Alternate Bicycle headlamp with LEDs.

[jokunen]

I contemplated doing a LED lamp for my bicycle with 3W LED and I already bought such a LED, before relevant article was published in Elektor. But then I noticed that I could buy MR16 -model LED "bulb" that has 12V AC/DC 1.5W rating using 18 5mm HB-LEDs. All this is encased in glass, so it's definitely watertight.

This bulb is obviously meant to be used with 12V halogen supply, not with bicycle dynamo. As it can be fed with AC I connected it anyway directly to my Shimano fronthub alternator. At 15 km/h there was light coming out, but not enough, as the voltage was around 8V AC, measured by multimeter. So one needs more voltage with this one. Easy solution was to use voltage doubling rectification, using 2 diodes and 2 electrolytic capasitors. I happened to have around 470uF/100V caps and 1N4007 diodes and with those the light begins at 5km/h (flickering) and with around 15 km/h the voltage is already more than 12V DC at the lamp terminals, giving bright steady illumination.

Probably that doubler would work even better with 40V/1A or 40V/3A schottky diodes and 2200uF/16V or 25V caps. Now I just need to find suitable enclosure/holder for the bulb and electronics. I hope this can inspire others to consider using MR16 bulb in their setup. It outshines 6V/2.4W halogen hands down and needs no frequent replacing.

Luxus setup would have (6V or 7.2V = 5 or 6xAA) NiMh battery recharged by dynamo and step-up converter for the 12V bulb. Then one could have light even while standing or as hand held torch.

--Petri

[grumbleduke]

Petri what article from Elektor are you referring to please?

Richard

[jokunen]

The latest EE issue delivered already to subscribers (2008 September) has article about 3W LED bicycle lamp construction. Look at 2008/09 contents:
http://www.elektor.com/magazines.46742.lynkx
and
http://www.elektor.com/magazines/2008/september/luxury-led-bicycle-light.639294.lynkx

--Petri

[jokunen]

First reference to this article was here:
http://www.i-trixx.com/uk/archief_uk/2008/080702.php
(Didnt find the relevant I-Trixx before I submitted earlier post).

--Petri'

[mr-motorvator]

Nice project, but a Cree R2 light engine already has its own Buck converter and operates from ~3V-12V. It uses 3Watts and emits 300 Lumens in a 3 degree beam. You can put a Fresnel lens from L2 Optics in front to get a wide, low-angle beam or an oval beam.

You MUST make sure it is screwed together properly and that it can dump its heat effectively - it WILL COOK otherwise! I have used a 28mm/22mm copper pipe reducer with a finned backplate soldered on.

[jokunen]

It uses 3Watts and emits 300 Lumens in a 3 degree beam.

Ok, it's good to know that there are alternatives. I know the LED lamp I did find is not the best solution in efficiency, but it's quite easy to get it working and it should not be fussy about cooling.

--Petri

[atcons]

DATA LOGER DELUXE
I made this project yesterday and after some issues everything is o.k .For more datails see
>

[jokunen]

DATA LOGER DELUXE
I made this project yesterday and after some issues everything is o.k .For more datails see
>

Is there some hidden reason why you want to put your announcement in this particular chain about Bicycle LED headlamp?

--Petri