Today's workshop disaster (minor) story

Discussion in 'General Electronics Chat' started by Treeman, Apr 14, 2015.

  1. Treeman

    Thread Starter Member

    May 22, 2014
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    15
    So there it was staring me in the face- I'd been looking for a ferrite toroid to make a joule thief for some time. The old Samsung came right in the end. How did I not spot it before?
    Joyously unwrapping the mains lead from it ; I was , like a magpie dazzled by something else on the board. Moving in I stubbed my finger with toroid on the bench and it promptly fell to the concrete floor.
    I remembered reading that ferrite was fragile just this morning.....


    Boo Hoo
     
  2. R!f@@

    AAC Fanatic!

    Apr 2, 2009
    8,733
    759
    Back to square one.
     
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  3. DickCappels

    Moderator

    Aug 21, 2008
    2,647
    631
    You don't need a toroid core.

    [​IMG]

    Fusty nail

    [​IMG]

    A piece of wood

    [​IMG]
    This is a closet lamp effectively using an air core

    Really, you can use almost anything or nothing as a core.

    A good place to find ferrite cores in in compact florescent lamps -be careful not to break the glass and get cut and/or let the mercury out.

    [​IMG]
     
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  4. takao21203

    Distinguished Member

    Apr 28, 2012
    3,577
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    why the same pictures keep repeating over years?
    These above are particulary bad even tough the circuits can light up single LEDs.

    You should buy ferrites + inductors which work well means you only need small amount of turns, can light up more LEDs.

    I used a Panasonic 10mH choke.

    Not sure if that works with a nail I doubt it.
     
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  5. Treeman

    Thread Starter Member

    May 22, 2014
    158
    15
    I tried a 10mm bolt last night with no luck - even after rechoosing the steel one from the Ali one I grabbed - skill. I like all these ideas, Dicks for ingenuity and scrap revaluation and takao because edfficiency is always king in the end.
    I am adding more turns to the bolt as we 'speak'.

    Thanks.
     
  6. takao21203

    Distinguished Member

    Apr 28, 2012
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    you get insane losses from iron core just starting at 1 KHz or so

    Ferrites for EMI arent particulary expensive.
     
  7. ian field

    Distinguished Member

    Oct 27, 2012
    4,413
    782
    Been looking for a use for those "E-E" ferrite ballasts from CFLs - all the ones I've salvaged so far, had no room for any more turns.

    Some CFLs have a diac in the startup circuit - you can get up to all kinds of mischief with them.

    Once you get the joule-thief going, wind a big secondary and add a diode/reservoir electrolytic. Put a DB3 diac in series with a bank of parallel LEDs and stick that combination across the electrolytic - every time it charges to about 32V, it dumps upto 2A into the bank of LEDs.
     
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