Introduction
Site list (GPS fixes) Walks (GPS tracks) Video clips Panoramas
Electronic projects:
Bat detector
Lamp tests
µ-controlled lamp
SEPIC-based lamp
ISP isolators
Making SMT boards
Expedition logs:
Spain 1973, 1974,
1975, 1976, 1977,
1979, 1982, 1983,
1985, 1986, 1987,
1988, 1989, 2000,
2001, 2002, 2003,
2004, 2005, 2006,
2007, 2008, 2009,
2010, 2011, 2012,
2013, 2014, 2015,
2016, 2017, 2018,
2019, 2020, 2021,
2022, 2023
Mexico
New England
Translation:
Luxeon LED caving lamp tests
Speleogroup is experimenting with circuits for driving high-power LED devices, such as the White LED Luxeon Star from Lumileds ». This device is rated at approximately one watt, giving typically 18 lumens at its rated current of 350mA. Their high dome Amber Luxeon star gives 36 lumens at a similar power, with a colour close to that of a sodium street lamp.
In July 2003 we tested a number of these lamps, using various conversions and drives, in real caving conditions in Spain.
The following notes are entirely subjective, reporting the reactions and conclusions of the Speleogroup team to the variety of different light sources in a particular cave. The cave chosen (Trumbio) was quite large (passages 10m high and/or wide), boulder-strewn (needing care to traverse) and somewhat monochrome (low reflectivity, dark mud-colored boulders).
The lamps we compared
In all, seven lamps were compared:
| Make | Color/type | Lum. | Drive |
|---|---|---|---|
| Luxeon Star/O | Red-Orange high dome | 55 | 2×NiMH direct drive (~2.4V, 290mA) |
| Luxeon Star/O | Amber high dome | 36 | 2×NiMH ‘Badboy’ drive (400mA) |
| Luxeon Star/O | Cyan low dome | 30 | 2×Alk direct drive (~3.1V) |
| Luxeon Star/O | White low dome | 18 | 4×NiMH ATtiny-A-3 (5-level constant current) drive |
| Luxeon Open Emitter | White low dome | 18 | 2×NiMH (100mA) and 2×Alk (200mA), FET blocking oscillator |
| Rayovac Adventure-Lite | White Rayovac T1 (incandescent) | ? | 2×Alk (“control”) |
| Photon Micro-light | 5mm White LED | ? | 2×Lithium button, as tested in El Cuevón de la Pruneda in June 2002 |
| Notes: |
|
||
Observations
Overall, results were much as expected.
- The inexpensive Rayovac used as a baseline control was comparable
in brightness to the White Star/O on full or half power, but with
a far less even light (bright and dark arcs, and variable around
the circumference).
- The open emitter (with simple FET drive and neither reflector
nor optics) was somewhat dim on 2×NiMH but quite acceptable
on 2×Alk. However it was distracting to other cavers as it often
blinded, even though it gave a good all-around illumination for the
wearer.
- The beam patterns from the Star/O devices (Luxeon Star with LumiLEDs
optics) were a good compromise of beam pattern.
- The Red-Orange high-dome Star/O was the brightest of the lamps
in the cave, but it did give an green-tinged after-image. Used on
its own one became adjusted to the color, but in combination with
other lamps it was distracting. Remarkable effects on digital cameras...
- The Amber high-dome Star/O was easily the most acceptable (pleasant
to work with and be around) of the monochromatic lamps, perhaps because
the color is familiar (being almost the same as sodium street-lamps)
and is a reasonable match to the typical colors found in many caves.
- The White Star/O was not as bright as the Red-Orange and Amber
lamps, but was much better for seeing detail and color (for example,
moon-milk and calcite in rocks). A slightly warmer white would have
been preferred (by cavers used to incandescent lamps) and the sample
we used gave an impression of a ‘purple spot’ in the
central part of the beam. (This was less noticeable in smaller passages,
where the lower power settings were found to be an advantage, too.)
- The Cyan Star/O was the least liked of the four Star/O lamps.
It’s light, though quite bright, was hard to work with (though with
some improvement after accommodation). Not recommended.
- The Photon Micro-light was compared to the 5-level White Star/O. It was confirmed that it was quite possible to navigate a cave with this level of light, which was equivalent to the Star/O at 1/8 power (about 40mA).
- LEDs need a reflector or optics for this application.
- White or Amber LEDs are the best colors (of those we tried)
for the task. The extra brightness of the Cyan or Red-Orange LEDs
did not compensate for the distraction effects.
- All of the Star/O devices were adequate for general caving.
Extra brightness in reserve would, of course, be better, but the
White Star/O was very usable (and would give 6 hours of full-power
light with each 4×NiMh 1800mAh battery pack carried).
Additional notes
The experiments described above were carried out and noted in Cueva Trumbio (N43°17'43" W5°01'56") on 4 July 2003, with additional notes from later caving trips in July 2003 added. All experiments were out of sight of daylight (no ambient light). The observers were in the age range 45-50.