Lago Ercina

Speleogroup  title


Site list (GPS fixes)

Walks (GPS tracks) 

Coordinates used

LED projects:

 Lamp tests
 ISP isolators
 SMT boards

Expedition logs:

 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


 The Battle of
 El Mazuco

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
Open Emitter
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
  1. Lumens are nominal (manufacturer’s numbers at maximum continuous power)
  2. Only the Badboy and ATtiny-A drives were repeatable constant-current.
  3. All lamps were helmet-mounted during testing, except for the Photon Micro-light.


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°17'47" W5°01'51") 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.

Expeditions to the Picos de Europa and elsewhere since 1973.
Please e-mail Mike Cowlishaw ( or Bill Collis (
if you have any corrections, suggestions, etc.   See also the SpeleoTrove speleology section ».
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This page was last edited on 2009-01-26 by mfc.