Site list (GPS fixes)
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Making SMT boards
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,
The Battle of
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
The lamps we compared
In all, seven lamps were compared:
||2×NiMH direct drive (~2.4V, 290mA)
||2×NiMH ‘Badboy’ drive (400mA)
||2×Alk direct drive (~3.1V)
||4×NiMH ATtiny-A-3 (5-level constant current)
||2×NiMH (100mA) and 2×Alk (200mA), FET blocking oscillator
||White Rayovac T1 (incandescent)
||5mm White LED
||2×Lithium button, as tested in El Cuevón de la Pruneda
in June 2002
- Lumens are nominal (manufacturer’s numbers at maximum continuous
- Only the Badboy and ATtiny-A drives were repeatable constant-current.
- All lamps were helmet-mounted during testing, except for the
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 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
- 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
- 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).
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.