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On Lights for Tents

Now I'm living in the Landrover, it is important to have a source of light which is bright enough for tent-type use and allows a long enough battery life to avoid pratting about changing batteries all the time.

So I did a few tests.

Results of comparative lifetime tests for camping illumination:

Fluorescent tube camping type torch: 4 AA nicads -> 2 hours of good light. OK outdoors

Candle lantern:- running 2inch normal hardware store candle (20mm diam) -> 2 hours dim light - fine when night adapted. But poor outdoors.

Petzl Micro headtorch:- 2 AA nicads -> 2 hours good light. OK outdoors

Monster Maglite:- 4 D nicads -> 5 hours light bright enough to fry low flying aircraft.

Mini Maglite:- 2 AA nicads -> 2 hours good light. OK outdoors.

So. Non of these are too impressive for long term use cos the batteries run out too quick if used regularly; The solution?.....

Mini Maglite with bulb replaced by 3mm Ultrabright (250mCd) LED:- The LED plugs straight in after filing off the mounting lip. This gives more than 12 hours of dim light from 2 AA nicads. The light is fine for dark adapted in tent use (can read fine by it) but I wouldn't want to do any serious caving with it........ About as much use as a candle lantern.

Red LEDs are slightly higher power, but eh extra sensitivity of the eye to green more than compensates for this. LEDs used are RS590-345.

The greatly extended battery life coupled with adequate light output for in-tent use means that this is the way I shall go for in-Landrover/tent use, and for an emergency backup light for caving.

Also, LEDs cost 30p and last for ever, standard Maglite bulbs cost a couple of quid in outdoor shops and don't.

The current drain of a Minimag running an LED is so small that old alkaline batteries retired from walkmans/radios still give good performance in the Minimag! Two Nicads are fine for driving LEDs but Alkaline batteries need a 40 Ohm resistor in series to drop the current.

azw@aber.ac.uk




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