Intro / Beginning dynamo LED project light question

[int19]

Hello everyone,

I just registered after lurking a while. I have a sturmey-archer AG3 dynamo hub, and I'd like to build a simple LED dynamo head and taillight for a fun first project. I'm thinking a system based on circuit 3 from this wonderful page:
http://www.pilom.com/BicycleElectronics/DynamoCircuits.htm

So what LEDs can you recommend for this project? Ideally I'd like some with various lens choices so I can experiment with different beams.

Thanks,
Richard

 

[Martin]

Hello Richard,
welcome to CPF and have fun with your first project !

For the headlight, I suggest you go with the Cree XR-E (at least Q5 bin and on a star PCB for easy handling) for a start. A good selection of single and multiple reflectors and collimators for these LEDs is now available from various sources.
I personally got most of mine from dealextreme.

The tail light is uncritical. You may combine several SMDs or use a single power LED. Just pick what mechanically fits best.

Here we don't see the Sturmey Archer AG 3 a lot. It's a dynamo + internal gearing hub. Nice combination. Your bike should look very tidy with this.

 

[int19]

Thanks a bunch! I'll pick one up...

Hello Richard,
welcome to CPF and have fun with your first project !

For the headlight, I suggest you go with the Cree XR-E (at least Q5 bin and on a star PCB for easy handling) for a start. A good selection of single and multiple reflectors and collimators for these LEDs is now available from various sources.
I personally got most of mine from dealextreme.

The tail light is uncritical. You may combine several SMDs or use a single power LED. Just pick what mechanically fits best.

Here we don't see the Sturmey Archer AG 3 a lot. It's a dynamo + internal gearing hub. Nice combination. Your bike should look very tidy with this.

 

[n4zou]

Don't bother doing a dynamo taillight. Running the wire to it is PITA and ugly and you still need a blinkie so you can be seen while stopped at that red light or stop sign. Here is where I get my optics.
http://www.luxeonstar.com/category.php?id=121&link_str=121

My headlight uses a 15X30 lens and holder and a 10 degree narrow lens and holder providing a very good pattern.

10 degree narrow on left and 15X30 on right.

Copper straps leach heat from copper sheet metal used to mount LED's and optics to the aluminum box keeping the LED's nice and cool.
Perf board is used to hold bridge rectifier diodes and 1000uF capacitor.

Note the amber blinkie allowing others to see you when your stopped.
Yes; thats a standard aluminum electrical outlet box and a plastic cover for 115v AC socket. There is a clear plastic lens cut from a blister pack between the cover and optics so the box is totally sealed.

 

[rideatnight]

Running wires to the tail light won't be a PITA, because it's a rear dyno hub.

After building my own housing for a 2x cree front light, I've come the conclusion that it's easier to mod a cheap headlight - everything fits inside much easier. My 2 cents.

 

[markus_i]

... I'm thinking a system based on circuit 3 from this wonderful page:
http://www.pilom.com/BicycleElectronics/DynamoCircuits.htm

So what LEDs can you recommend for this project? ....

First, I'd like to offer a few comments on the circuit: it will work, but
- you can get more light (although starting off at shigher speed) if you use two LEDs in series
- only use the capacitor if you're really, really sure that the connections between capacitor and LED(s) are safe. Any loose contact in there, and your (expensive) LEDs will be killed. This capacitor is also called 'killco' on some German bike groups.
- the rear light will be much too bright (comparable to a rear car foglight). In my experience, a red Luxeon at 20..30 mA with an elliptical beam optic is ample (and will fit inside most standard rear lights). Just connect it (together with a series resistor) in parallel to (one of) the front light LED(s).
- standing lights can be obtained by adding a goldcap + resistor in parallel to any LED


Regarding the LEDs - CREE XR-E for the front light, red Luxeon or CREE for the rear.


Bye
Markus

 

[int19]

Thanks everyone,

Markus, I do think I'll go with the two LED setup. Are there any circuit diagrams out there implementing a 'standlight'?

I'll post some pictures when its done...

 

[Martin]

Thanks everyone,

Markus, I do think I'll go with the two LED setup. Are there any circuit diagrams out there implementing a 'standlight'?

I'll post some pictures when its done...

Richard, assuming you need the standlight (safe-stop feature) on the tail light only (European requirement):
Build a 2-LED headlight, this way you get a voltage drop of around 7 V across your headlight.
Then connect a commercially-made safe-stop dynamo tail light in parallel to this headlight. It's then powered by DC and not AC, but most tail lights have no problem with this.
Trying to build your own safe-stop tail light is no longer economical, a good one is < EUR 10. My favorite is this one.