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Autoformer Pot Core Design

Discussion in 'Electronic Design' started by [email protected], Feb 24, 2007.

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  1. Guest

    Hi,

    I am trying to build the circuit at this site:

    http://www.williamson-labs.com/sdi.htm

    Its an ultrasonic dog trainer. The problem I am having is the
    autoformer.

    I understand it is some kind of transformer w/ a 12:1 ratio but I
    can't
    figure out exactly what parts to buy to make one. I plan on getting
    everying from digikey but could use some expert advice from this
    forum.

    if you are already at it, I also need someone to explain the overdrive
    protection. Thanks.
     
  2. Use the cannon.
    Ultrasound has little effect on some dogs.
    If the cannon is illegal, email the Whitehouse Iranian nukes are there.
     
  3. Bob Eld

    Bob Eld Guest

    Without designing the transformer from the ground up, there is insufficient
    information in at this site to properly wind your own. The author talks of
    pot cores yet the picture of the Williamson Labs coil is not a pot core.
    Secondly the single ended output FET driver puts DC in the tansformer. This
    requires a gaped core design. The Williamson part is a open core providing a
    large "gap", not closed like a pot core or torroid and is therefore suited
    for the DC unbalance that this circuit gives. Unless you use a powdered
    metal core, stay away form torroids, they do not have gaps. A pot core can
    be used but must be gaped. The particular core, number of turns, and gap
    length are unknown but can be calculated. Unfortunately the aritcle does not
    provide sufficient information to simply wind a part. Digikey doesn't have
    very many magnet parts in any case. If it were me, I'd try to find the
    Williamson Labs part used in the circuit already wound and ready to go. Good
    Luck.
     
  4. I think they've used the term potcore loosely. I'd be inclined to look at
    the tweeter maker's info.


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  5. From the website:

    * What type of pot core and winding? -- Actually, I used several pot cores
    stacked, such that the primaries were driven in parallel and the secondaries
    were connected in series--all phased correctly. This was done as a quick &
    dirty way of achieving a "step up" and allow for enough power--before core
    saturation. The specific pot core specs are only important relative to
    optimum operating frequency: ~10 kHz to ~40 Khz, peaking at ~ 20 kHz.
    However, this is not critical due to the broadband nature of ferrite
    transformers. One could use alternate transformer technology: single large
    ferrite torrid.
     
  6. Guest

    Thanks for the info. I've already asked the guy who designed it to
    provide some more info, but no luck yet.

    Any other ideas to get around this?
     
  7. I would look for the tweeter you are going to use and look at the design
    specs. See if they have a suggested driver circuit. I would also look on
    Amidon's site for information on a suitable transformer.


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  8. John  Larkin

    John Larkin Guest

    Right. I mean wrong. It's not a pot core. It's a ferrite drum core.

    John
     
  9. Looks like a bobbin but I'm not sure how much is ferrite.


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  10. Terry Given

    Terry Given Guest

    bobbin core = drum core

    I, too, was going to point this out.

    Interesting idea though, I'd been thinking about doing just that.
    Although a can of oven cleaner with the nozzle & tube from a can of
    CRC-556 is cheaper and easier (sort of a highly corrosive mace), albeit
    a lot less friendly.

    I got the idea from the tech who installed my last burglar alarm. it
    sounds like a pretty good idea for women living alone. Im sure a shot of
    caustic soda in the face will be quite a deterrent to a would-be rapist.

    Cheers
    Terry
     
  11. Diluted ammonia is effective on man and beast.


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  12. Look at Amidon parts B-77-1111 and B-77-1011. One of those might match the
    transformer used.


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