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G8MNY  > TECHNI   03.05.22 07:22z 81 Lines 4066 Bytes #17 (0) @ WW
BID : 1298_GB7CIP
Subj: Windup Torch info
Sent: 220503/0715Z @:GB7CIP.#32.GBR.EURO #:1298 [Caterham Surrey GBR] $:1298_GB

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
           旼컴컫컴컫컴컴컴쩡컴컴커      o컴컴컴컴컴컴컫컴컴커
          __  __       R4        旼>o off      D2__   __D3
          /_\  /_\      470   /      o컴커 D1     \_/   \_/
    旼컴컴캑       +     쳐컴캑T1     one 읕>쳐컴컴     1N5817
MOTOR AS   쿏4-7  ===    __   \___           旼컴컴)컴컴캑
GENERATOR         쿎1   /_\'    e            R1    R2    R3
    읕컴컴)컴컴   47uF  쿏W     ____        68   68   68
          __  __  25V   5.2V    複         __   __   __
          /_\  /_\              LIR         \_/  \_/  \_/
                             2032      LED1  LED2 LED3

A small motor spin from a 4 gear chain from the crank handle. The motor
generates over 5V & feeds a silicon bridge rectifier D4-7, which I guess is
there just in case the rotation is reversed. This DC feeds C1 & 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 & the voltage rises to cut off the
current from T1's emitter. With normal winding speed this takes only 30-60

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.

       旼컴컴쩡컴컴쩡컴컴컴쩡컴컴커       o  one
                __                   o컴컴컴컴컴컴컴컴컴컴
1N5817__       =\_/LED  1k         旼>o  all               
      /_\         쿒REEN      /       o컴컴컴쩡컴컴컴컴   
      +     +           쳐컴캑T1             쿮      /e   e\
  MOTOR AS  ===   220    __   \____        /     旼캑  PNP  쳐커
  GENERATOR  쿎1         /_\'    e        旼캑PNP 100k \ ____/  
  TURNED 1   47uF                ____  47k \                100k
  WAY ONLY   25V __      4.7V     複        쳐컴)컴컴)컴컴   
      -         /_\'            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 68 with wire links & replace the 3 Schotky diodes with
   the PNPs mounted right down for minimum headroom, add the base Rs to nearby

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 & solder the motor
   -ve to the -ve rail. Note the free unloaded generator action if reverse

3/ Battery Charged LED. First I found the original zener diode to be too high a
   voltage & 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 & also doubled the supply R to 1k. Then adding a GREEN LED
   with a 220 to monitor the generator voltage with the original zener.
   In use it lights up when the handle is cranked hard & then easily when the 
   battery is charged.

Why don't you write an interesting bul?

73 De John, G8MNY @ GB7CIP

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