Rebuild of Luxeon I Bicycle Headlight

This is a practical comparison between two light sources: an old 2-C cell halogen headlight and a single Luxeon I Star (with optics), both driven at the proper power. This is an image with no special adjustments and the sources about 5 feet away. It is easy to see that the Luxeon I has both more flux (total amount of light) and better throw (maximum intensity of beam). Note that halogen bulbs are known to be more efficient than traditional vacuum bulbs, see Lighting efficacy for more. According to my calculations, the power delivered to the halogen bulb is about 1.5 Watts, and the power to the Luxeon I (obviously) is 1 Watt. Note the spectrum of light output, and how this would make riding safer. This comparison allows the efficiency of the LED to really "shine".

Note that my power supply (limited to 1 amp) may not have been able to provide enough current to drive the Halogen bulb to the same power as the 2 C-cells, so the halogen light may get brighter with actual batteries. However, the power measurements quoted are absolutely correct and (together with the comparison picture) still illustrate the point of efficiency. Also note that only one Luxeon I (1-watt) is switched on in the comparison picture, whereas four are used in my headlight assembly.

The LED Dynamics BoostPuck 350mA current regulator came today. The model with lead wires attached was not available, so I had to solder on wires. It really is small as they say; even smaller than my rocker switch. I left the extra pins (reference voltage, and dim) not connected.


Using my power supply, I verified all the parts and connections were OK. The meter pictured is showing volts across the input power pins of the BoostPuck (out of frame). The system is was actually pulling down the voltage on my 1-amp-maximum power supply set at 6.0V by 200mV. You can see that the LED's are fully illuminated, which requires at least 12 Volts in their wiring configuration...


I soldered everything together as I mentioned I would in my last post (in series). I included a 270uF capacitor. The only problem with the BoostPuck is that it's a sealed unit and has no way to mount it to anything, unless you use the pins to anchor it (which I don't). It's not heavy, so I didn't think it's all that important. Using industrial hot glue, I fixed it to the rocker switch, and the capacitor to it as well. I expect the hot glue not to hold for long, especially if things heat up. I'll use some epoxy if all goes well--the hot glue comes off easily, epoxy won't.

The light output looks about right. It might be a little dimmer than the unregulated circuit, but it's worth the gains in battery efficiency/power delivery. The BoostPuck is producing over 12VDC across the four LED's in series, which is about what I expected. I haven't actually checked, but I'm assuming that the diode current is 350mA. I didn't make measurements of the current drawn from the batteries because of the AC components.


The light beam itself is continuous (as opposed to strobed); waving hands in front of the beam doesn't reveal individual light pulses as with other charge-pumping lights I've encountered. Also, the intensity differences between the new and old LED's is gone as I expected. The newer LED's needed a higher voltage than the older LED's to produce the same amount of light, and fixing the current at 350mA equalized the light intensity.

For clarity, below is a crude circuit diagram including all the parts.