Led Lighting

Bike Lights

With LEDs providing almost an order of magnitude improvement in luminous efficacy over a halogen globe it made sense to replace the bike lights. I was very happy with the Vistalite nightstick set I had been using so I decided to simply replace the MR11 globe with a single Cree XR-E.

Internally the LED chip is soldered to a solid copper plate which is then bonded with a conductive engineering epoxy to the aluminum casing of the light to maximise the heatsinking. A new acrylic front was machined to fit the contour of a MR11 globe and this both seals the front o-ring and presses the lens onto the LED.

The regulator (pictured left) shares its design with the current regulated buck-boost circuit used in my Petzl Duo refit, except in this case it is squeezed onto two sides of a 12.5x12.5mm board so it can fit in the space behind the LED. It has a high/low power jumper available but this is not used in the bike light and it is set for a constant 600mA (2.2W) output which easily embarrasses a 10W halogen light.


Left is a light commissioned for (and raced in) the 2005 Mont 24hr race. The machined aluminum casing was used as a heatsink and allowed the Luxeon 3W LED to run at its 1A (3.5W) power limit, the regulator was designed and built specifically for it and ran over 90% efficient. It was 82g total weight including regulator.


Hutlight

Before the second revision of the Petzl Duo refit I used this device as a fixed lamp whist traveling through high country huts. Its a rough and ready sort of light, a bare Luxeon III Star mounted to a sheet of aluminum with the regulator held in place by its wiring to the LED. The regulator is set for 4W and the heatsink gets quite warm in operation, some adhesive from some gaffer tape can be seen melted onto the aluminum in the picture.

This has spent many nights taped to the ceilings/rafters of various huts to save us from blinding people with focused headlamps but has now been retired with my new version 2 headlamp refit taking over the same role.