> If the
> generators simply reduced the winding turns, they would raise the short
> circuit current and lower the resistance enough to make it work much
> better with a single LED.

Yes, but then you've doubled the number of different dynamos needed,
unless the new design could be made to work equally well with
incandescent lamps.
 
On Mar 20, 2:46 pm, SMS <[email protected]> wrote:
> bob prohaska's usenet account wrote:
>
> > SMS <[email protected]> wrote:
> >> You can't reverse bias the LEDs, at least according to the data sheets.
> >> You might get away with it for a while, but you'll greatly shorten the
> >> service life. For example, the Cree LED specifies a maximum reverse
> >> voltage of 5 volts, while Luxeon just says 'don't do it.' While it's
> >> true that if you string three together in series you'll probably not go
> >> under -15V, the LEDs will only be forward biased and be on half the time
> >> (actually less) compared to a filament bulb. You're better off taking
> >> the 20% hit of the bridge rectifier than connecting them directly to the
> >> dynamo.
> > Ahh, but you're missing the whole point: Use a pair of LEDs wired inverse
> > parallel, and drive the common point with AC.
>
> Argh, please don't do this. It's extremely annoying.

Eh? Why no? What Bob has done is clever. I did it too, without ever
having heard of Bob. Now that I've read it, I like his simple
explanation and his simple diagram: makes everything brilliantly
clear. I didn't continue the experiment because I'm not having
anything that ugly on my bike, but that's an aesthetic judgement,
nothing to do with electronics that work. (It's a different matter
that my next experiment, an overvolted 20W MR16 operated on batteries,
provided *vastly more* light.)

Andre Jute
http://members.lycos.co.uk/fiultra/BICYCLE & CYCLING.html
 
On Mar 20, 1:23 am, "(PeteCresswell)" <[email protected]> wrote:
> Per [email protected]:
>
> >In a bike lighting system, the efficiency of an incandescent bulb -
> >even a halogen one - is terrible.
>
> Well, as the OP, I finally shut up and got a system.
>
> --------------------------------------------------------
> - SA (recent-model) XF-DD dynohub
>
> - Busche & Muller HL Lumotec N2 halogen head light.
>
> - Busche & Muller TL Seculite Plus LED tail light
> --------------------------------------------------------
>
> Coming from a hand-held Lowe's hardware "Task Master" flashlight
> with 2 "C" cells and a Cree 4w emitter, I've got to say that the
> halogen headlight is just plain pitiful in comparison.
>
> On a scale of 1 to 10
>         Halogen headlight: .3    
>         Lowe's handheld:        9.5
>
> That's not to say the halogen light is not adequate for the task
> - especially since many greater minds (and vastly more
> experienced riders) than mine/me think they are.  
>
> But, in comparison, the lumens are simply not there.  
>
> In fact, I know a guy who injured himself fairly grievously
> riding a bike path at night (with a headlight): rode right into
> some sort of construction debris and/or hole.  Now, having ridden
> briefly with the halogen light,  I understand how he managed to
> do that.
>
> OTOH, it might be an undercover safety feature at my sub-10 mph
> night time riding speed: drivers see this wobbly, flickering
> yellow light and it gets their attention more just because it
> looks so out of place.  -)
>
> OTOOH, the tail light seems tb pretty decent.  Gives out what I'd
> call sufficient light, and has a stand light feature that shines
> just as brightly when the bike is stopped.  
>
> My original intent was to hang several of those things on the
> back, leaving only a token LED front light - all lights always
> on.... but my limited knowledge of electricity led me to the
> conventional path.
>
> All-in-all, the system does what I set out to do: give my back
> some visibility and keep me out of jail of some cop wants to be a
> **** about having to have a "real" bicycle headlight.
>
> But in the end, although I'll turn on the dynohub system and feel
> better about my visibility from behind,  I'll keep using the
> Lowe's 4w Cree-based flashlight.   That is one *brave* little
> flashlight.
> --
> PeteCresswell

Yeah. This is where we came in: A battery system by itself cannot
provide 100% security, because the battery can run out. A dynohub
system by itself does not deliver enough light for all purposes.
Therefore the thoughful cyclist fits both a dynohub and a battery
light set, and uses them as appropriate. And ignores the outrages
screeching of the to-the-death partisans of either.

Congratulations on achieving a working system that suits you, Pete.
I'm still looking for that flashing front light, and my rear lights
are currently all battery, which isn't quite good enough.

Thanks for a most worthwhile thread, Pete. Even if I had little to
say, I read all the posts carefully, so thanks to all the contributors
to Pete's thread from me too.

Andre Jute
http://members.lycos.co.uk/fiultra/BICYCLE & CYCLING.html
 
On Mar 20, 2:47 pm, "(PeteCresswell)" <[email protected]> wrote:
> Per SMS:
>
> >Alas, not sure it's still available.
>
> I bought a half-dozen for gifts last week at a Lowe's in the
> Philadelphia area.   Hopefully it wasn't the last of them.
>
> >BTW, how did you fasten it to the handlebars?
>
> I went low tech:http://tinyurl.com/26ng7t

Never mind low tech. I love the pics that illustrate why cyclists wear
black shorts!
http://www.flickr.com/photos/48262653@N00/339745153/in/set-72157594449980969/
And I thought it was because SUV drivers frightened them. -- AJ

>
> For my kind of night riding, it's actually quite useful.
> With a bracket, the light's direction is fixed.  OTOH, I want to
> flip it from side to side sometimes to make sure there aren't any
> eye-level tree branches.
> --
> PeteCresswell
 
Andre Jute wrote:

> Eh? Why no? What Bob has done is clever. I did it too, without ever
> having heard of Bob. Now that I've read it, I like his simple
> explanation and his simple diagram: makes everything brilliantly
> clear.

I've seen these set ups and they flicker as the LEDs alternate being
illuminated. If he's eliminated the flickering, and isn't reverse
biasing the LEDs, then I stand corrected.

I didn't continue the experiment because I'm not having
> anything that ugly on my bike, but that's an aesthetic judgement,
> nothing to do with electronics that work. (It's a different matter
> that my next experiment, an overvolted 20W MR16 operated on batteries,
> provided *vastly more* light.)

It would be nice to have a hybrid system without having two separate
fixtures. A battery powered MR16 lamp for a "seeing" lamp, and a dynamo
powered lamp for a "being seen" light or simply as a back-up in case
your batteries go dead. You could also choose to charge the battery of
the MR16, at least partially, from the generator. A "plug-in" hybrid
type solution.
 
Andre Jute wrote:

> Yeah. This is where we came in: A battery system by itself cannot
> provide 100% security, because the battery can run out. A dynohub
> system by itself does not deliver enough light for all purposes.
> Therefore the thoughful cyclist fits both a dynohub and a battery
> light set, and uses them as appropriate. And ignores the outrages
> screeching of the to-the-death partisans of either.

It would be possible to have a dynohub that is sufficient, but it seems
there is no interest in a dynohub with any more drag or any more cost.
Even just a 12W dynohub would be able to power sufficient lights for
most purposes.
 
Frank Miles wrote:
> Just to be clear about these terms...
>
> On Thu, 20 Mar 2008, [email protected] wrote:
>
> [snip]
>
>> About the "peak current:" When LED data sheets show a maximum
>> current, they're referring to DC current.
>
> No, this refers to an "instantaneous" current level - which is independent
> of waveform. Of course, operating near an absolute maximum typically
> reduces the lifetime/reliability of a given device.

Yes, you have to be careful about continuous operation at "absolute
maximum" ratings.

> Absolutely! In fact, many high quality RMS voltmeters used the heating
> effect of the voltage to make that measurement.

Actually, one cheap solution, once you have implemented a
micro-controller based system anyway, is to have a temperature sensor
that reduces the current when the temperature gets too high. This is an
especially good solution for bicycle lighting because the light gets
forced air cooling over the heat sink when in motion, but no forced air
when stopped. The faster you ride, the more light is needed and the more
cooling effect you get. Some sockets for high power LEDs have integrated
fans, but this is getting a bit ridiculous for bicycle lights.
 
On Mar 20, 3:16 pm, Frank Miles <[email protected]> wrote:
> Just to be clear about these terms...
>
> On Thu, 20 Mar 2008, [email protected] wrote:
>
> [snip]
>
> > About the "peak current:" When LED data sheets show a maximum
> > current, they're referring to DC current.
>
> No, this refers to an "instantaneous" current level - which is independent
> of waveform.

I don't think so. At least, not for this emitter:
http://www.cree.com/products/pdf/XLamp7090XR-E.pdf

Take a look at page 4. They list the "maximum DC forward current" as
either 1000mA or 700mA, depending on model; but for both models, they
list the "Maximum DC Pulse Current (@ 1 kHz, 10% duty cycle)" as 1.8
A. Obviously, they're pointing out that the instantaneous current can
be higher than the normal "maximum" current.

Yes, their phrasing is a bit misleading (allowing a "peak" higher than
a "maximum") but the numbers make the situation clear.

> > If (as I believe) they're
> > really trying to limit thermal problems at the junction, then RMS
> > current would be the appropriate measurement for an AC source like a
> > bike generator.
>
> [snip]
>
> Absolutely!

Which means Bob's LEDs should last a long, long time.

- Frank Krygowski
 
On Mar 20, 8:22 pm, SMS <[email protected]> wrote:
> Andre Jute wrote:
> > Yeah. This is where we came in: A battery system by itself cannot
> > provide 100% security, because the battery can run out. A dynohub
> > system by itself does not deliver enough light for all purposes.
> > Therefore the thoughful cyclist fits both a dynohub and a battery
> > light set, and uses them as appropriate. And ignores the outrages
> > screeching of the to-the-death partisans of either.
>
> It would be possible to have a dynohub that is sufficient, but it seems
> there is no interest in a dynohub with any more drag or any more cost.
> Even just a 12W dynohub would be able to power sufficient lights for
> most purposes.

Because of my other hobby, tube audio amplifiers (see Jute on Amps at
http://members.lycos.co.uk/fiultra/ ), I know just about every high-
class wound magnetics custom specialist in the world. I could probably
get an existing hub rewound to 12V. But the problem is that I already
committed myself to the Cyber Nexus Groupset; the automatic gearbox
(which works well with my heart rate monitor to set my exercise rate
much more precisely than cadence can) is far more important to me than
lights can ever be (I work at home; I don't commute). So I'm tied in
to 6V electronics for the foreseeable future -- and I hope my Cyber
Nexus groupset will remain serviceable for the rest of my life. It
would be a waste for which my engineering chums will tar and feather
me to lash out on a custom 12V hub and then waste half of it in heat
to provide 6V for the Cyber Nexus electronics.

I looked at the BUMM 12V dynamo and thought it goddamn pricey for a
sidewall generator and, anyway, one of the main reasons I went to a
hub dynamo was because I find the stuck-on aesthetics of sidewall
dynamos most unappealing. Wasn't the SON chappie talking about a 12V
hub dynamo at one point? That might be worth lashing out for even at
his prices and even with my reluctance to depart from the cheap and
exceedingly fine standard Shimano sets in whichever component field
they enter.

Andre "You get more from Shimano" Jute
http://members.lycos.co.uk/fiultra/BICYCLE & CYCLING.html
 
Andre Jute wrote:

> Misunderstanding. I use a flashing Cateye 1100 at the rear for a
> daylight running lamp. I want a flashing light at the front for a
> daylight running lamp. It would be great to be able to run it off the
> dynohub but no such lamp is available at a reasonable price. (The
> SolidLights 1203D is a dynohub LED light with a flashing mode but it
> is very expensive.) So I thought I might add a little DIY electronics
> and make my Fly IQ flash...

I can't remember which was the thread discussing tail lights, but I did
see two good tail lights from Trek recently. The Flare 7 ($25) uses
seven very bright LEDs and provides 270 degree coverage. The Flare 10
($30) uses ten LEDs and provides 360 degrees coverage (which I find hard
to believe!). I guess I'd still opt for the TL-DL1100, but at least
there are a couple of more choices now.
 
On Mar 19, 7:25 am, Andreas Oehler <[email protected]> wrote:
>
>
> Wasn't your topic efficiency? A Cree XRE 7090 Q5 (and the best Luxeon
> Rebel too) reach 100 lm/W at medium power levels - if properly cooled.
> Small halogen bulbs of high quality don't deliver more than 20-25 lm/W.
> You loose some of the efficiency adavantage by the need of a rectifier and
> maybe other electronics and maybe not so refined optics - but the
> efficiency adavantage of high power LEDs is so big...
>
> But you are right in one aspect: There are a lot of LED lamps out there
> with so terrible electronics and optics that even cheap dynamo lamps with
> halogen bulbs give a more useful light, especially in the regard of
> vertical light distribution.

Andreas (and others) - any general tips on optics for LED homebrews?
I've briefly bench-tested two Crees powered by an antique Sturmey-
Archer Dynohub. The number of lumens seems satisfying (at least in my
dark workshop), but the beam seems very diffuse and undefined.
Especially, as you say, in regard to vertical light distribution.

What I'd like is a pattern tailored for road use, as I've described
elsewhere - not a lot wasted upwards, and ideally, brighter toward the
horizon.

I'd given some thought to hack-sawing into some of my old light
shells, but I'd prefer a bit of guidance over raw trial and error.
Anything to recommend?

- Frank Krygowski
 
(PeteCresswell) wrote:
>
> For my kind of night riding, it's actually quite useful.
> With a bracket, the light's direction is fixed. OTOH, I want to
> flip it from side to side sometimes to make sure there aren't any
> eye-level tree branches.

You've actually hit on a major problem with most of the mounts for
bicycle lights, especially if it's putting out more of a spot beam than
a flood beam. Some of the dual lamp systems have one spot and one flood
to solve this issue. For handlebar mounts it's often the case that the
handlebar is angled slightly and a mount that can't be adjusted slightly
is unsuitable because you can't point the light straight ahead.

I've tried to solve this issue on the mounts I've made. Even
"http://nordicgroup.us/s78/images/IMG_0239.JPG" while it looks fixed,
the holes for the bar clamp are actually quite large so the angle of the
aluminum flat bar can be adjusted slightly from side to side.
 
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