Now then!

Here is what I found on the first real test of the converted headlamp. The first section of my evening commute is on a completely unlit road. Visibility was good here, with a slightly wider beam distribution than the original components. This was at the cost of a slightly reduced intensity at the centre of the beam - little difference in practice.

When I came to the urban & lit sections of the ride I noticed an interesting effect. The reflection of the lamp in the glossy paint finish of other vehicles was very noticable, suggesting that I was offering good visibility of my presence to other road users. However, with the halogen bulb, I am used to seeing lots of light come back from red reflectors on vehicles, and also reflective road signs. This effect was less with the LED and I suspect that it is connected with the fact that there is much less orange thru red spectral content in the bulb's output. Visibility of the beam on the road ahead was similar.

On arriving home I set up another test - how do the lamps appear to other road users? Although this is arbitary, I set up my 4.2W halogen and the LED conversion and viewed each in turn from a distance of approx 30 yards. The LED was perceived as much brighter in this test, giving it the edge in visibility in my opinion.

All in all, I think the experiment has been quite successful. The LED is definitely useful in this application and offers some definite advantages:

1, Long life and high mechanical robustness.
2, Improved efficiency, translating to enhanced run-time.
3, Potentially better visibility to other road users.

I'll keep the test unit running for now, as I'm happy using it in place of the halogen bulb unit. If there is a chance I might be able to get some night time pictures.

Cheers,

Ed