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How to build L.E.D. torches
My son-in-law is a keen fisherman, and often spends the night fishing at the end of one of our local piers. He uses rod tip lights to indicate when he has a bite. However these things use button cells which don't last very long but do cost plenty to replace. He asked me if I could build him something to light the tips of his rods more economically.
I came up with the above L.E.D. torches, one to clamp onto the rod rest, pointing towards the rod tips, and one to hang above the tackle box, pointing into the box. The project box they are mounted in is the size of a cigarette packet. The switch is splash proof as is the box.
Calculations show that the 2 L.E.D. version should give approx 50 hours use on 3 AA alkaline cells. Which gives a running cost of approx 2-3pence per hour.
I thought this idea could be adapted for many uses. Perhaps as a head light, mounted on an elastic strap or a baseball cap (it is possible to mount the L.E.Ds and switch in different positions). If you want to try it for potholing you might need to improve the waterproofing but this should be possible as the lid already has a recess you could make a rubber gasket to fit. Also the splash proof cover could easily be sealed to the case to make it watertight. The torch is very small and would make a useful addition to any toolbox, or fit easily into a pocket.
My 2 L.E.D. version has parallel L.E.D.s and gives a fairly strong circular patch of light about 18 inches(50cm) or so at about 5 foot(1.5m). The three L.E.D. version has the L.E.D.s angled outwards at an angle of 10 degrees and gives a patch of light about 12 inches(30cm) by 24 inches(60cm) at 3 foot(1m).
This is what the torch looks like inside:-
From left to right you can see 3 L.E.D.s glued through holes drilled in the case, connections via a 27ohm resistor to the switch and the battery holder, and fixed in a rectangular hole in the lid is the switch.