Some time ago, and I can't for the life of me remember when, and it doesn't matter anyway, I bought a "Wind-up Torch" from a supermarket chain - ASDA I think, though I certainly wouldn't swear to it.
Frankly I was never very impressed with the performance of it from the day I bought it.
As I understand it, with a wind-up torch, one was supposed to crank the handle like billy-o and then one would have a usable torch for a while afterwards.
Well this thing I bought was never any good, any light after the cranking was short-lived, and if one wanted a steady light, one just had to keep on cranking steadily away which kind of defeated the object.
Anyway, as it was very cheap I never really got "wound up" (sorry!) about the problem, and kind of put it down to experience, as one does.
Anyhow, the day came when the thing finally refused to work AT ALL, and I decided to dispose of it, but being one who gets a bit of a kick out of recycling electronic components in home brew projects, I decided to disassemble it before I disposed of the the remainder. So out came the jewellers' screwdriver set.
Very soon after starting the dismantling process I spotted something rather odd - a lithium battery.
Why did my wind-up torch have a battery in it, and, frankly, not much else?
The attached photos show what I found :- a small "generator unit", a pcb with a lithium battery, some diodes, one small SMD capactor, a switch and three LEDs.
As soon as I saw this little collection, I smelled a rat! Surely, I am going to find that the battery is flat (thus explaining the lack of light), I thought. Guess what? Flat as a pancake! No surprise there . . .
I shall leave it to the reader to work out what can be done with :-
(a) a small electromechanical hand-cranked generator
(b) a dpco switch
(c) about half a dozen small rectifier diodes
(d) a 100nF capacitor
(e) Three white LEDs
(f) A coin (lithium) cell
(g) some small reduction gears . . .
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