Question about Gate Drive Transformer

Discussion in 'The Projects Forum' started by magnet18, Mar 16, 2011.

  1. magnet18

    Thread Starter Senior Member

    Dec 22, 2010
    1,232
    124
    Hi,
    I'm currently building the plasma speaker found here
    http://teravolt.org/Plasma_Speaker_2.htm
    Instructable here
    http://www.instructables.com/id/A-reliable-plasma-speaker/step2/Making-the-GDT/
    And I had a question about the GDT, Which is driving IRFP250 MOSFETs.
    It says that it is 14 turns of 22ga wire,on a 2.5cm ferrite; I was unable to fit that number of turns of a ferrite of that size, and was wondering if 8-9 turns would be acceptable to get it to work? I've attached some pictures.

    I don't know all that much about MOSFETs and less about transformers, and wanted to be sure, or at least somewhat sure, that it will work before wiring everything to it, or if I should just try again.

    I would ask on the instructable, but the question has already been asked and it appears the author's only response is to fiddle with it. I seem to lack the coordination to wrap one of these in anything under n hour, so I'd rather not do that.

    Here's the schematic
    [​IMG]

    If anyone knows enough about this to tell if it would work or knows of any good sites that deal with calculating this for beginners (other than the textbook here) I would greatly appreciate it.

    Thanks in advance :)
     
  2. magnet18

    Thread Starter Senior Member

    Dec 22, 2010
    1,232
    124
    You also might have noticed the plastic spacer under it, is that a bad idea? If not, would it be a no-no to run any wires through there?
    (yea, I'm n00b)
     
  3. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    He used AWG-24 wire from a Cat 5 cable, not AWG-22.

    If you don't have enough turns on the ferrite core, you won't get as much output current due to the lower coupling.

    Don't bother with the spacer. Once you have it working, just use a hot glue gun to secure the toroid to the board.
     
  4. magnet18

    Thread Starter Senior Member

    Dec 22, 2010
    1,232
    124
    OK, that makes sense

    So then I should re-wrap it with smaller wire?

    I just had it there because it was easier than trimming the wires. :p
     
  5. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    Only if you want sufficient current to drive the MOSFET gates.

    re: spacer
    You want the toroid held rigidly to the board so the wires don't flex and break.
     
  6. magnet18

    Thread Starter Senior Member

    Dec 22, 2010
    1,232
    124
    Thats a yes then, sorry, your first one said less, I wasn't sure how much less...

    I'd like to re-wrap it anyway and use some nicer colors :)

    Thanks for the tip on mounting it :)
     
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