After I built the previous light, Cree released the Cree XLamp XR-E with twice the efficiency of the Luxeon III. It was time to do a simple transplant of the LED and optics.
The Cree XR-E is 160 lumens at 700mA drive current for the best bin parts (65 lumens/watt), which according to Wikipedia is a similar efficiency to the best compact fluorescent lights. Cutter Electronics sell this star mount as an option. My LED was binned as 128 - 136 lumens at 700mA or about 170 lumens at 1000mA (45 lumens/watt). To get the same brightness from an incandescent globe (glass halogen 10-16 lumens/watt) would require about 12 watts vs an LED with 4 watts.
The Cree needs different optics to Luxeon devices, so this time I used the Fraen FC-N1-XR79-H . This gives a 9 degree beam (measured as full width half intensity with white light). This lens produces a much better beam shape than the L2 optics of V1. The old beam shape had a dark spot in the middle and irregular colouring of the beam. The new beam has a high intensity spot in the middle which is four times as bright. Ignore the discolouration that appears at the bottom of both images - that's part of the ceiling.
| |
|
| V1 beam, Luxeon III, L2-OP-005 optics | V1.5 beam, Cree XR-E, Fraen FC-N1 optics |
The battery pack was expanded from 8 to 10 cells of 2.4AH NiMH. This gives a slight longer run time, and sufficient voltage for the planned V2 light. Current draw from 12V is 370mA on high (4.5W) and 0.06A on low (0.7W). Run times are 6 hours on high and 40 hours on low.
Note that the XR-E data sheet has been revised since the initial release. Previously the maximum current was 700mA. This has been revised up to 1000mA. The beam width was 75 degrees (narrower than the XR with 100 degrees), and has been revised to 90 degrees. So it appears that optics intended for the XR are also suitable for the XR-E.
There are also plans for a Version 2 using three LEDs.
2007-02-18