Kaidomain is considering a dynamo light. Suggestions needed

[Calina]

Hi all,

I have tried for some times to interest Kai or Dx in selling a cycler's dynamo light . Apparently Kai is willing to consider doing it but he would appreciate your input. Instead of discussing the subject in CPFMP, I thought I would start a new thread here where it would get more visibility and feedback.

 

[alpg88]

Re: Kaidomain is considering to dynamo light. Suggestions needed

is there no other place to buy those dynamo lights????? why does it have to be kd or dx????

 

[Calina]

Re: Kaidomain is considering to dynamo light. Suggestions needed

I'll start with my own suggestion to Kaidomain.

I'm thinking about a light with 2 XP-G and elliptical or medium optics plus an XP-E and narrow optics for throw. A switch would also likely be appreciated by those using a hub dynamo (I'm using a bottle dynamo). A standlight of maybe 30 lm would be nice especially if it is possible to regulate its output.

Here is a very good thread discussing standlights:
http://www.candlepowerforums.com/vb/...=210602&page=3

You might also check the Pilom.com site.

The dynamo light could end up being much less expensive than a battery light (no charger nor batteries).

Other models with more sophisticated options could be offered later on for a price.

 

[yellow]

elliptical and anything other than spot optics are totally crap
(and even optics are sub-par, but thats individual sight of me, of course)
but You are not long enough a member to have followed the evolution of white led, their focusing devices and ways to build (bike) lights to know that (man, what have You "lost". Just a few years ago, but sooo exciting)

anyway: we all here learned, by try and error, that elliptical optics and wide beam optics are useless.
8 degree and not align the beams in parallel. Have them spread by a few degrees.

in case of the 8*20 elliptical optics: 2 led with them.
Compared to 2 led with 8 deg. optics, but their beams set to left and right, so that there is a small overlap in the middle ...
The elliptical beams get smoked!!! You would not believe how hard!
And dont even think about wide beams, its better not to power up the led with such an optic, total waste of energy.

Extremely rational "proof":
have You read in here about anything else than reflectored lights?
Maybe asphericals for extreme throw?
... usually this has a reason: survival of the fittest.
If all these things dont give good results, they are not used by the masses.
hihihi, "masses" of modders


You might believe it, or not. Anyway. Maybe best to make ones own experiences,
but dont blame anyone, when Your findings are the same (and costed some bucks)

 

[Fulgeo]

Extremely rational "proof":
have You read in here about anything else than reflectored lights?
Maybe asphericals for extreme throw?
... usually this has a reason: survival of the fittest.
If all these things dont give good results, they are not used by the masses.
hihihi, "masses" of modders

Not saying I disagree with this statement, but wanted to say that with a single die LED like a Cree R2 for example, I think a good aspheric lens in an adjustable head gives you the best of both worlds. On my aspherical lens flashlight builds I construct them in such a fashion that I can dial them down for excellent extreme throw and loosen them up a bit for a good cone of flood. Hows this for cycler's light idea? Get a good SST-50 single die LED and a 33-37mm aspherical lens. Glass or plastic lens but plastic might be preferred because of weight. Set up small fast motor driven focusing light head connected to a toggle switch mounted to your handle bars. With a flick of the toggle switch you can adjust your beam depending on you needs. In a tight forest track open up the cone for flood. On a fast open stretch toggle down for throw. You could even drive the SST-50 with (2) 4xAMC7135 drivers boards in parallel. Pull in one circuit you have 1.4 amps to the light. Pull in the other circuit and you have 2.8 amps to the light. This give you low and high beams. Well just some random thoughts stimulated by this thread. Happy mods and happy cycling.

 

[Calina]

Not saying I disagree with this statement, but wanted to say that with a single die LED like a Cree R2 for example, I think a good aspheric lens in an adjustable head gives you the best of both worlds. On my aspherical lens flashlight builds I construct them in such a fashion that I can dial them down for excellent extreme throw and loosen them up a bit for a good cone of flood. Hows this for cycler's light idea? Get a good SST-50 single die LED and a 33-37mm aspherical lens. Glass or plastic lens but plastic might be preferred because of weight. Set up small fast motor driven focusing light head connected to a toggle switch mounted to your handle bars. With a flick of the toggle switch you can adjust your beam depending on you needs. In a tight forest track open up the cone for flood. On a fast open stretch toggle down for throw. You could even drive the SST-50 with (2) 4xAMC7135 drivers boards in parallel. Pull in one circuit you have 1.4 amps to the light. Pull in the other circuit and you have 2.8 amps to the light. This give you low and high beams. Well just some random thoughts stimulated by this thread. Happy mods and happy cycling.

I don't know what type of dynamo you are using but I've never seen one providing 1.4 amps and certainly not 2.8 amps.:devil:

 

[alpg88]

i doubt he is using any dynamo, neither have i seen one that gives 2 amps, it is possible to make one, sure, but damn, pedaling will be extremely heavy task, unless you build unipolar dynamo.

i,m pretty sure that is the reason you don't see high power leds fed off dynamo, they need a lot more current than dynamo can provide, without making you work 2x as hard pedalling.

 

[Calina]

elliptical and anything other than spot optics are totally crap
(and even optics are sub-par, but thats individual sight of me, of course)
but You are not long enough a member to have followed the evolution of white led, their focusing devices and ways to build (bike) lights to know that (man, what have You "lost". Just a few years ago, but sooo exciting)

anyway: we all here learned, by try and error, that elliptical optics and wide beam optics are useless.
8 degree and not align the beams in parallel. Have them spread by a few degrees.

in case of the 8*20 elliptical optics: 2 led with them.
Compared to 2 led with 8 deg. optics, but their beams set to left and right, so that there is a small overlap in the middle ...
The elliptical beams get smoked!!! You would not believe how hard!
And dont even think about wide beams, its better not to power up the led with such an optic, total waste of energy.

Extremely rational "proof":
have You read in here about anything else than reflectored lights?
Maybe asphericals for extreme throw?
... usually this has a reason: survival of the fittest.
If all these things dont give good results, they are not used by the masses.
hihihi, "masses" of modders


You might believe it, or not. Anyway. Maybe best to make ones own experiences,
but dont blame anyone, when Your findings are the same (and costed some bucks)

I'm sure 2 x 8 deg. optics will smoke an 8*20 elliptical but it is not everybody who wants to see to the other side of a football field. For commuting I'd be perfectly happy with a flood light that project to 30 or 40 meters and a spot that throws to 60 or 70 meters. I must say though that around here the land is almost perfectly flat and I hardly ever exceed 30 km/h with my Giant Cypress.

Obviously your needs are different. That's fine we're here to throw ideas.

Ideally I would rather have optics specifically designed for a bike light (with beam cutoff and a beam that gets brighter farther away from the bike) rather than make do with flashlight's optics.

 

[ryball]

My perfect light would have: (bolded are higher priority)

standlight
built in reflector
dual beam with strobe option on one
multiple mounting options (I have no room on my handlebars)
ability to drive a tail light
no external switch (again, my handlebars are too crowded as it is and I hate cable mess)

I don't need it to be a throw monster. I am commuting in the city and mostly just need a light so that I can be seen. I do like to see what is ahead of me, too but I don't need to see a mile ahead. Ultimately, I realize that all of these desires in one package at a reasonable price are most likely completely unrealistic.

 

[Calina]

i doubt he is using any dynamo, neither have i seen one that gives 2 amps, it is possible to make one, sure, but damn, pedaling will be extremely heavy task, unless you build unipolar dynamo.

i,m pretty sure that is the reason you don't see high power leds fed off dynamo, they need a lot more current than dynamo can provide, without making you work 2x as hard pedalling.

My guesstimate is that you can get 450 lm. O.T.F. with three XP-G R5 and a dynamo. Maybe that is not enough for downhill racing but it sure would satisfy a lot of commuters and you never have to worry about getting out of juice, ever. Well almost ever, dynamo die too; always carry a backup flashlight.

 

[ryball]

Not sure what emitters these guys are using, but they claim 680 lumen

http://www.supernova-lights.com/shop/show_product.php?products_id=151

 

[Calina]

I have no idea as to what type of LED they are using, their claim could be inflated which is not unusual. According to jtr1962 the XP-G R5 gives 200 lm at 500 mA, that's why I think 450 lm O.T.F. is realistic. It is also possible that they tweaked the amps a little by adding a condenser in the circuit.

A dual beam would be nice and I think would simply requires a switch to activate the thrower. I don't think a strobe is a necessary complexity when you have 450 lm at your disposal; you should be seen don't worry.

As a tail light I run a cheap six LEDs blinky modded with 25000 mcd 5mm LEDs. It is bright and runs forever on 2 AA but I still recharge them every month or so.

 

[Fulgeo]

i doubt he is using any dynamo, neither have i seen one that gives 2 amps, it is possible to make one, sure, but damn, pedaling will be extremely heavy task, unless you build unipolar dynamo.

i,m pretty sure that is the reason you don't see high power leds fed off dynamo, they need a lot more current than dynamo can provide, without making you work 2x as hard pedalling.

I think Calina was being a little facetious. I guess he was pointing out to me that my post maybe a bit off topic since the setup I was suggesting would ideally be driven by 3xD NiMH. The real issue I was talking about was the versatility an aspherical lens adds to LED especially since it allows you to "dial in" the desired throw or flood of single die LED setups.

 

[yellow]

or possibly just summed up the individual currents of series wired led?

three in series is no problem for any dynamo,
4 i.S. should be possible with any hub dynamo

 

[Steve K]

or possibly just summed up the individual currents of series wired led?

three in series is no problem for any dynamo,
4 i.S. should be possible with any hub dynamo

The SST-50 datasheet doesn't show multiple dies on a single substrate. It's just a very large single semiconductor.

The Cree MC-E, with 4 dice, would let you wire up 4 led dice in series, though. It would be fine for most people, but wouldn't light up at slower speeds. My commute has a steep hill where my speed is only 4mph, and my Schmidt hub can barely light up two Cree XR-E's in series.

Steve K.

 

[Martin]

It's not a big deal converting 6V / 500mA into 3V / 1A.
Busch & Mueller are doing this in their mass-produced LED headlights for a long time now. Rectify, chop it 50:50, drive a single LED. Anyone who wants to build a dynamo LED headlight has probably already bought one from Busch & Mueller and reverse-engineered it.

And yes, if more power is desired, just chop the DC 20:70 and let the input voltage rise > 6V. As we know, dynamos deliver a limited current but voltage is not strictly limited (unless someone put a zener diode).

 

[Calina]

I was away at the begining of the last week with limited access to the internet and somehow I lost track of this thread.

I think Calina was being a little facetious. I guess he was pointing out to me that my post maybe a bit off topic since the setup I was suggesting would ideally be driven by 3xD NiMH. The real issue I was talking about was the versatility an aspherical lens adds to LED especially since it allows you to "dial in" the desired throw or flood of single die LED setups.

I was teasing of course.

I don't think the SST-50 is appropriate for a dynamo light as its power requirement is huge.

Troutie posted some very interesting beam shots here: http://www.candlepowerforums.com/vb/showpost.php?p=3125821&postcount=23

I can see that yellow's suggestion of using three narrows with diverging but overlapping beams would make for a very good light but I wouldn't count on KD to implement it.

It seems that the elliptical Carclo gives a pretty useful beam but lLooking at those shots, I'm wondering if one elliptical and two narrows wouldn't be better than two ellipticals and one narrow. Keep in mind that Troutie's tests were performed at 1A.

 

[ohropax]

I have some numbers on the eletrical side of things for you to consider.

First of all i already have a triple CREE XR-E Q5 dynamo headlight and while being quite satisfied with the amount of light, i do not like its homebrew casing. Inspired by the vastly succesful DX P7 bicycle light i digged into the eletronics section.

Based on internet research I created a Spice model that properly reflects the behaviour (inductivities, internal resistances etc) of a common SON/Shimano hub dynamo. Also I created Spice models for the CREE XR-E and SSC P7 LEDs, for ultralow Vdrop Mosfet rectifiers and Spice models for basic unregulated DC-DC converters. The latter are required for properly driving P7 LEDs.

Under ideal conditions, (ultralow Vdrop rectifier, best-fit series capacitor, best-fit load impedance) you can extract
3.9W at 13km/h
6.4W at 21km/h
7.6W at 27km/h
8.6W at 34km/h
9.1W at 43km/h
9.6W at 55km/h
from a stock hub dynamo.

After analyzing various simulations i basically i see two approaches to get the maximum amount of electrical power to the dies.

a) minimum loss by using minimum amount of parts, this means:
going for 3 or 4 series connected CREE XR-E or XP-G LEDs or one series connected MC-E LED, use the low-drop rectifier and select an appropriate series capacitance. This way you get 6W-7W from 21km/h to 34km/h when using 3s, or 5W-8W when using 4s/MCE.

b) maximum extraction by modelling an optimal adaptive load, this means:
going for a P7 or paralled connected MC-E LED, the low-drop rectifier of course, and using a custom-regulated DC-DC buck converter to track the maximum power point. The converter has to jitter the duty cycle and 'follow' the direction of increased output current/voltage. Additionally the converter might also jitter the input series capacitance but i suppose the costs would outweigh the wins. If the converter is a simple Mosfet/Schottky buck converter, the diode voltage drop accounts for about 10% efficiency loss. As a result you only get 6W-7W from 21km/h to 34km/h. In order to gain over the 'plain simple' method one should actually use a sychronous buck converter, putting an additional 0.5-1W to the dies.

Considering the improved efficiency of the new XP-G emitters, the simple solution probably looses in Watt terms but wins in Lumens terms. But the optics part might change this equation and is a different matter.

If anyone is interested i can expose further details or post the schematics.

so far,
my 2ct,
Marcus

 

[ohropax]

@Calina, Kai, DX

I assume that the simplest, least expensive and probably quickest time-to-market solution would be a stripped-down version of the DX P7 900 lumens bike light with the P7 emitter swapped against a series connected MC-E emitter. Variations would be
1a) no electronics at all
1b) include internal low Vdrop rectifier, but no internal series capacitance
1c) include internal low Vdrop rectifier and internal series capacitance
1d) include internal low Vdrop recitifer, ship with multiple 'adapter' cables containing different series capacitances so user can select his favourite.

Alternatively the emitter could be swapped against a 3s or 4s XP-G setup which would increase lumens output over the 'old' MC-E emitter.

While the DX P7 can be attached to the handlebar nicely and space-savingly, an option to permanently attach the bikelight (using the fork crown central screw or the usual front-light thingy) would be appreciated as well.

What about non rotational-symmetric optics similar to the IQ or Cyo LED lights?

If a low-drop rectifier is included: What about adding a voltage-regulated output jack so users can connect their backlights or other portable equipment (GPS or phone charging cables)? Adding such a 5V regulator module should be an easy task, the choice of connecter/jack type maybe not so..

best regards,
Marcus