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G8MNY  > TECH     01.07.25 18:20l 79 Lines 4080 Bytes #10 (0) @ WW
BID : 35868_GB7CIP
Subj: Windup Torch info
Path: JH4XSY<JE7YGF<LU4ECL<UA6ADV<OE6XPE<DB0ERF<DK0WUE<PD0LPM<VE3CGR<GB7YEW<
      GB7CIP
Sent: 250701/0646Z @:GB7CIP.#32.GBR.EURO #:35868 [Caterham Surrey GBR]
From: G8MNY@GB7CIP.#32.GBR.EURO
To  : TECH@WW

By G8MNY                                           (Updated Dec 05)
(8 Bit ASCII graphics use code page 437 or 850, Terminal Font)

Not being one to leave a new toy unexamined, here is info I reverse engineered
from one of these fairly cheap LED torches.

                                         o     all
           Ŀ      oĿ
          __  __       R4        >o off      D2__   __D3
          /_\  /_\      470R   /      oĿ D1     \_/   \_/
    Ĵ       +     ĴT1     one Ĵ>Ĵ     1N5817
MOTOR AS   D4-7  ===    __   \___           )Ĵ
GENERATOR         C1   /_\'    e            R1    R2    R3
    )Ĵ   47uF  DW     ____        68R   68R   68R
          __  __  25V   5.2V             __   __   __
          /_\  /_\              LIR         \_/  \_/  \_/
                             2032      LED1  LED2 LED3
           

HOW IT WORKS
A small motor spin from a 4 gear chain from the crank handle. The motor
generates over 5V and feeds a silicon bridge rectifier D4-7, which I guess is
there just in case the rotation is reversed. This DC feeds C1 and powers up the
zener DW to make T1 conduct current into the 3.6V Lithium Iron rechargeable
button cell until the cell if fully charged and the voltage rises to cut off
the current from T1's emitter. With normal winding speed this takes only 30-60
seconds.

A 4 way push action rotary switch powers the LEDs, either one or all 3 through
low voltage drop steering diodes D1-3 to a current limiting resistor to the
2.6 - 3V Hyper-Bright white LEDs. The battery can light all 3 LEDs for more
than 30 mins on one charge. The light output is quite feeble compared to a
normal torch of the same size, but it is quite enough to read at night etc.


MY IMPROVEMENTS
       Ŀ       o  one
                __                   oĿ
1N5817__       =\_/LED  1K         >o  all               
      /_\         GREEN      /       oĿ   
      +     +           ĴT1             e      /e   e\
  MOTOR AS  ===   220R    __   \____        /     Ĵ  PNP  Ŀ
  GENERATOR  C1         /_\'    e        ĴPNP 100K \ ____/  
  TURNED 1   47uF                ____  47K \                100K
  WAY ONLY   25V __      4.7V             ))Ŀ   
      -         /_\'            LIR        __      __  __  
                 5V           2032       \_/     \_/ \_/  
       

1/ Constant current to LEDs. Almost constant LED current until the battery
   fails with 3 small PNP transistors. The 47K/100K values on the bases depends
   on the PNP transistor gain to give the right LED currents of 10mA MAX,
   values in the range 22K to 220K may be needed.
   Replace the 3 LED 68R with wire links and replace the 3 Schotky diodes with
   the PNPs mounted right down for minimum headroom, add the base Rs to nearby
   grounds.

2/ Bridge losses removed. Replace the 4 silicon diodes with 1 of the 1N5817
   diodes. Make sure the generator is wired up for your favoured rotation
   direction. Swap 1 of the +ve rail diode for the 1N5817 and solder the motor
   -ve to the -ve rail. Note the free unloaded generator action if reverse
   wound.

3/ Battery Charged LED. First I found the original zener diode to be too high a
   voltage and the regulator never came in as the new 3.6V battery would not
   reach 4.5V to stop the current flow, so I replace the zener with a 4.7V one
   selected on test and also doubled the supply R to 1K. Then adding a GREEN
   LED with a 220R to monitor the generator voltage with the original zener.
   In use it lights up when the handle is cranked hard and then easily when the 
   battery is charged.


Why don't you write an interesting bul?

73 De John, G8MNY @ GB7CIP


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