Luxeon-based bike light, dynamo-powered

Prompted by another bike light post, I have worked out how to put pictures up, and here is mine.



Four 1W Luxeons.
Two 'six degree' Fraens (actually 10deg with white leds), two 30mm optics.

I love it. I have been using it for over a year and it is the best dynamo light I have ever owned - though I say so my self!

And.... before anyone explains to me that battery light is better...I am a long-distance all-night cyclist.
And, AFAIK, dynamos are less bad for the environment.

Steve

Nice /ubbthreads/images/graemlins/grin.gif

How did you wire them up - two in series, two parallel, current distribution resistors for the two chains - or simply wide beam or narrow beam as alternatives, 2 LEDs in series directly to the dynamo?

Bye
Markus

This version has a switch with all sorts of series-parallel options.
It was originally so I could see which beam shapes work best.

A Schmidt hub can drive 2 in series, 2 strings of 2 in series, and 4 in series.

The light difference between 2x2 and 4 in series is noticable, but not as much as you would hope as the high current through the leds makes them less efficient.

Steve

I'd suggest figuring out some way to make it less attractive, and thusly less prone to theft. /ubbthreads/images/graemlins/grin.gif
My own luxeon dynamo headlight looks like a 5 year old kid built it, so it's probably very safe from thieves.

A very nice bit of work! If I ever re-design my light, I'd be tempted to use one of the 30mm optics with a 3W Luxeon, if only to make it smaller and easier to mount. The downside is that the 3W Lux isn't as nicely matched to the typical bike dynamo. Maybe I'll just wait till Luxeon brings out an improved 5W led with better heatsinking?

Steve K.

GO BIKE DUDES!!!

That looks real nice!!

How do you find the 30mm optic VS the Fraens?? Are they the LP's??

What current are you driving the 1 watts from, in the '4 in series' mode??

What is the most current you can pull from one of these hub's??

Did you make the cases yourself??

Top work anyway...

Cheers

Ktronik

Wicked cool!!!

I don't know anything about dynamos, but is it possible to put a rechargeable battery in series with that thing? That way you could use the dynamo to charge the battery, and run the LEDs off the battery.

Hi Lux Luther,

Yes you can,

I am working on that system right now...

The battery is run in parallel...a few problem still I am working on are:
Not overcharging or over disspating, the NiMh batterys ( a simple LED indactor circuit will tell me if the batterys are charged or drained)
When they are charged, I could flick the dynamo to direct drive the LED's, or just switch the dynamo off to save on drag, using the batterys to run them, so idealy use the dynamo on the downhill only, depending on the sutation...

I would also add a 'CC1W' Constant current driver from George s (georges80) to the luxeon stars, from the batterys, I have made a mod for this PCB for 3 different outputs, so you can pick the output level depending on the sutation...

In direct drive mode (batterys switched off) & the dynamo droppes below regulation, the driver would go into direct drive mode...

The type of luxeon would be dependant on the output of the dynamo, I would start with 2 / 1watt LS in series or 2/ 3watt LS in series...(depending on the final voltage of the hub / dynamo, you may have to use a 'boost' circuit to run 2 or 3 LS, but is worth using a driver to keep the LS safe on screaming downhills)

If you want the best go for the HUB type system, as above, but with this, some hubs can not turn off...

The below info is thanks to the guys @ Twinbright Labs, for the web page click here

Electrical explanation

Fig. 1: Schematic diagram




Fig. 2: Volt-ampere characteristic of a bike alternator
The alternator, when in operation, makes 6V of AC which are rectified by the four Schottky diodes. The voltage is not necessary 6V. It accomodates the actual voltage of the batteries due to inherent volt-ampere characteristic of the alternator (Fig. 2). The graph shows characteristic of the alternator under saturated condition. As two schottky diodes have voltage drop around 1V, voltage on the alternator is about 7V and thus the alternator puts out some 465 mA of current when saturated. Saturation of the alternator occurs at some mild speed, say 15 km/h. With this current of 465mA, 1300mAh batteries are fully charged within 4 hours. The voltage of discharged batteries is 5.5V, of nominally charged 6V and of fully charged 6.75V. As the light output varies with these values, it is recommended to operate the batteries near full charge.

Under lights switched on, 465mA flow into the batteries and 500mA into the lights, so it results in 35mA flowing out of the batteries, which will discharge them in 37 hours. Standing with the bike discharges them rapidly, in 2.6 hours.

465mA of charging current is in the area of "quick charge" of the NiMH batteries. As batteries are well cooled by resulting wind when the bike goes, they are operated under good conditions. But overcharging must be avoided, because in such a case the batteries start warming rapidly and are in a risk of destruction. Checking them with a multimeter is necessary after prolonged charging.

Anyway I am still working on it, and may still find things I need to make / change, if you get ahead of me, please let me know how you went...

Enjoy

Ktronik

Ktronik asked:

> How do you find the 30mm optic VS the Fraens??

30mm is a narrower beam. I would say (and have said before on CPF):
30mm for road touring and Audax. Fraens for commuting and off road.

> Are they the LP's??

What are LPs?

> What current are you driving the 1 watts from, in the '4 in series' mode??

Standard dynamo current: 0.5A to 0.6A

> What is the most current you can pull from one of these hub's??

They are basically 0.5A (RMS, alternating)constant current sources.
You can't pull any more. The thing you have control over is output voltage.

> Did you make the cases yourself??

No, I gave the desired dimensions to a machine shop and paid lots!

This is the mark 3, I did make the mark 1 and 2 myself.

> Top work anyway...
Thanks, nice of you to say so.

Lux asked:
> is it possible to put a rechargeable battery in series with that thing? That way you could use the dynamo to charge the battery, and run the LEDs off the battery.

Yes, lots of schemes are possible, although charge control of NiCds (and NiMh) can be tricky.
AFAIK Steve K has used voltage-mode charging with some success.
Trickle charging is OK, but needs lots of cycling between stops. I have used this before, managed by a microcontroller.
Coulomb counting is ideal for fast charging, but is tricky.
There is not really enough current available for deltaV termination, and this requires a constnt environmental temperature.

Liions are easy to gas-gauge, but need much care when charging and also don't match well with Luxeon voltages.
I would like to use some form of lithium storage in a future version.

Steve

On the subject of charging batteries from the dynamo...
yes, it can be done, but as Steve/Bandgap says, there are "issues". /ubbthreads/images/graemlins/grin.gif

I used a voltage-mode charging scheme on 5 nicad cells, and then used the battery to run the headlight. It worked fine most of the time. The problem was in the winter, when the light was on most of the time, and the batteries were reluctant to charge in the cold weather. The battery would have little charge, and would run down quickly when stopped. It didn't perform as well as a standlight as I desired. (it worked great in the spring, summer, and fall, though).

My latest scheme has been to drive the light directly from the dynamo, but added a small led standlight in series. The Schmidt dynamo handles this nicely (the standlight adds about a 1.7v drop). The standlight consists of 10 yellow leds facing forward and 10 red leds facing aft. The voltage drop across the yellow leds is used to charge a single nicad cell (with a blocking diode in series with the nicad cell). When the dynamo stops, the nicad cell powers a small boost converter, which then powers 4 yellow leds. The 4 yellow leds are the actual standlight. The other leds form a bright taillight and a forward "be seen by" light. It might take a schematic to make it understandable.
/ubbthreads/images/graemlins/wink.gif

Steve K.

Yes,
adding a battery seems like to much hassle, when you can just hook them up to the hub & off you go...given what has been said, 2 / 3 watt LS in series would be another good option, they work just fine at 500-600mA / 6v & you would cut down on the lights needed on the bar...
I use the 30mm optics & like the punch!!! I have fitted the 30mm lens into a vistalite head & cateye head unit, & they fit straight in, no problem...this may be a cheaper option for head units...




I am always a fan of simple & lite...so keep up the good work!!

ktronik

the installation of the 30mm optics into the Cateye & Vista heads looks pretty slick! One question tho: how do you get the heat out of those housings??

If I ever upgrade from my cheesy 5W Luxeon installation, and can't get a decent commercial light, I think I'll use two of the 3W'ers in series, and with 30mm optics in this sort of housing. Maybe mount one on each fork blade?? Might even be an advantage in aiming one a bit low, and the other a bit high.

Steve K.

As always heatsinking is the biggest issue...the cateye has a lot of room in the back after you remove the huge plug that is in there, & the vistalite can be heatsinked to the alloy outside body & you can remove the guts for more room then, plug in the top, switch on the side, with a micropuck, in both for 'plug & play'...

I have been using a combo of stamped alloy, modded VGA alloy finned & copper RAM heatsinks.

But for overdriven stuff, I use remote drivers with low output mode, when stopped... as convection cooled heatsinks are always a big bonus with bike riding...

I have made a fully stripped down race prototype unit for the helmet that is less than 20gm on the head, using low mode for stopped & convection cooled VGA finned heatsink with a 5watt HD LS / NX-05...tiny with a flood type beam, I can build it up with 2/ 1 watt or 2/ 3 watt on the same heatsink these can be made with star/o's or LS & nicer lens, this 5 watt proto is finnished in expoy then wrapped in waterproof srinktape, to keep the weight to a min...remote driver & NiMh pack in the camelbak. This is just a proto 5watt version, but it stays nice & cool even when stopped,



These could also be mounted to the bar with zipties or clamp in the center of the two LS...





But, my best $4 mod of the week, is this unit...(the case cost $4) I added the rest, its super sold, waterproof, fits a 30mm lens out of the box & it wll take a huge heatsink in the body, with driver, switches, & the rest in the back section.

it goes on the head or can be mounted to the bar from a clamp at the bottom.

It will take any remote battery pack 4-30v & has a 3 level output switch using CC1W, CC buck driver, for up to 80hrs runtime on low power mode from a 12v NiMh AA 2000mAh pack, cool running even when over driven, use 1 or 3 watt & dirt cheap!!! Which can all be driven from a dynamo or hub...almost light for free /ubbthreads/images/graemlins/grin.gif



Enjoy

Ktronik

Ktronic.

I am most impressed with your bike lights.

I too have had no trouble getting the heat away from Luxeons on a bike, but I have always used aluminium housings.

The 30mm optic makes a lot of sense for bike lights. The beam is a good profile.
It is a shame they are so hard to get hold of.
Reflectors seem easier to get. I wonder how the beam compares for bike use.

Steve

It seems the faster you go the more 'PUNCH' you need...I like flood on the head & spot on the bar, so a reflector may be good on the head, they are more efficent, but optics are easier for mods...

Still working on the 'away night racing kit'...

NiMh battery pack car charger (cell phone car charger modded)
200-400mA solar charger.
dynamo/ NiMh charger system w full & empty charge LED's

The lights can be driven in 'Direct Drive' straight from the dynamo, from the battery with the dynamo charging, or just from the batterys...When in DD mode the LED's will show the charge state of the un-loaded battery. something like that anyway...

Light for FREE!!! /ubbthreads/images/graemlins/grin.gif

Hi, I'm curious what kind of equivalent lighting output are you getting from this? Ie. compared to other battery powered lighting systems, maybe 5W, 10W halogens (MR11 or MR16 bulbs)? What speed do you feel safe riding at with your system?

Thanks,