12.6 v - 2a Transformer question

Discussion in 'General Electronics Chat' started by SO$hocking, Jan 1, 2012.

  1. SO$hocking

    Thread Starter New Member

    Jan 1, 2012
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    I made a hot wire foam cutter with Radio Shack 12.6v-2a transformer, single pole dimmer switch and a guitar string.

    Q: Do I really need a fuse box?
    Do I need to hook the black middle wire on the transformer up?
    Will I blow this transformer with full dimmer on?

    Thanks. I'm new here and really like this forum already!!:)

    ps. sorry about my scematic pic.
    Transformer specs are wrong on it.
     
  2. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    It would be a good idea to put a fuse in the mains side, in case there is a fault in the transformer.

    No, you don't need to connect the center tap.

    As far as the transformer burning up if you turn the dimmer all the way up - hard to say, as we have no clue how much resistance your guitar string has. I think they are generally a type of stainless steel, but resistance would depend upon length, diameter, how much it's corroded, etc.

    If you add a slow-blow fuse on the secondary to, say, 1.5x the transformer's rating, that should take care of it.
     
  3. SO$hocking

    Thread Starter New Member

    Jan 1, 2012
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    Its a 16 gauge guitar string(i think it refers to thousands of an inch).
    21" long
    I don't have access to a slow burn fuse right now(nor any fuse), but i want to cut foam. BADLY!!!
    Think I can risk it without a fuse for a little while?
     
  4. bountyhunter

    Well-Known Member

    Sep 7, 2009
    2,498
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    If the transformer load is a guitar string, you are probably severely overloading the transformer and exceeding the current rating. An easy way to tell is stick a series Amp meter in and see the current.
     
  5. SO$hocking

    Thread Starter New Member

    Jan 1, 2012
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    I don't have a series Amp meter. I just cut some foam for a couple minuets. The transformer hummed. also stayed cool at the dimmer half way up.
     
  6. SgtWookie

    Expert

    Jul 17, 2007
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    Well, if the music wire is stainless steel (which I believe it is something similar), and it's 16 mils (same as 0.016", or 16/1000 of an inch), then a 21" length of it should measure roughly 3.79 Ohms. 12.6v / 3.79 Ohms = 3.32 Amperes.

    Do you have a multimeter that can measure AC volts? It would be helpful to know what the transformer measures with no output load on it.
     
  7. SO$hocking

    Thread Starter New Member

    Jan 1, 2012
    4
    0
    No meters at all. But this is all good stuff to know!!
     
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