Waipu Caves Camping & Caving Expedition
Wednesday 18 - Saturday 21 April 2007

Extra notes

The jet lighter and LEDs only arrived on Tuesday morning (17 April) and since I didn't have time to do anything with the LEDs before heading off I took them with us, and also packed multimeters and a soldering iron and other bits and pieces. I spent Thursday morning putting one of the LEDs on the front of my caving helmet to supplement the Luxeon K2 (and optics) already there. I'd heard great things about the Cree, so I was happy just leaving it bare, sans optics, and using it for wide angle lighting. I'd done a quick calculation in Dick Smith Electronics and worked out that a 2.2 ohm resistor would do the job very nicely for the current I wanted, and sure enough, after soldering it in I got about 760mA with fresh Eneloop AA cells. Perfect for a three or so hour trip.

The K2 was a mixed bag. I had set it up with two current controlled settings using an LM334 constant current controller in the high current configuration mentioned in the National Semiconductor datasheet, but there wasn't very much difference in perceived brightness between the two settings. I think I'll have to increase the top setting (or change it for another Cree and reduce the bottom setting). The elliptical beam disperser gave a wide and flat beam that might be best suited to a fixed-mount light such as on a bicycle. On a caving helmet it didn't do very well, because the light was too narrow vertically and with lots of head movement the beam shape was impractical and distracting.

When we stopped for scroggin after a couple of hours I took the wide beam disperser off the front of the K2 collimator, leaving it with a narrow spot beam, which strangely enough was easier to use than the wide beam from the disperser. It now had good throw, especially on the high setting, and came in very useful for lighting distant objects and tunnels. Together the spot Luxeon K2 and the wide angle Cree XR-E make a good combination, or will if I can come up with a robust housing for the Cree.

After caving on Friday our solar shower rope arrangements from earlier in the day weren't adequate for the shower when it weighed its full 20kg. It sagged and wasn't high enough. So more plotting, repositioning, pulling and tensioning the rope and we had it sorted. The water wasn't hot - I described it as "refreshing" at the time - but it was hugely better than the freezing water we had from the shower the previous trip, and it certainly did the job very nicely. If only I'd remembered some shampoo.

To keep the laptop going for long enough for the whole DVD movie and extra features, the laptop was plugged into the inverter, and the inverter in turn was plugged into the car (12V power socket in the boot). To keep the inverter fan from being distracting the inverter was placed just outside the back door of the car (on the chilly bin, I think) and the back door mostly closed.

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