LED Lighting for cavers

These notes were written in 2001 and have now been superseded by new technology in the form of high-power Luxeon LEDs and similar products. This page is therefore largely obsolete!

To save you the trouble of emailing me for free advice, please note that I am no longer working on any LED projects and I have nothing useful to tell you beyond what is written here - David Gibson

For more up-to-date information about LED lamps for cavers, see bcra.org.uk/creg/index.html#led

These notes by David Gibson and Stuart France describe the use of multiple white LEDs as a replacement for tungsten filament lamps. Our main interest is in using LEDs for caving cap-lamps, but these notes can obviously be extended to general lighting: lightweight flashlights, bicycle lamps, etc, and can apply to coloured as well as white LEDs.

The future will be white LEDs, but it has not yet arrived; the present market for raw components or finished products is mainly enthusiasts and early-adopters. Opto-electronics is an exciting area and white LEDs in a few years time may be powerful and cheap enough for house and street lighting when they move from being maximum 100mW devices to several watts each.

We have both made our own white LED lamps which contain 36 or 48 LEDs and which incorporate 'smart' power supplies to implement dimming and allow the lamps to operate from all common caving batteries (e.g. FX5/Kirby pack down to two AA cells). More recently, we have produced a seven-LED pilot light with a simple built-in regulator, which enhances its performance without adding much to the cost.

If a good LED caving lamp could be made from just a few LEDs and a bunch of cheap resistors we would have gone down that route, but there is no escaping the simple maths that you need a lot of LEDs to match halogen bulbs, and there is no such thing as a free lunch!

Further Reading

Equipment Review: The Nova Caving Lamp (298K PDF) | (low-res 49K PDF)

The Nova, from Speleo Technics, is the first commercially available caving lamp to use the Luxeon 5W single-chip LED. David Gibson describes how the lamp fared underground and offers some thoughts on how the design could be enhanced. This is a copy of a review from CREG journal 54 and is an expanded version of an article from Descent 175. (A low-resolution version of this file (49K PDF) is also available).

The future is not orange... but white

David Gibson and Stuart France describe the use of white LEDs for caving lamps and attempt to demolish a few persistent myths. This article is the first of a series that will include practical circuits for LED caving lamps. This article is a greatly expanded version of the article in Descent 157 (Dec.2000/Jan.2001), and similar to the article in CREG journal 42 (Dec.2000).

Improvements to caving lamps (95K PDF)

Filament lamps are fragile and inefficient, but their performance can be enhanced using switching regulators. New solid-state lamps using white LEDs offer further improvements. David Gibson describes some existing “high-tech” lamp drivers for filament lamps, discusses microprocessor-control and introduces his 4W 48-white-LED caving lamp (pictured above). This article is a corrected reprint from CREG journal 33. (Sept.98). If you need to know more about PDF files, click here

More notes from the CREG journal

• Candlepower! (25K PDF), CREGJ 26, p27, Dec. 1996
  David Gibson explains lumens and candelas, and why the candlepower rating of a lamp can be misleading. Page includes: Foot Candles, CREGJ 27, p21, March 1997.
   
• Foot-Candles: Photometric Units, CREGJ 29, pp9-10, Sept. 1997
  David Gibson explains the confusing range of optometric units. Also on p10 of CREGJ 29 is a short note listing a selection of references to circuits for driving fluorescent tubes.
   
• Foot Candles, CREGJ 39, p15, March 2000
  David Gibson discusses pulsed light sources. Also on p15 of CREGJ 39 is information about the emerging UK Photography Group
   

The Luxeon 5W LED

22-Sep-03: The Luxeon 5W LED is now available, after some lengthy production delays. See http://www.lumileds.com/ for details. This device runs at 700mA, approx 8.3V and produces 120 lumens at 21 lumen/Watt. This device is therefore usable for caplamps (e.g. see Speleo Technics. At GBP 27.00 it is still too expensive for room lighting. Some notes on this device appear in Speleology 3 published by BCRA and CREG journal 53. 12-Dec-03: Also see the review in CREG journal 54, reproduced here.

LEDs for Room Lighting

06-Nov-02: We continue to receive enquiries about using LEDs for room lighting, street lighting, car headlamps, and so on. The bottom line is this: white LEDs are about the same efficiency as tungsten halogen lamps, and use around 70mW of electrical power. simple mathematics tells you that if you want the equivalent of a 70W lamp you will need to use a thousand LEDs. No doubt LEDs will rise in efficiency, but it will be hard to beat the efficiency of gas discharge lamps (e.g. fluorescent lamps, sodium lamps for street-lighting). Further information.

This page last updated 22-May-06, with description as "obsolete".