Cree XML on a dynamo

[Wobbly John]

I've been running converted torches on hub dynamos on my bikes for about 5 years.

First off, a 3 Watt Luxeon torch with the battery compartment removed and a bit of machining to screw the switch straight into the head:

Then a year later a pair of 3 Watt Cree torches in series. http://homepages.nildram.co.uk/~talizmar/xntrick/cree.htm

The only other componts I have used in the circuit is a bridge rectifier.

I have recently started using one of the Magicshine clone Cree XML battery lights and am impressed at how it lights up the dark Fens where I ride.

I was wondering about running one of the cheap Cree XML torches from the dynamo. Anybody tried one with a simple rectifier in the circuit?

 

[jdp298]

Anybody tried one...

No, not directly.

You won't hurt the light output by using a big capacitor either. It won't give you a worthwhile standlight, but it will reduce flicker at lower speeds.

If you really wanted, you could put another switch to isolate the capcitor, making you flicker in town but not out on the roads. What do you do for a rear light?

 

[steveo_mcg]

I've been using a couple of xml on my bench whilst trying something else they are impressively bright. According to the datasheet 2 xml @500ma put out about the same lumens as 3 xr-e @ 500ma.

Thats a good looking bracket, where did you get it?

 

[Toaster79]

You could try with XM-L EZW 6V version Or MT-G2 6V.

 

[Wobbly John]

Thats a good looking bracket, where did you get it?

The handlebar clamp is fabricated from computer hard drive platter spacers, and the bit that clamps on the torch and bolts to the clamp is a brake cable stop for cantilever brakes.

 

[steveo_mcg]

Cool, good ideas.

 

[Wobbly John]

No, not directly.

You won't hurt the light output by using a big capacitor either. It won't give you a worthwhile standlight, but it will reduce flicker at lower speeds.

If you really wanted, you could put another switch to isolate the capcitor, making you flicker in town but not out on the roads. What do you do for a rear light?

The 3Watt lights I run at the moment only flicker noticably at below walking pace, so not a problem for me.

I use a couple of 1/2 Watt battery lights on the rear - one flasher, one constant. With flashing lights only in fully dark conditions, it makes it difficult for observers to judge speed & distance. On my recumbent bike, I also have blue Electro-luminescent cable (computer modding type connected to a battery pack) and red Christmas lights wound around the flag pole.

The reason I run dynamo front lights is that I sometime ride all night and powerful lights would drain a battery.

 

[jdp298]

Recumbents are excellent aren't they? Have you a link to the computer modding cable thingy? I've been wrestling with what to do on the flagpoles for some time now. Currenly they're only any good in the day, but there are 6 rear-facing lights between the mudguards, rack and seat back, so it's not bad really, if a little low.

http://www.flickr.com/photos/jdp298/sets/72157628194545663/

 

[yellow]

one single led is waisting the power the dynamo can give.
It is "restricted" in current, but not (really) in Voltage.
It can power up three to four of them.

Easiest build: get an MC-E, wire the four emitter plates in series + use a rectifier ...

 

[Toaster79]

one single led is waisting the power the dynamo can give.
It is "restricted" in current, but not (really) in Voltage.
It can power up three to four of them.

Easiest build: get an MC-E, wire the four emitter plates in series + use a rectifier ...

He'd be better off with EZW XM-L mentioned before. Due to it's lover Vf than MC-E and higher efficiency it would be feasible to use even 12V one.

 

[SimonInd]

I've been commuting for over a year with an XM-L up front and a red XP-E at the rear, wired in series with supercaps to provide standlight functionality. The circuit is in this thread http://www.candlepowerforums.com/vb...f-a-Supercap&p=3800413&viewfull=1#post3800413.
I find a single XM-L with a 50mm reflector is fine for commuting in London, I have thought about adding more light up front but I'm not sure the additional complication of a second headlamp in series with the circuit is worthwhile in town.
The EZW XM-L looks interesting but the higher Vf would make the standlight harder to realise.

 

[BobRoss]

I've been commuting for over a year with an XM-L up front and a red XP-E at the rear, wired in series with supercaps to provide standlight functionality.

I may as well share my embarrassing cap moment in my first post. My first DIY light build is (was?) going to be circuit 6 from http://www.pilom.com/BicycleElectronics/DynamoCircuits.htm.

I've been successfully prototyping (and obsessing over) the circuit with some resistors and really low powered leds while waiting for a DX order with some XMLs to come in. Finally, they came. My soldering skills are suspect at this point, so I decided to test the lights with alligator clips on a breadboard, first. Of course, they don't make good contact on my first attempt, but I continue to spin the wheel and charge the smoothing capacitor on an open circuit. Then, while messing around with the clips, I see a bright flash, and the LED is dead. More embarrassing is that I immediately did it again.

Anyway, I think I am starting to understand some of the reluctance to use capacitors in dynamo lights - true, I would still have two functioning XMLs if not for being an idiot, but I'd rather have an idiot proof light than learn by destruction. This is my way of voting against using a smoothing cap.

Very nice build, by the way.