12v DC to 1.2v DC

Discussion in 'The Projects Forum' started by Scotty762, Oct 23, 2015.

  1. Scotty762

    Thread Starter New Member

    Oct 23, 2015
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    Hi anyone,
    I have a spare torch I never use I want to mod , Led Lenser L7, want it to run full time from 12v.
    It normally runs off 3 x AAA 900mAh NiMH 1.2V batties.
    Does anyone have a diagram on how i could do it? I dont have alot of knowledge on electronics.

    It'd be cool to have the circuits in the torch barrel 20mm Dia x 60mm .

    The reason is, I need to have max performance all the time. Distance = production when night shooting. This torch just runs 4 hrs or so then its not enough to be worth carrying anymore.

    Any help Appreciated , Scott
     
  2. GS3

    Senior Member

    Sep 21, 2007
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    Where are the 12 V coming from? Because it seems to me carrying an extra set of batteries is easier than anything else you can do.

    Also, some, many, LED flashlights rely on the battery's internal resistance to limit current. If you supply too much current you can fry the LEDs.
     
  3. MikeML

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    Oct 2, 2009
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  4. Dodgydave

    Distinguished Member

    Jun 22, 2012
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    How is the torch going to be used, in the hand or on a tripod/ holder, how big is the 12V battery, you are still going to have to charge the 12V battery, surely it must be easier to take an extra set of nicads with you?
     
  5. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
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    If the 3 batteries are in series you would need a to make/buy a 3.6V supply not 1.2v..
    If the current limiting is built into the flashlight a 3.6V constant voltage supply is all thats needed.
     
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  6. Scotty762

    Thread Starter New Member

    Oct 23, 2015
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    Torch will be in hand or mounted on rifle scope. will run from sockets in 4x4 or boat .
    I understand theres tonnes of alternatives. I have heaps of spare batteries and a few other torches to use but want to make this for fun. Thats why i chose the cheaper plastic L7 not p7 or p7.2 .

    Im already drawing up a new endcap to hold a button and a 2.1x5.5 female plug.

    Will the needed circuits fit inside the torch tube? anyone have any diagrams?

    Chers,Scott
     
  7. mcgyvr

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    Oct 15, 2009
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    One would need to know the answers to my "ifs" above before you move forward..
     
  8. Dodgydave

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    Jun 22, 2012
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    He already says its 3.6v in post#1,
    SCOTTY,
    the best volt dropper is the buck down converter as per post#3,

    Lm2596 chip
     
  9. Scotty762

    Thread Starter New Member

    Oct 23, 2015
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    Yeah sorry , i had a reply open for hours before i clicked post.

    I believe the batteries are in series . Here is a link with someone that pulled a similar torch apart maybe you can understand what kind of regulations it has: http://budgetlightforum.com/node/34815

    Dodgydave , i had a quick look , Lm2596 chip looks ideal ! size and everything! now just to find it in NZ
     
    Last edited: Oct 23, 2015
  10. Dodgydave

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    Jun 22, 2012
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    Going from the data in post#1,
    900mah batteries for 4hours, so
    the leds take about 220ma,
     
  11. Scotty762

    Thread Starter New Member

    Oct 23, 2015
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  12. Dodgydave

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    Jun 22, 2012
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    Yep same thing, but no current limit pot, you can put one on it.
     
  13. mcgyvr

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    Oct 15, 2009
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    Doesn't need one if he leaves the resistors/switch in place it seems
     
  14. ian field

    Distinguished Member

    Oct 27, 2012
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    A 3 cell unit is almost certainly as you describe.
    A 2 cell type has insufficient voltage for a white LED, and pretty certainly has some form of built in voltage booster. Making a selection on that basis would be the best solution to the TS's problem.
     
  15. Scotty762

    Thread Starter New Member

    Oct 23, 2015
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    Thanks heaps everyone , Ill get making !
     
  16. Scotty762

    Thread Starter New Member

    Oct 23, 2015
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    Since Im(we) are modifying it, what would be the best cree and driver for maximum throw? with or without the buck converter. Truck is 12v ish , 50amp alternator.

    Something like 1m dia beam at 500m would be fine for example. Just one mode is fine too.

    All inside the L7 or P7 shell. I think the original driver is under 20mm Dia.

    Am i dreaming here?
     
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